diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4c97493550b..c78cb18e7df 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ project(pioneer LANGUAGES CXX)
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 set(CMAKE_CXX_STANDARD 17)
 
-set(PROJECT_VERSION "20240203"
+set(PROJECT_VERSION "20240203-dev"
 	CACHE STRING "Version identifier for current compiled build")
 
 set(PROJECT_VERSION_INFO ""
diff --git a/contrib/fmt/CMakeLists.txt b/contrib/fmt/CMakeLists.txt
index b74bd1da270..dec3e3f255c 100644
--- a/contrib/fmt/CMakeLists.txt
+++ b/contrib/fmt/CMakeLists.txt
@@ -1,61 +1,171 @@
-cmake_minimum_required(VERSION 3.1.0)
+cmake_minimum_required(VERSION 3.8...3.26)
 
-# Use newer policies if available, up to most recent tested version of CMake.
-if(${CMAKE_VERSION} VERSION_LESS 3.11)
+# Fallback for using newer policies on CMake <3.12.
+if (${CMAKE_VERSION} VERSION_LESS 3.12)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.11)
-endif()
+endif ()
 
 # Determine if fmt is built as a subproject (using add_subdirectory)
 # or if it is the master project.
-set(MASTER_PROJECT OFF)
-if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
-  set(MASTER_PROJECT ON)
-  message(STATUS "CMake version: ${CMAKE_VERSION}")
+if (NOT DEFINED FMT_MASTER_PROJECT)
+  set(FMT_MASTER_PROJECT OFF)
+  if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+    set(FMT_MASTER_PROJECT ON)
+    message(STATUS "CMake version: ${CMAKE_VERSION}")
+  endif ()
 endif ()
 
 # Joins arguments and places the results in ${result_var}.
 function(join result_var)
-  set(result )
+  set(result "")
   foreach (arg ${ARGN})
     set(result "${result}${arg}")
   endforeach ()
   set(${result_var} "${result}" PARENT_SCOPE)
 endfunction()
 
+# DEPRECATED! Should be merged into add_module_library.
+function(enable_module target)
+  if (MSVC)
+    set(BMI ${CMAKE_CURRENT_BINARY_DIR}/${target}.ifc)
+    target_compile_options(${target}
+      PRIVATE /interface /ifcOutput ${BMI}
+      INTERFACE /reference fmt=${BMI})
+    set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
+    set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
+  endif ()
+endfunction()
+
+# Adds a library compiled with C++20 module support.
+# `enabled` is a CMake variables that specifies if modules are enabled.
+# If modules are disabled `add_module_library` falls back to creating a
+# non-modular library.
+#
+# Usage:
+#   add_module_library(<name> [sources...] FALLBACK [sources...] [IF enabled])
+function(add_module_library name)
+  cmake_parse_arguments(AML "" "IF" "FALLBACK" ${ARGN})
+  set(sources ${AML_UNPARSED_ARGUMENTS})
+
+  add_library(${name})
+  set_target_properties(${name} PROPERTIES LINKER_LANGUAGE CXX)
+
+  if (NOT ${${AML_IF}})
+    # Create a non-modular library.
+    target_sources(${name} PRIVATE ${AML_FALLBACK})
+    return()
+  endif ()
+
+  # Modules require C++20.
+  target_compile_features(${name} PUBLIC cxx_std_20)
+  if (CMAKE_COMPILER_IS_GNUCXX)
+    target_compile_options(${name} PUBLIC -fmodules-ts)
+  endif ()
+
+  # `std` is affected by CMake options and may be higher than C++20.
+  get_target_property(std ${name} CXX_STANDARD)
+
+  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(pcms)
+    foreach (src ${sources})
+      get_filename_component(pcm ${src} NAME_WE)
+      set(pcm ${pcm}.pcm)
+
+      # Propagate -fmodule-file=*.pcm to targets that link with this library.
+      target_compile_options(
+        ${name} PUBLIC -fmodule-file=${CMAKE_CURRENT_BINARY_DIR}/${pcm})
+
+      # Use an absolute path to prevent target_link_libraries prepending -l
+      # to it.
+      set(pcms ${pcms} ${CMAKE_CURRENT_BINARY_DIR}/${pcm})
+      add_custom_command(
+        OUTPUT ${pcm}
+        COMMAND ${CMAKE_CXX_COMPILER}
+                -std=c++${std} -x c++-module --precompile -c
+                -o ${pcm} ${CMAKE_CURRENT_SOURCE_DIR}/${src}
+                "-I$<JOIN:$<TARGET_PROPERTY:${name},INCLUDE_DIRECTORIES>,;-I>"
+        # Required by the -I generator expression above.
+        COMMAND_EXPAND_LISTS
+        DEPENDS ${src})
+    endforeach ()
+
+    # Add .pcm files as sources to make sure they are built before the library.
+    set(sources)
+    foreach (pcm ${pcms})
+      get_filename_component(pcm_we ${pcm} NAME_WE)
+      set(obj ${pcm_we}.o)
+      # Use an absolute path to prevent target_link_libraries prepending -l.
+      set(sources ${sources} ${pcm} ${CMAKE_CURRENT_BINARY_DIR}/${obj})
+      add_custom_command(
+        OUTPUT ${obj}
+        COMMAND ${CMAKE_CXX_COMPILER} $<TARGET_PROPERTY:${name},COMPILE_OPTIONS>
+                -c -o ${obj} ${pcm}
+        DEPENDS ${pcm})
+    endforeach ()
+  endif ()
+  target_sources(${name} PRIVATE ${sources})
+endfunction()
+
+include(CMakeParseArguments)
+
 # Sets a cache variable with a docstring joined from multiple arguments:
 #   set(<variable> <value>... CACHE <type> <docstring>...)
 # This allows splitting a long docstring for readability.
 function(set_verbose)
-  cmake_parse_arguments(SET_VERBOSE "" "" "CACHE" ${ARGN})
-  list(GET SET_VERBOSE_CACHE 0 type)
-  list(REMOVE_AT SET_VERBOSE_CACHE 0)
-  join(doc ${SET_VERBOSE_CACHE})
-  set(${SET_VERBOSE_UNPARSED_ARGUMENTS} CACHE ${type} ${doc})
+  # cmake_parse_arguments is broken in CMake 3.4 (cannot parse CACHE) so use
+  # list instead.
+  list(GET ARGN 0 var)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 val)
+  list(REMOVE_AT ARGN 0)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 type)
+  list(REMOVE_AT ARGN 0)
+  join(doc ${ARGN})
+  set(${var} ${val} CACHE ${type} ${doc})
 endfunction()
 
 # Set the default CMAKE_BUILD_TYPE to Release.
 # This should be done before the project command since the latter can set
 # CMAKE_BUILD_TYPE itself (it does so for nmake).
-if (MASTER_PROJECT AND NOT CMAKE_BUILD_TYPE)
+if (FMT_MASTER_PROJECT AND NOT CMAKE_BUILD_TYPE)
   set_verbose(CMAKE_BUILD_TYPE Release CACHE STRING
               "Choose the type of build, options are: None(CMAKE_CXX_FLAGS or "
               "CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.")
 endif ()
 
+project(FMT CXX)
+include(GNUInstallDirs)
+set_verbose(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR} CACHE STRING
+            "Installation directory for include files, a relative path that "
+            "will be joined with ${CMAKE_INSTALL_PREFIX} or an absolute path.")
+
 option(FMT_PEDANTIC "Enable extra warnings and expensive tests." OFF)
 option(FMT_WERROR "Halt the compilation with an error on compiler warnings."
        OFF)
 
 # Options that control generation of various targets.
-option(FMT_DOC "Generate the doc target." ${MASTER_PROJECT})
-option(FMT_INSTALL "Generate the install target." ${MASTER_PROJECT})
-option(FMT_TEST "Generate the test target." ${MASTER_PROJECT})
+option(FMT_DOC "Generate the doc target." ${FMT_MASTER_PROJECT})
+option(FMT_INSTALL "Generate the install target." ON)
+option(FMT_TEST "Generate the test target." ${FMT_MASTER_PROJECT})
 option(FMT_FUZZ "Generate the fuzz target." OFF)
 option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
+option(FMT_OS "Include core requiring OS (Windows/Posix) " ON)
+option(FMT_MODULE "Build a module instead of a traditional library." OFF)
+option(FMT_SYSTEM_HEADERS "Expose headers with marking them as system." OFF)
 
-project(FMT CXX)
+if (FMT_TEST AND FMT_MODULE)
+  # The tests require {fmt} to be compiled as traditional library
+  message(STATUS "Testing is incompatible with build mode 'module'.")
+endif ()
+set(FMT_SYSTEM_HEADERS_ATTRIBUTE "")
+if (FMT_SYSTEM_HEADERS)
+  set(FMT_SYSTEM_HEADERS_ATTRIBUTE SYSTEM)
+endif ()
+if (CMAKE_SYSTEM_NAME STREQUAL "MSDOS")
+  set(FMT_TEST OFF)
+  message(STATUS "MSDOS is incompatible with gtest")
+endif ()
 
 # Get version from core.h
 file(READ include/fmt/core.h core_h)
@@ -73,41 +183,45 @@ message(STATUS "Version: ${FMT_VERSION}")
 message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
 
 if (NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
-  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 endif ()
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
   "${CMAKE_CURRENT_SOURCE_DIR}/support/cmake")
 
-include(cxx14)
 include(CheckCXXCompilerFlag)
+include(JoinPaths)
+
+if (FMT_MASTER_PROJECT AND NOT DEFINED CMAKE_CXX_VISIBILITY_PRESET)
+  set_verbose(CMAKE_CXX_VISIBILITY_PRESET hidden CACHE STRING
+              "Preset for the export of private symbols")
+  set_property(CACHE CMAKE_CXX_VISIBILITY_PRESET PROPERTY STRINGS
+               hidden default)
+endif ()
 
-list(FIND CMAKE_CXX_COMPILE_FEATURES "cxx_variadic_templates" index)
-if (${index} GREATER -1)
-  # Use cxx_variadic_templates instead of more appropriate cxx_std_11 for
-  # compatibility with older CMake versions.
-  set(FMT_REQUIRED_FEATURES cxx_variadic_templates)
+if (FMT_MASTER_PROJECT AND NOT DEFINED CMAKE_VISIBILITY_INLINES_HIDDEN)
+  set_verbose(CMAKE_VISIBILITY_INLINES_HIDDEN ON CACHE BOOL
+              "Whether to add a compile flag to hide symbols of inline functions")
 endif ()
-message(STATUS "Required features: ${FMT_REQUIRED_FEATURES}")
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
   set(PEDANTIC_COMPILE_FLAGS -pedantic-errors -Wall -Wextra -pedantic
       -Wold-style-cast -Wundef
       -Wredundant-decls -Wwrite-strings -Wpointer-arith
       -Wcast-qual -Wformat=2 -Wmissing-include-dirs
-      -Wcast-align -Wnon-virtual-dtor
+      -Wcast-align
       -Wctor-dtor-privacy -Wdisabled-optimization
       -Winvalid-pch -Woverloaded-virtual
-      -Wconversion -Wswitch-enum
-      -Wno-ctor-dtor-privacy -Wno-format-nonliteral -Wno-shadow)
+      -Wconversion -Wundef
+      -Wno-ctor-dtor-privacy -Wno-format-nonliteral)
   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
-      set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS} -Wnoexcept
+      set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS}
          -Wno-dangling-else -Wno-unused-local-typedefs)
   endif ()
   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
       set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS} -Wdouble-promotion
           -Wtrampolines -Wzero-as-null-pointer-constant -Wuseless-cast
-          -Wvector-operation-performance -Wsized-deallocation)
+          -Wvector-operation-performance -Wsized-deallocation -Wshadow)
   endif ()
   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
       set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS} -Wshift-overflow=2
@@ -117,8 +231,9 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
 endif ()
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-  set(PEDANTIC_COMPILE_FLAGS -Wall -Wextra -pedantic -Wconversion
-      -Wno-sign-conversion -Wdeprecated -Wweak-vtables)
+  set(PEDANTIC_COMPILE_FLAGS -Wall -Wextra -pedantic -Wconversion -Wundef
+      -Wdeprecated -Wweak-vtables -Wshadow
+      -Wno-gnu-zero-variadic-macro-arguments)
   check_cxx_compiler_flag(-Wzero-as-null-pointer-constant HAS_NULLPTR_WARNING)
   if (HAS_NULLPTR_WARNING)
     set(PEDANTIC_COMPILE_FLAGS ${PEDANTIC_COMPILE_FLAGS}
@@ -132,7 +247,7 @@ if (MSVC)
   set(WERROR_FLAG /WX)
 endif ()
 
-if (MASTER_PROJECT AND CMAKE_GENERATOR MATCHES "Visual Studio")
+if (FMT_MASTER_PROJECT AND CMAKE_GENERATOR MATCHES "Visual Studio")
   # If Microsoft SDK is installed create script run-msbuild.bat that
   # calls SetEnv.cmd to set up build environment and runs msbuild.
   # It is useful when building Visual Studio projects with the SDK
@@ -150,18 +265,6 @@ if (MASTER_PROJECT AND CMAKE_GENERATOR MATCHES "Visual Studio")
     ${CMAKE_MAKE_PROGRAM} -p:FrameworkPathOverride=\"${netfxpath}\" %*")
 endif ()
 
-set(strtod_l_headers stdlib.h)
-if (APPLE)
-  set(strtod_l_headers ${strtod_l_headers} xlocale.h)
-endif ()
-
-include(CheckSymbolExists)
-if (WIN32)
-  check_symbol_exists(_strtod_l "${strtod_l_headers}" HAVE_STRTOD_L)
-else ()
-  check_symbol_exists(strtod_l "${strtod_l_headers}" HAVE_STRTOD_L)
-endif ()
-
 function(add_headers VAR)
   set(headers ${${VAR}})
   foreach (header ${ARGN})
@@ -171,15 +274,20 @@ function(add_headers VAR)
 endfunction()
 
 # Define the fmt library, its includes and the needed defines.
-add_headers(FMT_HEADERS chrono.h color.h compile.h core.h format.h format-inl.h
-                        locale.h os.h ostream.h posix.h printf.h ranges.h)
-set(FMT_SOURCES src/format.cc src/os.cc)
+add_headers(FMT_HEADERS args.h chrono.h color.h compile.h core.h format.h
+                        format-inl.h os.h ostream.h printf.h ranges.h std.h
+                        xchar.h)
+set(FMT_SOURCES src/format.cc)
+if (FMT_OS)
+  set(FMT_SOURCES ${FMT_SOURCES} src/os.cc)
+endif ()
 
-add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS})
+add_module_library(fmt src/fmt.cc FALLBACK
+                   ${FMT_SOURCES} ${FMT_HEADERS} #README.md ChangeLog.md
+                   IF FMT_MODULE)
 add_library(fmt::fmt ALIAS fmt)
-
-if (HAVE_STRTOD_L)
-  target_compile_definitions(fmt PUBLIC FMT_LOCALE)
+if (FMT_MODULE)
+  enable_module(fmt)
 endif ()
 
 if (FMT_WERROR)
@@ -189,17 +297,30 @@ if (FMT_PEDANTIC)
   target_compile_options(fmt PRIVATE ${PEDANTIC_COMPILE_FLAGS})
 endif ()
 
-target_compile_features(fmt INTERFACE ${FMT_REQUIRED_FEATURES})
+if (cxx_std_11 IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+  target_compile_features(fmt PUBLIC cxx_std_11)
+else ()
+  message(WARNING "Feature cxx_std_11 is unknown for the CXX compiler")
+endif ()
 
-target_include_directories(fmt PUBLIC
+target_include_directories(fmt ${FMT_SYSTEM_HEADERS_ATTRIBUTE} PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
 set(FMT_DEBUG_POSTFIX d CACHE STRING "Debug library postfix.")
 
 set_target_properties(fmt PROPERTIES
   VERSION ${FMT_VERSION} SOVERSION ${CPACK_PACKAGE_VERSION_MAJOR}
-  DEBUG_POSTFIX "${FMT_DEBUG_POSTFIX}")
+  PUBLIC_HEADER "${FMT_HEADERS}"
+  DEBUG_POSTFIX "${FMT_DEBUG_POSTFIX}"
+
+  # Workaround for Visual Studio 2017:
+  # Ensure the .pdb is created with the same name and in the same directory
+  # as the .lib. Newer VS versions already do this by default, but there is no
+  # harm in setting it for those too. Ignored by other generators.
+  COMPILE_PDB_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
+  COMPILE_PDB_NAME "fmt"
+  COMPILE_PDB_NAME_DEBUG "fmt${FMT_DEBUG_POSTFIX}")
 
 # Set FMT_LIB_NAME for pkg-config fmt.pc. We cannot use the OUTPUT_NAME target
 # property because it's not set by default.
@@ -209,61 +330,53 @@ if (CMAKE_BUILD_TYPE STREQUAL "Debug")
 endif ()
 
 if (BUILD_SHARED_LIBS)
-  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
-    # Fix rpmlint warning:
-    # unused-direct-shlib-dependency /usr/lib/libformat.so.1.1.0 /lib/libm.so.6.
-    target_link_libraries(fmt -Wl,--as-needed)
-  endif ()
-  target_compile_definitions(fmt PRIVATE FMT_EXPORT INTERFACE FMT_SHARED)
+  target_compile_definitions(fmt PRIVATE FMT_LIB_EXPORT INTERFACE FMT_SHARED)
 endif ()
 if (FMT_SAFE_DURATION_CAST)
   target_compile_definitions(fmt PUBLIC FMT_SAFE_DURATION_CAST)
-endif()
+endif ()
 
 add_library(fmt-header-only INTERFACE)
 add_library(fmt::fmt-header-only ALIAS fmt-header-only)
 
 target_compile_definitions(fmt-header-only INTERFACE FMT_HEADER_ONLY=1)
-target_compile_features(fmt-header-only INTERFACE ${FMT_REQUIRED_FEATURES})
+target_compile_features(fmt-header-only INTERFACE cxx_std_11)
 
-target_include_directories(fmt-header-only INTERFACE
+target_include_directories(fmt-header-only
+  ${FMT_SYSTEM_HEADERS_ATTRIBUTE} INTERFACE
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
 # Install targets.
 if (FMT_INSTALL)
-  include(GNUInstallDirs)
   include(CMakePackageConfigHelpers)
   set_verbose(FMT_CMAKE_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/fmt CACHE STRING
-              "Installation directory for cmake files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+              "Installation directory for cmake files, a relative path that "
+              "will be joined with ${CMAKE_INSTALL_PREFIX} or an absolute "
+              "path.")
   set(version_config ${PROJECT_BINARY_DIR}/fmt-config-version.cmake)
   set(project_config ${PROJECT_BINARY_DIR}/fmt-config.cmake)
   set(pkgconfig ${PROJECT_BINARY_DIR}/fmt.pc)
   set(targets_export_name fmt-targets)
 
-  set (INSTALL_TARGETS fmt)
-  if (TARGET fmt-header-only)
-    set(INSTALL_TARGETS ${INSTALL_TARGETS} fmt-header-only)
-  endif ()
-
   set_verbose(FMT_LIB_DIR ${CMAKE_INSTALL_LIBDIR} CACHE STRING
-              "Installation directory for libraries, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
-
-  set_verbose(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR}/fmt CACHE STRING
-              "Installation directory for include files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+              "Installation directory for libraries, a relative path that "
+              "will be joined to ${CMAKE_INSTALL_PREFIX} or an absolute path.")
 
-  set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE PATH
-              "Installation directory for pkgconfig (.pc) files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+  set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE STRING
+              "Installation directory for pkgconfig (.pc) files, a relative "
+              "path that will be joined with ${CMAKE_INSTALL_PREFIX} or an "
+              "absolute path.")
 
   # Generate the version, config and target files into the build directory.
   write_basic_package_version_file(
     ${version_config}
     VERSION ${FMT_VERSION}
     COMPATIBILITY AnyNewerVersion)
+
+  join_paths(libdir_for_pc_file "\${exec_prefix}" "${FMT_LIB_DIR}")
+  join_paths(includedir_for_pc_file "\${prefix}" "${FMT_INC_DIR}")
+
   configure_file(
     "${PROJECT_SOURCE_DIR}/support/cmake/fmt.pc.in"
     "${pkgconfig}"
@@ -272,6 +385,16 @@ if (FMT_INSTALL)
     ${PROJECT_SOURCE_DIR}/support/cmake/fmt-config.cmake.in
     ${project_config}
     INSTALL_DESTINATION ${FMT_CMAKE_DIR})
+
+  set(INSTALL_TARGETS fmt fmt-header-only)
+
+  # Install the library and headers.
+  install(TARGETS ${INSTALL_TARGETS} EXPORT ${targets_export_name}
+          LIBRARY DESTINATION ${FMT_LIB_DIR}
+          ARCHIVE DESTINATION ${FMT_LIB_DIR}
+          PUBLIC_HEADER DESTINATION "${FMT_INC_DIR}/fmt"
+          RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
+
   # Use a namespace because CMake provides better diagnostics for namespaced
   # imported targets.
   export(TARGETS ${INSTALL_TARGETS} NAMESPACE fmt::
@@ -284,15 +407,6 @@ if (FMT_INSTALL)
   install(EXPORT ${targets_export_name} DESTINATION ${FMT_CMAKE_DIR}
           NAMESPACE fmt::)
 
-  # Install the library and headers.
-  install(TARGETS ${INSTALL_TARGETS} EXPORT ${targets_export_name}
-          LIBRARY DESTINATION ${FMT_LIB_DIR}
-          ARCHIVE DESTINATION ${FMT_LIB_DIR}
-          RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
-
-  install(FILES $<TARGET_PDB_FILE:${INSTALL_TARGETS}>
-          DESTINATION ${FMT_LIB_DIR} OPTIONAL)
-  install(FILES ${FMT_HEADERS} DESTINATION ${FMT_INC_DIR})
   install(FILES "${pkgconfig}" DESTINATION "${FMT_PKGCONFIG_DIR}")
 endif ()
 
@@ -308,10 +422,17 @@ endif ()
 # Control fuzzing independent of the unit tests.
 if (FMT_FUZZ)
   add_subdirectory(test/fuzzing)
+
+  # The FMT_FUZZ macro is used to prevent resource exhaustion in fuzzing
+  # mode and make fuzzing practically possible. It is similar to
+  # FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION but uses a different name to
+  # avoid interfering with fuzzing of projects that use {fmt}.
+  # See also https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode.
+  target_compile_definitions(fmt PUBLIC FMT_FUZZ)
 endif ()
 
 set(gitignore ${PROJECT_SOURCE_DIR}/.gitignore)
-if (MASTER_PROJECT AND EXISTS ${gitignore})
+if (FMT_MASTER_PROJECT AND EXISTS ${gitignore})
   # Get the list of ignored files from .gitignore.
   file (STRINGS ${gitignore} lines)
   list(REMOVE_ITEM lines /doc/html)
@@ -327,6 +448,6 @@ if (MASTER_PROJECT AND EXISTS ${gitignore})
   set(CPACK_SOURCE_IGNORE_FILES ${ignored_files})
   set(CPACK_SOURCE_PACKAGE_FILE_NAME fmt-${FMT_VERSION})
   set(CPACK_PACKAGE_NAME fmt)
-  set(CPACK_RESOURCE_FILE_README ${PROJECT_SOURCE_DIR}/README.rst)
+  set(CPACK_RESOURCE_FILE_README ${PROJECT_SOURCE_DIR}/README.md)
   include(CPack)
 endif ()
diff --git a/contrib/fmt/LICENSE.rst b/contrib/fmt/LICENSE
similarity index 95%
rename from contrib/fmt/LICENSE.rst
rename to contrib/fmt/LICENSE
index f0ec3db4d2a..1cd1ef92696 100644
--- a/contrib/fmt/LICENSE.rst
+++ b/contrib/fmt/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2012 - present, Victor Zverovich
+Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/contrib/fmt/include/fmt/args.h b/contrib/fmt/include/fmt/args.h
new file mode 100644
index 00000000000..ad1654bbb60
--- /dev/null
+++ b/contrib/fmt/include/fmt/args.h
@@ -0,0 +1,235 @@
+// Formatting library for C++ - dynamic argument lists
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_ARGS_H_
+#define FMT_ARGS_H_
+
+#include <functional>  // std::reference_wrapper
+#include <memory>      // std::unique_ptr
+#include <vector>
+
+#include "core.h"
+
+FMT_BEGIN_NAMESPACE
+
+namespace detail {
+
+template <typename T> struct is_reference_wrapper : std::false_type {};
+template <typename T>
+struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
+
+template <typename T> auto unwrap(const T& v) -> const T& { return v; }
+template <typename T>
+auto unwrap(const std::reference_wrapper<T>& v) -> const T& {
+  return static_cast<const T&>(v);
+}
+
+class dynamic_arg_list {
+  // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
+  // templates it doesn't complain about inability to deduce single translation
+  // unit for placing vtable. So storage_node_base is made a fake template.
+  template <typename = void> struct node {
+    virtual ~node() = default;
+    std::unique_ptr<node<>> next;
+  };
+
+  template <typename T> struct typed_node : node<> {
+    T value;
+
+    template <typename Arg>
+    FMT_CONSTEXPR typed_node(const Arg& arg) : value(arg) {}
+
+    template <typename Char>
+    FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg)
+        : value(arg.data(), arg.size()) {}
+  };
+
+  std::unique_ptr<node<>> head_;
+
+ public:
+  template <typename T, typename Arg> auto push(const Arg& arg) -> const T& {
+    auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
+    auto& value = new_node->value;
+    new_node->next = std::move(head_);
+    head_ = std::move(new_node);
+    return value;
+  }
+};
+}  // namespace detail
+
+/**
+  \rst
+  A dynamic version of `fmt::format_arg_store`.
+  It's equipped with a storage to potentially temporary objects which lifetimes
+  could be shorter than the format arguments object.
+
+  It can be implicitly converted into `~fmt::basic_format_args` for passing
+  into type-erased formatting functions such as `~fmt::vformat`.
+  \endrst
+ */
+template <typename Context>
+class dynamic_format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
+ private:
+  using char_type = typename Context::char_type;
+
+  template <typename T> struct need_copy {
+    static constexpr detail::type mapped_type =
+        detail::mapped_type_constant<T, Context>::value;
+
+    enum {
+      value = !(detail::is_reference_wrapper<T>::value ||
+                std::is_same<T, basic_string_view<char_type>>::value ||
+                std::is_same<T, detail::std_string_view<char_type>>::value ||
+                (mapped_type != detail::type::cstring_type &&
+                 mapped_type != detail::type::string_type &&
+                 mapped_type != detail::type::custom_type))
+    };
+  };
+
+  template <typename T>
+  using stored_type = conditional_t<
+      std::is_convertible<T, std::basic_string<char_type>>::value &&
+          !detail::is_reference_wrapper<T>::value,
+      std::basic_string<char_type>, T>;
+
+  // Storage of basic_format_arg must be contiguous.
+  std::vector<basic_format_arg<Context>> data_;
+  std::vector<detail::named_arg_info<char_type>> named_info_;
+
+  // Storage of arguments not fitting into basic_format_arg must grow
+  // without relocation because items in data_ refer to it.
+  detail::dynamic_arg_list dynamic_args_;
+
+  friend class basic_format_args<Context>;
+
+  auto get_types() const -> unsigned long long {
+    return detail::is_unpacked_bit | data_.size() |
+           (named_info_.empty()
+                ? 0ULL
+                : static_cast<unsigned long long>(detail::has_named_args_bit));
+  }
+
+  auto data() const -> const basic_format_arg<Context>* {
+    return named_info_.empty() ? data_.data() : data_.data() + 1;
+  }
+
+  template <typename T> void emplace_arg(const T& arg) {
+    data_.emplace_back(detail::make_arg<Context>(arg));
+  }
+
+  template <typename T>
+  void emplace_arg(const detail::named_arg<char_type, T>& arg) {
+    if (named_info_.empty()) {
+      constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
+      data_.insert(data_.begin(), {zero_ptr, 0});
+    }
+    data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
+    auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
+      data->pop_back();
+    };
+    std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
+        guard{&data_, pop_one};
+    named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
+    data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
+    guard.release();
+  }
+
+ public:
+  constexpr dynamic_format_arg_store() = default;
+
+  /**
+    \rst
+    Adds an argument into the dynamic store for later passing to a formatting
+    function.
+
+    Note that custom types and string types (but not string views) are copied
+    into the store dynamically allocating memory if necessary.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      store.push_back(42);
+      store.push_back("abc");
+      store.push_back(1.5f);
+      std::string result = fmt::vformat("{} and {} and {}", store);
+    \endrst
+  */
+  template <typename T> void push_back(const T& arg) {
+    if (detail::const_check(need_copy<T>::value))
+      emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
+    else
+      emplace_arg(detail::unwrap(arg));
+  }
+
+  /**
+    \rst
+    Adds a reference to the argument into the dynamic store for later passing to
+    a formatting function.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      char band[] = "Rolling Stones";
+      store.push_back(std::cref(band));
+      band[9] = 'c'; // Changing str affects the output.
+      std::string result = fmt::vformat("{}", store);
+      // result == "Rolling Scones"
+    \endrst
+  */
+  template <typename T> void push_back(std::reference_wrapper<T> arg) {
+    static_assert(
+        need_copy<T>::value,
+        "objects of built-in types and string views are always copied");
+    emplace_arg(arg.get());
+  }
+
+  /**
+    Adds named argument into the dynamic store for later passing to a formatting
+    function. ``std::reference_wrapper`` is supported to avoid copying of the
+    argument. The name is always copied into the store.
+  */
+  template <typename T>
+  void push_back(const detail::named_arg<char_type, T>& arg) {
+    const char_type* arg_name =
+        dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
+    if (detail::const_check(need_copy<T>::value)) {
+      emplace_arg(
+          fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
+    } else {
+      emplace_arg(fmt::arg(arg_name, arg.value));
+    }
+  }
+
+  /** Erase all elements from the store */
+  void clear() {
+    data_.clear();
+    named_info_.clear();
+    dynamic_args_ = detail::dynamic_arg_list();
+  }
+
+  /**
+    \rst
+    Reserves space to store at least *new_cap* arguments including
+    *new_cap_named* named arguments.
+    \endrst
+  */
+  void reserve(size_t new_cap, size_t new_cap_named) {
+    FMT_ASSERT(new_cap >= new_cap_named,
+               "Set of arguments includes set of named arguments");
+    data_.reserve(new_cap);
+    named_info_.reserve(new_cap_named);
+  }
+};
+
+FMT_END_NAMESPACE
+
+#endif  // FMT_ARGS_H_
diff --git a/contrib/fmt/include/fmt/chrono.h b/contrib/fmt/include/fmt/chrono.h
index 421d464ad8a..9d54574e168 100644
--- a/contrib/fmt/include/fmt/chrono.h
+++ b/contrib/fmt/include/fmt/chrono.h
@@ -8,16 +8,52 @@
 #ifndef FMT_CHRONO_H_
 #define FMT_CHRONO_H_
 
+#include <algorithm>
 #include <chrono>
+#include <cmath>    // std::isfinite
+#include <cstring>  // std::memcpy
 #include <ctime>
+#include <iterator>
 #include <locale>
-#include <sstream>
+#include <ostream>
+#include <type_traits>
 
-#include "format.h"
-#include "locale.h"
+#include "ostream.h"  // formatbuf
 
 FMT_BEGIN_NAMESPACE
 
+// Check if std::chrono::local_t is available.
+#ifndef FMT_USE_LOCAL_TIME
+#  ifdef __cpp_lib_chrono
+#    define FMT_USE_LOCAL_TIME (__cpp_lib_chrono >= 201907L)
+#  else
+#    define FMT_USE_LOCAL_TIME 0
+#  endif
+#endif
+
+// Check if std::chrono::utc_timestamp is available.
+#ifndef FMT_USE_UTC_TIME
+#  ifdef __cpp_lib_chrono
+#    define FMT_USE_UTC_TIME (__cpp_lib_chrono >= 201907L)
+#  else
+#    define FMT_USE_UTC_TIME 0
+#  endif
+#endif
+
+// Enable tzset.
+#ifndef FMT_USE_TZSET
+// UWP doesn't provide _tzset.
+#  if FMT_HAS_INCLUDE("winapifamily.h")
+#    include <winapifamily.h>
+#  endif
+#  if defined(_WIN32) && (!defined(WINAPI_FAMILY) || \
+                          (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#    define FMT_USE_TZSET 1
+#  else
+#    define FMT_USE_TZSET 0
+#  endif
+#endif
+
 // Enable safe chrono durations, unless explicitly disabled.
 #ifndef FMT_SAFE_DURATION_CAST
 #  define FMT_SAFE_DURATION_CAST 1
@@ -36,7 +72,8 @@ template <typename To, typename From,
           FMT_ENABLE_IF(!std::is_same<From, To>::value &&
                         std::numeric_limits<From>::is_signed ==
                             std::numeric_limits<To>::is_signed)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+FMT_CONSTEXPR auto lossless_integral_conversion(const From from, int& ec)
+    -> To {
   ec = 0;
   using F = std::numeric_limits<From>;
   using T = std::numeric_limits<To>;
@@ -44,11 +81,11 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
   static_assert(T::is_integer, "To must be integral");
 
   // A and B are both signed, or both unsigned.
-  if (F::digits <= T::digits) {
+  if (detail::const_check(F::digits <= T::digits)) {
     // From fits in To without any problem.
   } else {
     // From does not always fit in To, resort to a dynamic check.
-    if (from < T::min() || from > T::max()) {
+    if (from < (T::min)() || from > (T::max)()) {
       // outside range.
       ec = 1;
       return {};
@@ -65,54 +102,41 @@ template <typename To, typename From,
           FMT_ENABLE_IF(!std::is_same<From, To>::value &&
                         std::numeric_limits<From>::is_signed !=
                             std::numeric_limits<To>::is_signed)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+FMT_CONSTEXPR auto lossless_integral_conversion(const From from, int& ec)
+    -> To {
   ec = 0;
   using F = std::numeric_limits<From>;
   using T = std::numeric_limits<To>;
   static_assert(F::is_integer, "From must be integral");
   static_assert(T::is_integer, "To must be integral");
 
-  if (F::is_signed && !T::is_signed) {
+  if (detail::const_check(F::is_signed && !T::is_signed)) {
     // From may be negative, not allowed!
-    if (fmt::internal::is_negative(from)) {
+    if (fmt::detail::is_negative(from)) {
       ec = 1;
       return {};
     }
-
     // From is positive. Can it always fit in To?
-    if (F::digits <= T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        ec = 1;
-        return {};
-      }
+    if (detail::const_check(F::digits > T::digits) &&
+        from > static_cast<From>(detail::max_value<To>())) {
+      ec = 1;
+      return {};
     }
   }
 
-  if (!F::is_signed && T::is_signed) {
-    // can from be held in To?
-    if (F::digits < T::digits) {
-      // yes, From always fits in To.
-    } else {
-      // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
-        // outside range.
-        ec = 1;
-        return {};
-      }
-    }
+  if (detail::const_check(!F::is_signed && T::is_signed &&
+                          F::digits >= T::digits) &&
+      from > static_cast<From>(detail::max_value<To>())) {
+    ec = 1;
+    return {};
   }
-
-  // reaching here means all is ok for lossless conversion.
-  return static_cast<To>(from);
-
-}  // function
+  return static_cast<To>(from);  // Lossless conversion.
+}
 
 template <typename To, typename From,
           FMT_ENABLE_IF(std::is_same<From, To>::value)>
-FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+FMT_CONSTEXPR auto lossless_integral_conversion(const From from, int& ec)
+    -> To {
   ec = 0;
   return from;
 }  // function
@@ -133,7 +157,7 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
 // clang-format on
 template <typename To, typename From,
           FMT_ENABLE_IF(!std::is_same<From, To>::value)>
-FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+FMT_CONSTEXPR auto safe_float_conversion(const From from, int& ec) -> To {
   ec = 0;
   using T = std::numeric_limits<To>;
   static_assert(std::is_floating_point<From>::value, "From must be floating");
@@ -141,7 +165,7 @@ FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
 
   // catch the only happy case
   if (std::isfinite(from)) {
-    if (from >= T::lowest() && from <= T::max()) {
+    if (from >= T::lowest() && from <= (T::max)()) {
       return static_cast<To>(from);
     }
     // not within range.
@@ -155,7 +179,7 @@ FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
 
 template <typename To, typename From,
           FMT_ENABLE_IF(std::is_same<From, To>::value)>
-FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+FMT_CONSTEXPR auto safe_float_conversion(const From from, int& ec) -> To {
   ec = 0;
   static_assert(std::is_floating_point<From>::value, "From must be floating");
   return from;
@@ -167,8 +191,8 @@ FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
 template <typename To, typename FromRep, typename FromPeriod,
           FMT_ENABLE_IF(std::is_integral<FromRep>::value),
           FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
-To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
-                      int& ec) {
+auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                        int& ec) -> To {
   using From = std::chrono::duration<FromRep, FromPeriod>;
   ec = 0;
   // the basic idea is that we need to convert from count() in the from type
@@ -190,35 +214,27 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
   // safe conversion to IntermediateRep
   IntermediateRep count =
       lossless_integral_conversion<IntermediateRep>(from.count(), ec);
-  if (ec) {
-    return {};
-  }
+  if (ec) return {};
   // multiply with Factor::num without overflow or underflow
-  if (Factor::num != 1) {
-    const auto max1 = internal::max_value<IntermediateRep>() / Factor::num;
+  if (detail::const_check(Factor::num != 1)) {
+    const auto max1 = detail::max_value<IntermediateRep>() / Factor::num;
     if (count > max1) {
       ec = 1;
       return {};
     }
-    const auto min1 = std::numeric_limits<IntermediateRep>::min() / Factor::num;
-    if (count < min1) {
+    const auto min1 =
+        (std::numeric_limits<IntermediateRep>::min)() / Factor::num;
+    if (detail::const_check(!std::is_unsigned<IntermediateRep>::value) &&
+        count < min1) {
       ec = 1;
       return {};
     }
     count *= Factor::num;
   }
 
-  // this can't go wrong, right? den>0 is checked earlier.
-  if (Factor::den != 1) {
-    count /= Factor::den;
-  }
-  // convert to the to type, safely
-  using ToRep = typename To::rep;
-  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
-  if (ec) {
-    return {};
-  }
-  return To{tocount};
+  if (detail::const_check(Factor::den != 1)) count /= Factor::den;
+  auto tocount = lossless_integral_conversion<typename To::rep>(count, ec);
+  return ec ? To() : To(tocount);
 }
 
 /**
@@ -227,8 +243,8 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
 template <typename To, typename FromRep, typename FromPeriod,
           FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
           FMT_ENABLE_IF(std::is_floating_point<typename To::rep>::value)>
-To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
-                      int& ec) {
+auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                        int& ec) -> To {
   using From = std::chrono::duration<FromRep, FromPeriod>;
   ec = 0;
   if (std::isnan(from.count())) {
@@ -268,8 +284,8 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
   }
 
   // multiply with Factor::num without overflow or underflow
-  if (Factor::num != 1) {
-    constexpr auto max1 = internal::max_value<IntermediateRep>() /
+  if (detail::const_check(Factor::num != 1)) {
+    constexpr auto max1 = detail::max_value<IntermediateRep>() /
                           static_cast<IntermediateRep>(Factor::num);
     if (count > max1) {
       ec = 1;
@@ -285,7 +301,7 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
   }
 
   // this can't go wrong, right? den>0 is checked earlier.
-  if (Factor::den != 1) {
+  if (detail::const_check(Factor::den != 1)) {
     using common_t = typename std::common_type<IntermediateRep, intmax_t>::type;
     count /= static_cast<common_t>(Factor::den);
   }
@@ -306,38 +322,194 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
 // Usage: f FMT_NOMACRO()
 #define FMT_NOMACRO
 
-namespace internal {
-inline null<> localtime_r FMT_NOMACRO(...) { return null<>(); }
-inline null<> localtime_s(...) { return null<>(); }
-inline null<> gmtime_r(...) { return null<>(); }
-inline null<> gmtime_s(...) { return null<>(); }
-}  // namespace internal
+namespace detail {
+template <typename T = void> struct null {};
+inline auto localtime_r FMT_NOMACRO(...) -> null<> { return null<>(); }
+inline auto localtime_s(...) -> null<> { return null<>(); }
+inline auto gmtime_r(...) -> null<> { return null<>(); }
+inline auto gmtime_s(...) -> null<> { return null<>(); }
+
+inline auto get_classic_locale() -> const std::locale& {
+  static const auto& locale = std::locale::classic();
+  return locale;
+}
+
+template <typename CodeUnit> struct codecvt_result {
+  static constexpr const size_t max_size = 32;
+  CodeUnit buf[max_size];
+  CodeUnit* end;
+};
+
+template <typename CodeUnit>
+void write_codecvt(codecvt_result<CodeUnit>& out, string_view in_buf,
+                   const std::locale& loc) {
+#if FMT_CLANG_VERSION
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wdeprecated"
+  auto& f = std::use_facet<std::codecvt<CodeUnit, char, std::mbstate_t>>(loc);
+#  pragma clang diagnostic pop
+#else
+  auto& f = std::use_facet<std::codecvt<CodeUnit, char, std::mbstate_t>>(loc);
+#endif
+  auto mb = std::mbstate_t();
+  const char* from_next = nullptr;
+  auto result = f.in(mb, in_buf.begin(), in_buf.end(), from_next,
+                     std::begin(out.buf), std::end(out.buf), out.end);
+  if (result != std::codecvt_base::ok)
+    FMT_THROW(format_error("failed to format time"));
+}
+
+template <typename OutputIt>
+auto write_encoded_tm_str(OutputIt out, string_view in, const std::locale& loc)
+    -> OutputIt {
+  if (detail::is_utf8() && loc != get_classic_locale()) {
+    // char16_t and char32_t codecvts are broken in MSVC (linkage errors) and
+    // gcc-4.
+#if FMT_MSC_VERSION != 0 || \
+    (defined(__GLIBCXX__) && !defined(_GLIBCXX_USE_DUAL_ABI))
+    // The _GLIBCXX_USE_DUAL_ABI macro is always defined in libstdc++ from gcc-5
+    // and newer.
+    using code_unit = wchar_t;
+#else
+    using code_unit = char32_t;
+#endif
+
+    using unit_t = codecvt_result<code_unit>;
+    unit_t unit;
+    write_codecvt(unit, in, loc);
+    // In UTF-8 is used one to four one-byte code units.
+    auto u =
+        to_utf8<code_unit, basic_memory_buffer<char, unit_t::max_size * 4>>();
+    if (!u.convert({unit.buf, to_unsigned(unit.end - unit.buf)}))
+      FMT_THROW(format_error("failed to format time"));
+    return copy_str<char>(u.c_str(), u.c_str() + u.size(), out);
+  }
+  return copy_str<char>(in.data(), in.data() + in.size(), out);
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+auto write_tm_str(OutputIt out, string_view sv, const std::locale& loc)
+    -> OutputIt {
+  codecvt_result<Char> unit;
+  write_codecvt(unit, sv, loc);
+  return copy_str<Char>(unit.buf, unit.end, out);
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+auto write_tm_str(OutputIt out, string_view sv, const std::locale& loc)
+    -> OutputIt {
+  return write_encoded_tm_str(out, sv, loc);
+}
+
+template <typename Char>
+inline void do_write(buffer<Char>& buf, const std::tm& time,
+                     const std::locale& loc, char format, char modifier) {
+  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
+  auto&& os = std::basic_ostream<Char>(&format_buf);
+  os.imbue(loc);
+  const auto& facet = std::use_facet<std::time_put<Char>>(loc);
+  auto end = facet.put(os, os, Char(' '), &time, format, modifier);
+  if (end.failed()) FMT_THROW(format_error("failed to format time"));
+}
 
-// Thread-safe replacement for std::localtime
-inline std::tm localtime(std::time_t time) {
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+auto write(OutputIt out, const std::tm& time, const std::locale& loc,
+           char format, char modifier = 0) -> OutputIt {
+  auto&& buf = get_buffer<Char>(out);
+  do_write<Char>(buf, time, loc, format, modifier);
+  return get_iterator(buf, out);
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+auto write(OutputIt out, const std::tm& time, const std::locale& loc,
+           char format, char modifier = 0) -> OutputIt {
+  auto&& buf = basic_memory_buffer<Char>();
+  do_write<char>(buf, time, loc, format, modifier);
+  return write_encoded_tm_str(out, string_view(buf.data(), buf.size()), loc);
+}
+
+template <typename Rep1, typename Rep2>
+struct is_same_arithmetic_type
+    : public std::integral_constant<bool,
+                                    (std::is_integral<Rep1>::value &&
+                                     std::is_integral<Rep2>::value) ||
+                                        (std::is_floating_point<Rep1>::value &&
+                                         std::is_floating_point<Rep2>::value)> {
+};
+
+template <
+    typename To, typename FromRep, typename FromPeriod,
+    FMT_ENABLE_IF(is_same_arithmetic_type<FromRep, typename To::rep>::value)>
+auto fmt_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
+#if FMT_SAFE_DURATION_CAST
+  // Throwing version of safe_duration_cast is only available for
+  // integer to integer or float to float casts.
+  int ec;
+  To to = safe_duration_cast::safe_duration_cast<To>(from, ec);
+  if (ec) FMT_THROW(format_error("cannot format duration"));
+  return to;
+#else
+  // Standard duration cast, may overflow.
+  return std::chrono::duration_cast<To>(from);
+#endif
+}
+
+template <
+    typename To, typename FromRep, typename FromPeriod,
+    FMT_ENABLE_IF(!is_same_arithmetic_type<FromRep, typename To::rep>::value)>
+auto fmt_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
+  // Mixed integer <-> float cast is not supported by safe_duration_cast.
+  return std::chrono::duration_cast<To>(from);
+}
+
+template <typename Duration>
+auto to_time_t(
+    std::chrono::time_point<std::chrono::system_clock, Duration> time_point)
+    -> std::time_t {
+  // Cannot use std::chrono::system_clock::to_time_t since this would first
+  // require a cast to std::chrono::system_clock::time_point, which could
+  // overflow.
+  return fmt_duration_cast<std::chrono::duration<std::time_t>>(
+             time_point.time_since_epoch())
+      .count();
+}
+}  // namespace detail
+
+FMT_BEGIN_EXPORT
+
+/**
+  Converts given time since epoch as ``std::time_t`` value into calendar time,
+  expressed in local time. Unlike ``std::localtime``, this function is
+  thread-safe on most platforms.
+ */
+inline auto localtime(std::time_t time) -> std::tm {
   struct dispatcher {
     std::time_t time_;
     std::tm tm_;
 
     dispatcher(std::time_t t) : time_(t) {}
 
-    bool run() {
-      using namespace fmt::internal;
+    auto run() -> bool {
+      using namespace fmt::detail;
       return handle(localtime_r(&time_, &tm_));
     }
 
-    bool handle(std::tm* tm) { return tm != nullptr; }
+    auto handle(std::tm* tm) -> bool { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    auto handle(detail::null<>) -> bool {
+      using namespace fmt::detail;
       return fallback(localtime_s(&tm_, &time_));
     }
 
-    bool fallback(int res) { return res == 0; }
+    auto fallback(int res) -> bool { return res == 0; }
 
-#if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
-      using namespace fmt::internal;
+#if !FMT_MSC_VERSION
+    auto fallback(detail::null<>) -> bool {
+      using namespace fmt::detail;
       std::tm* tm = std::localtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -350,122 +522,121 @@ inline std::tm localtime(std::time_t time) {
   return lt.tm_;
 }
 
-// Thread-safe replacement for std::gmtime
-inline std::tm gmtime(std::time_t time) {
+#if FMT_USE_LOCAL_TIME
+template <typename Duration>
+inline auto localtime(std::chrono::local_time<Duration> time) -> std::tm {
+  return localtime(
+      detail::to_time_t(std::chrono::current_zone()->to_sys(time)));
+}
+#endif
+
+/**
+  Converts given time since epoch as ``std::time_t`` value into calendar time,
+  expressed in Coordinated Universal Time (UTC). Unlike ``std::gmtime``, this
+  function is thread-safe on most platforms.
+ */
+inline auto gmtime(std::time_t time) -> std::tm {
   struct dispatcher {
     std::time_t time_;
     std::tm tm_;
 
     dispatcher(std::time_t t) : time_(t) {}
 
-    bool run() {
-      using namespace fmt::internal;
+    auto run() -> bool {
+      using namespace fmt::detail;
       return handle(gmtime_r(&time_, &tm_));
     }
 
-    bool handle(std::tm* tm) { return tm != nullptr; }
+    auto handle(std::tm* tm) -> bool { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    auto handle(detail::null<>) -> bool {
+      using namespace fmt::detail;
       return fallback(gmtime_s(&tm_, &time_));
     }
 
-    bool fallback(int res) { return res == 0; }
+    auto fallback(int res) -> bool { return res == 0; }
 
-#if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
+#if !FMT_MSC_VERSION
+    auto fallback(detail::null<>) -> bool {
       std::tm* tm = std::gmtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
     }
 #endif
   };
-  dispatcher gt(time);
+  auto gt = dispatcher(time);
   // Too big time values may be unsupported.
   if (!gt.run()) FMT_THROW(format_error("time_t value out of range"));
   return gt.tm_;
 }
 
-namespace internal {
-inline std::size_t strftime(char* str, std::size_t count, const char* format,
-                            const std::tm* time) {
-  return std::strftime(str, count, format, time);
-}
-
-inline std::size_t strftime(wchar_t* str, std::size_t count,
-                            const wchar_t* format, const std::tm* time) {
-  return std::wcsftime(str, count, format, time);
+template <typename Duration>
+inline auto gmtime(
+    std::chrono::time_point<std::chrono::system_clock, Duration> time_point)
+    -> std::tm {
+  return gmtime(detail::to_time_t(time_point));
 }
-}  // namespace internal
-
-template <typename Char> struct formatter<std::tm, Char> {
-  template <typename ParseContext>
-  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    auto it = ctx.begin();
-    if (it != ctx.end() && *it == ':') ++it;
-    auto end = it;
-    while (end != ctx.end() && *end != '}') ++end;
-    tm_format.reserve(internal::to_unsigned(end - it + 1));
-    tm_format.append(it, end);
-    tm_format.push_back('\0');
-    return end;
-  }
 
-  template <typename FormatContext>
-  auto format(const std::tm& tm, FormatContext& ctx) -> decltype(ctx.out()) {
-    basic_memory_buffer<Char> buf;
-    std::size_t start = buf.size();
-    for (;;) {
-      std::size_t size = buf.capacity() - start;
-      std::size_t count =
-          internal::strftime(&buf[start], size, &tm_format[0], &tm);
-      if (count != 0) {
-        buf.resize(start + count);
-        break;
-      }
-      if (size >= tm_format.size() * 256) {
-        // If the buffer is 256 times larger than the format string, assume
-        // that `strftime` gives an empty result. There doesn't seem to be a
-        // better way to distinguish the two cases:
-        // https://github.com/fmtlib/fmt/issues/367
-        break;
-      }
-      const std::size_t MIN_GROWTH = 10;
-      buf.reserve(buf.capacity() + (size > MIN_GROWTH ? size : MIN_GROWTH));
-    }
-    return std::copy(buf.begin(), buf.end(), ctx.out());
+namespace detail {
+
+// Writes two-digit numbers a, b and c separated by sep to buf.
+// The method by Pavel Novikov based on
+// https://johnnylee-sde.github.io/Fast-unsigned-integer-to-time-string/.
+inline void write_digit2_separated(char* buf, unsigned a, unsigned b,
+                                   unsigned c, char sep) {
+  unsigned long long digits =
+      a | (b << 24) | (static_cast<unsigned long long>(c) << 48);
+  // Convert each value to BCD.
+  // We have x = a * 10 + b and we want to convert it to BCD y = a * 16 + b.
+  // The difference is
+  //   y - x = a * 6
+  // a can be found from x:
+  //   a = floor(x / 10)
+  // then
+  //   y = x + a * 6 = x + floor(x / 10) * 6
+  // floor(x / 10) is (x * 205) >> 11 (needs 16 bits).
+  digits += (((digits * 205) >> 11) & 0x000f00000f00000f) * 6;
+  // Put low nibbles to high bytes and high nibbles to low bytes.
+  digits = ((digits & 0x00f00000f00000f0) >> 4) |
+           ((digits & 0x000f00000f00000f) << 8);
+  auto usep = static_cast<unsigned long long>(sep);
+  // Add ASCII '0' to each digit byte and insert separators.
+  digits |= 0x3030003030003030 | (usep << 16) | (usep << 40);
+
+  constexpr const size_t len = 8;
+  if (const_check(is_big_endian())) {
+    char tmp[len];
+    std::memcpy(tmp, &digits, len);
+    std::reverse_copy(tmp, tmp + len, buf);
+  } else {
+    std::memcpy(buf, &digits, len);
   }
+}
 
-  basic_memory_buffer<Char> tm_format;
-};
-
-namespace internal {
-template <typename Period> FMT_CONSTEXPR const char* get_units() {
+template <typename Period>
+FMT_CONSTEXPR inline auto get_units() -> const char* {
+  if (std::is_same<Period, std::atto>::value) return "as";
+  if (std::is_same<Period, std::femto>::value) return "fs";
+  if (std::is_same<Period, std::pico>::value) return "ps";
+  if (std::is_same<Period, std::nano>::value) return "ns";
+  if (std::is_same<Period, std::micro>::value) return "µs";
+  if (std::is_same<Period, std::milli>::value) return "ms";
+  if (std::is_same<Period, std::centi>::value) return "cs";
+  if (std::is_same<Period, std::deci>::value) return "ds";
+  if (std::is_same<Period, std::ratio<1>>::value) return "s";
+  if (std::is_same<Period, std::deca>::value) return "das";
+  if (std::is_same<Period, std::hecto>::value) return "hs";
+  if (std::is_same<Period, std::kilo>::value) return "ks";
+  if (std::is_same<Period, std::mega>::value) return "Ms";
+  if (std::is_same<Period, std::giga>::value) return "Gs";
+  if (std::is_same<Period, std::tera>::value) return "Ts";
+  if (std::is_same<Period, std::peta>::value) return "Ps";
+  if (std::is_same<Period, std::exa>::value) return "Es";
+  if (std::is_same<Period, std::ratio<60>>::value) return "min";
+  if (std::is_same<Period, std::ratio<3600>>::value) return "h";
+  if (std::is_same<Period, std::ratio<86400>>::value) return "d";
   return nullptr;
 }
-template <> FMT_CONSTEXPR const char* get_units<std::atto>() { return "as"; }
-template <> FMT_CONSTEXPR const char* get_units<std::femto>() { return "fs"; }
-template <> FMT_CONSTEXPR const char* get_units<std::pico>() { return "ps"; }
-template <> FMT_CONSTEXPR const char* get_units<std::nano>() { return "ns"; }
-template <> FMT_CONSTEXPR const char* get_units<std::micro>() { return "µs"; }
-template <> FMT_CONSTEXPR const char* get_units<std::milli>() { return "ms"; }
-template <> FMT_CONSTEXPR const char* get_units<std::centi>() { return "cs"; }
-template <> FMT_CONSTEXPR const char* get_units<std::deci>() { return "ds"; }
-template <> FMT_CONSTEXPR const char* get_units<std::ratio<1>>() { return "s"; }
-template <> FMT_CONSTEXPR const char* get_units<std::deca>() { return "das"; }
-template <> FMT_CONSTEXPR const char* get_units<std::hecto>() { return "hs"; }
-template <> FMT_CONSTEXPR const char* get_units<std::kilo>() { return "ks"; }
-template <> FMT_CONSTEXPR const char* get_units<std::mega>() { return "Ms"; }
-template <> FMT_CONSTEXPR const char* get_units<std::giga>() { return "Gs"; }
-template <> FMT_CONSTEXPR const char* get_units<std::tera>() { return "Ts"; }
-template <> FMT_CONSTEXPR const char* get_units<std::peta>() { return "Ps"; }
-template <> FMT_CONSTEXPR const char* get_units<std::exa>() { return "Es"; }
-template <> FMT_CONSTEXPR const char* get_units<std::ratio<60>>() {
-  return "m";
-}
-template <> FMT_CONSTEXPR const char* get_units<std::ratio<3600>>() {
-  return "h";
-}
 
 enum class numeric_system {
   standard,
@@ -473,12 +644,38 @@ enum class numeric_system {
   alternative
 };
 
+// Glibc extensions for formatting numeric values.
+enum class pad_type {
+  unspecified,
+  // Do not pad a numeric result string.
+  none,
+  // Pad a numeric result string with zeros even if the conversion specifier
+  // character uses space-padding by default.
+  zero,
+  // Pad a numeric result string with spaces.
+  space,
+};
+
+template <typename OutputIt>
+auto write_padding(OutputIt out, pad_type pad, int width) -> OutputIt {
+  if (pad == pad_type::none) return out;
+  return std::fill_n(out, width, pad == pad_type::space ? ' ' : '0');
+}
+
+template <typename OutputIt>
+auto write_padding(OutputIt out, pad_type pad) -> OutputIt {
+  if (pad != pad_type::none) *out++ = pad == pad_type::space ? ' ' : '0';
+  return out;
+}
+
 // Parses a put_time-like format string and invokes handler actions.
 template <typename Char, typename Handler>
-FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
-                                              const Char* end,
-                                              Handler&& handler) {
+FMT_CONSTEXPR auto parse_chrono_format(const Char* begin, const Char* end,
+                                       Handler&& handler) -> const Char* {
+  if (begin == end || *begin == '}') return begin;
+  if (*begin != '%') FMT_THROW(format_error("invalid format"));
   auto ptr = begin;
+  pad_type pad = pad_type::unspecified;
   while (ptr != end) {
     auto c = *ptr;
     if (c == '}') break;
@@ -489,6 +686,22 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
     if (begin != ptr) handler.on_text(begin, ptr);
     ++ptr;  // consume '%'
     if (ptr == end) FMT_THROW(format_error("invalid format"));
+    c = *ptr;
+    switch (c) {
+    case '_':
+      pad = pad_type::space;
+      ++ptr;
+      break;
+    case '-':
+      pad = pad_type::none;
+      ++ptr;
+      break;
+    case '0':
+      pad = pad_type::zero;
+      ++ptr;
+      break;
+    }
+    if (ptr == end) FMT_THROW(format_error("invalid format"));
     c = *ptr++;
     switch (c) {
     case '%':
@@ -504,6 +717,22 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       handler.on_text(tab, tab + 1);
       break;
     }
+    // Year:
+    case 'Y':
+      handler.on_year(numeric_system::standard);
+      break;
+    case 'y':
+      handler.on_short_year(numeric_system::standard);
+      break;
+    case 'C':
+      handler.on_century(numeric_system::standard);
+      break;
+    case 'G':
+      handler.on_iso_week_based_year();
+      break;
+    case 'g':
+      handler.on_iso_week_based_short_year();
+      break;
     // Day of the week:
     case 'a':
       handler.on_abbr_weekday();
@@ -519,23 +748,46 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       break;
     // Month:
     case 'b':
+    case 'h':
       handler.on_abbr_month();
       break;
     case 'B':
       handler.on_full_month();
       break;
+    case 'm':
+      handler.on_dec_month(numeric_system::standard);
+      break;
+    // Day of the year/month:
+    case 'U':
+      handler.on_dec0_week_of_year(numeric_system::standard);
+      break;
+    case 'W':
+      handler.on_dec1_week_of_year(numeric_system::standard);
+      break;
+    case 'V':
+      handler.on_iso_week_of_year(numeric_system::standard);
+      break;
+    case 'j':
+      handler.on_day_of_year();
+      break;
+    case 'd':
+      handler.on_day_of_month(numeric_system::standard);
+      break;
+    case 'e':
+      handler.on_day_of_month_space(numeric_system::standard);
+      break;
     // Hour, minute, second:
     case 'H':
-      handler.on_24_hour(numeric_system::standard);
+      handler.on_24_hour(numeric_system::standard, pad);
       break;
     case 'I':
-      handler.on_12_hour(numeric_system::standard);
+      handler.on_12_hour(numeric_system::standard, pad);
       break;
     case 'M':
-      handler.on_minute(numeric_system::standard);
+      handler.on_minute(numeric_system::standard, pad);
       break;
     case 'S':
-      handler.on_second(numeric_system::standard);
+      handler.on_second(numeric_system::standard, pad);
       break;
     // Other:
     case 'c':
@@ -572,7 +824,7 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       handler.on_duration_unit();
       break;
     case 'z':
-      handler.on_utc_offset();
+      handler.on_utc_offset(numeric_system::standard);
       break;
     case 'Z':
       handler.on_tz_name();
@@ -582,6 +834,15 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       if (ptr == end) FMT_THROW(format_error("invalid format"));
       c = *ptr++;
       switch (c) {
+      case 'Y':
+        handler.on_year(numeric_system::alternative);
+        break;
+      case 'y':
+        handler.on_offset_year();
+        break;
+      case 'C':
+        handler.on_century(numeric_system::alternative);
+        break;
       case 'c':
         handler.on_datetime(numeric_system::alternative);
         break;
@@ -591,6 +852,9 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       case 'X':
         handler.on_loc_time(numeric_system::alternative);
         break;
+      case 'z':
+        handler.on_utc_offset(numeric_system::alternative);
+        break;
       default:
         FMT_THROW(format_error("invalid format"));
       }
@@ -600,6 +864,27 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
       if (ptr == end) FMT_THROW(format_error("invalid format"));
       c = *ptr++;
       switch (c) {
+      case 'y':
+        handler.on_short_year(numeric_system::alternative);
+        break;
+      case 'm':
+        handler.on_dec_month(numeric_system::alternative);
+        break;
+      case 'U':
+        handler.on_dec0_week_of_year(numeric_system::alternative);
+        break;
+      case 'W':
+        handler.on_dec1_week_of_year(numeric_system::alternative);
+        break;
+      case 'V':
+        handler.on_iso_week_of_year(numeric_system::alternative);
+        break;
+      case 'd':
+        handler.on_day_of_month(numeric_system::alternative);
+        break;
+      case 'e':
+        handler.on_day_of_month_space(numeric_system::alternative);
+        break;
       case 'w':
         handler.on_dec0_weekday(numeric_system::alternative);
         break;
@@ -607,16 +892,19 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
         handler.on_dec1_weekday(numeric_system::alternative);
         break;
       case 'H':
-        handler.on_24_hour(numeric_system::alternative);
+        handler.on_24_hour(numeric_system::alternative, pad);
         break;
       case 'I':
-        handler.on_12_hour(numeric_system::alternative);
+        handler.on_12_hour(numeric_system::alternative, pad);
         break;
       case 'M':
-        handler.on_minute(numeric_system::alternative);
+        handler.on_minute(numeric_system::alternative, pad);
         break;
       case 'S':
-        handler.on_second(numeric_system::alternative);
+        handler.on_second(numeric_system::alternative, pad);
+        break;
+      case 'z':
+        handler.on_utc_offset(numeric_system::alternative);
         break;
       default:
         FMT_THROW(format_error("invalid format"));
@@ -631,75 +919,741 @@ FMT_CONSTEXPR const Char* parse_chrono_format(const Char* begin,
   return ptr;
 }
 
-struct chrono_format_checker {
-  FMT_NORETURN void report_no_date() { FMT_THROW(format_error("no date")); }
-
-  template <typename Char> void on_text(const Char*, const Char*) {}
-  FMT_NORETURN void on_abbr_weekday() { report_no_date(); }
-  FMT_NORETURN void on_full_weekday() { report_no_date(); }
-  FMT_NORETURN void on_dec0_weekday(numeric_system) { report_no_date(); }
-  FMT_NORETURN void on_dec1_weekday(numeric_system) { report_no_date(); }
-  FMT_NORETURN void on_abbr_month() { report_no_date(); }
-  FMT_NORETURN void on_full_month() { report_no_date(); }
-  void on_24_hour(numeric_system) {}
-  void on_12_hour(numeric_system) {}
-  void on_minute(numeric_system) {}
-  void on_second(numeric_system) {}
-  FMT_NORETURN void on_datetime(numeric_system) { report_no_date(); }
-  FMT_NORETURN void on_loc_date(numeric_system) { report_no_date(); }
-  FMT_NORETURN void on_loc_time(numeric_system) { report_no_date(); }
-  FMT_NORETURN void on_us_date() { report_no_date(); }
-  FMT_NORETURN void on_iso_date() { report_no_date(); }
-  void on_12_hour_time() {}
-  void on_24_hour_time() {}
-  void on_iso_time() {}
-  void on_am_pm() {}
-  void on_duration_value() {}
-  void on_duration_unit() {}
-  FMT_NORETURN void on_utc_offset() { report_no_date(); }
-  FMT_NORETURN void on_tz_name() { report_no_date(); }
+template <typename Derived> struct null_chrono_spec_handler {
+  FMT_CONSTEXPR void unsupported() {
+    static_cast<Derived*>(this)->unsupported();
+  }
+  FMT_CONSTEXPR void on_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_short_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_offset_year() { unsupported(); }
+  FMT_CONSTEXPR void on_century(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_iso_week_based_year() { unsupported(); }
+  FMT_CONSTEXPR void on_iso_week_based_short_year() { unsupported(); }
+  FMT_CONSTEXPR void on_abbr_weekday() { unsupported(); }
+  FMT_CONSTEXPR void on_full_weekday() { unsupported(); }
+  FMT_CONSTEXPR void on_dec0_weekday(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_dec1_weekday(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_abbr_month() { unsupported(); }
+  FMT_CONSTEXPR void on_full_month() { unsupported(); }
+  FMT_CONSTEXPR void on_dec_month(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_dec0_week_of_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_dec1_week_of_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_iso_week_of_year(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_day_of_year() { unsupported(); }
+  FMT_CONSTEXPR void on_day_of_month(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_day_of_month_space(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_24_hour(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_12_hour(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_minute(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_second(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_datetime(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_loc_date(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_loc_time(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_us_date() { unsupported(); }
+  FMT_CONSTEXPR void on_iso_date() { unsupported(); }
+  FMT_CONSTEXPR void on_12_hour_time() { unsupported(); }
+  FMT_CONSTEXPR void on_24_hour_time() { unsupported(); }
+  FMT_CONSTEXPR void on_iso_time() { unsupported(); }
+  FMT_CONSTEXPR void on_am_pm() { unsupported(); }
+  FMT_CONSTEXPR void on_duration_value() { unsupported(); }
+  FMT_CONSTEXPR void on_duration_unit() { unsupported(); }
+  FMT_CONSTEXPR void on_utc_offset(numeric_system) { unsupported(); }
+  FMT_CONSTEXPR void on_tz_name() { unsupported(); }
 };
 
-template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-inline bool isnan(T) {
-  return false;
+struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
+  FMT_NORETURN void unsupported() { FMT_THROW(format_error("no format")); }
+
+  template <typename Char>
+  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+  FMT_CONSTEXPR void on_year(numeric_system) {}
+  FMT_CONSTEXPR void on_short_year(numeric_system) {}
+  FMT_CONSTEXPR void on_offset_year() {}
+  FMT_CONSTEXPR void on_century(numeric_system) {}
+  FMT_CONSTEXPR void on_iso_week_based_year() {}
+  FMT_CONSTEXPR void on_iso_week_based_short_year() {}
+  FMT_CONSTEXPR void on_abbr_weekday() {}
+  FMT_CONSTEXPR void on_full_weekday() {}
+  FMT_CONSTEXPR void on_dec0_weekday(numeric_system) {}
+  FMT_CONSTEXPR void on_dec1_weekday(numeric_system) {}
+  FMT_CONSTEXPR void on_abbr_month() {}
+  FMT_CONSTEXPR void on_full_month() {}
+  FMT_CONSTEXPR void on_dec_month(numeric_system) {}
+  FMT_CONSTEXPR void on_dec0_week_of_year(numeric_system) {}
+  FMT_CONSTEXPR void on_dec1_week_of_year(numeric_system) {}
+  FMT_CONSTEXPR void on_iso_week_of_year(numeric_system) {}
+  FMT_CONSTEXPR void on_day_of_year() {}
+  FMT_CONSTEXPR void on_day_of_month(numeric_system) {}
+  FMT_CONSTEXPR void on_day_of_month_space(numeric_system) {}
+  FMT_CONSTEXPR void on_24_hour(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_12_hour(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_minute(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_second(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_datetime(numeric_system) {}
+  FMT_CONSTEXPR void on_loc_date(numeric_system) {}
+  FMT_CONSTEXPR void on_loc_time(numeric_system) {}
+  FMT_CONSTEXPR void on_us_date() {}
+  FMT_CONSTEXPR void on_iso_date() {}
+  FMT_CONSTEXPR void on_12_hour_time() {}
+  FMT_CONSTEXPR void on_24_hour_time() {}
+  FMT_CONSTEXPR void on_iso_time() {}
+  FMT_CONSTEXPR void on_am_pm() {}
+  FMT_CONSTEXPR void on_utc_offset(numeric_system) {}
+  FMT_CONSTEXPR void on_tz_name() {}
+};
+
+inline auto tm_wday_full_name(int wday) -> const char* {
+  static constexpr const char* full_name_list[] = {
+      "Sunday",   "Monday", "Tuesday", "Wednesday",
+      "Thursday", "Friday", "Saturday"};
+  return wday >= 0 && wday <= 6 ? full_name_list[wday] : "?";
 }
-template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-inline bool isnan(T value) {
-  return std::isnan(value);
+inline auto tm_wday_short_name(int wday) -> const char* {
+  static constexpr const char* short_name_list[] = {"Sun", "Mon", "Tue", "Wed",
+                                                    "Thu", "Fri", "Sat"};
+  return wday >= 0 && wday <= 6 ? short_name_list[wday] : "???";
 }
 
-template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-inline bool isfinite(T) {
-  return true;
+inline auto tm_mon_full_name(int mon) -> const char* {
+  static constexpr const char* full_name_list[] = {
+      "January", "February", "March",     "April",   "May",      "June",
+      "July",    "August",   "September", "October", "November", "December"};
+  return mon >= 0 && mon <= 11 ? full_name_list[mon] : "?";
 }
-template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-inline bool isfinite(T value) {
-  return std::isfinite(value);
+inline auto tm_mon_short_name(int mon) -> const char* {
+  static constexpr const char* short_name_list[] = {
+      "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+      "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
+  };
+  return mon >= 0 && mon <= 11 ? short_name_list[mon] : "???";
 }
 
-// Converts value to int and checks that it's in the range [0, upper).
-template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-inline int to_nonnegative_int(T value, int upper) {
-  FMT_ASSERT(value >= 0 && value <= upper, "invalid value");
-  (void)upper;
-  return static_cast<int>(value);
+template <typename T, typename = void>
+struct has_member_data_tm_gmtoff : std::false_type {};
+template <typename T>
+struct has_member_data_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>>
+    : std::true_type {};
+
+template <typename T, typename = void>
+struct has_member_data_tm_zone : std::false_type {};
+template <typename T>
+struct has_member_data_tm_zone<T, void_t<decltype(T::tm_zone)>>
+    : std::true_type {};
+
+#if FMT_USE_TZSET
+inline void tzset_once() {
+  static bool init = []() -> bool {
+    _tzset();
+    return true;
+  }();
+  ignore_unused(init);
 }
-template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-inline int to_nonnegative_int(T value, int upper) {
-  FMT_ASSERT(
-      std::isnan(value) || (value >= 0 && value <= static_cast<T>(upper)),
-      "invalid value");
-  (void)upper;
-  return static_cast<int>(value);
+#endif
+
+// Converts value to Int and checks that it's in the range [0, upper).
+template <typename T, typename Int, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline auto to_nonnegative_int(T value, Int upper) -> Int {
+  if (!std::is_unsigned<Int>::value &&
+      (value < 0 || to_unsigned(value) > to_unsigned(upper))) {
+    FMT_THROW(fmt::format_error("chrono value is out of range"));
+  }
+  return static_cast<Int>(value);
+}
+template <typename T, typename Int, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline auto to_nonnegative_int(T value, Int upper) -> Int {
+  if (value < 0 || value > static_cast<T>(upper))
+    FMT_THROW(format_error("invalid value"));
+  return static_cast<Int>(value);
+}
+
+constexpr auto pow10(std::uint32_t n) -> long long {
+  return n == 0 ? 1 : 10 * pow10(n - 1);
+}
+
+// Counts the number of fractional digits in the range [0, 18] according to the
+// C++20 spec. If more than 18 fractional digits are required then returns 6 for
+// microseconds precision.
+template <long long Num, long long Den, int N = 0,
+          bool Enabled = (N < 19) && (Num <= max_value<long long>() / 10)>
+struct count_fractional_digits {
+  static constexpr int value =
+      Num % Den == 0 ? N : count_fractional_digits<Num * 10, Den, N + 1>::value;
+};
+
+// Base case that doesn't instantiate any more templates
+// in order to avoid overflow.
+template <long long Num, long long Den, int N>
+struct count_fractional_digits<Num, Den, N, false> {
+  static constexpr int value = (Num % Den == 0) ? N : 6;
+};
+
+// Format subseconds which are given as an integer type with an appropriate
+// number of digits.
+template <typename Char, typename OutputIt, typename Duration>
+void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
+  constexpr auto num_fractional_digits =
+      count_fractional_digits<Duration::period::num,
+                              Duration::period::den>::value;
+
+  using subsecond_precision = std::chrono::duration<
+      typename std::common_type<typename Duration::rep,
+                                std::chrono::seconds::rep>::type,
+      std::ratio<1, detail::pow10(num_fractional_digits)>>;
+
+  const auto fractional = d - fmt_duration_cast<std::chrono::seconds>(d);
+  const auto subseconds =
+      std::chrono::treat_as_floating_point<
+          typename subsecond_precision::rep>::value
+          ? fractional.count()
+          : fmt_duration_cast<subsecond_precision>(fractional).count();
+  auto n = static_cast<uint32_or_64_or_128_t<long long>>(subseconds);
+  const int num_digits = detail::count_digits(n);
+
+  int leading_zeroes = (std::max)(0, num_fractional_digits - num_digits);
+  if (precision < 0) {
+    FMT_ASSERT(!std::is_floating_point<typename Duration::rep>::value, "");
+    if (std::ratio_less<typename subsecond_precision::period,
+                        std::chrono::seconds::period>::value) {
+      *out++ = '.';
+      out = std::fill_n(out, leading_zeroes, '0');
+      out = format_decimal<Char>(out, n, num_digits).end;
+    }
+  } else {
+    *out++ = '.';
+    leading_zeroes = (std::min)(leading_zeroes, precision);
+    out = std::fill_n(out, leading_zeroes, '0');
+    int remaining = precision - leading_zeroes;
+    if (remaining != 0 && remaining < num_digits) {
+      n /= to_unsigned(detail::pow10(to_unsigned(num_digits - remaining)));
+      out = format_decimal<Char>(out, n, remaining).end;
+      return;
+    }
+    out = format_decimal<Char>(out, n, num_digits).end;
+    remaining -= num_digits;
+    out = std::fill_n(out, remaining, '0');
+  }
+}
+
+// Format subseconds which are given as a floating point type with an
+// appropriate number of digits. We cannot pass the Duration here, as we
+// explicitly need to pass the Rep value in the chrono_formatter.
+template <typename Duration>
+void write_floating_seconds(memory_buffer& buf, Duration duration,
+                            int num_fractional_digits = -1) {
+  using rep = typename Duration::rep;
+  FMT_ASSERT(std::is_floating_point<rep>::value, "");
+
+  auto val = duration.count();
+
+  if (num_fractional_digits < 0) {
+    // For `std::round` with fallback to `round`:
+    // On some toolchains `std::round` is not available (e.g. GCC 6).
+    using namespace std;
+    num_fractional_digits =
+        count_fractional_digits<Duration::period::num,
+                                Duration::period::den>::value;
+    if (num_fractional_digits < 6 && static_cast<rep>(round(val)) != val)
+      num_fractional_digits = 6;
+  }
+
+  fmt::format_to(std::back_inserter(buf), FMT_STRING("{:.{}f}"),
+                 std::fmod(val * static_cast<rep>(Duration::period::num) /
+                               static_cast<rep>(Duration::period::den),
+                           static_cast<rep>(60)),
+                 num_fractional_digits);
+}
+
+template <typename OutputIt, typename Char,
+          typename Duration = std::chrono::seconds>
+class tm_writer {
+ private:
+  static constexpr int days_per_week = 7;
+
+  const std::locale& loc_;
+  const bool is_classic_;
+  OutputIt out_;
+  const Duration* subsecs_;
+  const std::tm& tm_;
+
+  auto tm_sec() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_sec >= 0 && tm_.tm_sec <= 61, "");
+    return tm_.tm_sec;
+  }
+  auto tm_min() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_min >= 0 && tm_.tm_min <= 59, "");
+    return tm_.tm_min;
+  }
+  auto tm_hour() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_hour >= 0 && tm_.tm_hour <= 23, "");
+    return tm_.tm_hour;
+  }
+  auto tm_mday() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_mday >= 1 && tm_.tm_mday <= 31, "");
+    return tm_.tm_mday;
+  }
+  auto tm_mon() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_mon >= 0 && tm_.tm_mon <= 11, "");
+    return tm_.tm_mon;
+  }
+  auto tm_year() const noexcept -> long long { return 1900ll + tm_.tm_year; }
+  auto tm_wday() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_wday >= 0 && tm_.tm_wday <= 6, "");
+    return tm_.tm_wday;
+  }
+  auto tm_yday() const noexcept -> int {
+    FMT_ASSERT(tm_.tm_yday >= 0 && tm_.tm_yday <= 365, "");
+    return tm_.tm_yday;
+  }
+
+  auto tm_hour12() const noexcept -> int {
+    const auto h = tm_hour();
+    const auto z = h < 12 ? h : h - 12;
+    return z == 0 ? 12 : z;
+  }
+
+  // POSIX and the C Standard are unclear or inconsistent about what %C and %y
+  // do if the year is negative or exceeds 9999. Use the convention that %C
+  // concatenated with %y yields the same output as %Y, and that %Y contains at
+  // least 4 characters, with more only if necessary.
+  auto split_year_lower(long long year) const noexcept -> int {
+    auto l = year % 100;
+    if (l < 0) l = -l;  // l in [0, 99]
+    return static_cast<int>(l);
+  }
+
+  // Algorithm: https://en.wikipedia.org/wiki/ISO_week_date.
+  auto iso_year_weeks(long long curr_year) const noexcept -> int {
+    const auto prev_year = curr_year - 1;
+    const auto curr_p =
+        (curr_year + curr_year / 4 - curr_year / 100 + curr_year / 400) %
+        days_per_week;
+    const auto prev_p =
+        (prev_year + prev_year / 4 - prev_year / 100 + prev_year / 400) %
+        days_per_week;
+    return 52 + ((curr_p == 4 || prev_p == 3) ? 1 : 0);
+  }
+  auto iso_week_num(int tm_yday, int tm_wday) const noexcept -> int {
+    return (tm_yday + 11 - (tm_wday == 0 ? days_per_week : tm_wday)) /
+           days_per_week;
+  }
+  auto tm_iso_week_year() const noexcept -> long long {
+    const auto year = tm_year();
+    const auto w = iso_week_num(tm_yday(), tm_wday());
+    if (w < 1) return year - 1;
+    if (w > iso_year_weeks(year)) return year + 1;
+    return year;
+  }
+  auto tm_iso_week_of_year() const noexcept -> int {
+    const auto year = tm_year();
+    const auto w = iso_week_num(tm_yday(), tm_wday());
+    if (w < 1) return iso_year_weeks(year - 1);
+    if (w > iso_year_weeks(year)) return 1;
+    return w;
+  }
+
+  void write1(int value) {
+    *out_++ = static_cast<char>('0' + to_unsigned(value) % 10);
+  }
+  void write2(int value) {
+    const char* d = digits2(to_unsigned(value) % 100);
+    *out_++ = *d++;
+    *out_++ = *d;
+  }
+  void write2(int value, pad_type pad) {
+    unsigned int v = to_unsigned(value) % 100;
+    if (v >= 10) {
+      const char* d = digits2(v);
+      *out_++ = *d++;
+      *out_++ = *d;
+    } else {
+      out_ = detail::write_padding(out_, pad);
+      *out_++ = static_cast<char>('0' + v);
+    }
+  }
+
+  void write_year_extended(long long year) {
+    // At least 4 characters.
+    int width = 4;
+    if (year < 0) {
+      *out_++ = '-';
+      year = 0 - year;
+      --width;
+    }
+    uint32_or_64_or_128_t<long long> n = to_unsigned(year);
+    const int num_digits = count_digits(n);
+    if (width > num_digits) out_ = std::fill_n(out_, width - num_digits, '0');
+    out_ = format_decimal<Char>(out_, n, num_digits).end;
+  }
+  void write_year(long long year) {
+    if (year >= 0 && year < 10000) {
+      write2(static_cast<int>(year / 100));
+      write2(static_cast<int>(year % 100));
+    } else {
+      write_year_extended(year);
+    }
+  }
+
+  void write_utc_offset(long offset, numeric_system ns) {
+    if (offset < 0) {
+      *out_++ = '-';
+      offset = -offset;
+    } else {
+      *out_++ = '+';
+    }
+    offset /= 60;
+    write2(static_cast<int>(offset / 60));
+    if (ns != numeric_system::standard) *out_++ = ':';
+    write2(static_cast<int>(offset % 60));
+  }
+  template <typename T, FMT_ENABLE_IF(has_member_data_tm_gmtoff<T>::value)>
+  void format_utc_offset_impl(const T& tm, numeric_system ns) {
+    write_utc_offset(tm.tm_gmtoff, ns);
+  }
+  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_gmtoff<T>::value)>
+  void format_utc_offset_impl(const T& tm, numeric_system ns) {
+#if defined(_WIN32) && defined(_UCRT)
+#  if FMT_USE_TZSET
+    tzset_once();
+#  endif
+    long offset = 0;
+    _get_timezone(&offset);
+    if (tm.tm_isdst) {
+      long dstbias = 0;
+      _get_dstbias(&dstbias);
+      offset += dstbias;
+    }
+    write_utc_offset(-offset, ns);
+#else
+    if (ns == numeric_system::standard) return format_localized('z');
+
+    // Extract timezone offset from timezone conversion functions.
+    std::tm gtm = tm;
+    std::time_t gt = std::mktime(&gtm);
+    std::tm ltm = gmtime(gt);
+    std::time_t lt = std::mktime(&ltm);
+    long offset = gt - lt;
+    write_utc_offset(offset, ns);
+#endif
+  }
+
+  template <typename T, FMT_ENABLE_IF(has_member_data_tm_zone<T>::value)>
+  void format_tz_name_impl(const T& tm) {
+    if (is_classic_)
+      out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
+    else
+      format_localized('Z');
+  }
+  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_zone<T>::value)>
+  void format_tz_name_impl(const T&) {
+    format_localized('Z');
+  }
+
+  void format_localized(char format, char modifier = 0) {
+    out_ = write<Char>(out_, tm_, loc_, format, modifier);
+  }
+
+ public:
+  tm_writer(const std::locale& loc, OutputIt out, const std::tm& tm,
+            const Duration* subsecs = nullptr)
+      : loc_(loc),
+        is_classic_(loc_ == get_classic_locale()),
+        out_(out),
+        subsecs_(subsecs),
+        tm_(tm) {}
+
+  auto out() const -> OutputIt { return out_; }
+
+  FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
+    out_ = copy_str<Char>(begin, end, out_);
+  }
+
+  void on_abbr_weekday() {
+    if (is_classic_)
+      out_ = write(out_, tm_wday_short_name(tm_wday()));
+    else
+      format_localized('a');
+  }
+  void on_full_weekday() {
+    if (is_classic_)
+      out_ = write(out_, tm_wday_full_name(tm_wday()));
+    else
+      format_localized('A');
+  }
+  void on_dec0_weekday(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) return write1(tm_wday());
+    format_localized('w', 'O');
+  }
+  void on_dec1_weekday(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) {
+      auto wday = tm_wday();
+      write1(wday == 0 ? days_per_week : wday);
+    } else {
+      format_localized('u', 'O');
+    }
+  }
+
+  void on_abbr_month() {
+    if (is_classic_)
+      out_ = write(out_, tm_mon_short_name(tm_mon()));
+    else
+      format_localized('b');
+  }
+  void on_full_month() {
+    if (is_classic_)
+      out_ = write(out_, tm_mon_full_name(tm_mon()));
+    else
+      format_localized('B');
+  }
+
+  void on_datetime(numeric_system ns) {
+    if (is_classic_) {
+      on_abbr_weekday();
+      *out_++ = ' ';
+      on_abbr_month();
+      *out_++ = ' ';
+      on_day_of_month_space(numeric_system::standard);
+      *out_++ = ' ';
+      on_iso_time();
+      *out_++ = ' ';
+      on_year(numeric_system::standard);
+    } else {
+      format_localized('c', ns == numeric_system::standard ? '\0' : 'E');
+    }
+  }
+  void on_loc_date(numeric_system ns) {
+    if (is_classic_)
+      on_us_date();
+    else
+      format_localized('x', ns == numeric_system::standard ? '\0' : 'E');
+  }
+  void on_loc_time(numeric_system ns) {
+    if (is_classic_)
+      on_iso_time();
+    else
+      format_localized('X', ns == numeric_system::standard ? '\0' : 'E');
+  }
+  void on_us_date() {
+    char buf[8];
+    write_digit2_separated(buf, to_unsigned(tm_mon() + 1),
+                           to_unsigned(tm_mday()),
+                           to_unsigned(split_year_lower(tm_year())), '/');
+    out_ = copy_str<Char>(std::begin(buf), std::end(buf), out_);
+  }
+  void on_iso_date() {
+    auto year = tm_year();
+    char buf[10];
+    size_t offset = 0;
+    if (year >= 0 && year < 10000) {
+      copy2(buf, digits2(static_cast<size_t>(year / 100)));
+    } else {
+      offset = 4;
+      write_year_extended(year);
+      year = 0;
+    }
+    write_digit2_separated(buf + 2, static_cast<unsigned>(year % 100),
+                           to_unsigned(tm_mon() + 1), to_unsigned(tm_mday()),
+                           '-');
+    out_ = copy_str<Char>(std::begin(buf) + offset, std::end(buf), out_);
+  }
+
+  void on_utc_offset(numeric_system ns) { format_utc_offset_impl(tm_, ns); }
+  void on_tz_name() { format_tz_name_impl(tm_); }
+
+  void on_year(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write_year(tm_year());
+    format_localized('Y', 'E');
+  }
+  void on_short_year(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(split_year_lower(tm_year()));
+    format_localized('y', 'O');
+  }
+  void on_offset_year() {
+    if (is_classic_) return write2(split_year_lower(tm_year()));
+    format_localized('y', 'E');
+  }
+
+  void on_century(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) {
+      auto year = tm_year();
+      auto upper = year / 100;
+      if (year >= -99 && year < 0) {
+        // Zero upper on negative year.
+        *out_++ = '-';
+        *out_++ = '0';
+      } else if (upper >= 0 && upper < 100) {
+        write2(static_cast<int>(upper));
+      } else {
+        out_ = write<Char>(out_, upper);
+      }
+    } else {
+      format_localized('C', 'E');
+    }
+  }
+
+  void on_dec_month(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(tm_mon() + 1);
+    format_localized('m', 'O');
+  }
+
+  void on_dec0_week_of_year(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2((tm_yday() + days_per_week - tm_wday()) / days_per_week);
+    format_localized('U', 'O');
+  }
+  void on_dec1_week_of_year(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) {
+      auto wday = tm_wday();
+      write2((tm_yday() + days_per_week -
+              (wday == 0 ? (days_per_week - 1) : (wday - 1))) /
+             days_per_week);
+    } else {
+      format_localized('W', 'O');
+    }
+  }
+  void on_iso_week_of_year(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(tm_iso_week_of_year());
+    format_localized('V', 'O');
+  }
+
+  void on_iso_week_based_year() { write_year(tm_iso_week_year()); }
+  void on_iso_week_based_short_year() {
+    write2(split_year_lower(tm_iso_week_year()));
+  }
+
+  void on_day_of_year() {
+    auto yday = tm_yday() + 1;
+    write1(yday / 100);
+    write2(yday % 100);
+  }
+  void on_day_of_month(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) return write2(tm_mday());
+    format_localized('d', 'O');
+  }
+  void on_day_of_month_space(numeric_system ns) {
+    if (is_classic_ || ns == numeric_system::standard) {
+      auto mday = to_unsigned(tm_mday()) % 100;
+      const char* d2 = digits2(mday);
+      *out_++ = mday < 10 ? ' ' : d2[0];
+      *out_++ = d2[1];
+    } else {
+      format_localized('e', 'O');
+    }
+  }
+
+  void on_24_hour(numeric_system ns, pad_type pad) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(tm_hour(), pad);
+    format_localized('H', 'O');
+  }
+  void on_12_hour(numeric_system ns, pad_type pad) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(tm_hour12(), pad);
+    format_localized('I', 'O');
+  }
+  void on_minute(numeric_system ns, pad_type pad) {
+    if (is_classic_ || ns == numeric_system::standard)
+      return write2(tm_min(), pad);
+    format_localized('M', 'O');
+  }
+
+  void on_second(numeric_system ns, pad_type pad) {
+    if (is_classic_ || ns == numeric_system::standard) {
+      write2(tm_sec(), pad);
+      if (subsecs_) {
+        if (std::is_floating_point<typename Duration::rep>::value) {
+          auto buf = memory_buffer();
+          write_floating_seconds(buf, *subsecs_);
+          if (buf.size() > 1) {
+            // Remove the leading "0", write something like ".123".
+            out_ = std::copy(buf.begin() + 1, buf.end(), out_);
+          }
+        } else {
+          write_fractional_seconds<Char>(out_, *subsecs_);
+        }
+      }
+    } else {
+      // Currently no formatting of subseconds when a locale is set.
+      format_localized('S', 'O');
+    }
+  }
+
+  void on_12_hour_time() {
+    if (is_classic_) {
+      char buf[8];
+      write_digit2_separated(buf, to_unsigned(tm_hour12()),
+                             to_unsigned(tm_min()), to_unsigned(tm_sec()), ':');
+      out_ = copy_str<Char>(std::begin(buf), std::end(buf), out_);
+      *out_++ = ' ';
+      on_am_pm();
+    } else {
+      format_localized('r');
+    }
+  }
+  void on_24_hour_time() {
+    write2(tm_hour());
+    *out_++ = ':';
+    write2(tm_min());
+  }
+  void on_iso_time() {
+    on_24_hour_time();
+    *out_++ = ':';
+    on_second(numeric_system::standard, pad_type::unspecified);
+  }
+
+  void on_am_pm() {
+    if (is_classic_) {
+      *out_++ = tm_hour() < 12 ? 'A' : 'P';
+      *out_++ = 'M';
+    } else {
+      format_localized('p');
+    }
+  }
+
+  // These apply to chrono durations but not tm.
+  void on_duration_value() {}
+  void on_duration_unit() {}
+};
+
+struct chrono_format_checker : null_chrono_spec_handler<chrono_format_checker> {
+  bool has_precision_integral = false;
+
+  FMT_NORETURN void unsupported() { FMT_THROW(format_error("no date")); }
+
+  template <typename Char>
+  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+  FMT_CONSTEXPR void on_day_of_year() {}
+  FMT_CONSTEXPR void on_24_hour(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_12_hour(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_minute(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_second(numeric_system, pad_type) {}
+  FMT_CONSTEXPR void on_12_hour_time() {}
+  FMT_CONSTEXPR void on_24_hour_time() {}
+  FMT_CONSTEXPR void on_iso_time() {}
+  FMT_CONSTEXPR void on_am_pm() {}
+  FMT_CONSTEXPR void on_duration_value() const {
+    if (has_precision_integral) {
+      FMT_THROW(format_error("precision not allowed for this argument type"));
+    }
+  }
+  FMT_CONSTEXPR void on_duration_unit() {}
+};
+
+template <typename T,
+          FMT_ENABLE_IF(std::is_integral<T>::value&& has_isfinite<T>::value)>
+inline auto isfinite(T) -> bool {
+  return true;
 }
 
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-inline T mod(T x, int y) {
+inline auto mod(T x, int y) -> T {
   return x % static_cast<T>(y);
 }
 template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-inline T mod(T x, int y) {
+inline auto mod(T x, int y) -> T {
   return std::fmod(x, static_cast<T>(y));
 }
 
@@ -714,83 +1668,100 @@ template <typename T> struct make_unsigned_or_unchanged<T, true> {
   using type = typename std::make_unsigned<T>::type;
 };
 
-#if FMT_SAFE_DURATION_CAST
-// throwing version of safe_duration_cast
-template <typename To, typename FromRep, typename FromPeriod>
-To fmt_safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from) {
-  int ec;
-  To to = safe_duration_cast::safe_duration_cast<To>(from, ec);
-  if (ec) FMT_THROW(format_error("cannot format duration"));
-  return to;
-}
-#endif
-
 template <typename Rep, typename Period,
           FMT_ENABLE_IF(std::is_integral<Rep>::value)>
-inline std::chrono::duration<Rep, std::milli> get_milliseconds(
-    std::chrono::duration<Rep, Period> d) {
+inline auto get_milliseconds(std::chrono::duration<Rep, Period> d)
+    -> std::chrono::duration<Rep, std::milli> {
   // this may overflow and/or the result may not fit in the
   // target type.
 #if FMT_SAFE_DURATION_CAST
   using CommonSecondsType =
       typename std::common_type<decltype(d), std::chrono::seconds>::type;
-  const auto d_as_common = fmt_safe_duration_cast<CommonSecondsType>(d);
+  const auto d_as_common = fmt_duration_cast<CommonSecondsType>(d);
   const auto d_as_whole_seconds =
-      fmt_safe_duration_cast<std::chrono::seconds>(d_as_common);
+      fmt_duration_cast<std::chrono::seconds>(d_as_common);
   // this conversion should be nonproblematic
   const auto diff = d_as_common - d_as_whole_seconds;
   const auto ms =
-      fmt_safe_duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
+      fmt_duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
   return ms;
 #else
-  auto s = std::chrono::duration_cast<std::chrono::seconds>(d);
-  return std::chrono::duration_cast<std::chrono::milliseconds>(d - s);
+  auto s = fmt_duration_cast<std::chrono::seconds>(d);
+  return fmt_duration_cast<std::chrono::milliseconds>(d - s);
 #endif
 }
 
-template <typename Rep, typename Period,
+template <typename Char, typename Rep, typename OutputIt,
+          FMT_ENABLE_IF(std::is_integral<Rep>::value)>
+auto format_duration_value(OutputIt out, Rep val, int) -> OutputIt {
+  return write<Char>(out, val);
+}
+
+template <typename Char, typename Rep, typename OutputIt,
           FMT_ENABLE_IF(std::is_floating_point<Rep>::value)>
-inline std::chrono::duration<Rep, std::milli> get_milliseconds(
-    std::chrono::duration<Rep, Period> d) {
-  using common_type = typename std::common_type<Rep, std::intmax_t>::type;
-  auto ms = mod(d.count() * static_cast<common_type>(Period::num) /
-                    static_cast<common_type>(Period::den) * 1000,
-                1000);
-  return std::chrono::duration<Rep, std::milli>(static_cast<Rep>(ms));
+auto format_duration_value(OutputIt out, Rep val, int precision) -> OutputIt {
+  auto specs = format_specs<Char>();
+  specs.precision = precision;
+  specs.type = precision >= 0 ? presentation_type::fixed_lower
+                              : presentation_type::general_lower;
+  return write<Char>(out, val, specs);
+}
+
+template <typename Char, typename OutputIt>
+auto copy_unit(string_view unit, OutputIt out, Char) -> OutputIt {
+  return std::copy(unit.begin(), unit.end(), out);
 }
 
-template <typename Char, typename Rep, typename OutputIt>
-OutputIt format_duration_value(OutputIt out, Rep val, int precision) {
-  const Char pr_f[] = {'{', ':', '.', '{', '}', 'f', '}', 0};
-  if (precision >= 0) return format_to(out, pr_f, val, precision);
-  const Char fp_f[] = {'{', ':', 'g', '}', 0};
-  const Char format[] = {'{', '}', 0};
-  return format_to(out, std::is_floating_point<Rep>::value ? fp_f : format,
-                   val);
+template <typename OutputIt>
+auto copy_unit(string_view unit, OutputIt out, wchar_t) -> OutputIt {
+  // This works when wchar_t is UTF-32 because units only contain characters
+  // that have the same representation in UTF-16 and UTF-32.
+  utf8_to_utf16 u(unit);
+  return std::copy(u.c_str(), u.c_str() + u.size(), out);
 }
 
 template <typename Char, typename Period, typename OutputIt>
-OutputIt format_duration_unit(OutputIt out) {
-  if (const char* unit = get_units<Period>()) {
-    string_view s(unit);
-    if (const_check(std::is_same<Char, wchar_t>())) {
-      utf8_to_utf16 u(s);
-      return std::copy(u.c_str(), u.c_str() + u.size(), out);
-    }
-    return std::copy(s.begin(), s.end(), out);
+auto format_duration_unit(OutputIt out) -> OutputIt {
+  if (const char* unit = get_units<Period>())
+    return copy_unit(string_view(unit), out, Char());
+  *out++ = '[';
+  out = write<Char>(out, Period::num);
+  if (const_check(Period::den != 1)) {
+    *out++ = '/';
+    out = write<Char>(out, Period::den);
   }
-  const Char num_f[] = {'[', '{', '}', ']', 's', 0};
-  if (Period::den == 1) return format_to(out, num_f, Period::num);
-  const Char num_def_f[] = {'[', '{', '}', '/', '{', '}', ']', 's', 0};
-  return format_to(out, num_def_f, Period::num, Period::den);
+  *out++ = ']';
+  *out++ = 's';
+  return out;
 }
 
+class get_locale {
+ private:
+  union {
+    std::locale locale_;
+  };
+  bool has_locale_ = false;
+
+ public:
+  get_locale(bool localized, locale_ref loc) : has_locale_(localized) {
+    if (localized)
+      ::new (&locale_) std::locale(loc.template get<std::locale>());
+  }
+  ~get_locale() {
+    if (has_locale_) locale_.~locale();
+  }
+  operator const std::locale&() const {
+    return has_locale_ ? locale_ : get_classic_locale();
+  }
+};
+
 template <typename FormatContext, typename OutputIt, typename Rep,
           typename Period>
 struct chrono_formatter {
   FormatContext& context;
   OutputIt out;
   int precision;
+  bool localized = false;
   // rep is unsigned to avoid overflow.
   using rep =
       conditional_t<std::is_integral<Rep>::value && sizeof(Rep) < sizeof(int),
@@ -802,9 +1773,10 @@ struct chrono_formatter {
   bool negative;
 
   using char_type = typename FormatContext::char_type;
+  using tm_writer_type = tm_writer<OutputIt, char_type>;
 
-  explicit chrono_formatter(FormatContext& ctx, OutputIt o,
-                            std::chrono::duration<Rep, Period> d)
+  chrono_formatter(FormatContext& ctx, OutputIt o,
+                   std::chrono::duration<Rep, Period> d)
       : context(ctx),
         out(o),
         val(static_cast<rep>(d.count())),
@@ -816,18 +1788,12 @@ struct chrono_formatter {
 
     // this may overflow and/or the result may not fit in the
     // target type.
-#if FMT_SAFE_DURATION_CAST
     // might need checked conversion (rep!=Rep)
-    auto tmpval = std::chrono::duration<rep, Period>(val);
-    s = fmt_safe_duration_cast<seconds>(tmpval);
-#else
-    s = std::chrono::duration_cast<seconds>(
-        std::chrono::duration<rep, Period>(val));
-#endif
+    s = fmt_duration_cast<seconds>(std::chrono::duration<rep, Period>(val));
   }
 
   // returns true if nan or inf, writes to out.
-  bool handle_nan_inf() {
+  auto handle_nan_inf() -> bool {
     if (isfinite(val)) {
       return false;
     }
@@ -844,17 +1810,22 @@ struct chrono_formatter {
     return true;
   }
 
-  Rep hour() const { return static_cast<Rep>(mod((s.count() / 3600), 24)); }
+  auto days() const -> Rep { return static_cast<Rep>(s.count() / 86400); }
+  auto hour() const -> Rep {
+    return static_cast<Rep>(mod((s.count() / 3600), 24));
+  }
 
-  Rep hour12() const {
+  auto hour12() const -> Rep {
     Rep hour = static_cast<Rep>(mod((s.count() / 3600), 12));
     return hour <= 0 ? 12 : hour;
   }
 
-  Rep minute() const { return static_cast<Rep>(mod((s.count() / 60), 60)); }
-  Rep second() const { return static_cast<Rep>(mod(s.count(), 60)); }
+  auto minute() const -> Rep {
+    return static_cast<Rep>(mod((s.count() / 60), 60));
+  }
+  auto second() const -> Rep { return static_cast<Rep>(mod(s.count(), 60)); }
 
-  std::tm time() const {
+  auto time() const -> std::tm {
     auto time = std::tm();
     time.tm_hour = to_nonnegative_int(hour(), 24);
     time.tm_min = to_nonnegative_int(minute(), 60);
@@ -869,29 +1840,29 @@ struct chrono_formatter {
     }
   }
 
-  void write(Rep value, int width) {
+  void write(Rep value, int width, pad_type pad = pad_type::unspecified) {
     write_sign();
     if (isnan(value)) return write_nan();
     uint32_or_64_or_128_t<int> n =
         to_unsigned(to_nonnegative_int(value, max_value<int>()));
-    int num_digits = internal::count_digits(n);
-    if (width > num_digits) out = std::fill_n(out, width - num_digits, '0');
-    out = format_decimal<char_type>(out, n, num_digits);
+    int num_digits = detail::count_digits(n);
+    if (width > num_digits) {
+      out = detail::write_padding(out, pad, width - num_digits);
+    }
+    out = format_decimal<char_type>(out, n, num_digits).end;
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }
   void write_pinf() { std::copy_n("inf", 3, out); }
   void write_ninf() { std::copy_n("-inf", 4, out); }
 
-  void format_localized(const tm& time, char format, char modifier = 0) {
+  template <typename Callback, typename... Args>
+  void format_tm(const tm& time, Callback cb, Args... args) {
     if (isnan(val)) return write_nan();
-    auto locale = context.locale().template get<std::locale>();
-    auto& facet = std::use_facet<std::time_put<char_type>>(locale);
-    std::basic_ostringstream<char_type> os;
-    os.imbue(locale);
-    facet.put(os, os, ' ', &time, format, modifier);
-    auto str = os.str();
-    std::copy(str.begin(), str.end(), out);
+    get_locale loc(localized, context.locale());
+    auto w = tm_writer_type(loc, out, time);
+    (w.*cb)(args...);
+    out = w.out();
   }
 
   void on_text(const char_type* begin, const char_type* end) {
@@ -910,64 +1881,81 @@ struct chrono_formatter {
   void on_loc_time(numeric_system) {}
   void on_us_date() {}
   void on_iso_date() {}
-  void on_utc_offset() {}
+  void on_utc_offset(numeric_system) {}
   void on_tz_name() {}
+  void on_year(numeric_system) {}
+  void on_short_year(numeric_system) {}
+  void on_offset_year() {}
+  void on_century(numeric_system) {}
+  void on_iso_week_based_year() {}
+  void on_iso_week_based_short_year() {}
+  void on_dec_month(numeric_system) {}
+  void on_dec0_week_of_year(numeric_system) {}
+  void on_dec1_week_of_year(numeric_system) {}
+  void on_iso_week_of_year(numeric_system) {}
+  void on_day_of_month(numeric_system) {}
+  void on_day_of_month_space(numeric_system) {}
+
+  void on_day_of_year() {
+    if (handle_nan_inf()) return;
+    write(days(), 0);
+  }
 
-  void on_24_hour(numeric_system ns) {
+  void on_24_hour(numeric_system ns, pad_type pad) {
     if (handle_nan_inf()) return;
 
-    if (ns == numeric_system::standard) return write(hour(), 2);
+    if (ns == numeric_system::standard) return write(hour(), 2, pad);
     auto time = tm();
     time.tm_hour = to_nonnegative_int(hour(), 24);
-    format_localized(time, 'H', 'O');
+    format_tm(time, &tm_writer_type::on_24_hour, ns, pad);
   }
 
-  void on_12_hour(numeric_system ns) {
+  void on_12_hour(numeric_system ns, pad_type pad) {
     if (handle_nan_inf()) return;
 
-    if (ns == numeric_system::standard) return write(hour12(), 2);
+    if (ns == numeric_system::standard) return write(hour12(), 2, pad);
     auto time = tm();
     time.tm_hour = to_nonnegative_int(hour12(), 12);
-    format_localized(time, 'I', 'O');
+    format_tm(time, &tm_writer_type::on_12_hour, ns, pad);
   }
 
-  void on_minute(numeric_system ns) {
+  void on_minute(numeric_system ns, pad_type pad) {
     if (handle_nan_inf()) return;
 
-    if (ns == numeric_system::standard) return write(minute(), 2);
+    if (ns == numeric_system::standard) return write(minute(), 2, pad);
     auto time = tm();
     time.tm_min = to_nonnegative_int(minute(), 60);
-    format_localized(time, 'M', 'O');
+    format_tm(time, &tm_writer_type::on_minute, ns, pad);
   }
 
-  void on_second(numeric_system ns) {
+  void on_second(numeric_system ns, pad_type pad) {
     if (handle_nan_inf()) return;
 
     if (ns == numeric_system::standard) {
-      write(second(), 2);
-#if FMT_SAFE_DURATION_CAST
-      // convert rep->Rep
-      using duration_rep = std::chrono::duration<rep, Period>;
-      using duration_Rep = std::chrono::duration<Rep, Period>;
-      auto tmpval = fmt_safe_duration_cast<duration_Rep>(duration_rep{val});
-#else
-      auto tmpval = std::chrono::duration<Rep, Period>(val);
-#endif
-      auto ms = get_milliseconds(tmpval);
-      if (ms != std::chrono::milliseconds(0)) {
-        *out++ = '.';
-        write(ms.count(), 3);
+      if (std::is_floating_point<rep>::value) {
+        auto buf = memory_buffer();
+        write_floating_seconds(buf, std::chrono::duration<rep, Period>(val),
+                               precision);
+        if (negative) *out++ = '-';
+        if (buf.size() < 2 || buf[1] == '.') {
+          out = detail::write_padding(out, pad);
+        }
+        out = std::copy(buf.begin(), buf.end(), out);
+      } else {
+        write(second(), 2, pad);
+        write_fractional_seconds<char_type>(
+            out, std::chrono::duration<rep, Period>(val), precision);
       }
       return;
     }
     auto time = tm();
     time.tm_sec = to_nonnegative_int(second(), 60);
-    format_localized(time, 'S', 'O');
+    format_tm(time, &tm_writer_type::on_second, ns, pad);
   }
 
   void on_12_hour_time() {
     if (handle_nan_inf()) return;
-    format_localized(time(), 'r');
+    format_tm(time(), &tm_writer_type::on_12_hour_time);
   }
 
   void on_24_hour_time() {
@@ -986,12 +1974,12 @@ struct chrono_formatter {
     on_24_hour_time();
     *out++ = ':';
     if (handle_nan_inf()) return;
-    write(second(), 2);
+    on_second(numeric_system::standard, pad_type::unspecified);
   }
 
   void on_am_pm() {
     if (handle_nan_inf()) return;
-    format_localized(time(), 'p');
+    format_tm(time(), &tm_writer_type::on_am_pm);
   }
 
   void on_duration_value() {
@@ -1004,116 +1992,249 @@ struct chrono_formatter {
     out = format_duration_unit<char_type, Period>(out);
   }
 };
-}  // namespace internal
 
-template <typename Rep, typename Period, typename Char>
-struct formatter<std::chrono::duration<Rep, Period>, Char> {
- private:
-  basic_format_specs<Char> specs;
-  int precision;
-  using arg_ref_type = internal::arg_ref<Char>;
-  arg_ref_type width_ref;
-  arg_ref_type precision_ref;
-  mutable basic_string_view<Char> format_str;
-  using duration = std::chrono::duration<Rep, Period>;
-
-  struct spec_handler {
-    formatter& f;
-    basic_format_parse_context<Char>& context;
-    basic_string_view<Char> format_str;
-
-    template <typename Id> FMT_CONSTEXPR arg_ref_type make_arg_ref(Id arg_id) {
-      context.check_arg_id(arg_id);
-      return arg_ref_type(arg_id);
-    }
+}  // namespace detail
 
-    FMT_CONSTEXPR arg_ref_type make_arg_ref(basic_string_view<Char> arg_id) {
-      context.check_arg_id(arg_id);
-      return arg_ref_type(arg_id);
-    }
-
-    FMT_CONSTEXPR arg_ref_type make_arg_ref(internal::auto_id) {
-      return arg_ref_type(context.next_arg_id());
-    }
-
-    void on_error(const char* msg) { FMT_THROW(format_error(msg)); }
-    void on_fill(basic_string_view<Char> fill) { f.specs.fill = fill; }
-    void on_align(align_t align) { f.specs.align = align; }
-    void on_width(int width) { f.specs.width = width; }
-    void on_precision(int _precision) { f.precision = _precision; }
-    void end_precision() {}
+#if defined(__cpp_lib_chrono) && __cpp_lib_chrono >= 201907
+using weekday = std::chrono::weekday;
+#else
+// A fallback version of weekday.
+class weekday {
+ private:
+  unsigned char value;
 
-    template <typename Id> void on_dynamic_width(Id arg_id) {
-      f.width_ref = make_arg_ref(arg_id);
-    }
+ public:
+  weekday() = default;
+  explicit constexpr weekday(unsigned wd) noexcept
+      : value(static_cast<unsigned char>(wd != 7 ? wd : 0)) {}
+  constexpr auto c_encoding() const noexcept -> unsigned { return value; }
+};
 
-    template <typename Id> void on_dynamic_precision(Id arg_id) {
-      f.precision_ref = make_arg_ref(arg_id);
-    }
-  };
+class year_month_day {};
+#endif
 
-  using iterator = typename basic_format_parse_context<Char>::iterator;
-  struct parse_range {
-    iterator begin;
-    iterator end;
-  };
+// A rudimentary weekday formatter.
+template <typename Char> struct formatter<weekday, Char> {
+ private:
+  bool localized = false;
 
-  FMT_CONSTEXPR parse_range do_parse(basic_format_parse_context<Char>& ctx) {
+ public:
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
     auto begin = ctx.begin(), end = ctx.end();
-    if (begin == end || *begin == '}') return {begin, begin};
-    spec_handler handler{*this, ctx, format_str};
-    begin = internal::parse_align(begin, end, handler);
-    if (begin == end) return {begin, begin};
-    begin = internal::parse_width(begin, end, handler);
-    if (begin == end) return {begin, begin};
-    if (*begin == '.') {
-      if (std::is_floating_point<Rep>::value)
-        begin = internal::parse_precision(begin, end, handler);
-      else
-        handler.on_error("precision not allowed for this argument type");
+    if (begin != end && *begin == 'L') {
+      ++begin;
+      localized = true;
     }
-    end = parse_chrono_format(begin, end, internal::chrono_format_checker());
-    return {begin, end};
+    return begin;
   }
 
- public:
-  formatter() : precision(-1) {}
+  template <typename FormatContext>
+  auto format(weekday wd, FormatContext& ctx) const -> decltype(ctx.out()) {
+    auto time = std::tm();
+    time.tm_wday = static_cast<int>(wd.c_encoding());
+    detail::get_locale loc(localized, ctx.locale());
+    auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
+    w.on_abbr_weekday();
+    return w.out();
+  }
+};
+
+template <typename Rep, typename Period, typename Char>
+struct formatter<std::chrono::duration<Rep, Period>, Char> {
+ private:
+  format_specs<Char> specs_;
+  detail::arg_ref<Char> width_ref_;
+  detail::arg_ref<Char> precision_ref_;
+  bool localized_ = false;
+  basic_string_view<Char> format_str_;
 
+ public:
   FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
       -> decltype(ctx.begin()) {
-    auto range = do_parse(ctx);
-    format_str = basic_string_view<Char>(
-        &*range.begin, internal::to_unsigned(range.end - range.begin));
-    return range.end;
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end || *it == '}') return it;
+
+    it = detail::parse_align(it, end, specs_);
+    if (it == end) return it;
+
+    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
+    if (it == end) return it;
+
+    auto checker = detail::chrono_format_checker();
+    if (*it == '.') {
+      checker.has_precision_integral = !std::is_floating_point<Rep>::value;
+      it = detail::parse_precision(it, end, specs_.precision, precision_ref_,
+                                   ctx);
+    }
+    if (it != end && *it == 'L') {
+      localized_ = true;
+      ++it;
+    }
+    end = detail::parse_chrono_format(it, end, checker);
+    format_str_ = {it, detail::to_unsigned(end - it)};
+    return end;
   }
 
   template <typename FormatContext>
-  auto format(const duration& d, FormatContext& ctx) -> decltype(ctx.out()) {
-    auto begin = format_str.begin(), end = format_str.end();
+  auto format(std::chrono::duration<Rep, Period> d, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto specs = specs_;
+    auto precision = specs.precision;
+    specs.precision = -1;
+    auto begin = format_str_.begin(), end = format_str_.end();
     // As a possible future optimization, we could avoid extra copying if width
     // is not specified.
-    basic_memory_buffer<Char> buf;
+    auto buf = basic_memory_buffer<Char>();
     auto out = std::back_inserter(buf);
-    using range = internal::output_range<decltype(ctx.out()), Char>;
-    internal::basic_writer<range> w(range(ctx.out()));
-    internal::handle_dynamic_spec<internal::width_checker>(specs.width,
-                                                           width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
-        precision, precision_ref, ctx);
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
+                                                       ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(precision,
+                                                           precision_ref_, ctx);
     if (begin == end || *begin == '}') {
-      out = internal::format_duration_value<Char>(out, d.count(), precision);
-      internal::format_duration_unit<Char, Period>(out);
+      out = detail::format_duration_value<Char>(out, d.count(), precision);
+      detail::format_duration_unit<Char, Period>(out);
     } else {
-      internal::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
-          ctx, out, d);
+      using chrono_formatter =
+          detail::chrono_formatter<FormatContext, decltype(out), Rep, Period>;
+      auto f = chrono_formatter(ctx, out, d);
       f.precision = precision;
-      parse_chrono_format(begin, end, f);
+      f.localized = localized_;
+      detail::parse_chrono_format(begin, end, f);
     }
-    w.write(buf.data(), buf.size(), specs);
-    return w.out();
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
+  }
+};
+
+template <typename Char, typename Duration>
+struct formatter<std::chrono::time_point<std::chrono::system_clock, Duration>,
+                 Char> : formatter<std::tm, Char> {
+  FMT_CONSTEXPR formatter() {
+    this->format_str_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>{};
+  }
+
+  template <typename FormatContext>
+  auto format(std::chrono::time_point<std::chrono::system_clock, Duration> val,
+              FormatContext& ctx) const -> decltype(ctx.out()) {
+    using period = typename Duration::period;
+    if (detail::const_check(
+            period::num != 1 || period::den != 1 ||
+            std::is_floating_point<typename Duration::rep>::value)) {
+      const auto epoch = val.time_since_epoch();
+      auto subsecs = detail::fmt_duration_cast<Duration>(
+          epoch - detail::fmt_duration_cast<std::chrono::seconds>(epoch));
+
+      if (subsecs.count() < 0) {
+        auto second =
+            detail::fmt_duration_cast<Duration>(std::chrono::seconds(1));
+        if (epoch.count() < ((Duration::min)() + second).count())
+          FMT_THROW(format_error("duration is too small"));
+        subsecs += second;
+        val -= second;
+      }
+
+      return formatter<std::tm, Char>::do_format(gmtime(val), ctx, &subsecs);
+    }
+
+    return formatter<std::tm, Char>::format(gmtime(val), ctx);
+  }
+};
+
+#if FMT_USE_LOCAL_TIME
+template <typename Char, typename Duration>
+struct formatter<std::chrono::local_time<Duration>, Char>
+    : formatter<std::tm, Char> {
+  FMT_CONSTEXPR formatter() {
+    this->format_str_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>{};
+  }
+
+  template <typename FormatContext>
+  auto format(std::chrono::local_time<Duration> val, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    using period = typename Duration::period;
+    if (period::num != 1 || period::den != 1 ||
+        std::is_floating_point<typename Duration::rep>::value) {
+      const auto epoch = val.time_since_epoch();
+      const auto subsecs = detail::fmt_duration_cast<Duration>(
+          epoch - detail::fmt_duration_cast<std::chrono::seconds>(epoch));
+
+      return formatter<std::tm, Char>::do_format(localtime(val), ctx, &subsecs);
+    }
+
+    return formatter<std::tm, Char>::format(localtime(val), ctx);
+  }
+};
+#endif
+
+#if FMT_USE_UTC_TIME
+template <typename Char, typename Duration>
+struct formatter<std::chrono::time_point<std::chrono::utc_clock, Duration>,
+                 Char>
+    : formatter<std::chrono::time_point<std::chrono::system_clock, Duration>,
+                Char> {
+  template <typename FormatContext>
+  auto format(std::chrono::time_point<std::chrono::utc_clock, Duration> val,
+              FormatContext& ctx) const -> decltype(ctx.out()) {
+    return formatter<
+        std::chrono::time_point<std::chrono::system_clock, Duration>,
+        Char>::format(std::chrono::utc_clock::to_sys(val), ctx);
+  }
+};
+#endif
+
+template <typename Char> struct formatter<std::tm, Char> {
+ private:
+  format_specs<Char> specs_;
+  detail::arg_ref<Char> width_ref_;
+
+ protected:
+  basic_string_view<Char> format_str_;
+
+  template <typename FormatContext, typename Duration>
+  auto do_format(const std::tm& tm, FormatContext& ctx,
+                 const Duration* subsecs) const -> decltype(ctx.out()) {
+    auto specs = specs_;
+    auto buf = basic_memory_buffer<Char>();
+    auto out = std::back_inserter(buf);
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
+                                                       ctx);
+
+    auto loc_ref = ctx.locale();
+    detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
+    auto w =
+        detail::tm_writer<decltype(out), Char, Duration>(loc, out, tm, subsecs);
+    detail::parse_chrono_format(format_str_.begin(), format_str_.end(), w);
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
+  }
+
+ public:
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end || *it == '}') return it;
+
+    it = detail::parse_align(it, end, specs_);
+    if (it == end) return it;
+
+    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
+    if (it == end) return it;
+
+    end = detail::parse_chrono_format(it, end, detail::tm_format_checker());
+    // Replace the default format_str only if the new spec is not empty.
+    if (end != it) format_str_ = {it, detail::to_unsigned(end - it)};
+    return end;
+  }
+
+  template <typename FormatContext>
+  auto format(const std::tm& tm, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return do_format<FormatContext, std::chrono::seconds>(tm, ctx, nullptr);
   }
 };
 
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_CHRONO_H_
diff --git a/contrib/fmt/include/fmt/color.h b/contrib/fmt/include/fmt/color.h
index 96d9ab6b438..367849a86a7 100644
--- a/contrib/fmt/include/fmt/color.h
+++ b/contrib/fmt/include/fmt/color.h
@@ -11,6 +11,7 @@
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
+FMT_BEGIN_EXPORT
 
 enum class color : uint32_t {
   alice_blue = 0xF0F8FF,               // rgb(240,248,255)
@@ -177,9 +178,13 @@ enum class terminal_color : uint8_t {
 
 enum class emphasis : uint8_t {
   bold = 1,
-  italic = 1 << 1,
-  underline = 1 << 2,
-  strikethrough = 1 << 3
+  faint = 1 << 1,
+  italic = 1 << 2,
+  underline = 1 << 3,
+  blink = 1 << 4,
+  reverse = 1 << 5,
+  conceal = 1 << 6,
+  strikethrough = 1 << 7,
 };
 
 // rgb is a struct for red, green and blue colors.
@@ -198,21 +203,20 @@ struct rgb {
   uint8_t b;
 };
 
-namespace internal {
+namespace detail {
 
 // color is a struct of either a rgb color or a terminal color.
 struct color_type {
-  FMT_CONSTEXPR color_type() FMT_NOEXCEPT : is_rgb(), value{} {}
-  FMT_CONSTEXPR color_type(color rgb_color) FMT_NOEXCEPT : is_rgb(true),
-                                                           value{} {
+  FMT_CONSTEXPR color_type() noexcept : is_rgb(), value{} {}
+  FMT_CONSTEXPR color_type(color rgb_color) noexcept : is_rgb(true), value{} {
     value.rgb_color = static_cast<uint32_t>(rgb_color);
   }
-  FMT_CONSTEXPR color_type(rgb rgb_color) FMT_NOEXCEPT : is_rgb(true), value{} {
+  FMT_CONSTEXPR color_type(rgb rgb_color) noexcept : is_rgb(true), value{} {
     value.rgb_color = (static_cast<uint32_t>(rgb_color.r) << 16) |
                       (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b;
   }
-  FMT_CONSTEXPR color_type(terminal_color term_color) FMT_NOEXCEPT : is_rgb(),
-                                                                     value{} {
+  FMT_CONSTEXPR color_type(terminal_color term_color) noexcept
+      : is_rgb(), value{} {
     value.term_color = static_cast<uint8_t>(term_color);
   }
   bool is_rgb;
@@ -221,17 +225,15 @@ struct color_type {
     uint32_t rgb_color;
   } value;
 };
-}  // namespace internal
+}  // namespace detail
 
-// Experimental text formatting support.
+/** A text style consisting of foreground and background colors and emphasis. */
 class text_style {
  public:
-  FMT_CONSTEXPR text_style(emphasis em = emphasis()) FMT_NOEXCEPT
-      : set_foreground_color(),
-        set_background_color(),
-        ems(em) {}
+  FMT_CONSTEXPR text_style(emphasis em = emphasis()) noexcept
+      : set_foreground_color(), set_background_color(), ems(em) {}
 
-  FMT_CONSTEXPR text_style& operator|=(const text_style& rhs) {
+  FMT_CONSTEXPR auto operator|=(const text_style& rhs) -> text_style& {
     if (!set_foreground_color) {
       set_foreground_color = rhs.set_foreground_color;
       foreground_color = rhs.foreground_color;
@@ -255,68 +257,37 @@ class text_style {
     return *this;
   }
 
-  friend FMT_CONSTEXPR text_style operator|(text_style lhs,
-                                            const text_style& rhs) {
+  friend FMT_CONSTEXPR auto operator|(text_style lhs, const text_style& rhs)
+      -> text_style {
     return lhs |= rhs;
   }
 
-  FMT_CONSTEXPR text_style& operator&=(const text_style& rhs) {
-    if (!set_foreground_color) {
-      set_foreground_color = rhs.set_foreground_color;
-      foreground_color = rhs.foreground_color;
-    } else if (rhs.set_foreground_color) {
-      if (!foreground_color.is_rgb || !rhs.foreground_color.is_rgb)
-        FMT_THROW(format_error("can't AND a terminal color"));
-      foreground_color.value.rgb_color &= rhs.foreground_color.value.rgb_color;
-    }
-
-    if (!set_background_color) {
-      set_background_color = rhs.set_background_color;
-      background_color = rhs.background_color;
-    } else if (rhs.set_background_color) {
-      if (!background_color.is_rgb || !rhs.background_color.is_rgb)
-        FMT_THROW(format_error("can't AND a terminal color"));
-      background_color.value.rgb_color &= rhs.background_color.value.rgb_color;
-    }
-
-    ems = static_cast<emphasis>(static_cast<uint8_t>(ems) &
-                                static_cast<uint8_t>(rhs.ems));
-    return *this;
-  }
-
-  friend FMT_CONSTEXPR text_style operator&(text_style lhs,
-                                            const text_style& rhs) {
-    return lhs &= rhs;
-  }
-
-  FMT_CONSTEXPR bool has_foreground() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto has_foreground() const noexcept -> bool {
     return set_foreground_color;
   }
-  FMT_CONSTEXPR bool has_background() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto has_background() const noexcept -> bool {
     return set_background_color;
   }
-  FMT_CONSTEXPR bool has_emphasis() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto has_emphasis() const noexcept -> bool {
     return static_cast<uint8_t>(ems) != 0;
   }
-  FMT_CONSTEXPR internal::color_type get_foreground() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto get_foreground() const noexcept -> detail::color_type {
     FMT_ASSERT(has_foreground(), "no foreground specified for this style");
     return foreground_color;
   }
-  FMT_CONSTEXPR internal::color_type get_background() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto get_background() const noexcept -> detail::color_type {
     FMT_ASSERT(has_background(), "no background specified for this style");
     return background_color;
   }
-  FMT_CONSTEXPR emphasis get_emphasis() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto get_emphasis() const noexcept -> emphasis {
     FMT_ASSERT(has_emphasis(), "no emphasis specified for this style");
     return ems;
   }
 
  private:
   FMT_CONSTEXPR text_style(bool is_foreground,
-                           internal::color_type text_color) FMT_NOEXCEPT
-      : set_foreground_color(),
-        set_background_color(),
-        ems() {
+                           detail::color_type text_color) noexcept
+      : set_foreground_color(), set_background_color(), ems() {
     if (is_foreground) {
       foreground_color = text_color;
       set_foreground_color = true;
@@ -326,45 +297,51 @@ class text_style {
     }
   }
 
-  friend FMT_CONSTEXPR_DECL text_style fg(internal::color_type foreground)
-      FMT_NOEXCEPT;
-  friend FMT_CONSTEXPR_DECL text_style bg(internal::color_type background)
-      FMT_NOEXCEPT;
+  friend FMT_CONSTEXPR auto fg(detail::color_type foreground) noexcept
+      -> text_style;
+
+  friend FMT_CONSTEXPR auto bg(detail::color_type background) noexcept
+      -> text_style;
 
-  internal::color_type foreground_color;
-  internal::color_type background_color;
+  detail::color_type foreground_color;
+  detail::color_type background_color;
   bool set_foreground_color;
   bool set_background_color;
   emphasis ems;
 };
 
-FMT_CONSTEXPR text_style fg(internal::color_type foreground) FMT_NOEXCEPT {
-  return text_style(/*is_foreground=*/true, foreground);
+/** Creates a text style from the foreground (text) color. */
+FMT_CONSTEXPR inline auto fg(detail::color_type foreground) noexcept
+    -> text_style {
+  return text_style(true, foreground);
 }
 
-FMT_CONSTEXPR text_style bg(internal::color_type background) FMT_NOEXCEPT {
-  return text_style(/*is_foreground=*/false, background);
+/** Creates a text style from the background color. */
+FMT_CONSTEXPR inline auto bg(detail::color_type background) noexcept
+    -> text_style {
+  return text_style(false, background);
 }
 
-FMT_CONSTEXPR text_style operator|(emphasis lhs, emphasis rhs) FMT_NOEXCEPT {
+FMT_CONSTEXPR inline auto operator|(emphasis lhs, emphasis rhs) noexcept
+    -> text_style {
   return text_style(lhs) | rhs;
 }
 
-namespace internal {
+namespace detail {
 
 template <typename Char> struct ansi_color_escape {
-  FMT_CONSTEXPR ansi_color_escape(internal::color_type text_color,
-                                  const char* esc) FMT_NOEXCEPT {
+  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
+                                  const char* esc) noexcept {
     // If we have a terminal color, we need to output another escape code
     // sequence.
     if (!text_color.is_rgb) {
-      bool is_background = esc == internal::data::background_color;
+      bool is_background = esc == string_view("\x1b[48;2;");
       uint32_t value = text_color.value.term_color;
       // Background ASCII codes are the same as the foreground ones but with
       // 10 more.
       if (is_background) value += 10u;
 
-      std::size_t index = 0;
+      size_t index = 0;
       buffer[index++] = static_cast<Char>('\x1b');
       buffer[index++] = static_cast<Char>('[');
 
@@ -389,17 +366,19 @@ template <typename Char> struct ansi_color_escape {
     to_esc(color.b, buffer + 15, 'm');
     buffer[19] = static_cast<Char>(0);
   }
-  FMT_CONSTEXPR ansi_color_escape(emphasis em) FMT_NOEXCEPT {
-    uint8_t em_codes[4] = {};
-    uint8_t em_bits = static_cast<uint8_t>(em);
-    if (em_bits & static_cast<uint8_t>(emphasis::bold)) em_codes[0] = 1;
-    if (em_bits & static_cast<uint8_t>(emphasis::italic)) em_codes[1] = 3;
-    if (em_bits & static_cast<uint8_t>(emphasis::underline)) em_codes[2] = 4;
-    if (em_bits & static_cast<uint8_t>(emphasis::strikethrough))
-      em_codes[3] = 9;
-
-    std::size_t index = 0;
-    for (int i = 0; i < 4; ++i) {
+  FMT_CONSTEXPR ansi_color_escape(emphasis em) noexcept {
+    uint8_t em_codes[num_emphases] = {};
+    if (has_emphasis(em, emphasis::bold)) em_codes[0] = 1;
+    if (has_emphasis(em, emphasis::faint)) em_codes[1] = 2;
+    if (has_emphasis(em, emphasis::italic)) em_codes[2] = 3;
+    if (has_emphasis(em, emphasis::underline)) em_codes[3] = 4;
+    if (has_emphasis(em, emphasis::blink)) em_codes[4] = 5;
+    if (has_emphasis(em, emphasis::reverse)) em_codes[5] = 7;
+    if (has_emphasis(em, emphasis::conceal)) em_codes[6] = 8;
+    if (has_emphasis(em, emphasis::strikethrough)) em_codes[7] = 9;
+
+    size_t index = 0;
+    for (size_t i = 0; i < num_emphases; ++i) {
       if (!em_codes[i]) continue;
       buffer[index++] = static_cast<Char>('\x1b');
       buffer[index++] = static_cast<Char>('[');
@@ -408,139 +387,143 @@ template <typename Char> struct ansi_color_escape {
     }
     buffer[index++] = static_cast<Char>(0);
   }
-  FMT_CONSTEXPR operator const Char*() const FMT_NOEXCEPT { return buffer; }
+  FMT_CONSTEXPR operator const Char*() const noexcept { return buffer; }
 
-  FMT_CONSTEXPR const Char* begin() const FMT_NOEXCEPT { return buffer; }
-  FMT_CONSTEXPR const Char* end() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR auto begin() const noexcept -> const Char* { return buffer; }
+  FMT_CONSTEXPR_CHAR_TRAITS auto end() const noexcept -> const Char* {
     return buffer + std::char_traits<Char>::length(buffer);
   }
 
  private:
-  Char buffer[7u + 3u * 4u + 1u];
+  static constexpr size_t num_emphases = 8;
+  Char buffer[7u + 3u * num_emphases + 1u];
 
   static FMT_CONSTEXPR void to_esc(uint8_t c, Char* out,
-                                   char delimiter) FMT_NOEXCEPT {
+                                   char delimiter) noexcept {
     out[0] = static_cast<Char>('0' + c / 100);
     out[1] = static_cast<Char>('0' + c / 10 % 10);
     out[2] = static_cast<Char>('0' + c % 10);
     out[3] = static_cast<Char>(delimiter);
   }
+  static FMT_CONSTEXPR auto has_emphasis(emphasis em, emphasis mask) noexcept
+      -> bool {
+    return static_cast<uint8_t>(em) & static_cast<uint8_t>(mask);
+  }
 };
 
 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_foreground_color(
-    internal::color_type foreground) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(foreground, internal::data::foreground_color);
+FMT_CONSTEXPR auto make_foreground_color(detail::color_type foreground) noexcept
+    -> ansi_color_escape<Char> {
+  return ansi_color_escape<Char>(foreground, "\x1b[38;2;");
 }
 
 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_background_color(
-    internal::color_type background) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(background, internal::data::background_color);
+FMT_CONSTEXPR auto make_background_color(detail::color_type background) noexcept
+    -> ansi_color_escape<Char> {
+  return ansi_color_escape<Char>(background, "\x1b[48;2;");
 }
 
 template <typename Char>
-FMT_CONSTEXPR ansi_color_escape<Char> make_emphasis(emphasis em) FMT_NOEXCEPT {
+FMT_CONSTEXPR auto make_emphasis(emphasis em) noexcept
+    -> ansi_color_escape<Char> {
   return ansi_color_escape<Char>(em);
 }
 
-template <typename Char>
-inline void fputs(const Char* chars, FILE* stream) FMT_NOEXCEPT {
-  std::fputs(chars, stream);
-}
-
-template <>
-inline void fputs<wchar_t>(const wchar_t* chars, FILE* stream) FMT_NOEXCEPT {
-  std::fputws(chars, stream);
-}
-
-template <typename Char> inline void reset_color(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::reset_color, stream);
-}
-
-template <> inline void reset_color<wchar_t>(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::wreset_color, stream);
+template <typename Char> inline void reset_color(buffer<Char>& buffer) {
+  auto reset_color = string_view("\x1b[0m");
+  buffer.append(reset_color.begin(), reset_color.end());
 }
 
-template <typename Char>
-inline void reset_color(basic_memory_buffer<Char>& buffer) FMT_NOEXCEPT {
-  const char* begin = data::reset_color;
-  const char* end = begin + sizeof(data::reset_color) - 1;
-  buffer.append(begin, end);
-}
+template <typename T> struct styled_arg : detail::view {
+  const T& value;
+  text_style style;
+  styled_arg(const T& v, text_style s) : value(v), style(s) {}
+};
 
 template <typename Char>
-void vformat_to(basic_memory_buffer<Char>& buf, const text_style& ts,
+void vformat_to(buffer<Char>& buf, const text_style& ts,
                 basic_string_view<Char> format_str,
-                basic_format_args<buffer_context<Char>> args) {
+                basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   bool has_style = false;
   if (ts.has_emphasis()) {
     has_style = true;
-    auto emphasis = internal::make_emphasis<Char>(ts.get_emphasis());
+    auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
     buf.append(emphasis.begin(), emphasis.end());
   }
   if (ts.has_foreground()) {
     has_style = true;
-    auto foreground =
-        internal::make_foreground_color<Char>(ts.get_foreground());
+    auto foreground = detail::make_foreground_color<Char>(ts.get_foreground());
     buf.append(foreground.begin(), foreground.end());
   }
   if (ts.has_background()) {
     has_style = true;
-    auto background =
-        internal::make_background_color<Char>(ts.get_background());
+    auto background = detail::make_background_color<Char>(ts.get_background());
     buf.append(background.begin(), background.end());
   }
-  internal::vformat_to(buf, format_str, args);
-  if (has_style) internal::reset_color<Char>(buf);
+  detail::vformat_to(buf, format_str, args, {});
+  if (has_style) detail::reset_color<Char>(buf);
 }
-}  // namespace internal
 
-template <typename S, typename Char = char_t<S>>
-void vprint(std::FILE* f, const text_style& ts, const S& format,
-            basic_format_args<buffer_context<Char>> args) {
-  basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format), args);
-  buf.push_back(Char(0));
-  internal::fputs(buf.data(), f);
+}  // namespace detail
+
+inline void vprint(std::FILE* f, const text_style& ts, string_view fmt,
+                   format_args args) {
+  // Legacy wide streams are not supported.
+  auto buf = memory_buffer();
+  detail::vformat_to(buf, ts, fmt, args);
+  if (detail::is_utf8()) {
+    detail::print(f, string_view(buf.begin(), buf.size()));
+    return;
+  }
+  buf.push_back('\0');
+  int result = std::fputs(buf.data(), f);
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }
 
 /**
+  \rst
   Formats a string and prints it to the specified file stream using ANSI
   escape sequences to specify text formatting.
-  Example:
+
+  **Example**::
+
     fmt::print(fmt::emphasis::bold | fg(fmt::color::red),
                "Elapsed time: {0:.2f} seconds", 1.23);
+  \endrst
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(std::FILE* f, const text_style& ts, const S& format_str,
            const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = buffer_context<char_t<S>>;
-  format_arg_store<context, Args...> as{args...};
-  vprint(f, ts, format_str, basic_format_args<context>(as));
+  vprint(f, ts, format_str,
+         fmt::make_format_args<buffer_context<char_t<S>>>(args...));
 }
 
 /**
+  \rst
   Formats a string and prints it to stdout using ANSI escape sequences to
   specify text formatting.
-  Example:
+
+  **Example**::
+
     fmt::print(fmt::emphasis::bold | fg(fmt::color::red),
                "Elapsed time: {0:.2f} seconds", 1.23);
+  \endrst
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(const text_style& ts, const S& format_str, const Args&... args) {
   return print(stdout, ts, format_str, args...);
 }
 
 template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
+inline auto vformat(
     const text_style& ts, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
+    basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
   basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format_str), args);
+  detail::vformat_to(buf, ts, detail::to_string_view(format_str), args);
   return fmt::to_string(buf);
 }
 
@@ -557,12 +540,104 @@ inline std::basic_string<Char> vformat(
   \endrst
 */
 template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
-                                      const Args&... args) {
-  return vformat(ts, to_string_view(format_str),
-                 internal::make_args_checked<Args...>(format_str, args...));
+inline auto format(const text_style& ts, const S& format_str,
+                   const Args&... args) -> std::basic_string<Char> {
+  return fmt::vformat(ts, detail::to_string_view(format_str),
+                      fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+/**
+  Formats a string with the given text_style and writes the output to ``out``.
+ */
+template <typename OutputIt, typename Char,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value)>
+auto vformat_to(OutputIt out, const text_style& ts,
+                basic_string_view<Char> format_str,
+                basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> OutputIt {
+  auto&& buf = detail::get_buffer<Char>(out);
+  detail::vformat_to(buf, ts, format_str, args);
+  return detail::get_iterator(buf, out);
+}
+
+/**
+  \rst
+  Formats arguments with the given text_style, writes the result to the output
+  iterator ``out`` and returns the iterator past the end of the output range.
+
+  **Example**::
+
+    std::vector<char> out;
+    fmt::format_to(std::back_inserter(out),
+                   fmt::emphasis::bold | fg(fmt::color::red), "{}", 42);
+  \endrst
+*/
+template <
+    typename OutputIt, typename S, typename... Args,
+    bool enable = detail::is_output_iterator<OutputIt, char_t<S>>::value &&
+                  detail::is_string<S>::value>
+inline auto format_to(OutputIt out, const text_style& ts, const S& format_str,
+                      Args&&... args) ->
+    typename std::enable_if<enable, OutputIt>::type {
+  return vformat_to(out, ts, detail::to_string_view(format_str),
+                    fmt::make_format_args<buffer_context<char_t<S>>>(args...));
+}
+
+template <typename T, typename Char>
+struct formatter<detail::styled_arg<T>, Char> : formatter<T, Char> {
+  template <typename FormatContext>
+  auto format(const detail::styled_arg<T>& arg, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    const auto& ts = arg.style;
+    const auto& value = arg.value;
+    auto out = ctx.out();
+
+    bool has_style = false;
+    if (ts.has_emphasis()) {
+      has_style = true;
+      auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
+      out = std::copy(emphasis.begin(), emphasis.end(), out);
+    }
+    if (ts.has_foreground()) {
+      has_style = true;
+      auto foreground =
+          detail::make_foreground_color<Char>(ts.get_foreground());
+      out = std::copy(foreground.begin(), foreground.end(), out);
+    }
+    if (ts.has_background()) {
+      has_style = true;
+      auto background =
+          detail::make_background_color<Char>(ts.get_background());
+      out = std::copy(background.begin(), background.end(), out);
+    }
+    out = formatter<T, Char>::format(value, ctx);
+    if (has_style) {
+      auto reset_color = string_view("\x1b[0m");
+      out = std::copy(reset_color.begin(), reset_color.end(), out);
+    }
+    return out;
+  }
+};
+
+/**
+  \rst
+  Returns an argument that will be formatted using ANSI escape sequences,
+  to be used in a formatting function.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {0:.2f} seconds",
+               fmt::styled(1.23, fmt::fg(fmt::color::green) |
+                                 fmt::bg(fmt::color::blue)));
+  \endrst
+ */
+template <typename T>
+FMT_CONSTEXPR auto styled(const T& value, text_style ts)
+    -> detail::styled_arg<remove_cvref_t<T>> {
+  return detail::styled_arg<remove_cvref_t<T>>{value, ts};
 }
 
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_COLOR_H_
diff --git a/contrib/fmt/include/fmt/compile.h b/contrib/fmt/include/fmt/compile.h
index e4b12f349e9..3b3f166e0cd 100644
--- a/contrib/fmt/include/fmt/compile.h
+++ b/contrib/fmt/include/fmt/compile.h
@@ -8,344 +8,84 @@
 #ifndef FMT_COMPILE_H_
 #define FMT_COMPILE_H_
 
-#include <vector>
-
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
-
-// Part of a compiled format string. It can be either literal text or a
-// replacement field.
-template <typename Char> struct format_part {
-  enum class kind { arg_index, arg_name, text, replacement };
-
-  struct replacement {
-    arg_ref<Char> arg_id;
-    dynamic_format_specs<Char> specs;
-  };
-
-  kind part_kind;
-  union value {
-    int arg_index;
-    basic_string_view<Char> str;
-    replacement repl;
-
-    FMT_CONSTEXPR value(int index = 0) : arg_index(index) {}
-    FMT_CONSTEXPR value(basic_string_view<Char> s) : str(s) {}
-    FMT_CONSTEXPR value(replacement r) : repl(r) {}
-  } val;
-  // Position past the end of the argument id.
-  const Char* arg_id_end = nullptr;
-
-  FMT_CONSTEXPR format_part(kind k = kind::arg_index, value v = {})
-      : part_kind(k), val(v) {}
-
-  static FMT_CONSTEXPR format_part make_arg_index(int index) {
-    return format_part(kind::arg_index, index);
-  }
-  static FMT_CONSTEXPR format_part make_arg_name(basic_string_view<Char> name) {
-    return format_part(kind::arg_name, name);
-  }
-  static FMT_CONSTEXPR format_part make_text(basic_string_view<Char> text) {
-    return format_part(kind::text, text);
-  }
-  static FMT_CONSTEXPR format_part make_replacement(replacement repl) {
-    return format_part(kind::replacement, repl);
-  }
-};
-
-template <typename Char> struct part_counter {
-  unsigned num_parts = 0;
-
-  FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
-    if (begin != end) ++num_parts;
-  }
-
-  FMT_CONSTEXPR void on_arg_id() { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(int) { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) { ++num_parts; }
-
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
-
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
-                                            const Char* end) {
-    // Find the matching brace.
-    unsigned brace_counter = 0;
-    for (; begin != end; ++begin) {
-      if (*begin == '{') {
-        ++brace_counter;
-      } else if (*begin == '}') {
-        if (brace_counter == 0u) break;
-        --brace_counter;
-      }
-    }
-    return begin;
-  }
-
-  FMT_CONSTEXPR void on_error(const char*) {}
-};
-
-// Counts the number of parts in a format string.
-template <typename Char>
-FMT_CONSTEXPR unsigned count_parts(basic_string_view<Char> format_str) {
-  part_counter<Char> counter;
-  parse_format_string<true>(format_str, counter);
-  return counter.num_parts;
-}
-
-template <typename Char, typename PartHandler>
-class format_string_compiler : public error_handler {
- private:
-  using part = format_part<Char>;
-
-  PartHandler handler_;
-  part part_;
-  basic_string_view<Char> format_str_;
-  basic_format_parse_context<Char> parse_context_;
-
- public:
-  FMT_CONSTEXPR format_string_compiler(basic_string_view<Char> format_str,
-                                       PartHandler handler)
-      : handler_(handler),
-        format_str_(format_str),
-        parse_context_(format_str) {}
-
-  FMT_CONSTEXPR void on_text(const Char* begin, const Char* end) {
-    if (begin != end)
-      handler_(part::make_text({begin, to_unsigned(end - begin)}));
-  }
-
-  FMT_CONSTEXPR void on_arg_id() {
-    part_ = part::make_arg_index(parse_context_.next_arg_id());
-  }
-
-  FMT_CONSTEXPR void on_arg_id(int id) {
-    parse_context_.check_arg_id(id);
-    part_ = part::make_arg_index(id);
-  }
-
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char> id) {
-    part_ = part::make_arg_name(id);
-  }
-
-  FMT_CONSTEXPR void on_replacement_field(const Char* ptr) {
-    part_.arg_id_end = ptr;
-    handler_(part_);
-  }
-
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
-                                            const Char* end) {
-    auto repl = typename part::replacement();
-    dynamic_specs_handler<basic_format_parse_context<Char>> handler(
-        repl.specs, parse_context_);
-    auto it = parse_format_specs(begin, end, handler);
-    if (*it != '}') on_error("missing '}' in format string");
-    repl.arg_id = part_.part_kind == part::kind::arg_index
-                      ? arg_ref<Char>(part_.val.arg_index)
-                      : arg_ref<Char>(part_.val.str);
-    auto part = part::make_replacement(repl);
-    part.arg_id_end = begin;
-    handler_(part);
-    return it;
-  }
-};
-
-// Compiles a format string and invokes handler(part) for each parsed part.
-template <bool IS_CONSTEXPR, typename Char, typename PartHandler>
-FMT_CONSTEXPR void compile_format_string(basic_string_view<Char> format_str,
-                                         PartHandler handler) {
-  parse_format_string<IS_CONSTEXPR>(
-      format_str,
-      format_string_compiler<Char, PartHandler>(format_str, handler));
-}
-
-template <typename Range, typename Context, typename Id>
-void format_arg(
-    basic_format_parse_context<typename Range::value_type>& parse_ctx,
-    Context& ctx, Id arg_id) {
-  ctx.advance_to(
-      visit_format_arg(arg_formatter<Range>(ctx, &parse_ctx), ctx.arg(arg_id)));
-}
-
-// vformat_to is defined in a subnamespace to prevent ADL.
-namespace cf {
-template <typename Context, typename Range, typename CompiledFormat>
-auto vformat_to(Range out, CompiledFormat& cf, basic_format_args<Context> args)
-    -> typename Context::iterator {
-  using char_type = typename Context::char_type;
-  basic_format_parse_context<char_type> parse_ctx(
-      to_string_view(cf.format_str_));
-  Context ctx(out.begin(), args);
-
-  const auto& parts = cf.parts();
-  for (auto part_it = std::begin(parts); part_it != std::end(parts);
-       ++part_it) {
-    const auto& part = *part_it;
-    const auto& value = part.val;
-
-    using format_part_t = format_part<char_type>;
-    switch (part.part_kind) {
-    case format_part_t::kind::text: {
-      const auto text = value.str;
-      auto output = ctx.out();
-      auto&& it = reserve(output, text.size());
-      it = std::copy_n(text.begin(), text.size(), it);
-      ctx.advance_to(output);
-      break;
-    }
-
-    case format_part_t::kind::arg_index:
-      advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.arg_index);
-      break;
-
-    case format_part_t::kind::arg_name:
-      advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.str);
-      break;
-
-    case format_part_t::kind::replacement: {
-      const auto& arg_id_value = value.repl.arg_id.val;
-      const auto arg = value.repl.arg_id.kind == arg_id_kind::index
-                           ? ctx.arg(arg_id_value.index)
-                           : ctx.arg(arg_id_value.name);
-
-      auto specs = value.repl.specs;
-
-      handle_dynamic_spec<width_checker>(specs.width, specs.width_ref, ctx);
-      handle_dynamic_spec<precision_checker>(specs.precision,
-                                             specs.precision_ref, ctx);
-
-      error_handler h;
-      numeric_specs_checker<error_handler> checker(h, arg.type());
-      if (specs.align == align::numeric) checker.require_numeric_argument();
-      if (specs.sign != sign::none) checker.check_sign();
-      if (specs.alt) checker.require_numeric_argument();
-      if (specs.precision >= 0) checker.check_precision();
-
-      advance_to(parse_ctx, part.arg_id_end);
-      ctx.advance_to(
-          visit_format_arg(arg_formatter<Range>(ctx, nullptr, &specs), arg));
-      break;
-    }
-    }
-  }
-  return ctx.out();
-}
-}  // namespace cf
-
-struct basic_compiled_format {};
+namespace detail {
 
-template <typename S, typename = void>
-struct compiled_format_base : basic_compiled_format {
-  using char_type = char_t<S>;
-  using parts_container = std::vector<internal::format_part<char_type>>;
-
-  parts_container compiled_parts;
-
-  explicit compiled_format_base(basic_string_view<char_type> format_str) {
-    compile_format_string<false>(format_str,
-                                 [this](const format_part<char_type>& part) {
-                                   compiled_parts.push_back(part);
-                                 });
-  }
-
-  const parts_container& parts() const { return compiled_parts; }
-};
-
-template <typename Char, unsigned N> struct format_part_array {
-  format_part<Char> data[N] = {};
-  FMT_CONSTEXPR format_part_array() = default;
-};
-
-template <typename Char, unsigned N>
-FMT_CONSTEXPR format_part_array<Char, N> compile_to_parts(
-    basic_string_view<Char> format_str) {
-  format_part_array<Char, N> parts;
-  unsigned counter = 0;
-  // This is not a lambda for compatibility with older compilers.
-  struct {
-    format_part<Char>* parts;
-    unsigned* counter;
-    FMT_CONSTEXPR void operator()(const format_part<Char>& part) {
-      parts[(*counter)++] = part;
-    }
-  } collector{parts.data, &counter};
-  compile_format_string<true>(format_str, collector);
-  if (counter < N) {
-    parts.data[counter] =
-        format_part<Char>::make_text(basic_string_view<Char>());
-  }
-  return parts;
+template <typename Char, typename InputIt>
+FMT_CONSTEXPR inline auto copy_str(InputIt begin, InputIt end,
+                                   counting_iterator it) -> counting_iterator {
+  return it + (end - begin);
 }
 
-template <typename T> constexpr const T& constexpr_max(const T& a, const T& b) {
-  return (a < b) ? b : a;
-}
+// A compile-time string which is compiled into fast formatting code.
+class compiled_string {};
 
 template <typename S>
-struct compiled_format_base<S, enable_if_t<is_compile_string<S>::value>>
-    : basic_compiled_format {
-  using char_type = char_t<S>;
-
-  FMT_CONSTEXPR explicit compiled_format_base(basic_string_view<char_type>) {}
-
-// Workaround for old compilers. Format string compilation will not be
-// performed there anyway.
-#if FMT_USE_CONSTEXPR
-  static FMT_CONSTEXPR_DECL const unsigned num_format_parts =
-      constexpr_max(count_parts(to_string_view(S())), 1u);
+struct is_compiled_string : std::is_base_of<compiled_string, S> {};
+
+/**
+  \rst
+  Converts a string literal *s* into a format string that will be parsed at
+  compile time and converted into efficient formatting code. Requires C++17
+  ``constexpr if`` compiler support.
+
+  **Example**::
+
+    // Converts 42 into std::string using the most efficient method and no
+    // runtime format string processing.
+    std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+  \endrst
+ */
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
+#  define FMT_COMPILE(s) \
+    FMT_STRING_IMPL(s, fmt::detail::compiled_string, explicit)
 #else
-  static const unsigned num_format_parts = 1;
+#  define FMT_COMPILE(s) FMT_STRING(s)
 #endif
 
-  using parts_container = format_part<char_type>[num_format_parts];
-
-  const parts_container& parts() const {
-    static FMT_CONSTEXPR_DECL const auto compiled_parts =
-        compile_to_parts<char_type, num_format_parts>(
-            internal::to_string_view(S()));
-    return compiled_parts.data;
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <typename Char, size_t N,
+          fmt::detail_exported::fixed_string<Char, N> Str>
+struct udl_compiled_string : compiled_string {
+  using char_type = Char;
+  explicit constexpr operator basic_string_view<char_type>() const {
+    return {Str.data, N - 1};
   }
 };
+#endif
 
-template <typename S, typename... Args>
-class compiled_format : private compiled_format_base<S> {
- public:
-  using typename compiled_format_base<S>::char_type;
-
- private:
-  basic_string_view<char_type> format_str_;
-
-  template <typename Context, typename Range, typename CompiledFormat>
-  friend auto cf::vformat_to(Range out, CompiledFormat& cf,
-                             basic_format_args<Context> args) ->
-      typename Context::iterator;
-
- public:
-  compiled_format() = delete;
-  explicit constexpr compiled_format(basic_string_view<char_type> format_str)
-      : compiled_format_base<S>(format_str), format_str_(format_str) {}
-};
+template <typename T, typename... Tail>
+auto first(const T& value, const Tail&...) -> const T& {
+  return value;
+}
 
-#ifdef __cpp_if_constexpr
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 template <typename... Args> struct type_list {};
 
 // Returns a reference to the argument at index N from [first, rest...].
 template <int N, typename T, typename... Args>
-constexpr const auto& get(const T& first, const Args&... rest) {
+constexpr const auto& get([[maybe_unused]] const T& first,
+                          [[maybe_unused]] const Args&... rest) {
   static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
   if constexpr (N == 0)
     return first;
   else
-    return get<N - 1>(rest...);
+    return detail::get<N - 1>(rest...);
+}
+
+template <typename Char, typename... Args>
+constexpr int get_arg_index_by_name(basic_string_view<Char> name,
+                                    type_list<Args...>) {
+  return get_arg_index_by_name<Args...>(name);
 }
 
 template <int N, typename> struct get_type_impl;
 
 template <int N, typename... Args> struct get_type_impl<N, type_list<Args...>> {
-  using type = remove_cvref_t<decltype(get<N>(std::declval<Args>()...))>;
+  using type =
+      remove_cvref_t<decltype(detail::get<N>(std::declval<Args>()...))>;
 };
 
 template <int N, typename T>
@@ -358,9 +98,8 @@ template <typename Char> struct text {
   using char_type = Char;
 
   template <typename OutputIt, typename... Args>
-  OutputIt format(OutputIt out, const Args&...) const {
-    // TODO: reserve
-    return copy_str<Char>(data.begin(), data.end(), out);
+  constexpr OutputIt format(OutputIt out, const Args&...) const {
+    return write<Char>(out, data);
   }
 };
 
@@ -373,55 +112,106 @@ constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
   return {{&s[pos], size}};
 }
 
-template <typename Char, typename OutputIt, typename T,
-          std::enable_if_t<std::is_integral_v<T>, int> = 0>
-OutputIt format_default(OutputIt out, T value) {
-  // TODO: reserve
-  format_int fi(value);
-  return std::copy(fi.data(), fi.data() + fi.size(), out);
-}
+template <typename Char> struct code_unit {
+  Char value;
+  using char_type = Char;
 
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, double value) {
-  writer w(out);
-  w.write(value);
-  return w.out();
-}
+  template <typename OutputIt, typename... Args>
+  constexpr OutputIt format(OutputIt out, const Args&...) const {
+    *out++ = value;
+    return out;
+  }
+};
 
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, Char value) {
-  *out++ = value;
-  return out;
+// This ensures that the argument type is convertible to `const T&`.
+template <typename T, int N, typename... Args>
+constexpr const T& get_arg_checked(const Args&... args) {
+  const auto& arg = detail::get<N>(args...);
+  if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
+    return arg.value;
+  } else {
+    return arg;
+  }
 }
 
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, const Char* value) {
-  auto length = std::char_traits<Char>::length(value);
-  return copy_str<Char>(value, value + length, out);
-}
+template <typename Char>
+struct is_compiled_format<code_unit<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N.
 template <typename Char, typename T, int N> struct field {
   using char_type = Char;
 
   template <typename OutputIt, typename... Args>
-  OutputIt format(OutputIt out, const Args&... args) const {
-    // This ensures that the argument type is convertile to `const T&`.
-    const T& arg = get<N>(args...);
-    return format_default<Char>(out, arg);
+  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+    const T& arg = get_arg_checked<T, N>(args...);
+    if constexpr (std::is_convertible_v<T, basic_string_view<Char>>) {
+      auto s = basic_string_view<Char>(arg);
+      return copy_str<Char>(s.begin(), s.end(), out);
+    }
+    return write<Char>(out, arg);
   }
 };
 
 template <typename Char, typename T, int N>
 struct is_compiled_format<field<Char, T, N>> : std::true_type {};
 
+// A replacement field that refers to argument with name.
+template <typename Char> struct runtime_named_field {
+  using char_type = Char;
+  basic_string_view<Char> name;
+
+  template <typename OutputIt, typename T>
+  constexpr static bool try_format_argument(
+      OutputIt& out,
+      // [[maybe_unused]] due to unused-but-set-parameter warning in GCC 7,8,9
+      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) {
+    if constexpr (is_named_arg<typename std::remove_cv<T>::type>::value) {
+      if (arg_name == arg.name) {
+        out = write<Char>(out, arg.value);
+        return true;
+      }
+    }
+    return false;
+  }
+
+  template <typename OutputIt, typename... Args>
+  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+    bool found = (try_format_argument(out, name, args) || ...);
+    if (!found) {
+      FMT_THROW(format_error("argument with specified name is not found"));
+    }
+    return out;
+  }
+};
+
+template <typename Char>
+struct is_compiled_format<runtime_named_field<Char>> : std::true_type {};
+
+// A replacement field that refers to argument N and has format specifiers.
+template <typename Char, typename T, int N> struct spec_field {
+  using char_type = Char;
+  formatter<T, Char> fmt;
+
+  template <typename OutputIt, typename... Args>
+  constexpr FMT_INLINE OutputIt format(OutputIt out,
+                                       const Args&... args) const {
+    const auto& vargs =
+        fmt::make_format_args<basic_format_context<OutputIt, Char>>(args...);
+    basic_format_context<OutputIt, Char> ctx(out, vargs);
+    return fmt.format(get_arg_checked<T, N>(args...), ctx);
+  }
+};
+
+template <typename Char, typename T, int N>
+struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
+
 template <typename L, typename R> struct concat {
   L lhs;
   R rhs;
   using char_type = typename L::char_type;
 
   template <typename OutputIt, typename... Args>
-  OutputIt format(OutputIt out, const Args&... args) const {
+  constexpr OutputIt format(OutputIt out, const Args&... args) const {
     out = lhs.format(out, args...);
     return rhs.format(out, args...);
   }
@@ -450,7 +240,8 @@ constexpr auto compile_format_string(S format_str);
 
 template <typename Args, size_t POS, int ID, typename T, typename S>
 constexpr auto parse_tail(T head, S format_str) {
-  if constexpr (POS != to_string_view(format_str).size()) {
+  if constexpr (POS !=
+                basic_string_view<typename S::char_type>(format_str).size()) {
     constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
     if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
                                unknown_format>())
@@ -462,134 +253,283 @@ constexpr auto parse_tail(T head, S format_str) {
   }
 }
 
+template <typename T, typename Char> struct parse_specs_result {
+  formatter<T, Char> fmt;
+  size_t end;
+  int next_arg_id;
+};
+
+enum { manual_indexing_id = -1 };
+
+template <typename T, typename Char>
+constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
+                                                  size_t pos, int next_arg_id) {
+  str.remove_prefix(pos);
+  auto ctx =
+      compile_parse_context<Char>(str, max_value<int>(), nullptr, next_arg_id);
+  auto f = formatter<T, Char>();
+  auto end = f.parse(ctx);
+  return {f, pos + fmt::detail::to_unsigned(end - str.data()),
+          next_arg_id == 0 ? manual_indexing_id : ctx.next_arg_id()};
+}
+
+template <typename Char> struct arg_id_handler {
+  arg_ref<Char> arg_id;
+
+  constexpr int on_auto() {
+    FMT_ASSERT(false, "handler cannot be used with automatic indexing");
+    return 0;
+  }
+  constexpr int on_index(int id) {
+    arg_id = arg_ref<Char>(id);
+    return 0;
+  }
+  constexpr int on_name(basic_string_view<Char> id) {
+    arg_id = arg_ref<Char>(id);
+    return 0;
+  }
+};
+
+template <typename Char> struct parse_arg_id_result {
+  arg_ref<Char> arg_id;
+  const Char* arg_id_end;
+};
+
+template <int ID, typename Char>
+constexpr auto parse_arg_id(const Char* begin, const Char* end) {
+  auto handler = arg_id_handler<Char>{arg_ref<Char>{}};
+  auto arg_id_end = parse_arg_id(begin, end, handler);
+  return parse_arg_id_result<Char>{handler.arg_id, arg_id_end};
+}
+
+template <typename T, typename Enable = void> struct field_type {
+  using type = remove_cvref_t<T>;
+};
+
+template <typename T>
+struct field_type<T, enable_if_t<detail::is_named_arg<T>::value>> {
+  using type = remove_cvref_t<decltype(T::value)>;
+};
+
+template <typename T, typename Args, size_t END_POS, int ARG_INDEX, int NEXT_ID,
+          typename S>
+constexpr auto parse_replacement_field_then_tail(S format_str) {
+  using char_type = typename S::char_type;
+  constexpr auto str = basic_string_view<char_type>(format_str);
+  constexpr char_type c = END_POS != str.size() ? str[END_POS] : char_type();
+  if constexpr (c == '}') {
+    return parse_tail<Args, END_POS + 1, NEXT_ID>(
+        field<char_type, typename field_type<T>::type, ARG_INDEX>(),
+        format_str);
+  } else if constexpr (c != ':') {
+    FMT_THROW(format_error("expected ':'"));
+  } else {
+    constexpr auto result = parse_specs<typename field_type<T>::type>(
+        str, END_POS + 1, NEXT_ID == manual_indexing_id ? 0 : NEXT_ID);
+    if constexpr (result.end >= str.size() || str[result.end] != '}') {
+      FMT_THROW(format_error("expected '}'"));
+      return 0;
+    } else {
+      return parse_tail<Args, result.end + 1, result.next_arg_id>(
+          spec_field<char_type, typename field_type<T>::type, ARG_INDEX>{
+              result.fmt},
+          format_str);
+    }
+  }
+}
+
 // Compiles a non-empty format string and returns the compiled representation
 // or unknown_format() on unrecognized input.
 template <typename Args, size_t POS, int ID, typename S>
 constexpr auto compile_format_string(S format_str) {
   using char_type = typename S::char_type;
-  constexpr basic_string_view<char_type> str = format_str;
+  constexpr auto str = basic_string_view<char_type>(format_str);
   if constexpr (str[POS] == '{') {
-    if (POS + 1 == str.size())
-      throw format_error("unmatched '{' in format string");
+    if constexpr (POS + 1 == str.size())
+      FMT_THROW(format_error("unmatched '{' in format string"));
     if constexpr (str[POS + 1] == '{') {
       return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
-    } else if constexpr (str[POS + 1] == '}') {
-      using type = get_type<ID, Args>;
-      if constexpr (std::is_same<type, int>::value) {
-        return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
-                                                 format_str);
-      } else {
-        return unknown_format();
-      }
+    } else if constexpr (str[POS + 1] == '}' || str[POS + 1] == ':') {
+      static_assert(ID != manual_indexing_id,
+                    "cannot switch from manual to automatic argument indexing");
+      constexpr auto next_id =
+          ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
+      return parse_replacement_field_then_tail<get_type<ID, Args>, Args,
+                                               POS + 1, ID, next_id>(
+          format_str);
     } else {
-      return unknown_format();
+      constexpr auto arg_id_result =
+          parse_arg_id<ID>(str.data() + POS + 1, str.data() + str.size());
+      constexpr auto arg_id_end_pos = arg_id_result.arg_id_end - str.data();
+      constexpr char_type c =
+          arg_id_end_pos != str.size() ? str[arg_id_end_pos] : char_type();
+      static_assert(c == '}' || c == ':', "missing '}' in format string");
+      if constexpr (arg_id_result.arg_id.kind == arg_id_kind::index) {
+        static_assert(
+            ID == manual_indexing_id || ID == 0,
+            "cannot switch from automatic to manual argument indexing");
+        constexpr auto arg_index = arg_id_result.arg_id.val.index;
+        return parse_replacement_field_then_tail<get_type<arg_index, Args>,
+                                                 Args, arg_id_end_pos,
+                                                 arg_index, manual_indexing_id>(
+            format_str);
+      } else if constexpr (arg_id_result.arg_id.kind == arg_id_kind::name) {
+        constexpr auto arg_index =
+            get_arg_index_by_name(arg_id_result.arg_id.val.name, Args{});
+        if constexpr (arg_index >= 0) {
+          constexpr auto next_id =
+              ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
+          return parse_replacement_field_then_tail<
+              decltype(get_type<arg_index, Args>::value), Args, arg_id_end_pos,
+              arg_index, next_id>(format_str);
+        } else if constexpr (c == '}') {
+          return parse_tail<Args, arg_id_end_pos + 1, ID>(
+              runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
+              format_str);
+        } else if constexpr (c == ':') {
+          return unknown_format();  // no type info for specs parsing
+        }
+      }
     }
   } else if constexpr (str[POS] == '}') {
-    if (POS + 1 == str.size())
-      throw format_error("unmatched '}' in format string");
+    if constexpr (POS + 1 == str.size())
+      FMT_THROW(format_error("unmatched '}' in format string"));
     return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
   } else {
     constexpr auto end = parse_text(str, POS + 1);
-    return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
-                                     format_str);
+    if constexpr (end - POS > 1) {
+      return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
+                                       format_str);
+    } else {
+      return parse_tail<Args, end, ID>(code_unit<char_type>{str[POS]},
+                                       format_str);
+    }
   }
 }
-#endif  // __cpp_if_constexpr
-}  // namespace internal
 
-#if FMT_USE_CONSTEXPR
-#  ifdef __cpp_if_constexpr
 template <typename... Args, typename S,
-          FMT_ENABLE_IF(is_compile_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
 constexpr auto compile(S format_str) {
-  constexpr basic_string_view<typename S::char_type> str = format_str;
+  constexpr auto str = basic_string_view<typename S::char_type>(format_str);
   if constexpr (str.size() == 0) {
-    return internal::make_text(str, 0, 0);
+    return detail::make_text(str, 0, 0);
   } else {
     constexpr auto result =
-        internal::compile_format_string<internal::type_list<Args...>, 0, 0>(
+        detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
             format_str);
-    if constexpr (std::is_same<remove_cvref_t<decltype(result)>,
-                               internal::unknown_format>()) {
-      return internal::compiled_format<S, Args...>(to_string_view(format_str));
-    } else {
-      return result;
-    }
+    return result;
   }
 }
+#endif  // defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
+}  // namespace detail
+
+FMT_BEGIN_EXPORT
+
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 
 template <typename CompiledFormat, typename... Args,
           typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(internal::is_compiled_format<CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
-  basic_memory_buffer<Char> buffer;
-  cf.format(std::back_inserter(buffer), args...);
-  return to_string(buffer);
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
+                                          const Args&... args) {
+  auto s = std::basic_string<Char>();
+  cf.format(std::back_inserter(s), args...);
+  return s;
 }
 
 template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(internal::is_compiled_format<CompiledFormat>::value)>
-OutputIt format_to(OutputIt out, const CompiledFormat& cf,
-                   const Args&... args) {
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+constexpr FMT_INLINE OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+                                        const Args&... args) {
   return cf.format(out, args...);
 }
-#  else
-template <typename... Args, typename S,
-          FMT_ENABLE_IF(is_compile_string<S>::value)>
-constexpr auto compile(S format_str) -> internal::compiled_format<S, Args...> {
-  return internal::compiled_format<S, Args...>(to_string_view(format_str));
+
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
+                                                           Args&&... args) {
+  if constexpr (std::is_same<typename S::char_type, char>::value) {
+    constexpr auto str = basic_string_view<typename S::char_type>(S());
+    if constexpr (str.size() == 2 && str[0] == '{' && str[1] == '}') {
+      const auto& first = detail::first(args...);
+      if constexpr (detail::is_named_arg<
+                        remove_cvref_t<decltype(first)>>::value) {
+        return fmt::to_string(first.value);
+      } else {
+        return fmt::to_string(first);
+      }
+    }
+  }
+  constexpr auto compiled = detail::compile<Args...>(S());
+  if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
+                             detail::unknown_format>()) {
+    return fmt::format(
+        static_cast<basic_string_view<typename S::char_type>>(S()),
+        std::forward<Args>(args)...);
+  } else {
+    return fmt::format(compiled, std::forward<Args>(args)...);
+  }
+}
+
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {
+  constexpr auto compiled = detail::compile<Args...>(S());
+  if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
+                             detail::unknown_format>()) {
+    return fmt::format_to(
+        out, static_cast<basic_string_view<typename S::char_type>>(S()),
+        std::forward<Args>(args)...);
+  } else {
+    return fmt::format_to(out, compiled, std::forward<Args>(args)...);
+  }
 }
-#  endif  // __cpp_if_constexpr
-#endif    // FMT_USE_CONSTEXPR
-
-// Compiles the format string which must be a string literal.
-template <typename... Args, typename Char, size_t N>
-auto compile(const Char (&format_str)[N])
-    -> internal::compiled_format<const Char*, Args...> {
-  return internal::compiled_format<const Char*, Args...>(
-      basic_string_view<Char>(format_str, N - 1));
+#endif
+
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+auto format_to_n(OutputIt out, size_t n, const S& format_str, Args&&... args)
+    -> format_to_n_result<OutputIt> {
+  using traits = detail::fixed_buffer_traits;
+  auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
+  fmt::format_to(std::back_inserter(buf), format_str,
+                 std::forward<Args>(args)...);
+  return {buf.out(), buf.count()};
 }
 
-template <typename CompiledFormat, typename... Args,
-          typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
-                                        CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
-  basic_memory_buffer<Char> buffer;
-  using range = buffer_range<Char>;
-  using context = buffer_context<Char>;
-  internal::cf::vformat_to<context>(range(buffer), cf,
-                                    make_format_args<context>(args...));
-  return to_string(buffer);
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_CONSTEXPR20 auto formatted_size(const S& format_str, const Args&... args)
+    -> size_t {
+  return fmt::format_to(detail::counting_iterator(), format_str, args...)
+      .count();
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
-                                        CompiledFormat>::value)>
-OutputIt format_to(OutputIt out, const CompiledFormat& cf,
-                   const Args&... args) {
-  using char_type = typename CompiledFormat::char_type;
-  using range = internal::output_range<OutputIt, char_type>;
-  using context = format_context_t<OutputIt, char_type>;
-  return internal::cf::vformat_to<context>(range(out), cf,
-                                           make_format_args<context>(args...));
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+void print(std::FILE* f, const S& format_str, const Args&... args) {
+  memory_buffer buffer;
+  fmt::format_to(std::back_inserter(buffer), format_str, args...);
+  detail::print(f, {buffer.data(), buffer.size()});
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
-format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
-                                         const CompiledFormat& cf,
-                                         const Args&... args) {
-  auto it =
-      format_to(internal::truncating_iterator<OutputIt>(out, n), cf, args...);
-  return {it.base(), it.count()};
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+void print(const S& format_str, const Args&... args) {
+  print(stdout, format_str, args...);
 }
 
-template <typename CompiledFormat, typename... Args>
-std::size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
-  return format_to(internal::counting_iterator(), cf, args...).count();
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+inline namespace literals {
+template <detail_exported::fixed_string Str> constexpr auto operator""_cf() {
+  using char_t = remove_cvref_t<decltype(Str.data[0])>;
+  return detail::udl_compiled_string<char_t, sizeof(Str.data) / sizeof(char_t),
+                                     Str>();
 }
+}  // namespace literals
+#endif
 
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_COMPILE_H_
diff --git a/contrib/fmt/include/fmt/core.h b/contrib/fmt/include/fmt/core.h
index 0e0824f5fe7..b51c1406a99 100644
--- a/contrib/fmt/include/fmt/core.h
+++ b/contrib/fmt/include/fmt/core.h
@@ -1,4 +1,4 @@
-// Formatting library for C++ - the core API
+// Formatting library for C++ - the core API for char/UTF-8
 //
 // Copyright (c) 2012 - present, Victor Zverovich
 // All rights reserved.
@@ -8,250 +8,268 @@
 #ifndef FMT_CORE_H_
 #define FMT_CORE_H_
 
-#include <cstdio>  // std::FILE
-#include <cstring>
-#include <functional>
+#include <cstddef>  // std::byte
+#include <cstdio>   // std::FILE
+#include <cstring>  // std::strlen
 #include <iterator>
-#include <memory>
+#include <limits>
+#include <memory>  // std::addressof
 #include <string>
 #include <type_traits>
-#include <vector>
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 60201
+#define FMT_VERSION 100201
 
-#ifdef __has_feature
-#  define FMT_HAS_FEATURE(x) __has_feature(x)
+#if defined(__clang__) && !defined(__ibmxl__)
+#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
 #else
-#  define FMT_HAS_FEATURE(x) 0
+#  define FMT_CLANG_VERSION 0
 #endif
 
-#if defined(__has_include) && !defined(__INTELLISENSE__) && \
-    !(defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1600)
-#  define FMT_HAS_INCLUDE(x) __has_include(x)
+#if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER) && \
+    !defined(__NVCOMPILER)
+#  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
 #else
-#  define FMT_HAS_INCLUDE(x) 0
+#  define FMT_GCC_VERSION 0
 #endif
 
-#ifdef __has_cpp_attribute
-#  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
-#else
-#  define FMT_HAS_CPP_ATTRIBUTE(x) 0
+#ifndef FMT_GCC_PRAGMA
+// Workaround _Pragma bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59884.
+#  if FMT_GCC_VERSION >= 504
+#    define FMT_GCC_PRAGMA(arg) _Pragma(arg)
+#  else
+#    define FMT_GCC_PRAGMA(arg)
+#  endif
 #endif
 
-#define FMT_HAS_CPP14_ATTRIBUTE(attribute) \
-  (__cplusplus >= 201402L && FMT_HAS_CPP_ATTRIBUTE(attribute))
-
-#define FMT_HAS_CPP17_ATTRIBUTE(attribute) \
-  (__cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+#ifdef __ICL
+#  define FMT_ICC_VERSION __ICL
+#elif defined(__INTEL_COMPILER)
+#  define FMT_ICC_VERSION __INTEL_COMPILER
+#else
+#  define FMT_ICC_VERSION 0
+#endif
 
-#ifdef __clang__
-#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
+#ifdef _MSC_VER
+#  define FMT_MSC_VERSION _MSC_VER
+#  define FMT_MSC_WARNING(...) __pragma(warning(__VA_ARGS__))
 #else
-#  define FMT_CLANG_VERSION 0
+#  define FMT_MSC_VERSION 0
+#  define FMT_MSC_WARNING(...)
 #endif
 
-#if defined(__GNUC__) && !defined(__clang__)
-#  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
+#ifdef _MSVC_LANG
+#  define FMT_CPLUSPLUS _MSVC_LANG
 #else
-#  define FMT_GCC_VERSION 0
+#  define FMT_CPLUSPLUS __cplusplus
 #endif
 
-#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
-#  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
+#ifdef __has_feature
+#  define FMT_HAS_FEATURE(x) __has_feature(x)
 #else
-#  define FMT_HAS_GXX_CXX11 0
+#  define FMT_HAS_FEATURE(x) 0
 #endif
 
-#ifdef __NVCC__
-#  define FMT_NVCC __NVCC__
+#if defined(__has_include) || FMT_ICC_VERSION >= 1600 || FMT_MSC_VERSION > 1900
+#  define FMT_HAS_INCLUDE(x) __has_include(x)
 #else
-#  define FMT_NVCC 0
+#  define FMT_HAS_INCLUDE(x) 0
 #endif
 
-#ifdef _MSC_VER
-#  define FMT_MSC_VER _MSC_VER
+#ifdef __has_cpp_attribute
+#  define FMT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
 #else
-#  define FMT_MSC_VER 0
+#  define FMT_HAS_CPP_ATTRIBUTE(x) 0
 #endif
 
+#define FMT_HAS_CPP14_ATTRIBUTE(attribute) \
+  (FMT_CPLUSPLUS >= 201402L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
+#define FMT_HAS_CPP17_ATTRIBUTE(attribute) \
+  (FMT_CPLUSPLUS >= 201703L && FMT_HAS_CPP_ATTRIBUTE(attribute))
+
 // Check if relaxed C++14 constexpr is supported.
 // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
 #ifndef FMT_USE_CONSTEXPR
-#  define FMT_USE_CONSTEXPR                                           \
-    (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
-     (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
-        !FMT_NVCC
+#  if (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VERSION >= 1912 || \
+       (FMT_GCC_VERSION >= 600 && FMT_CPLUSPLUS >= 201402L)) &&             \
+      !FMT_ICC_VERSION && (!defined(__NVCC__) || FMT_CPLUSPLUS >= 202002L)
+#    define FMT_USE_CONSTEXPR 1
+#  else
+#    define FMT_USE_CONSTEXPR 0
+#  endif
 #endif
 #if FMT_USE_CONSTEXPR
 #  define FMT_CONSTEXPR constexpr
-#  define FMT_CONSTEXPR_DECL constexpr
 #else
-#  define FMT_CONSTEXPR inline
-#  define FMT_CONSTEXPR_DECL
+#  define FMT_CONSTEXPR
 #endif
 
-#ifndef FMT_OVERRIDE
-#  if FMT_HAS_FEATURE(cxx_override) || \
-      (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
-#    define FMT_OVERRIDE override
-#  else
-#    define FMT_OVERRIDE
+#if (FMT_CPLUSPLUS >= 202002L ||                                \
+     (FMT_CPLUSPLUS >= 201709L && FMT_GCC_VERSION >= 1002)) &&  \
+    ((!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 10) &&  \
+     (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 10000) && \
+     (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1928)) &&          \
+    defined(__cpp_lib_is_constant_evaluated)
+#  define FMT_CONSTEXPR20 constexpr
+#else
+#  define FMT_CONSTEXPR20
+#endif
+
+// Check if constexpr std::char_traits<>::{compare,length} are supported.
+#if defined(__GLIBCXX__)
+#  if FMT_CPLUSPLUS >= 201703L && defined(_GLIBCXX_RELEASE) && \
+      _GLIBCXX_RELEASE >= 7  // GCC 7+ libstdc++ has _GLIBCXX_RELEASE.
+#    define FMT_CONSTEXPR_CHAR_TRAITS constexpr
 #  endif
+#elif defined(_LIBCPP_VERSION) && FMT_CPLUSPLUS >= 201703L && \
+    _LIBCPP_VERSION >= 4000
+#  define FMT_CONSTEXPR_CHAR_TRAITS constexpr
+#elif FMT_MSC_VERSION >= 1914 && FMT_CPLUSPLUS >= 201703L
+#  define FMT_CONSTEXPR_CHAR_TRAITS constexpr
+#endif
+#ifndef FMT_CONSTEXPR_CHAR_TRAITS
+#  define FMT_CONSTEXPR_CHAR_TRAITS
 #endif
 
 // Check if exceptions are disabled.
 #ifndef FMT_EXCEPTIONS
 #  if (defined(__GNUC__) && !defined(__EXCEPTIONS)) || \
-      FMT_MSC_VER && !_HAS_EXCEPTIONS
+      (FMT_MSC_VERSION && !_HAS_EXCEPTIONS)
 #    define FMT_EXCEPTIONS 0
 #  else
 #    define FMT_EXCEPTIONS 1
 #  endif
 #endif
 
-// Define FMT_USE_NOEXCEPT to make fmt use noexcept (C++11 feature).
-#ifndef FMT_USE_NOEXCEPT
-#  define FMT_USE_NOEXCEPT 0
-#endif
-
-#if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
-    (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || FMT_MSC_VER >= 1900
-#  define FMT_DETECTED_NOEXCEPT noexcept
-#  define FMT_HAS_CXX11_NOEXCEPT 1
-#else
-#  define FMT_DETECTED_NOEXCEPT throw()
-#  define FMT_HAS_CXX11_NOEXCEPT 0
-#endif
-
-#ifndef FMT_NOEXCEPT
-#  if FMT_EXCEPTIONS || FMT_HAS_CXX11_NOEXCEPT
-#    define FMT_NOEXCEPT FMT_DETECTED_NOEXCEPT
-#  else
-#    define FMT_NOEXCEPT
-#  endif
-#endif
-
-// [[noreturn]] is disabled on MSVC and NVCC because of bogus unreachable code
-// warnings.
-#if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VER && \
-    !FMT_NVCC
+// Disable [[noreturn]] on MSVC/NVCC because of bogus unreachable code warnings.
+#if FMT_EXCEPTIONS && FMT_HAS_CPP_ATTRIBUTE(noreturn) && !FMT_MSC_VERSION && \
+    !defined(__NVCC__)
 #  define FMT_NORETURN [[noreturn]]
 #else
 #  define FMT_NORETURN
 #endif
 
-#ifndef FMT_MAYBE_UNUSED
-#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
-#    define FMT_MAYBE_UNUSED [[maybe_unused]]
+#ifndef FMT_NODISCARD
+#  if FMT_HAS_CPP17_ATTRIBUTE(nodiscard)
+#    define FMT_NODISCARD [[nodiscard]]
 #  else
-#    define FMT_MAYBE_UNUSED
+#    define FMT_NODISCARD
 #  endif
 #endif
 
-#ifndef FMT_DEPRECATED
-#  if FMT_HAS_CPP14_ATTRIBUTE(deprecated) || FMT_MSC_VER >= 1900
-#    define FMT_DEPRECATED [[deprecated]]
+#ifndef FMT_INLINE
+#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#    define FMT_INLINE inline __attribute__((always_inline))
 #  else
-#    if defined(__GNUC__) || defined(__clang__)
-#      define FMT_DEPRECATED __attribute__((deprecated))
-#    elif FMT_MSC_VER
-#      define FMT_DEPRECATED __declspec(deprecated)
-#    else
-#      define FMT_DEPRECATED /* deprecated */
-#    endif
+#    define FMT_INLINE inline
 #  endif
 #endif
 
-// Workaround broken [[deprecated]] in the Intel, PGI and NVCC compilers.
-#if defined(__INTEL_COMPILER) || defined(__PGI) || FMT_NVCC
-#  define FMT_DEPRECATED_ALIAS
+#ifdef _MSC_VER
+#  define FMT_UNCHECKED_ITERATOR(It) \
+    using _Unchecked_type = It  // Mark iterator as checked.
 #else
-#  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
+#  define FMT_UNCHECKED_ITERATOR(It) using unchecked_type = It
 #endif
 
 #ifndef FMT_BEGIN_NAMESPACE
-#  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
-      FMT_MSC_VER >= 1900
-#    define FMT_INLINE_NAMESPACE inline namespace
-#    define FMT_END_NAMESPACE \
-      }                       \
-      }
-#  else
-#    define FMT_INLINE_NAMESPACE namespace
-#    define FMT_END_NAMESPACE \
-      }                       \
-      using namespace v6;     \
-      }
-#  endif
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    FMT_INLINE_NAMESPACE v6 {
+    inline namespace v10 {
+#  define FMT_END_NAMESPACE \
+    }                       \
+    }
+#endif
+
+#ifndef FMT_EXPORT
+#  define FMT_EXPORT
+#  define FMT_BEGIN_EXPORT
+#  define FMT_END_EXPORT
+#endif
+
+#if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_VISIBILITY(value) __attribute__((visibility(value)))
+#else
+#  define FMT_VISIBILITY(value)
 #endif
 
 #if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
-#  if FMT_MSC_VER
-#    define FMT_NO_W4275 __pragma(warning(suppress : 4275))
-#  else
-#    define FMT_NO_W4275
-#  endif
-#  define FMT_CLASS_API FMT_NO_W4275
-#  ifdef FMT_EXPORT
+#  if defined(FMT_LIB_EXPORT)
 #    define FMT_API __declspec(dllexport)
 #  elif defined(FMT_SHARED)
 #    define FMT_API __declspec(dllimport)
-#    define FMT_EXTERN_TEMPLATE_API FMT_API
 #  endif
-#endif
-#ifndef FMT_CLASS_API
-#  define FMT_CLASS_API
+#elif defined(FMT_LIB_EXPORT) || defined(FMT_SHARED)
+#  define FMT_API FMT_VISIBILITY("default")
 #endif
 #ifndef FMT_API
-#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
-#    define FMT_API __attribute__((visibility("default")))
-#    define FMT_EXTERN_TEMPLATE_API FMT_API
-#    define FMT_INSTANTIATION_DEF_API
-#  else
-#    define FMT_API
-#  endif
-#endif
-#ifndef FMT_EXTERN_TEMPLATE_API
-#  define FMT_EXTERN_TEMPLATE_API
-#endif
-#ifndef FMT_INSTANTIATION_DEF_API
-#  define FMT_INSTANTIATION_DEF_API FMT_API
-#endif
-
-#ifndef FMT_HEADER_ONLY
-#  define FMT_EXTERN extern
-#else
-#  define FMT_EXTERN
+#  define FMT_API
 #endif
 
 // libc++ supports string_view in pre-c++17.
-#if (FMT_HAS_INCLUDE(<string_view>) &&                       \
-     (__cplusplus > 201402L || defined(_LIBCPP_VERSION))) || \
-    (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
+#if FMT_HAS_INCLUDE(<string_view>) && \
+    (FMT_CPLUSPLUS >= 201703L || defined(_LIBCPP_VERSION))
 #  include <string_view>
 #  define FMT_USE_STRING_VIEW
-#elif FMT_HAS_INCLUDE("experimental/string_view") && __cplusplus >= 201402L
+#elif FMT_HAS_INCLUDE("experimental/string_view") && FMT_CPLUSPLUS >= 201402L
 #  include <experimental/string_view>
 #  define FMT_USE_EXPERIMENTAL_STRING_VIEW
 #endif
 
 #ifndef FMT_UNICODE
-#  define FMT_UNICODE !FMT_MSC_VER
+#  define FMT_UNICODE !FMT_MSC_VERSION
+#endif
+
+#ifndef FMT_CONSTEVAL
+#  if ((FMT_GCC_VERSION >= 1000 || FMT_CLANG_VERSION >= 1101) && \
+       (!defined(__apple_build_version__) ||                     \
+        __apple_build_version__ >= 14000029L) &&                 \
+       FMT_CPLUSPLUS >= 202002L) ||                              \
+      (defined(__cpp_consteval) &&                               \
+       (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1929))
+// consteval is broken in MSVC before VS2019 version 16.10 and Apple clang
+// before 14.
+#    define FMT_CONSTEVAL consteval
+#    define FMT_HAS_CONSTEVAL
+#  else
+#    define FMT_CONSTEVAL
+#  endif
+#endif
+
+#ifndef FMT_USE_NONTYPE_TEMPLATE_ARGS
+#  if defined(__cpp_nontype_template_args) &&                  \
+      ((FMT_GCC_VERSION >= 903 && FMT_CPLUSPLUS >= 201709L) || \
+       __cpp_nontype_template_args >= 201911L) &&              \
+      !defined(__NVCOMPILER) && !defined(__LCC__)
+#    define FMT_USE_NONTYPE_TEMPLATE_ARGS 1
+#  else
+#    define FMT_USE_NONTYPE_TEMPLATE_ARGS 0
+#  endif
+#endif
+
+// GCC < 5 requires this-> in decltype
+#ifndef FMT_DECLTYPE_THIS
+#  if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
+#    define FMT_DECLTYPE_THIS this->
+#  else
+#    define FMT_DECLTYPE_THIS
+#  endif
 #endif
-#if FMT_UNICODE && FMT_MSC_VER
-#  pragma execution_character_set("utf-8")
+
+// Enable minimal optimizations for more compact code in debug mode.
+FMT_GCC_PRAGMA("GCC push_options")
+#if !defined(__OPTIMIZE__) && !defined(__NVCOMPILER) && !defined(__LCC__) && \
+    !defined(__CUDACC__)
+FMT_GCC_PRAGMA("GCC optimize(\"Og\")")
 #endif
 
 FMT_BEGIN_NAMESPACE
 
 // Implementations of enable_if_t and other metafunctions for older systems.
-template <bool B, class T = void>
+template <bool B, typename T = void>
 using enable_if_t = typename std::enable_if<B, T>::type;
-template <bool B, class T, class F>
+template <bool B, typename T, typename F>
 using conditional_t = typename std::conditional<B, T, F>::type;
 template <bool B> using bool_constant = std::integral_constant<bool, B>;
 template <typename T>
@@ -260,37 +278,82 @@ template <typename T>
 using remove_const_t = typename std::remove_const<T>::type;
 template <typename T>
 using remove_cvref_t = typename std::remove_cv<remove_reference_t<T>>::type;
-template <typename T> struct type_identity { using type = T; };
+template <typename T> struct type_identity {
+  using type = T;
+};
 template <typename T> using type_identity_t = typename type_identity<T>::type;
+template <typename T>
+using underlying_t = typename std::underlying_type<T>::type;
 
-struct monostate {};
+// Checks whether T is a container with contiguous storage.
+template <typename T> struct is_contiguous : std::false_type {};
+template <typename Char>
+struct is_contiguous<std::basic_string<Char>> : std::true_type {};
+
+struct monostate {
+  constexpr monostate() {}
+};
 
 // An enable_if helper to be used in template parameters which results in much
 // shorter symbols: https://godbolt.org/z/sWw4vP. Extra parentheses are needed
 // to workaround a bug in MSVC 2019 (see #1140 and #1186).
-#define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
+#ifdef FMT_DOC
+#  define FMT_ENABLE_IF(...)
+#else
+#  define FMT_ENABLE_IF(...) fmt::enable_if_t<(__VA_ARGS__), int> = 0
+#endif
 
-namespace internal {
+// This is defined in core.h instead of format.h to avoid injecting in std.
+// It is a template to avoid undesirable implicit conversions to std::byte.
+#ifdef __cpp_lib_byte
+template <typename T, FMT_ENABLE_IF(std::is_same<T, std::byte>::value)>
+inline auto format_as(T b) -> unsigned char {
+  return static_cast<unsigned char>(b);
+}
+#endif
 
-// A helper function to suppress bogus "conditional expression is constant"
-// warnings.
-template <typename T> FMT_CONSTEXPR T const_check(T value) { return value; }
+namespace detail {
+// Suppresses "unused variable" warnings with the method described in
+// https://herbsutter.com/2009/10/18/mailbag-shutting-up-compiler-warnings/.
+// (void)var does not work on many Intel compilers.
+template <typename... T> FMT_CONSTEXPR void ignore_unused(const T&...) {}
+
+constexpr FMT_INLINE auto is_constant_evaluated(
+    bool default_value = false) noexcept -> bool {
+// Workaround for incompatibility between libstdc++ consteval-based
+// std::is_constant_evaluated() implementation and clang-14.
+// https://github.com/fmtlib/fmt/issues/3247
+#if FMT_CPLUSPLUS >= 202002L && defined(_GLIBCXX_RELEASE) && \
+    _GLIBCXX_RELEASE >= 12 &&                                \
+    (FMT_CLANG_VERSION >= 1400 && FMT_CLANG_VERSION < 1500)
+  ignore_unused(default_value);
+  return __builtin_is_constant_evaluated();
+#elif defined(__cpp_lib_is_constant_evaluated)
+  ignore_unused(default_value);
+  return std::is_constant_evaluated();
+#else
+  return default_value;
+#endif
+}
 
-// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
-template <typename... Ts> struct void_t_impl { using type = void; };
+// Suppresses "conditional expression is constant" warnings.
+template <typename T> constexpr FMT_INLINE auto const_check(T value) -> T {
+  return value;
+}
 
 FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
                                       const char* message);
 
 #ifndef FMT_ASSERT
 #  ifdef NDEBUG
-// FMT_ASSERT is not empty to avoid -Werror=empty-body.
-#    define FMT_ASSERT(condition, message) ((void)0)
+// FMT_ASSERT is not empty to avoid -Wempty-body.
+#    define FMT_ASSERT(condition, message) \
+      fmt::detail::ignore_unused((condition), (message))
 #  else
 #    define FMT_ASSERT(condition, message)                                    \
       ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
            ? (void)0                                                          \
-           : ::fmt::internal::assert_fail(__FILE__, __LINE__, (message)))
+           : fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
 #  endif
 #endif
 
@@ -305,41 +368,41 @@ template <typename T> struct std_string_view {};
 
 #ifdef FMT_USE_INT128
 // Do nothing.
-#elif defined(__SIZEOF_INT128__) && !FMT_NVCC
+#elif defined(__SIZEOF_INT128__) && !defined(__NVCC__) && \
+    !(FMT_CLANG_VERSION && FMT_MSC_VERSION)
 #  define FMT_USE_INT128 1
-using int128_t = __int128_t;
-using uint128_t = __uint128_t;
+using int128_opt = __int128_t;  // An optional native 128-bit integer.
+using uint128_opt = __uint128_t;
+template <typename T> inline auto convert_for_visit(T value) -> T {
+  return value;
+}
 #else
 #  define FMT_USE_INT128 0
 #endif
 #if !FMT_USE_INT128
-struct int128_t {};
-struct uint128_t {};
+enum class int128_opt {};
+enum class uint128_opt {};
+// Reduce template instantiations.
+template <typename T> auto convert_for_visit(T) -> monostate { return {}; }
 #endif
 
 // Casts a nonnegative integer to unsigned.
 template <typename Int>
-FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
-  FMT_ASSERT(value >= 0, "negative value");
+FMT_CONSTEXPR auto to_unsigned(Int value) ->
+    typename std::make_unsigned<Int>::type {
+  FMT_ASSERT(std::is_unsigned<Int>::value || value >= 0, "negative value");
   return static_cast<typename std::make_unsigned<Int>::type>(value);
 }
 
-constexpr unsigned char micro[] = "\u00B5";
+FMT_CONSTEXPR inline auto is_utf8() -> bool {
+  FMT_MSC_WARNING(suppress : 4566) constexpr unsigned char section[] = "\u00A7";
 
-template <typename Char> constexpr bool is_unicode() {
-  return FMT_UNICODE || sizeof(Char) != 1 ||
-         (sizeof(micro) == 3 && micro[0] == 0xC2 && micro[1] == 0xB5);
+  // Avoid buggy sign extensions in MSVC's constant evaluation mode (#2297).
+  using uchar = unsigned char;
+  return FMT_UNICODE || (sizeof(section) == 3 && uchar(section[0]) == 0xC2 &&
+                         uchar(section[1]) == 0xA7);
 }
-
-#ifdef __cpp_char8_t
-using char8_type = char8_t;
-#else
-enum char8_type : unsigned char {};
-#endif
-}  // namespace internal
-
-template <typename... Ts>
-using void_t = typename internal::void_t_impl<Ts...>::type;
+}  // namespace detail
 
 /**
   An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
@@ -348,22 +411,21 @@ using void_t = typename internal::void_t_impl<Ts...>::type;
   compiled with a different ``-std`` option than the client code (which is not
   recommended).
  */
+FMT_EXPORT
 template <typename Char> class basic_string_view {
  private:
   const Char* data_;
   size_t size_;
 
  public:
-  using char_type FMT_DEPRECATED_ALIAS = Char;
   using value_type = Char;
   using iterator = const Char*;
 
-  FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
+  constexpr basic_string_view() noexcept : data_(nullptr), size_(0) {}
 
   /** Constructs a string reference object from a C string and a size. */
-  FMT_CONSTEXPR basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
-      : data_(s),
-        size_(count) {}
+  constexpr basic_string_view(const Char* s, size_t count) noexcept
+      : data_(s), size_(count) {}
 
   /**
     \rst
@@ -371,43 +433,58 @@ template <typename Char> class basic_string_view {
     the size with ``std::char_traits<Char>::length``.
     \endrst
    */
-#if __cplusplus >= 201703L  // C++17's char_traits::length() is constexpr.
-  FMT_CONSTEXPR
-#endif
+  FMT_CONSTEXPR_CHAR_TRAITS
+  FMT_INLINE
   basic_string_view(const Char* s)
-      : data_(s), size_(std::char_traits<Char>::length(s)) {}
+      : data_(s),
+        size_(detail::const_check(std::is_same<Char, char>::value &&
+                                  !detail::is_constant_evaluated(true))
+                  ? std::strlen(reinterpret_cast<const char*>(s))
+                  : std::char_traits<Char>::length(s)) {}
 
   /** Constructs a string reference from a ``std::basic_string`` object. */
   template <typename Traits, typename Alloc>
   FMT_CONSTEXPR basic_string_view(
-      const std::basic_string<Char, Traits, Alloc>& s) FMT_NOEXCEPT
-      : data_(s.data()),
-        size_(s.size()) {}
+      const std::basic_string<Char, Traits, Alloc>& s) noexcept
+      : data_(s.data()), size_(s.size()) {}
 
-  template <
-      typename S,
-      FMT_ENABLE_IF(std::is_same<S, internal::std_string_view<Char>>::value)>
-  FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
-                                                      size_(s.size()) {}
+  template <typename S, FMT_ENABLE_IF(std::is_same<
+                                      S, detail::std_string_view<Char>>::value)>
+  FMT_CONSTEXPR basic_string_view(S s) noexcept
+      : data_(s.data()), size_(s.size()) {}
 
   /** Returns a pointer to the string data. */
-  FMT_CONSTEXPR const Char* data() const { return data_; }
+  constexpr auto data() const noexcept -> const Char* { return data_; }
 
   /** Returns the string size. */
-  FMT_CONSTEXPR size_t size() const { return size_; }
+  constexpr auto size() const noexcept -> size_t { return size_; }
 
-  FMT_CONSTEXPR iterator begin() const { return data_; }
-  FMT_CONSTEXPR iterator end() const { return data_ + size_; }
+  constexpr auto begin() const noexcept -> iterator { return data_; }
+  constexpr auto end() const noexcept -> iterator { return data_ + size_; }
 
-  FMT_CONSTEXPR const Char& operator[](size_t pos) const { return data_[pos]; }
+  constexpr auto operator[](size_t pos) const noexcept -> const Char& {
+    return data_[pos];
+  }
 
-  FMT_CONSTEXPR void remove_prefix(size_t n) {
+  FMT_CONSTEXPR void remove_prefix(size_t n) noexcept {
     data_ += n;
     size_ -= n;
   }
 
+  FMT_CONSTEXPR_CHAR_TRAITS auto starts_with(
+      basic_string_view<Char> sv) const noexcept -> bool {
+    return size_ >= sv.size_ &&
+           std::char_traits<Char>::compare(data_, sv.data_, sv.size_) == 0;
+  }
+  FMT_CONSTEXPR_CHAR_TRAITS auto starts_with(Char c) const noexcept -> bool {
+    return size_ >= 1 && std::char_traits<Char>::eq(*data_, c);
+  }
+  FMT_CONSTEXPR_CHAR_TRAITS auto starts_with(const Char* s) const -> bool {
+    return starts_with(basic_string_view<Char>(s));
+  }
+
   // Lexicographically compare this string reference to other.
-  int compare(basic_string_view other) const {
+  FMT_CONSTEXPR_CHAR_TRAITS auto compare(basic_string_view other) const -> int {
     size_t str_size = size_ < other.size_ ? size_ : other.size_;
     int result = std::char_traits<Char>::compare(data_, other.data_, str_size);
     if (result == 0)
@@ -415,103 +492,77 @@ template <typename Char> class basic_string_view {
     return result;
   }
 
-  friend bool operator==(basic_string_view lhs, basic_string_view rhs) {
+  FMT_CONSTEXPR_CHAR_TRAITS friend auto operator==(basic_string_view lhs,
+                                                   basic_string_view rhs)
+      -> bool {
     return lhs.compare(rhs) == 0;
   }
-  friend bool operator!=(basic_string_view lhs, basic_string_view rhs) {
+  friend auto operator!=(basic_string_view lhs, basic_string_view rhs) -> bool {
     return lhs.compare(rhs) != 0;
   }
-  friend bool operator<(basic_string_view lhs, basic_string_view rhs) {
+  friend auto operator<(basic_string_view lhs, basic_string_view rhs) -> bool {
     return lhs.compare(rhs) < 0;
   }
-  friend bool operator<=(basic_string_view lhs, basic_string_view rhs) {
+  friend auto operator<=(basic_string_view lhs, basic_string_view rhs) -> bool {
     return lhs.compare(rhs) <= 0;
   }
-  friend bool operator>(basic_string_view lhs, basic_string_view rhs) {
+  friend auto operator>(basic_string_view lhs, basic_string_view rhs) -> bool {
     return lhs.compare(rhs) > 0;
   }
-  friend bool operator>=(basic_string_view lhs, basic_string_view rhs) {
+  friend auto operator>=(basic_string_view lhs, basic_string_view rhs) -> bool {
     return lhs.compare(rhs) >= 0;
   }
 };
 
+FMT_EXPORT
 using string_view = basic_string_view<char>;
-using wstring_view = basic_string_view<wchar_t>;
-
-#ifndef __cpp_char8_t
-// char8_t is deprecated; use char instead.
-using char8_t FMT_DEPRECATED_ALIAS = internal::char8_type;
-#endif
 
 /** Specifies if ``T`` is a character type. Can be specialized by users. */
+FMT_EXPORT
 template <typename T> struct is_char : std::false_type {};
 template <> struct is_char<char> : std::true_type {};
-template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<internal::char8_type> : std::true_type {};
-template <> struct is_char<char16_t> : std::true_type {};
-template <> struct is_char<char32_t> : std::true_type {};
 
-/**
-  \rst
-  Returns a string view of `s`. In order to add custom string type support to
-  {fmt} provide an overload of `to_string_view` for it in the same namespace as
-  the type for the argument-dependent lookup to work.
+namespace detail {
 
-  **Example**::
+// A base class for compile-time strings.
+struct compile_string {};
+
+template <typename S>
+struct is_compile_string : std::is_base_of<compile_string, S> {};
 
-    namespace my_ns {
-    inline string_view to_string_view(const my_string& s) {
-      return {s.data(), s.length()};
-    }
-    }
-    std::string message = fmt::format(my_string("The answer is {}"), 42);
-  \endrst
- */
 template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
-inline basic_string_view<Char> to_string_view(const Char* s) {
+FMT_INLINE auto to_string_view(const Char* s) -> basic_string_view<Char> {
   return s;
 }
-
 template <typename Char, typename Traits, typename Alloc>
-inline basic_string_view<Char> to_string_view(
-    const std::basic_string<Char, Traits, Alloc>& s) {
+inline auto to_string_view(const std::basic_string<Char, Traits, Alloc>& s)
+    -> basic_string_view<Char> {
   return s;
 }
-
 template <typename Char>
-inline basic_string_view<Char> to_string_view(basic_string_view<Char> s) {
+constexpr auto to_string_view(basic_string_view<Char> s)
+    -> basic_string_view<Char> {
   return s;
 }
-
 template <typename Char,
-          FMT_ENABLE_IF(!std::is_empty<internal::std_string_view<Char>>::value)>
-inline basic_string_view<Char> to_string_view(
-    internal::std_string_view<Char> s) {
+          FMT_ENABLE_IF(!std::is_empty<std_string_view<Char>>::value)>
+inline auto to_string_view(std_string_view<Char> s) -> basic_string_view<Char> {
   return s;
 }
-
-// A base class for compile-time strings. It is defined in the fmt namespace to
-// make formatting functions visible via ADL, e.g. format(fmt("{}"), 42).
-struct compile_string {};
-
-template <typename S>
-struct is_compile_string : std::is_base_of<compile_string, S> {};
-
 template <typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
-constexpr basic_string_view<typename S::char_type> to_string_view(const S& s) {
-  return s;
+constexpr auto to_string_view(const S& s)
+    -> basic_string_view<typename S::char_type> {
+  return basic_string_view<typename S::char_type>(s);
 }
-
-namespace internal {
 void to_string_view(...);
-using fmt::v6::to_string_view;
 
 // Specifies whether S is a string type convertible to fmt::basic_string_view.
 // It should be a constexpr function but MSVC 2017 fails to compile it in
 // enable_if and MSVC 2015 fails to compile it as an alias template.
+// ADL is intentionally disabled as to_string_view is not an extension point.
 template <typename S>
-struct is_string : std::is_class<decltype(to_string_view(std::declval<S>()))> {
-};
+struct is_string
+    : std::is_class<decltype(detail::to_string_view(std::declval<S>()))> {};
 
 template <typename S, typename = void> struct char_t_impl {};
 template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
@@ -519,152 +570,275 @@ template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
   using type = typename result::value_type;
 };
 
+enum class type {
+  none_type,
+  // Integer types should go first,
+  int_type,
+  uint_type,
+  long_long_type,
+  ulong_long_type,
+  int128_type,
+  uint128_type,
+  bool_type,
+  char_type,
+  last_integer_type = char_type,
+  // followed by floating-point types.
+  float_type,
+  double_type,
+  long_double_type,
+  last_numeric_type = long_double_type,
+  cstring_type,
+  string_type,
+  pointer_type,
+  custom_type
+};
+
+// Maps core type T to the corresponding type enum constant.
+template <typename T, typename Char>
+struct type_constant : std::integral_constant<type, type::custom_type> {};
+
+#define FMT_TYPE_CONSTANT(Type, constant) \
+  template <typename Char>                \
+  struct type_constant<Type, Char>        \
+      : std::integral_constant<type, type::constant> {}
+
+FMT_TYPE_CONSTANT(int, int_type);
+FMT_TYPE_CONSTANT(unsigned, uint_type);
+FMT_TYPE_CONSTANT(long long, long_long_type);
+FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
+FMT_TYPE_CONSTANT(int128_opt, int128_type);
+FMT_TYPE_CONSTANT(uint128_opt, uint128_type);
+FMT_TYPE_CONSTANT(bool, bool_type);
+FMT_TYPE_CONSTANT(Char, char_type);
+FMT_TYPE_CONSTANT(float, float_type);
+FMT_TYPE_CONSTANT(double, double_type);
+FMT_TYPE_CONSTANT(long double, long_double_type);
+FMT_TYPE_CONSTANT(const Char*, cstring_type);
+FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
+FMT_TYPE_CONSTANT(const void*, pointer_type);
+
+constexpr auto is_integral_type(type t) -> bool {
+  return t > type::none_type && t <= type::last_integer_type;
+}
+constexpr auto is_arithmetic_type(type t) -> bool {
+  return t > type::none_type && t <= type::last_numeric_type;
+}
+
+constexpr auto set(type rhs) -> int { return 1 << static_cast<int>(rhs); }
+constexpr auto in(type t, int set) -> bool {
+  return ((set >> static_cast<int>(t)) & 1) != 0;
+}
+
+// Bitsets of types.
+enum {
+  sint_set =
+      set(type::int_type) | set(type::long_long_type) | set(type::int128_type),
+  uint_set = set(type::uint_type) | set(type::ulong_long_type) |
+             set(type::uint128_type),
+  bool_set = set(type::bool_type),
+  char_set = set(type::char_type),
+  float_set = set(type::float_type) | set(type::double_type) |
+              set(type::long_double_type),
+  string_set = set(type::string_type),
+  cstring_set = set(type::cstring_type),
+  pointer_set = set(type::pointer_type)
+};
+
+// DEPRECATED!
+FMT_NORETURN FMT_API void throw_format_error(const char* message);
+
 struct error_handler {
-  FMT_CONSTEXPR error_handler() = default;
-  FMT_CONSTEXPR error_handler(const error_handler&) = default;
+  constexpr error_handler() = default;
 
   // This function is intentionally not constexpr to give a compile-time error.
-  FMT_NORETURN FMT_API void on_error(const char* message);
+  FMT_NORETURN void on_error(const char* message) {
+    throw_format_error(message);
+  }
 };
-}  // namespace internal
+}  // namespace detail
+
+/** Throws ``format_error`` with a given message. */
+using detail::throw_format_error;
 
 /** String's character type. */
-template <typename S> using char_t = typename internal::char_t_impl<S>::type;
+template <typename S> using char_t = typename detail::char_t_impl<S>::type;
 
 /**
   \rst
   Parsing context consisting of a format string range being parsed and an
   argument counter for automatic indexing.
-
-  You can use one of the following type aliases for common character types:
-
-  +-----------------------+-------------------------------------+
-  | Type                  | Definition                          |
-  +=======================+=====================================+
-  | format_parse_context  | basic_format_parse_context<char>    |
-  +-----------------------+-------------------------------------+
-  | wformat_parse_context | basic_format_parse_context<wchar_t> |
-  +-----------------------+-------------------------------------+
+  You can use the ``format_parse_context`` type alias for ``char`` instead.
   \endrst
  */
-template <typename Char, typename ErrorHandler = internal::error_handler>
-class basic_format_parse_context : private ErrorHandler {
+FMT_EXPORT
+template <typename Char> class basic_format_parse_context {
  private:
   basic_string_view<Char> format_str_;
   int next_arg_id_;
 
+  FMT_CONSTEXPR void do_check_arg_id(int id);
+
  public:
   using char_type = Char;
-  using iterator = typename basic_string_view<Char>::iterator;
+  using iterator = const Char*;
 
-  explicit FMT_CONSTEXPR basic_format_parse_context(
-      basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
-      : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
+  explicit constexpr basic_format_parse_context(
+      basic_string_view<Char> format_str, int next_arg_id = 0)
+      : format_str_(format_str), next_arg_id_(next_arg_id) {}
 
   /**
     Returns an iterator to the beginning of the format string range being
     parsed.
    */
-  FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
+  constexpr auto begin() const noexcept -> iterator {
     return format_str_.begin();
   }
 
   /**
     Returns an iterator past the end of the format string range being parsed.
    */
-  FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
+  constexpr auto end() const noexcept -> iterator { return format_str_.end(); }
 
   /** Advances the begin iterator to ``it``. */
   FMT_CONSTEXPR void advance_to(iterator it) {
-    format_str_.remove_prefix(internal::to_unsigned(it - begin()));
+    format_str_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 
   /**
     Reports an error if using the manual argument indexing; otherwise returns
     the next argument index and switches to the automatic indexing.
    */
-  FMT_CONSTEXPR int next_arg_id() {
-    if (next_arg_id_ >= 0) return next_arg_id_++;
-    on_error("cannot switch from manual to automatic argument indexing");
-    return 0;
+  FMT_CONSTEXPR auto next_arg_id() -> int {
+    if (next_arg_id_ < 0) {
+      detail::throw_format_error(
+          "cannot switch from manual to automatic argument indexing");
+      return 0;
+    }
+    int id = next_arg_id_++;
+    do_check_arg_id(id);
+    return id;
   }
 
   /**
     Reports an error if using the automatic argument indexing; otherwise
     switches to the manual indexing.
    */
-  FMT_CONSTEXPR void check_arg_id(int) {
-    if (next_arg_id_ > 0)
-      on_error("cannot switch from automatic to manual argument indexing");
-    else
-      next_arg_id_ = -1;
+  FMT_CONSTEXPR void check_arg_id(int id) {
+    if (next_arg_id_ > 0) {
+      detail::throw_format_error(
+          "cannot switch from automatic to manual argument indexing");
+      return;
+    }
+    next_arg_id_ = -1;
+    do_check_arg_id(id);
   }
-
   FMT_CONSTEXPR void check_arg_id(basic_string_view<Char>) {}
-
-  FMT_CONSTEXPR void on_error(const char* message) {
-    ErrorHandler::on_error(message);
-  }
-
-  FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
+  FMT_CONSTEXPR void check_dynamic_spec(int arg_id);
 };
 
+FMT_EXPORT
 using format_parse_context = basic_format_parse_context<char>;
-using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
-template <typename Char, typename ErrorHandler = internal::error_handler>
-using basic_parse_context FMT_DEPRECATED_ALIAS =
-    basic_format_parse_context<Char, ErrorHandler>;
-using parse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<char>;
-using wparse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<wchar_t>;
+namespace detail {
+// A parse context with extra data used only in compile-time checks.
+template <typename Char>
+class compile_parse_context : public basic_format_parse_context<Char> {
+ private:
+  int num_args_;
+  const type* types_;
+  using base = basic_format_parse_context<Char>;
 
-template <typename Context> class basic_format_arg;
-template <typename Context> class basic_format_args;
+ public:
+  explicit FMT_CONSTEXPR compile_parse_context(
+      basic_string_view<Char> format_str, int num_args, const type* types,
+      int next_arg_id = 0)
+      : base(format_str, next_arg_id), num_args_(num_args), types_(types) {}
+
+  constexpr auto num_args() const -> int { return num_args_; }
+  constexpr auto arg_type(int id) const -> type { return types_[id]; }
+
+  FMT_CONSTEXPR auto next_arg_id() -> int {
+    int id = base::next_arg_id();
+    if (id >= num_args_) throw_format_error("argument not found");
+    return id;
+  }
 
-// A formatter for objects of type T.
-template <typename T, typename Char = char, typename Enable = void>
-struct formatter {
-  // A deleted default constructor indicates a disabled formatter.
-  formatter() = delete;
+  FMT_CONSTEXPR void check_arg_id(int id) {
+    base::check_arg_id(id);
+    if (id >= num_args_) throw_format_error("argument not found");
+  }
+  using base::check_arg_id;
+
+  FMT_CONSTEXPR void check_dynamic_spec(int arg_id) {
+    detail::ignore_unused(arg_id);
+#if !defined(__LCC__)
+    if (arg_id < num_args_ && types_ && !is_integral_type(types_[arg_id]))
+      throw_format_error("width/precision is not integer");
+#endif
+  }
 };
 
-template <typename T, typename Char, typename Enable = void>
-struct FMT_DEPRECATED convert_to_int
-    : bool_constant<!std::is_arithmetic<T>::value &&
-                    std::is_convertible<T, int>::value> {};
+// Extracts a reference to the container from back_insert_iterator.
+template <typename Container>
+inline auto get_container(std::back_insert_iterator<Container> it)
+    -> Container& {
+  using base = std::back_insert_iterator<Container>;
+  struct accessor : base {
+    accessor(base b) : base(b) {}
+    using base::container;
+  };
+  return *accessor(it).container;
+}
 
-// Specifies if T has an enabled formatter specialization. A type can be
-// formattable even if it doesn't have a formatter e.g. via a conversion.
-template <typename T, typename Context>
-using has_formatter =
-    std::is_constructible<typename Context::template formatter_type<T>>;
+template <typename Char, typename InputIt, typename OutputIt>
+FMT_CONSTEXPR auto copy_str(InputIt begin, InputIt end, OutputIt out)
+    -> OutputIt {
+  while (begin != end) *out++ = static_cast<Char>(*begin++);
+  return out;
+}
 
-namespace internal {
+template <typename Char, typename T, typename U,
+          FMT_ENABLE_IF(
+              std::is_same<remove_const_t<T>, U>::value&& is_char<U>::value)>
+FMT_CONSTEXPR auto copy_str(T* begin, T* end, U* out) -> U* {
+  if (is_constant_evaluated()) return copy_str<Char, T*, U*>(begin, end, out);
+  auto size = to_unsigned(end - begin);
+  if (size > 0) memcpy(out, begin, size * sizeof(U));
+  return out + size;
+}
 
-/** A contiguous memory buffer with an optional growing ability. */
+/**
+  \rst
+  A contiguous memory buffer with an optional growing ability. It is an internal
+  class and shouldn't be used directly, only via `~fmt::basic_memory_buffer`.
+  \endrst
+ */
 template <typename T> class buffer {
  private:
   T* ptr_;
-  std::size_t size_;
-  std::size_t capacity_;
+  size_t size_;
+  size_t capacity_;
 
  protected:
   // Don't initialize ptr_ since it is not accessed to save a few cycles.
-  buffer(std::size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
+  FMT_MSC_WARNING(suppress : 26495)
+  FMT_CONSTEXPR buffer(size_t sz) noexcept : size_(sz), capacity_(sz) {}
+
+  FMT_CONSTEXPR20 buffer(T* p = nullptr, size_t sz = 0, size_t cap = 0) noexcept
+      : ptr_(p), size_(sz), capacity_(cap) {}
 
-  buffer(T* p = nullptr, std::size_t sz = 0, std::size_t cap = 0) FMT_NOEXCEPT
-      : ptr_(p),
-        size_(sz),
-        capacity_(cap) {}
+  FMT_CONSTEXPR20 ~buffer() = default;
+  buffer(buffer&&) = default;
 
   /** Sets the buffer data and capacity. */
-  void set(T* buf_data, std::size_t buf_capacity) FMT_NOEXCEPT {
+  FMT_CONSTEXPR void set(T* buf_data, size_t buf_capacity) noexcept {
     ptr_ = buf_data;
     capacity_ = buf_capacity;
   }
 
   /** Increases the buffer capacity to hold at least *capacity* elements. */
-  virtual void grow(std::size_t capacity) = 0;
+  // DEPRECATED!
+  virtual FMT_CONSTEXPR20 void grow(size_t capacity) = 0;
 
  public:
   using value_type = T;
@@ -672,166 +846,411 @@ template <typename T> class buffer {
 
   buffer(const buffer&) = delete;
   void operator=(const buffer&) = delete;
-  virtual ~buffer() = default;
 
-  T* begin() FMT_NOEXCEPT { return ptr_; }
-  T* end() FMT_NOEXCEPT { return ptr_ + size_; }
+  FMT_INLINE auto begin() noexcept -> T* { return ptr_; }
+  FMT_INLINE auto end() noexcept -> T* { return ptr_ + size_; }
 
-  const T* begin() const FMT_NOEXCEPT { return ptr_; }
-  const T* end() const FMT_NOEXCEPT { return ptr_ + size_; }
+  FMT_INLINE auto begin() const noexcept -> const T* { return ptr_; }
+  FMT_INLINE auto end() const noexcept -> const T* { return ptr_ + size_; }
 
   /** Returns the size of this buffer. */
-  std::size_t size() const FMT_NOEXCEPT { return size_; }
+  constexpr auto size() const noexcept -> size_t { return size_; }
 
   /** Returns the capacity of this buffer. */
-  std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }
+  constexpr auto capacity() const noexcept -> size_t { return capacity_; }
 
-  /** Returns a pointer to the buffer data. */
-  T* data() FMT_NOEXCEPT { return ptr_; }
-
-  /** Returns a pointer to the buffer data. */
-  const T* data() const FMT_NOEXCEPT { return ptr_; }
-
-  /**
-    Resizes the buffer. If T is a POD type new elements may not be initialized.
-   */
-  void resize(std::size_t new_size) {
-    reserve(new_size);
-    size_ = new_size;
-  }
+  /** Returns a pointer to the buffer data (not null-terminated). */
+  FMT_CONSTEXPR auto data() noexcept -> T* { return ptr_; }
+  FMT_CONSTEXPR auto data() const noexcept -> const T* { return ptr_; }
 
   /** Clears this buffer. */
   void clear() { size_ = 0; }
 
-  /** Reserves space to store at least *capacity* elements. */
-  void reserve(std::size_t new_capacity) {
+  // Tries resizing the buffer to contain *count* elements. If T is a POD type
+  // the new elements may not be initialized.
+  FMT_CONSTEXPR20 void try_resize(size_t count) {
+    try_reserve(count);
+    size_ = count <= capacity_ ? count : capacity_;
+  }
+
+  // Tries increasing the buffer capacity to *new_capacity*. It can increase the
+  // capacity by a smaller amount than requested but guarantees there is space
+  // for at least one additional element either by increasing the capacity or by
+  // flushing the buffer if it is full.
+  FMT_CONSTEXPR20 void try_reserve(size_t new_capacity) {
     if (new_capacity > capacity_) grow(new_capacity);
   }
 
-  void push_back(const T& value) {
-    reserve(size_ + 1);
+  FMT_CONSTEXPR20 void push_back(const T& value) {
+    try_reserve(size_ + 1);
     ptr_[size_++] = value;
   }
 
   /** Appends data to the end of the buffer. */
   template <typename U> void append(const U* begin, const U* end);
 
-  template <typename I> T& operator[](I index) { return ptr_[index]; }
-  template <typename I> const T& operator[](I index) const {
+  template <typename Idx> FMT_CONSTEXPR auto operator[](Idx index) -> T& {
     return ptr_[index];
   }
-};
+  template <typename Idx>
+  FMT_CONSTEXPR auto operator[](Idx index) const -> const T& {
+    return ptr_[index];
+  }
+};
+
+struct buffer_traits {
+  explicit buffer_traits(size_t) {}
+  auto count() const -> size_t { return 0; }
+  auto limit(size_t size) -> size_t { return size; }
+};
+
+class fixed_buffer_traits {
+ private:
+  size_t count_ = 0;
+  size_t limit_;
+
+ public:
+  explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
+  auto count() const -> size_t { return count_; }
+  auto limit(size_t size) -> size_t {
+    size_t n = limit_ > count_ ? limit_ - count_ : 0;
+    count_ += size;
+    return size < n ? size : n;
+  }
+};
+
+// A buffer that writes to an output iterator when flushed.
+template <typename OutputIt, typename T, typename Traits = buffer_traits>
+class iterator_buffer final : public Traits, public buffer<T> {
+ private:
+  OutputIt out_;
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+
+ protected:
+  FMT_CONSTEXPR20 void grow(size_t) override {
+    if (this->size() == buffer_size) flush();
+  }
+
+  void flush() {
+    auto size = this->size();
+    this->clear();
+    out_ = copy_str<T>(data_, data_ + this->limit(size), out_);
+  }
+
+ public:
+  explicit iterator_buffer(OutputIt out, size_t n = buffer_size)
+      : Traits(n), buffer<T>(data_, 0, buffer_size), out_(out) {}
+  iterator_buffer(iterator_buffer&& other)
+      : Traits(other), buffer<T>(data_, 0, buffer_size), out_(other.out_) {}
+  ~iterator_buffer() { flush(); }
+
+  auto out() -> OutputIt {
+    flush();
+    return out_;
+  }
+  auto count() const -> size_t { return Traits::count() + this->size(); }
+};
 
-// A container-backed buffer.
+template <typename T>
+class iterator_buffer<T*, T, fixed_buffer_traits> final
+    : public fixed_buffer_traits,
+      public buffer<T> {
+ private:
+  T* out_;
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+
+ protected:
+  FMT_CONSTEXPR20 void grow(size_t) override {
+    if (this->size() == this->capacity()) flush();
+  }
+
+  void flush() {
+    size_t n = this->limit(this->size());
+    if (this->data() == out_) {
+      out_ += n;
+      this->set(data_, buffer_size);
+    }
+    this->clear();
+  }
+
+ public:
+  explicit iterator_buffer(T* out, size_t n = buffer_size)
+      : fixed_buffer_traits(n), buffer<T>(out, 0, n), out_(out) {}
+  iterator_buffer(iterator_buffer&& other)
+      : fixed_buffer_traits(other),
+        buffer<T>(std::move(other)),
+        out_(other.out_) {
+    if (this->data() != out_) {
+      this->set(data_, buffer_size);
+      this->clear();
+    }
+  }
+  ~iterator_buffer() { flush(); }
+
+  auto out() -> T* {
+    flush();
+    return out_;
+  }
+  auto count() const -> size_t {
+    return fixed_buffer_traits::count() + this->size();
+  }
+};
+
+template <typename T> class iterator_buffer<T*, T> final : public buffer<T> {
+ protected:
+  FMT_CONSTEXPR20 void grow(size_t) override {}
+
+ public:
+  explicit iterator_buffer(T* out, size_t = 0) : buffer<T>(out, 0, ~size_t()) {}
+
+  auto out() -> T* { return &*this->end(); }
+};
+
+// A buffer that writes to a container with the contiguous storage.
 template <typename Container>
-class container_buffer : public buffer<typename Container::value_type> {
+class iterator_buffer<std::back_insert_iterator<Container>,
+                      enable_if_t<is_contiguous<Container>::value,
+                                  typename Container::value_type>>
+    final : public buffer<typename Container::value_type> {
  private:
   Container& container_;
 
  protected:
-  void grow(std::size_t capacity) FMT_OVERRIDE {
+  FMT_CONSTEXPR20 void grow(size_t capacity) override {
     container_.resize(capacity);
     this->set(&container_[0], capacity);
   }
 
  public:
-  explicit container_buffer(Container& c)
+  explicit iterator_buffer(Container& c)
       : buffer<typename Container::value_type>(c.size()), container_(c) {}
+  explicit iterator_buffer(std::back_insert_iterator<Container> out, size_t = 0)
+      : iterator_buffer(get_container(out)) {}
+
+  auto out() -> std::back_insert_iterator<Container> {
+    return std::back_inserter(container_);
+  }
 };
 
-// Extracts a reference to the container from back_insert_iterator.
-template <typename Container>
-inline Container& get_container(std::back_insert_iterator<Container> it) {
-  using bi_iterator = std::back_insert_iterator<Container>;
-  struct accessor : bi_iterator {
-    accessor(bi_iterator iter) : bi_iterator(iter) {}
-    using bi_iterator::container;
-  };
-  return *accessor(it).container;
+// A buffer that counts the number of code units written discarding the output.
+template <typename T = char> class counting_buffer final : public buffer<T> {
+ private:
+  enum { buffer_size = 256 };
+  T data_[buffer_size];
+  size_t count_ = 0;
+
+ protected:
+  FMT_CONSTEXPR20 void grow(size_t) override {
+    if (this->size() != buffer_size) return;
+    count_ += this->size();
+    this->clear();
+  }
+
+ public:
+  counting_buffer() : buffer<T>(data_, 0, buffer_size) {}
+
+  auto count() -> size_t { return count_ + this->size(); }
+};
+}  // namespace detail
+
+template <typename Char>
+FMT_CONSTEXPR void basic_format_parse_context<Char>::do_check_arg_id(int id) {
+  // Argument id is only checked at compile-time during parsing because
+  // formatting has its own validation.
+  if (detail::is_constant_evaluated() &&
+      (!FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200)) {
+    using context = detail::compile_parse_context<Char>;
+    if (id >= static_cast<context*>(this)->num_args())
+      detail::throw_format_error("argument not found");
+  }
+}
+
+template <typename Char>
+FMT_CONSTEXPR void basic_format_parse_context<Char>::check_dynamic_spec(
+    int arg_id) {
+  if (detail::is_constant_evaluated() &&
+      (!FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200)) {
+    using context = detail::compile_parse_context<Char>;
+    static_cast<context*>(this)->check_dynamic_spec(arg_id);
+  }
 }
 
+FMT_EXPORT template <typename Context> class basic_format_arg;
+FMT_EXPORT template <typename Context> class basic_format_args;
+FMT_EXPORT template <typename Context> class dynamic_format_arg_store;
+
+// A formatter for objects of type T.
+FMT_EXPORT
 template <typename T, typename Char = char, typename Enable = void>
-struct fallback_formatter {
-  fallback_formatter() = delete;
+struct formatter {
+  // A deleted default constructor indicates a disabled formatter.
+  formatter() = delete;
 };
 
-// Specifies if T has an enabled fallback_formatter specialization.
+// Specifies if T has an enabled formatter specialization. A type can be
+// formattable even if it doesn't have a formatter e.g. via a conversion.
 template <typename T, typename Context>
-using has_fallback_formatter =
-    std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
+using has_formatter =
+    std::is_constructible<typename Context::template formatter_type<T>>;
 
-template <typename Char> struct named_arg_base;
-template <typename T, typename Char> struct named_arg;
+// An output iterator that appends to a buffer.
+// It is used to reduce symbol sizes for the common case.
+class appender : public std::back_insert_iterator<detail::buffer<char>> {
+  using base = std::back_insert_iterator<detail::buffer<char>>;
 
-enum class type {
-  none_type,
-  named_arg_type,
-  // Integer types should go first,
-  int_type,
-  uint_type,
-  long_long_type,
-  ulong_long_type,
-  int128_type,
-  uint128_type,
-  bool_type,
-  char_type,
-  last_integer_type = char_type,
-  // followed by floating-point types.
-  float_type,
-  double_type,
-  long_double_type,
-  last_numeric_type = long_double_type,
-  cstring_type,
-  string_type,
-  pointer_type,
-  custom_type
+ public:
+  using std::back_insert_iterator<detail::buffer<char>>::back_insert_iterator;
+  appender(base it) noexcept : base(it) {}
+  FMT_UNCHECKED_ITERATOR(appender);
+
+  auto operator++() noexcept -> appender& { return *this; }
+  auto operator++(int) noexcept -> appender { return *this; }
 };
 
-// Maps core type T to the corresponding type enum constant.
+namespace detail {
+
+template <typename Context, typename T>
+constexpr auto has_const_formatter_impl(T*)
+    -> decltype(typename Context::template formatter_type<T>().format(
+                    std::declval<const T&>(), std::declval<Context&>()),
+                true) {
+  return true;
+}
+template <typename Context>
+constexpr auto has_const_formatter_impl(...) -> bool {
+  return false;
+}
+template <typename T, typename Context>
+constexpr auto has_const_formatter() -> bool {
+  return has_const_formatter_impl<Context>(static_cast<T*>(nullptr));
+}
+
+template <typename T>
+using buffer_appender = conditional_t<std::is_same<T, char>::value, appender,
+                                      std::back_insert_iterator<buffer<T>>>;
+
+// Maps an output iterator to a buffer.
+template <typename T, typename OutputIt>
+auto get_buffer(OutputIt out) -> iterator_buffer<OutputIt, T> {
+  return iterator_buffer<OutputIt, T>(out);
+}
+template <typename T, typename Buf,
+          FMT_ENABLE_IF(std::is_base_of<buffer<char>, Buf>::value)>
+auto get_buffer(std::back_insert_iterator<Buf> out) -> buffer<char>& {
+  return get_container(out);
+}
+
+template <typename Buf, typename OutputIt>
+FMT_INLINE auto get_iterator(Buf& buf, OutputIt) -> decltype(buf.out()) {
+  return buf.out();
+}
+template <typename T, typename OutputIt>
+auto get_iterator(buffer<T>&, OutputIt out) -> OutputIt {
+  return out;
+}
+
+struct view {};
+
+template <typename Char, typename T> struct named_arg : view {
+  const Char* name;
+  const T& value;
+  named_arg(const Char* n, const T& v) : name(n), value(v) {}
+};
+
+template <typename Char> struct named_arg_info {
+  const Char* name;
+  int id;
+};
+
+template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+struct arg_data {
+  // args_[0].named_args points to named_args_ to avoid bloating format_args.
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : +1)];
+  named_arg_info<Char> named_args_[NUM_NAMED_ARGS];
+
+  template <typename... U>
+  arg_data(const U&... init) : args_{T(named_args_, NUM_NAMED_ARGS), init...} {}
+  arg_data(const arg_data& other) = delete;
+  auto args() const -> const T* { return args_ + 1; }
+  auto named_args() -> named_arg_info<Char>* { return named_args_; }
+};
+
+template <typename T, typename Char, size_t NUM_ARGS>
+struct arg_data<T, Char, NUM_ARGS, 0> {
+  // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
+  T args_[NUM_ARGS != 0 ? NUM_ARGS : +1];
+
+  template <typename... U>
+  FMT_CONSTEXPR FMT_INLINE arg_data(const U&... init) : args_{init...} {}
+  FMT_CONSTEXPR FMT_INLINE auto args() const -> const T* { return args_; }
+  FMT_CONSTEXPR FMT_INLINE auto named_args() -> std::nullptr_t {
+    return nullptr;
+  }
+};
+
+template <typename Char>
+inline void init_named_args(named_arg_info<Char>*, int, int) {}
+
+template <typename T> struct is_named_arg : std::false_type {};
+template <typename T> struct is_statically_named_arg : std::false_type {};
+
 template <typename T, typename Char>
-struct type_constant : std::integral_constant<type, type::custom_type> {};
+struct is_named_arg<named_arg<Char, T>> : std::true_type {};
 
-#define FMT_TYPE_CONSTANT(Type, constant) \
-  template <typename Char>                \
-  struct type_constant<Type, Char>        \
-      : std::integral_constant<type, type::constant> {}
+template <typename Char, typename T, typename... Tail,
+          FMT_ENABLE_IF(!is_named_arg<T>::value)>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const T&, const Tail&... args) {
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
 
-FMT_TYPE_CONSTANT(const named_arg_base<Char>&, named_arg_type);
-FMT_TYPE_CONSTANT(int, int_type);
-FMT_TYPE_CONSTANT(unsigned, uint_type);
-FMT_TYPE_CONSTANT(long long, long_long_type);
-FMT_TYPE_CONSTANT(unsigned long long, ulong_long_type);
-FMT_TYPE_CONSTANT(int128_t, int128_type);
-FMT_TYPE_CONSTANT(uint128_t, uint128_type);
-FMT_TYPE_CONSTANT(bool, bool_type);
-FMT_TYPE_CONSTANT(Char, char_type);
-FMT_TYPE_CONSTANT(float, float_type);
-FMT_TYPE_CONSTANT(double, double_type);
-FMT_TYPE_CONSTANT(long double, long_double_type);
-FMT_TYPE_CONSTANT(const Char*, cstring_type);
-FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
-FMT_TYPE_CONSTANT(const void*, pointer_type);
+template <typename Char, typename T, typename... Tail,
+          FMT_ENABLE_IF(is_named_arg<T>::value)>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const T& arg, const Tail&... args) {
+  named_args[named_arg_count++] = {arg.name, arg_count};
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
 
-FMT_CONSTEXPR bool is_integral_type(type t) {
-  FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
-  return t > type::none_type && t <= type::last_integer_type;
+template <typename... Args>
+FMT_CONSTEXPR FMT_INLINE void init_named_args(std::nullptr_t, int, int,
+                                              const Args&...) {}
+
+template <bool B = false> constexpr auto count() -> size_t { return B ? 1 : 0; }
+template <bool B1, bool B2, bool... Tail> constexpr auto count() -> size_t {
+  return (B1 ? 1 : 0) + count<B2, Tail...>();
 }
 
-FMT_CONSTEXPR bool is_arithmetic_type(type t) {
-  FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
-  return t > type::none_type && t <= type::last_numeric_type;
+template <typename... Args> constexpr auto count_named_args() -> size_t {
+  return count<is_named_arg<Args>::value...>();
+}
+
+template <typename... Args>
+constexpr auto count_statically_named_args() -> size_t {
+  return count<is_statically_named_arg<Args>::value...>();
 }
 
+struct unformattable {};
+struct unformattable_char : unformattable {};
+struct unformattable_pointer : unformattable {};
+
 template <typename Char> struct string_value {
   const Char* data;
-  std::size_t size;
+  size_t size;
+};
+
+template <typename Char> struct named_arg_value {
+  const named_arg_info<Char>* data;
+  size_t size;
 };
 
 template <typename Context> struct custom_value {
-  using parse_context = basic_format_parse_context<typename Context::char_type>;
-  const void* value;
-  void (*format)(const void* arg,
-                 typename Context::parse_context_type& parse_ctx, Context& ctx);
+  using parse_context = typename Context::parse_context_type;
+  void* value;
+  void (*format)(void* arg, parse_context& parse_ctx, Context& ctx);
 };
 
 // A formatting argument value.
@@ -840,12 +1259,13 @@ template <typename Context> class value {
   using char_type = typename Context::char_type;
 
   union {
+    monostate no_value;
     int int_value;
     unsigned uint_value;
     long long long_long_value;
     unsigned long long ulong_long_value;
-    int128_t int128_value;
-    uint128_t uint128_value;
+    int128_opt int128_value;
+    uint128_opt uint128_value;
     bool bool_value;
     char_type char_value;
     float float_value;
@@ -854,172 +1274,224 @@ template <typename Context> class value {
     const void* pointer;
     string_value<char_type> string;
     custom_value<Context> custom;
-    const named_arg_base<char_type>* named_arg;
+    named_arg_value<char_type> named_args;
   };
 
-  FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
-  FMT_CONSTEXPR value(unsigned val) : uint_value(val) {}
-  value(long long val) : long_long_value(val) {}
-  value(unsigned long long val) : ulong_long_value(val) {}
-  value(int128_t val) : int128_value(val) {}
-  value(uint128_t val) : uint128_value(val) {}
-  value(float val) : float_value(val) {}
-  value(double val) : double_value(val) {}
-  value(long double val) : long_double_value(val) {}
-  value(bool val) : bool_value(val) {}
-  value(char_type val) : char_value(val) {}
-  value(const char_type* val) { string.data = val; }
-  value(basic_string_view<char_type> val) {
+  constexpr FMT_INLINE value() : no_value() {}
+  constexpr FMT_INLINE value(int val) : int_value(val) {}
+  constexpr FMT_INLINE value(unsigned val) : uint_value(val) {}
+  constexpr FMT_INLINE value(long long val) : long_long_value(val) {}
+  constexpr FMT_INLINE value(unsigned long long val) : ulong_long_value(val) {}
+  FMT_INLINE value(int128_opt val) : int128_value(val) {}
+  FMT_INLINE value(uint128_opt val) : uint128_value(val) {}
+  constexpr FMT_INLINE value(float val) : float_value(val) {}
+  constexpr FMT_INLINE value(double val) : double_value(val) {}
+  FMT_INLINE value(long double val) : long_double_value(val) {}
+  constexpr FMT_INLINE value(bool val) : bool_value(val) {}
+  constexpr FMT_INLINE value(char_type val) : char_value(val) {}
+  FMT_CONSTEXPR FMT_INLINE value(const char_type* val) {
+    string.data = val;
+    if (is_constant_evaluated()) string.size = {};
+  }
+  FMT_CONSTEXPR FMT_INLINE value(basic_string_view<char_type> val) {
     string.data = val.data();
     string.size = val.size();
   }
-  value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const named_arg_info<char_type>* args, size_t size)
+      : named_args{args, size} {}
 
-  template <typename T> value(const T& val) {
-    custom.value = &val;
+  template <typename T> FMT_CONSTEXPR20 FMT_INLINE value(T& val) {
+    using value_type = remove_const_t<T>;
+    custom.value = const_cast<value_type*>(std::addressof(val));
     // Get the formatter type through the context to allow different contexts
     // have different extension points, e.g. `formatter<T>` for `format` and
     // `printf_formatter<T>` for `printf`.
     custom.format = format_custom_arg<
-        T, conditional_t<has_formatter<T, Context>::value,
-                         typename Context::template formatter_type<T>,
-                         fallback_formatter<T, char_type>>>;
+        value_type, typename Context::template formatter_type<value_type>>;
   }
-
-  value(const named_arg_base<char_type>& val) { named_arg = &val; }
+  value(unformattable);
+  value(unformattable_char);
+  value(unformattable_pointer);
 
  private:
   // Formats an argument of a custom type, such as a user-defined class.
   template <typename T, typename Formatter>
-  static void format_custom_arg(const void* arg,
+  static void format_custom_arg(void* arg,
                                 typename Context::parse_context_type& parse_ctx,
                                 Context& ctx) {
-    Formatter f;
+    auto f = Formatter();
     parse_ctx.advance_to(f.parse(parse_ctx));
-    ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
+    using qualified_type =
+        conditional_t<has_const_formatter<T, Context>(), const T, T>;
+    // Calling format through a mutable reference is deprecated.
+    ctx.advance_to(f.format(*static_cast<qualified_type*>(arg), ctx));
   }
 };
 
-template <typename Context, typename T>
-FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value);
-
 // To minimize the number of types we need to deal with, long is translated
 // either to int or to long long depending on its size.
 enum { long_short = sizeof(long) == sizeof(int) };
 using long_type = conditional_t<long_short, int, long long>;
 using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
 
+template <typename T> struct format_as_result {
+  template <typename U,
+            FMT_ENABLE_IF(std::is_enum<U>::value || std::is_class<U>::value)>
+  static auto map(U*) -> remove_cvref_t<decltype(format_as(std::declval<U>()))>;
+  static auto map(...) -> void;
+
+  using type = decltype(map(static_cast<T*>(nullptr)));
+};
+template <typename T> using format_as_t = typename format_as_result<T>::type;
+
+template <typename T>
+struct has_format_as
+    : bool_constant<!std::is_same<format_as_t<T>, void>::value> {};
+
 // Maps formatting arguments to core types.
+// arg_mapper reports errors by returning unformattable instead of using
+// static_assert because it's used in the is_formattable trait.
 template <typename Context> struct arg_mapper {
   using char_type = typename Context::char_type;
 
-  FMT_CONSTEXPR int map(signed char val) { return val; }
-  FMT_CONSTEXPR unsigned map(unsigned char val) { return val; }
-  FMT_CONSTEXPR int map(short val) { return val; }
-  FMT_CONSTEXPR unsigned map(unsigned short val) { return val; }
-  FMT_CONSTEXPR int map(int val) { return val; }
-  FMT_CONSTEXPR unsigned map(unsigned val) { return val; }
-  FMT_CONSTEXPR long_type map(long val) { return val; }
-  FMT_CONSTEXPR ulong_type map(unsigned long val) { return val; }
-  FMT_CONSTEXPR long long map(long long val) { return val; }
-  FMT_CONSTEXPR unsigned long long map(unsigned long long val) { return val; }
-  FMT_CONSTEXPR int128_t map(int128_t val) { return val; }
-  FMT_CONSTEXPR uint128_t map(uint128_t val) { return val; }
-  FMT_CONSTEXPR bool map(bool val) { return val; }
-
-  template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
-  FMT_CONSTEXPR char_type map(T val) {
-    static_assert(
-        std::is_same<T, char>::value || std::is_same<T, char_type>::value,
-        "mixing character types is disallowed");
+  FMT_CONSTEXPR FMT_INLINE auto map(signed char val) -> int { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned char val) -> unsigned {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(short val) -> int { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned short val) -> unsigned {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(int val) -> int { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned val) -> unsigned { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(long val) -> long_type { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned long val) -> ulong_type {
     return val;
   }
+  FMT_CONSTEXPR FMT_INLINE auto map(long long val) -> long long { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned long long val)
+      -> unsigned long long {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(int128_opt val) -> int128_opt {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(uint128_opt val) -> uint128_opt {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(bool val) -> bool { return val; }
 
-  FMT_CONSTEXPR float map(float val) { return val; }
-  FMT_CONSTEXPR double map(double val) { return val; }
-  FMT_CONSTEXPR long double map(long double val) { return val; }
+  template <typename T, FMT_ENABLE_IF(std::is_same<T, char>::value ||
+                                      std::is_same<T, char_type>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(T val) -> char_type {
+    return val;
+  }
+  template <typename T, enable_if_t<(std::is_same<T, wchar_t>::value ||
+#ifdef __cpp_char8_t
+                                     std::is_same<T, char8_t>::value ||
+#endif
+                                     std::is_same<T, char16_t>::value ||
+                                     std::is_same<T, char32_t>::value) &&
+                                        !std::is_same<T, char_type>::value,
+                                    int> = 0>
+  FMT_CONSTEXPR FMT_INLINE auto map(T) -> unformattable_char {
+    return {};
+  }
+
+  FMT_CONSTEXPR FMT_INLINE auto map(float val) -> float { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(double val) -> double { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(long double val) -> long double {
+    return val;
+  }
 
-  FMT_CONSTEXPR const char_type* map(char_type* val) { return val; }
-  FMT_CONSTEXPR const char_type* map(const char_type* val) { return val; }
-  template <typename T, FMT_ENABLE_IF(is_string<T>::value)>
-  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
-    static_assert(std::is_same<char_type, char_t<T>>::value,
-                  "mixing character types is disallowed");
+  FMT_CONSTEXPR FMT_INLINE auto map(char_type* val) -> const char_type* {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(const char_type* val) -> const char_type* {
+    return val;
+  }
+  template <typename T,
+            FMT_ENABLE_IF(is_string<T>::value && !std::is_pointer<T>::value &&
+                          std::is_same<char_type, char_t<T>>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
+      -> basic_string_view<char_type> {
     return to_string_view(val);
   }
   template <typename T,
-            FMT_ENABLE_IF(
-                std::is_constructible<basic_string_view<char_type>, T>::value &&
-                !is_string<T>::value && !has_formatter<T, Context>::value &&
-                !has_fallback_formatter<T, Context>::value)>
-  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
-    return basic_string_view<char_type>(val);
+            FMT_ENABLE_IF(is_string<T>::value && !std::is_pointer<T>::value &&
+                          !std::is_same<char_type, char_t<T>>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(const T&) -> unformattable_char {
+    return {};
+  }
+
+  FMT_CONSTEXPR FMT_INLINE auto map(void* val) -> const void* { return val; }
+  FMT_CONSTEXPR FMT_INLINE auto map(const void* val) -> const void* {
+    return val;
+  }
+  FMT_CONSTEXPR FMT_INLINE auto map(std::nullptr_t val) -> const void* {
+    return val;
   }
+
+  // Use SFINAE instead of a const T* parameter to avoid a conflict with the
+  // array overload.
   template <
       typename T,
       FMT_ENABLE_IF(
-          std::is_constructible<std_string_view<char_type>, T>::value &&
-          !std::is_constructible<basic_string_view<char_type>, T>::value &&
-          !is_string<T>::value && !has_formatter<T, Context>::value &&
-          !has_fallback_formatter<T, Context>::value)>
-  FMT_CONSTEXPR basic_string_view<char_type> map(const T& val) {
-    return std_string_view<char_type>(val);
-  }
-  FMT_CONSTEXPR const char* map(const signed char* val) {
-    static_assert(std::is_same<char_type, char>::value, "invalid string type");
-    return reinterpret_cast<const char*>(val);
-  }
-  FMT_CONSTEXPR const char* map(const unsigned char* val) {
-    static_assert(std::is_same<char_type, char>::value, "invalid string type");
-    return reinterpret_cast<const char*>(val);
-  }
-
-  FMT_CONSTEXPR const void* map(void* val) { return val; }
-  FMT_CONSTEXPR const void* map(const void* val) { return val; }
-  FMT_CONSTEXPR const void* map(std::nullptr_t val) { return val; }
-  template <typename T> FMT_CONSTEXPR int map(const T*) {
-    // Formatting of arbitrary pointers is disallowed. If you want to output
-    // a pointer cast it to "void *" or "const void *". In particular, this
-    // forbids formatting of "[const] volatile char *" which is printed as bool
-    // by iostreams.
-    static_assert(!sizeof(T), "formatting of non-void pointers is disallowed");
-    return 0;
+          std::is_pointer<T>::value || std::is_member_pointer<T>::value ||
+          std::is_function<typename std::remove_pointer<T>::type>::value ||
+          (std::is_array<T>::value &&
+           !std::is_convertible<T, const char_type*>::value))>
+  FMT_CONSTEXPR auto map(const T&) -> unformattable_pointer {
+    return {};
   }
 
-  template <typename T,
-            FMT_ENABLE_IF(std::is_enum<T>::value &&
-                          !has_formatter<T, Context>::value &&
-                          !has_fallback_formatter<T, Context>::value)>
-  FMT_CONSTEXPR auto map(const T& val)
-      -> decltype(std::declval<arg_mapper>().map(
-          static_cast<typename std::underlying_type<T>::type>(val))) {
-    return map(static_cast<typename std::underlying_type<T>::type>(val));
+  template <typename T, std::size_t N,
+            FMT_ENABLE_IF(!std::is_same<T, wchar_t>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(const T (&values)[N]) -> const T (&)[N] {
+    return values;
   }
-  template <typename T,
-            FMT_ENABLE_IF(!is_string<T>::value && !is_char<T>::value &&
-                          (has_formatter<T, Context>::value ||
-                           has_fallback_formatter<T, Context>::value))>
-  FMT_CONSTEXPR const T& map(const T& val) {
-    return val;
+
+  // Only map owning types because mapping views can be unsafe.
+  template <typename T, typename U = format_as_t<T>,
+            FMT_ENABLE_IF(std::is_arithmetic<U>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
+      -> decltype(FMT_DECLTYPE_THIS map(U())) {
+    return map(format_as(val));
   }
 
-  template <typename T>
-  FMT_CONSTEXPR const named_arg_base<char_type>& map(
-      const named_arg<T, char_type>& val) {
-    auto arg = make_arg<Context>(val.value);
-    std::memcpy(val.data, &arg, sizeof(arg));
+  template <typename T, typename U = remove_const_t<T>>
+  struct formattable : bool_constant<has_const_formatter<U, Context>() ||
+                                     (has_formatter<U, Context>::value &&
+                                      !std::is_const<T>::value)> {};
+
+  template <typename T, FMT_ENABLE_IF(formattable<T>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto do_map(T& val) -> T& {
     return val;
   }
+  template <typename T, FMT_ENABLE_IF(!formattable<T>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto do_map(T&) -> unformattable {
+    return {};
+  }
 
-  int map(...) {
-    constexpr bool formattable = sizeof(Context) == 0;
-    static_assert(
-        formattable,
-        "Cannot format argument. To make type T formattable provide a "
-        "formatter<T> specialization: "
-        "https://fmt.dev/latest/api.html#formatting-user-defined-types");
-    return 0;
+  template <typename T, typename U = remove_const_t<T>,
+            FMT_ENABLE_IF((std::is_class<U>::value || std::is_enum<U>::value ||
+                           std::is_union<U>::value) &&
+                          !is_string<U>::value && !is_char<U>::value &&
+                          !is_named_arg<U>::value &&
+                          !std::is_arithmetic<format_as_t<U>>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(T& val)
+      -> decltype(FMT_DECLTYPE_THIS do_map(val)) {
+    return do_map(val);
+  }
+
+  template <typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
+  FMT_CONSTEXPR FMT_INLINE auto map(const T& named_arg)
+      -> decltype(FMT_DECLTYPE_THIS map(named_arg.value)) {
+    return map(named_arg.value);
   }
+
+  auto map(...) -> unformattable { return {}; }
 };
 
 // A type constant after applying arg_mapper<Context>.
@@ -1028,24 +1500,138 @@ using mapped_type_constant =
     type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
                   typename Context::char_type>;
 
-enum { packed_arg_bits = 5 };
+enum { packed_arg_bits = 4 };
 // Maximum number of arguments with packed types.
-enum { max_packed_args = 63 / packed_arg_bits };
+enum { max_packed_args = 62 / packed_arg_bits };
 enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
+enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
+
+template <typename Char, typename InputIt>
+auto copy_str(InputIt begin, InputIt end, appender out) -> appender {
+  get_container(out).append(begin, end);
+  return out;
+}
+template <typename Char, typename InputIt>
+auto copy_str(InputIt begin, InputIt end,
+              std::back_insert_iterator<std::string> out)
+    -> std::back_insert_iterator<std::string> {
+  get_container(out).append(begin, end);
+  return out;
+}
+
+template <typename Char, typename R, typename OutputIt>
+FMT_CONSTEXPR auto copy_str(R&& rng, OutputIt out) -> OutputIt {
+  return detail::copy_str<Char>(rng.begin(), rng.end(), out);
+}
+
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
+// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
+template <typename...> struct void_t_impl {
+  using type = void;
+};
+template <typename... T> using void_t = typename void_t_impl<T...>::type;
+#else
+template <typename...> using void_t = void;
+#endif
+
+template <typename It, typename T, typename Enable = void>
+struct is_output_iterator : std::false_type {};
+
+template <typename It, typename T>
+struct is_output_iterator<
+    It, T,
+    void_t<typename std::iterator_traits<It>::iterator_category,
+           decltype(*std::declval<It>() = std::declval<T>())>>
+    : std::true_type {};
+
+template <typename It> struct is_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_back_insert_iterator<std::back_insert_iterator<Container>>
+    : std::true_type {};
+
+// A type-erased reference to an std::locale to avoid a heavy <locale> include.
+class locale_ref {
+ private:
+  const void* locale_;  // A type-erased pointer to std::locale.
+
+ public:
+  constexpr FMT_INLINE locale_ref() : locale_(nullptr) {}
+  template <typename Locale> explicit locale_ref(const Locale& loc);
+
+  explicit operator bool() const noexcept { return locale_ != nullptr; }
+
+  template <typename Locale> auto get() const -> Locale;
+};
+
+template <typename> constexpr auto encode_types() -> unsigned long long {
+  return 0;
+}
+
+template <typename Context, typename Arg, typename... Args>
+constexpr auto encode_types() -> unsigned long long {
+  return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
+         (encode_types<Context, Args...>() << packed_arg_bits);
+}
+
+#if defined(__cpp_if_constexpr)
+// This type is intentionally undefined, only used for errors
+template <typename T, typename Char> struct type_is_unformattable_for;
+#endif
 
-template <typename Context> class arg_map;
-}  // namespace internal
+template <bool PACKED, typename Context, typename T, FMT_ENABLE_IF(PACKED)>
+FMT_CONSTEXPR FMT_INLINE auto make_arg(T& val) -> value<Context> {
+  using arg_type = remove_cvref_t<decltype(arg_mapper<Context>().map(val))>;
+
+  constexpr bool formattable_char =
+      !std::is_same<arg_type, unformattable_char>::value;
+  static_assert(formattable_char, "Mixing character types is disallowed.");
+
+  // Formatting of arbitrary pointers is disallowed. If you want to format a
+  // pointer cast it to `void*` or `const void*`. In particular, this forbids
+  // formatting of `[const] volatile char*` printed as bool by iostreams.
+  constexpr bool formattable_pointer =
+      !std::is_same<arg_type, unformattable_pointer>::value;
+  static_assert(formattable_pointer,
+                "Formatting of non-void pointers is disallowed.");
+
+  constexpr bool formattable = !std::is_same<arg_type, unformattable>::value;
+#if defined(__cpp_if_constexpr)
+  if constexpr (!formattable) {
+    type_is_unformattable_for<T, typename Context::char_type> _;
+  }
+#endif
+  static_assert(
+      formattable,
+      "Cannot format an argument. To make type T formattable provide a "
+      "formatter<T> specialization: https://fmt.dev/latest/api.html#udt");
+  return {arg_mapper<Context>().map(val)};
+}
 
-// A formatting argument. It is a trivially copyable/constructible type to
-// allow storage in basic_memory_buffer.
+template <typename Context, typename T>
+FMT_CONSTEXPR auto make_arg(T& val) -> basic_format_arg<Context> {
+  auto arg = basic_format_arg<Context>();
+  arg.type_ = mapped_type_constant<T, Context>::value;
+  arg.value_ = make_arg<true, Context>(val);
+  return arg;
+}
+
+template <bool PACKED, typename Context, typename T, FMT_ENABLE_IF(!PACKED)>
+FMT_CONSTEXPR inline auto make_arg(T& val) -> basic_format_arg<Context> {
+  return make_arg<Context>(val);
+}
+}  // namespace detail
+FMT_BEGIN_EXPORT
+
+// A formatting argument. Context is a template parameter for the compiled API
+// where output can be unbuffered.
 template <typename Context> class basic_format_arg {
  private:
-  internal::value<Context> value_;
-  internal::type type_;
+  detail::value<Context> value_;
+  detail::type type_;
 
   template <typename ContextType, typename T>
-  friend FMT_CONSTEXPR basic_format_arg<ContextType> internal::make_arg(
-      const T& value);
+  friend FMT_CONSTEXPR auto detail::make_arg(T& value)
+      -> basic_format_arg<ContextType>;
 
   template <typename Visitor, typename Ctx>
   friend FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
@@ -1053,14 +1639,20 @@ template <typename Context> class basic_format_arg {
       -> decltype(vis(0));
 
   friend class basic_format_args<Context>;
-  friend class internal::arg_map<Context>;
+  friend class dynamic_format_arg_store<Context>;
 
   using char_type = typename Context::char_type;
 
+  template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+  friend struct detail::arg_data;
+
+  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
+      : value_(args, size) {}
+
  public:
   class handle {
    public:
-    explicit handle(internal::custom_value<Context> custom) : custom_(custom) {}
+    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
 
     void format(typename Context::parse_context_type& parse_ctx,
                 Context& ctx) const {
@@ -1068,19 +1660,30 @@ template <typename Context> class basic_format_arg {
     }
 
    private:
-    internal::custom_value<Context> custom_;
+    detail::custom_value<Context> custom_;
   };
 
-  FMT_CONSTEXPR basic_format_arg() : type_(internal::type::none_type) {}
+  constexpr basic_format_arg() : type_(detail::type::none_type) {}
 
-  FMT_CONSTEXPR explicit operator bool() const FMT_NOEXCEPT {
-    return type_ != internal::type::none_type;
+  constexpr explicit operator bool() const noexcept {
+    return type_ != detail::type::none_type;
   }
 
-  internal::type type() const { return type_; }
+  auto type() const -> detail::type { return type_; }
+
+  auto is_integral() const -> bool { return detail::is_integral_type(type_); }
+  auto is_arithmetic() const -> bool {
+    return detail::is_arithmetic_type(type_);
+  }
 
-  bool is_integral() const { return internal::is_integral_type(type_); }
-  bool is_arithmetic() const { return internal::is_arithmetic_type(type_); }
+  FMT_INLINE auto format_custom(const char_type* parse_begin,
+                                typename Context::parse_context_type& parse_ctx,
+                                Context& ctx) -> bool {
+    if (type_ != detail::type::custom_type) return false;
+    parse_ctx.advance_to(parse_begin);
+    value_.custom.format(value_.custom.value, parse_ctx, ctx);
+    return true;
+  }
 };
 
 /**
@@ -1090,230 +1693,109 @@ template <typename Context> class basic_format_arg {
   ``vis(value)`` will be called with the value of type ``double``.
   \endrst
  */
+// DEPRECATED!
 template <typename Visitor, typename Context>
-FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
-                                    const basic_format_arg<Context>& arg)
-    -> decltype(vis(0)) {
-  using char_type = typename Context::char_type;
+FMT_CONSTEXPR FMT_INLINE auto visit_format_arg(
+    Visitor&& vis, const basic_format_arg<Context>& arg) -> decltype(vis(0)) {
   switch (arg.type_) {
-  case internal::type::none_type:
-    break;
-  case internal::type::named_arg_type:
-    FMT_ASSERT(false, "invalid argument type");
+  case detail::type::none_type:
     break;
-  case internal::type::int_type:
+  case detail::type::int_type:
     return vis(arg.value_.int_value);
-  case internal::type::uint_type:
+  case detail::type::uint_type:
     return vis(arg.value_.uint_value);
-  case internal::type::long_long_type:
+  case detail::type::long_long_type:
     return vis(arg.value_.long_long_value);
-  case internal::type::ulong_long_type:
+  case detail::type::ulong_long_type:
     return vis(arg.value_.ulong_long_value);
-#if FMT_USE_INT128
-  case internal::type::int128_type:
-    return vis(arg.value_.int128_value);
-  case internal::type::uint128_type:
-    return vis(arg.value_.uint128_value);
-#else
-  case internal::type::int128_type:
-  case internal::type::uint128_type:
-    break;
-#endif
-  case internal::type::bool_type:
+  case detail::type::int128_type:
+    return vis(detail::convert_for_visit(arg.value_.int128_value));
+  case detail::type::uint128_type:
+    return vis(detail::convert_for_visit(arg.value_.uint128_value));
+  case detail::type::bool_type:
     return vis(arg.value_.bool_value);
-  case internal::type::char_type:
+  case detail::type::char_type:
     return vis(arg.value_.char_value);
-  case internal::type::float_type:
+  case detail::type::float_type:
     return vis(arg.value_.float_value);
-  case internal::type::double_type:
+  case detail::type::double_type:
     return vis(arg.value_.double_value);
-  case internal::type::long_double_type:
+  case detail::type::long_double_type:
     return vis(arg.value_.long_double_value);
-  case internal::type::cstring_type:
+  case detail::type::cstring_type:
     return vis(arg.value_.string.data);
-  case internal::type::string_type:
-    return vis(basic_string_view<char_type>(arg.value_.string.data,
-                                            arg.value_.string.size));
-  case internal::type::pointer_type:
+  case detail::type::string_type:
+    using sv = basic_string_view<typename Context::char_type>;
+    return vis(sv(arg.value_.string.data, arg.value_.string.size));
+  case detail::type::pointer_type:
     return vis(arg.value_.pointer);
-  case internal::type::custom_type:
+  case detail::type::custom_type:
     return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
   }
   return vis(monostate());
 }
 
-namespace internal {
-// A map from argument names to their values for named arguments.
-template <typename Context> class arg_map {
- private:
-  using char_type = typename Context::char_type;
-
-  struct entry {
-    basic_string_view<char_type> name;
-    basic_format_arg<Context> arg;
-  };
-
-  entry* map_;
-  unsigned size_;
-
-  void push_back(value<Context> val) {
-    const auto& named = *val.named_arg;
-    map_[size_] = {named.name, named.template deserialize<Context>()};
-    ++size_;
-  }
-
- public:
-  arg_map(const arg_map&) = delete;
-  void operator=(const arg_map&) = delete;
-  arg_map() : map_(nullptr), size_(0) {}
-  void init(const basic_format_args<Context>& args);
-  ~arg_map() { delete[] map_; }
-
-  basic_format_arg<Context> find(basic_string_view<char_type> name) const {
-    // The list is unsorted, so just return the first matching name.
-    for (entry *it = map_, *end = map_ + size_; it != end; ++it) {
-      if (it->name == name) return it->arg;
-    }
-    return {};
-  }
-};
-
-// A type-erased reference to an std::locale to avoid heavy <locale> include.
-class locale_ref {
- private:
-  const void* locale_;  // A type-erased pointer to std::locale.
-
- public:
-  locale_ref() : locale_(nullptr) {}
-  template <typename Locale> explicit locale_ref(const Locale& loc);
-
-  explicit operator bool() const FMT_NOEXCEPT { return locale_ != nullptr; }
-
-  template <typename Locale> Locale get() const;
-};
-
-template <typename> constexpr unsigned long long encode_types() { return 0; }
-
-template <typename Context, typename Arg, typename... Args>
-constexpr unsigned long long encode_types() {
-  return static_cast<unsigned>(mapped_type_constant<Arg, Context>::value) |
-         (encode_types<Context, Args...>() << packed_arg_bits);
-}
-
-template <typename Context, typename T>
-FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
-  basic_format_arg<Context> arg;
-  arg.type_ = mapped_type_constant<T, Context>::value;
-  arg.value_ = arg_mapper<Context>().map(value);
-  return arg;
-}
-
-// The type template parameter is there to avoid an ODR violation when using
-// a fallback formatter in one translation unit and an implicit conversion in
-// another (not recommended).
-template <bool IS_PACKED, typename Context, type, typename T,
-          FMT_ENABLE_IF(IS_PACKED)>
-inline value<Context> make_arg(const T& val) {
-  return arg_mapper<Context>().map(val);
-}
-
-template <bool IS_PACKED, typename Context, type, typename T,
-          FMT_ENABLE_IF(!IS_PACKED)>
-inline basic_format_arg<Context> make_arg(const T& value) {
-  return make_arg<Context>(value);
-}
-
-template <typename T> struct is_reference_wrapper : std::false_type {};
-
-template <typename T>
-struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
-
-class dynamic_arg_list {
-  // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
-  // templates it doesn't complain about inability to deduce single translation
-  // unit for placing vtable. So storage_node_base is made a fake template.
-  template <typename = void> struct node {
-    virtual ~node() = default;
-    std::unique_ptr<node<>> next;
-  };
-
-  template <typename T> struct typed_node : node<> {
-    T value;
-
-    template <typename Arg>
-    FMT_CONSTEXPR typed_node(const Arg& arg) : value(arg) {}
-
-    template <typename Char>
-    FMT_CONSTEXPR typed_node(const basic_string_view<Char>& arg)
-        : value(arg.data(), arg.size()) {}
-  };
-
-  std::unique_ptr<node<>> head_;
-
- public:
-  template <typename T, typename Arg> const T& push(const Arg& arg) {
-    auto node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
-    auto& value = node->value;
-    node->next = std::move(head_);
-    head_ = std::move(node);
-    return value;
-  }
-};
-}  // namespace internal
-
 // Formatting context.
 template <typename OutputIt, typename Char> class basic_format_context {
- public:
-  /** The character type for the output. */
-  using char_type = Char;
-
  private:
   OutputIt out_;
   basic_format_args<basic_format_context> args_;
-  internal::arg_map<basic_format_context> map_;
-  internal::locale_ref loc_;
+  detail::locale_ref loc_;
 
  public:
   using iterator = OutputIt;
   using format_arg = basic_format_arg<basic_format_context>;
+  using format_args = basic_format_args<basic_format_context>;
   using parse_context_type = basic_format_parse_context<Char>;
-  template <typename T> using formatter_type = formatter<T, char_type>;
+  template <typename T> using formatter_type = formatter<T, Char>;
 
+  /** The character type for the output. */
+  using char_type = Char;
+
+  basic_format_context(basic_format_context&&) = default;
   basic_format_context(const basic_format_context&) = delete;
   void operator=(const basic_format_context&) = delete;
   /**
-   Constructs a ``basic_format_context`` object. References to the arguments are
-   stored in the object so make sure they have appropriate lifetimes.
+    Constructs a ``basic_format_context`` object. References to the arguments
+    are stored in the object so make sure they have appropriate lifetimes.
    */
-  basic_format_context(OutputIt out,
-                       basic_format_args<basic_format_context> ctx_args,
-                       internal::locale_ref loc = internal::locale_ref())
+  constexpr basic_format_context(OutputIt out, format_args ctx_args,
+                                 detail::locale_ref loc = {})
       : out_(out), args_(ctx_args), loc_(loc) {}
 
-  format_arg arg(int id) const { return args_.get(id); }
-
-  // Checks if manual indexing is used and returns the argument with the
-  // specified name.
-  format_arg arg(basic_string_view<char_type> name);
+  constexpr auto arg(int id) const -> format_arg { return args_.get(id); }
+  FMT_CONSTEXPR auto arg(basic_string_view<Char> name) -> format_arg {
+    return args_.get(name);
+  }
+  FMT_CONSTEXPR auto arg_id(basic_string_view<Char> name) -> int {
+    return args_.get_id(name);
+  }
+  auto args() const -> const format_args& { return args_; }
 
-  internal::error_handler error_handler() { return {}; }
+  // DEPRECATED!
+  FMT_CONSTEXPR auto error_handler() -> detail::error_handler { return {}; }
   void on_error(const char* message) { error_handler().on_error(message); }
 
   // Returns an iterator to the beginning of the output range.
-  iterator out() { return out_; }
+  FMT_CONSTEXPR auto out() -> iterator { return out_; }
 
   // Advances the begin iterator to ``it``.
-  void advance_to(iterator it) { out_ = it; }
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
+  }
 
-  internal::locale_ref locale() { return loc_; }
+  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
 };
 
 template <typename Char>
 using buffer_context =
-    basic_format_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
+    basic_format_context<detail::buffer_appender<Char>, Char>;
 using format_context = buffer_context<char>;
-using wformat_context = buffer_context<wchar_t>;
+
+template <typename T, typename Char = char>
+using is_formattable = bool_constant<!std::is_base_of<
+    detail::unformattable, decltype(detail::arg_mapper<buffer_context<Char>>()
+                                        .map(std::declval<T&>()))>::value>;
 
 /**
   \rst
@@ -1331,141 +1813,70 @@ class format_arg_store
 {
  private:
   static const size_t num_args = sizeof...(Args);
-  static const bool is_packed = num_args < internal::max_packed_args;
+  static constexpr size_t num_named_args = detail::count_named_args<Args...>();
+  static const bool is_packed = num_args <= detail::max_packed_args;
 
-  using value_type = conditional_t<is_packed, internal::value<Context>,
+  using value_type = conditional_t<is_packed, detail::value<Context>,
                                    basic_format_arg<Context>>;
 
-  // If the arguments are not packed, add one more element to mark the end.
-  value_type data_[num_args + (num_args == 0 ? 1 : 0)];
+  detail::arg_data<value_type, typename Context::char_type, num_args,
+                   num_named_args>
+      data_;
 
   friend class basic_format_args<Context>;
 
- public:
-  static constexpr unsigned long long types =
-      is_packed ? internal::encode_types<Context, Args...>()
-                : internal::is_unpacked_bit | num_args;
+  static constexpr unsigned long long desc =
+      (is_packed ? detail::encode_types<Context, Args...>()
+                 : detail::is_unpacked_bit | num_args) |
+      (num_named_args != 0
+           ? static_cast<unsigned long long>(detail::has_named_args_bit)
+           : 0);
 
-  format_arg_store(const Args&... args)
+ public:
+  template <typename... T>
+  FMT_CONSTEXPR FMT_INLINE format_arg_store(T&... args)
       :
 #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
         basic_format_args<Context>(*this),
 #endif
-        data_{internal::make_arg<
-            is_packed, Context,
-            internal::mapped_type_constant<Args, Context>::value>(args)...} {
+        data_{detail::make_arg<is_packed, Context>(args)...} {
+    if (detail::const_check(num_named_args != 0))
+      detail::init_named_args(data_.named_args(), 0, 0, args...);
   }
 };
 
 /**
-  \rst
-  Constructs an `~fmt::format_arg_store` object that contains references to
-  arguments and can be implicitly converted to `~fmt::format_args`. `Context`
-  can be omitted in which case it defaults to `~fmt::context`.
-  See `~fmt::arg` for lifetime considerations.
-  \endrst
- */
-template <typename Context = format_context, typename... Args>
-inline format_arg_store<Context, Args...> make_format_args(
-    const Args&... args) {
-  return {args...};
-}
-
-/**
-  \rst
-  A dynamic version of `fmt::format_arg_store<>`.
-  It's equipped with a storage to potentially temporary objects which lifetime
-  could be shorter than the format arguments object.
-
-  It can be implicitly converted into `~fmt::basic_format_args` for passing
-  into type-erased formatting functions such as `~fmt::vformat`.
-  \endrst
- */
-template <typename Context>
-class dynamic_format_arg_store
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-    // Workaround a GCC template argument substitution bug.
-    : public basic_format_args<Context>
-#endif
-{
- private:
-  using char_type = typename Context::char_type;
-
-  template <typename T> struct need_copy {
-    static constexpr internal::type mapped_type =
-        internal::mapped_type_constant<T, Context>::value;
-
-    enum {
-      value = !(internal::is_reference_wrapper<T>::value ||
-                std::is_same<T, basic_string_view<char_type>>::value ||
-                std::is_same<T, internal::std_string_view<char_type>>::value ||
-                (mapped_type != internal::type::cstring_type &&
-                 mapped_type != internal::type::string_type &&
-                 mapped_type != internal::type::custom_type &&
-                 mapped_type != internal::type::named_arg_type))
-    };
-  };
-
-  template <typename T>
-  using stored_type = conditional_t<internal::is_string<T>::value,
-                                    std::basic_string<char_type>, T>;
-
-  // Storage of basic_format_arg must be contiguous.
-  std::vector<basic_format_arg<Context>> data_;
-
-  // Storage of arguments not fitting into basic_format_arg must grow
-  // without relocation because items in data_ refer to it.
-  internal::dynamic_arg_list dynamic_args_;
-
-  friend class basic_format_args<Context>;
-
-  unsigned long long get_types() const {
-    return internal::is_unpacked_bit | data_.size();
-  }
-
-  template <typename T> void emplace_arg(const T& arg) {
-    data_.emplace_back(internal::make_arg<Context>(arg));
-  }
-
- public:
-  /**
-    \rst
-    Adds an argument into the dynamic store for later passing to a formating
-    function.
-
-    Note that custom types and string types (but not string views!) are copied
-    into the store with dynamic memory (in addition to resizing vector).
+  \rst
+  Constructs a `~fmt::format_arg_store` object that contains references to
+  arguments and can be implicitly converted to `~fmt::format_args`. `Context`
+  can be omitted in which case it defaults to `~fmt::format_context`.
+  See `~fmt::arg` for lifetime considerations.
+  \endrst
+ */
+// Arguments are taken by lvalue references to avoid some lifetime issues.
+template <typename Context = format_context, typename... T>
+constexpr auto make_format_args(T&... args)
+    -> format_arg_store<Context, remove_cvref_t<T>...> {
+  return {args...};
+}
 
-    **Example**::
+/**
+  \rst
+  Returns a named argument to be used in a formatting function.
+  It should only be used in a call to a formatting function or
+  `dynamic_format_arg_store::push_back`.
 
-      fmt::dynamic_format_arg_store<fmt::format_context> store;
-      store.push_back(42);
-      store.push_back("abc");
-      store.push_back(1.5f);
-      std::string result = fmt::vformat("{} and {} and {}", store);
-    \endrst
-  */
-  template <typename T> void push_back(const T& arg) {
-    static_assert(
-        !std::is_base_of<internal::named_arg_base<char_type>, T>::value,
-        "named arguments are not supported yet");
-    if (internal::const_check(need_copy<T>::value))
-      emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
-    else
-      emplace_arg(arg);
-  }
+  **Example**::
 
-  /**
-    Adds a reference to the argument into the dynamic store for later passing to
-    a formating function.
-  */
-  template <typename T> void push_back(std::reference_wrapper<T> arg) {
-    static_assert(
-        need_copy<T>::value,
-        "objects of built-in types and string views are always copied");
-    emplace_arg(arg.get());
-  }
-};
+    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+  \endrst
+ */
+template <typename Char, typename T>
+inline auto arg(const Char* name, const T& arg) -> detail::named_arg<Char, T> {
+  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
+  return {name, arg};
+}
+FMT_END_EXPORT
 
 /**
   \rst
@@ -1474,7 +1885,7 @@ class dynamic_format_arg_store
   ``vformat``::
 
     void vlog(string_view format_str, format_args args);  // OK
-    format_args args = make_format_args(42);  // Error: dangling reference
+    format_args args = make_format_args();  // Error: dangling reference
   \endrst
  */
 template <typename Context> class basic_format_args {
@@ -1483,49 +1894,42 @@ template <typename Context> class basic_format_args {
   using format_arg = basic_format_arg<Context>;
 
  private:
-  // To reduce compiled code size per formatting function call, types of first
-  // max_packed_args arguments are passed in the types_ field.
-  unsigned long long types_;
+  // A descriptor that contains information about formatting arguments.
+  // If the number of arguments is less or equal to max_packed_args then
+  // argument types are passed in the descriptor. This reduces binary code size
+  // per formatting function call.
+  unsigned long long desc_;
   union {
-    // If the number of arguments is less than max_packed_args, the argument
-    // values are stored in values_, otherwise they are stored in args_.
-    // This is done to reduce compiled code size as storing larger objects
+    // If is_packed() returns true then argument values are stored in values_;
+    // otherwise they are stored in args_. This is done to improve cache
+    // locality and reduce compiled code size since storing larger objects
     // may require more code (at least on x86-64) even if the same amount of
     // data is actually copied to stack. It saves ~10% on the bloat test.
-    const internal::value<Context>* values_;
+    const detail::value<Context>* values_;
     const format_arg* args_;
   };
 
-  bool is_packed() const { return (types_ & internal::is_unpacked_bit) == 0; }
-
-  internal::type type(int index) const {
-    int shift = index * internal::packed_arg_bits;
-    unsigned int mask = (1 << internal::packed_arg_bits) - 1;
-    return static_cast<internal::type>((types_ >> shift) & mask);
+  constexpr auto is_packed() const -> bool {
+    return (desc_ & detail::is_unpacked_bit) == 0;
+  }
+  auto has_named_args() const -> bool {
+    return (desc_ & detail::has_named_args_bit) != 0;
   }
 
-  friend class internal::arg_map<Context>;
-
-  void set_data(const internal::value<Context>* values) { values_ = values; }
-  void set_data(const format_arg* args) { args_ = args; }
-
-  format_arg do_get(int index) const {
-    format_arg arg;
-    if (!is_packed()) {
-      auto num_args = max_size();
-      if (index < num_args) arg = args_[index];
-      return arg;
-    }
-    if (index > internal::max_packed_args) return arg;
-    arg.type_ = type(index);
-    if (arg.type_ == internal::type::none_type) return arg;
-    internal::value<Context>& val = arg.value_;
-    val = values_[index];
-    return arg;
+  FMT_CONSTEXPR auto type(int index) const -> detail::type {
+    int shift = index * detail::packed_arg_bits;
+    unsigned int mask = (1 << detail::packed_arg_bits) - 1;
+    return static_cast<detail::type>((desc_ >> shift) & mask);
   }
 
+  constexpr FMT_INLINE basic_format_args(unsigned long long desc,
+                                         const detail::value<Context>* values)
+      : desc_(desc), values_(values) {}
+  constexpr basic_format_args(unsigned long long desc, const format_arg* args)
+      : desc_(desc), args_(args) {}
+
  public:
-  basic_format_args() : types_(0) {}
+  constexpr basic_format_args() : desc_(0), args_(nullptr) {}
 
   /**
    \rst
@@ -1533,10 +1937,10 @@ template <typename Context> class basic_format_args {
    \endrst
    */
   template <typename... Args>
-  basic_format_args(const format_arg_store<Context, Args...>& store)
-      : types_(store.types) {
-    set_data(store.data_);
-  }
+  constexpr FMT_INLINE basic_format_args(
+      const format_arg_store<Context, Args...>& store)
+      : basic_format_args(format_arg_store<Context, Args...>::desc,
+                          store.data_.args()) {}
 
   /**
    \rst
@@ -1544,253 +1948,1022 @@ template <typename Context> class basic_format_args {
    `~fmt::dynamic_format_arg_store`.
    \endrst
    */
-  basic_format_args(const dynamic_format_arg_store<Context>& store)
-      : types_(store.get_types()) {
-    set_data(store.data_.data());
-  }
+  constexpr FMT_INLINE basic_format_args(
+      const dynamic_format_arg_store<Context>& store)
+      : basic_format_args(store.get_types(), store.data()) {}
 
   /**
    \rst
    Constructs a `basic_format_args` object from a dynamic set of arguments.
    \endrst
    */
-  basic_format_args(const format_arg* args, int count)
-      : types_(internal::is_unpacked_bit | internal::to_unsigned(count)) {
-    set_data(args);
-  }
+  constexpr basic_format_args(const format_arg* args, int count)
+      : basic_format_args(detail::is_unpacked_bit | detail::to_unsigned(count),
+                          args) {}
 
-  /** Returns the argument at specified index. */
-  format_arg get(int index) const {
-    format_arg arg = do_get(index);
-    if (arg.type_ == internal::type::named_arg_type)
-      arg = arg.value_.named_arg->template deserialize<Context>();
+  /** Returns the argument with the specified id. */
+  FMT_CONSTEXPR auto get(int id) const -> format_arg {
+    format_arg arg;
+    if (!is_packed()) {
+      if (id < max_size()) arg = args_[id];
+      return arg;
+    }
+    if (id >= detail::max_packed_args) return arg;
+    arg.type_ = type(id);
+    if (arg.type_ == detail::type::none_type) return arg;
+    arg.value_ = values_[id];
     return arg;
   }
 
-  int max_size() const {
-    unsigned long long max_packed = internal::max_packed_args;
+  template <typename Char>
+  auto get(basic_string_view<Char> name) const -> format_arg {
+    int id = get_id(name);
+    return id >= 0 ? get(id) : format_arg();
+  }
+
+  template <typename Char>
+  auto get_id(basic_string_view<Char> name) const -> int {
+    if (!has_named_args()) return -1;
+    const auto& named_args =
+        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
+    for (size_t i = 0; i < named_args.size; ++i) {
+      if (named_args.data[i].name == name) return named_args.data[i].id;
+    }
+    return -1;
+  }
+
+  auto max_size() const -> int {
+    unsigned long long max_packed = detail::max_packed_args;
     return static_cast<int>(is_packed() ? max_packed
-                                        : types_ & ~internal::is_unpacked_bit);
+                                        : desc_ & ~detail::is_unpacked_bit);
   }
 };
 
-/** An alias to ``basic_format_args<context>``. */
-// It is a separate type rather than an alias to make symbols readable.
-struct format_args : basic_format_args<format_context> {
-  template <typename... Args>
-  format_args(Args&&... args)
-      : basic_format_args<format_context>(static_cast<Args&&>(args)...) {}
+/** An alias to ``basic_format_args<format_context>``. */
+// A separate type would result in shorter symbols but break ABI compatibility
+// between clang and gcc on ARM (#1919).
+FMT_EXPORT using format_args = basic_format_args<format_context>;
+
+// We cannot use enum classes as bit fields because of a gcc bug, so we put them
+// in namespaces instead (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414).
+// Additionally, if an underlying type is specified, older gcc incorrectly warns
+// that the type is too small. Both bugs are fixed in gcc 9.3.
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 903
+#  define FMT_ENUM_UNDERLYING_TYPE(type)
+#else
+#  define FMT_ENUM_UNDERLYING_TYPE(type) : type
+#endif
+namespace align {
+enum type FMT_ENUM_UNDERLYING_TYPE(unsigned char){none, left, right, center,
+                                                  numeric};
+}
+using align_t = align::type;
+namespace sign {
+enum type FMT_ENUM_UNDERLYING_TYPE(unsigned char){none, minus, plus, space};
+}
+using sign_t = sign::type;
+
+namespace detail {
+
+// Workaround an array initialization issue in gcc 4.8.
+template <typename Char> struct fill_t {
+ private:
+  enum { max_size = 4 };
+  Char data_[max_size] = {Char(' '), Char(0), Char(0), Char(0)};
+  unsigned char size_ = 1;
+
+ public:
+  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
+    auto size = s.size();
+    FMT_ASSERT(size <= max_size, "invalid fill");
+    for (size_t i = 0; i < size; ++i) data_[i] = s[i];
+    size_ = static_cast<unsigned char>(size);
+  }
+
+  constexpr auto size() const -> size_t { return size_; }
+  constexpr auto data() const -> const Char* { return data_; }
+
+  FMT_CONSTEXPR auto operator[](size_t index) -> Char& { return data_[index]; }
+  FMT_CONSTEXPR auto operator[](size_t index) const -> const Char& {
+    return data_[index];
+  }
 };
-struct wformat_args : basic_format_args<wformat_context> {
-  template <typename... Args>
-  wformat_args(Args&&... args)
-      : basic_format_args<wformat_context>(static_cast<Args&&>(args)...) {}
+}  // namespace detail
+
+enum class presentation_type : unsigned char {
+  none,
+  dec,             // 'd'
+  oct,             // 'o'
+  hex_lower,       // 'x'
+  hex_upper,       // 'X'
+  bin_lower,       // 'b'
+  bin_upper,       // 'B'
+  hexfloat_lower,  // 'a'
+  hexfloat_upper,  // 'A'
+  exp_lower,       // 'e'
+  exp_upper,       // 'E'
+  fixed_lower,     // 'f'
+  fixed_upper,     // 'F'
+  general_lower,   // 'g'
+  general_upper,   // 'G'
+  chr,             // 'c'
+  string,          // 's'
+  pointer,         // 'p'
+  debug            // '?'
+};
+
+// Format specifiers for built-in and string types.
+template <typename Char = char> struct format_specs {
+  int width;
+  int precision;
+  presentation_type type;
+  align_t align : 4;
+  sign_t sign : 3;
+  bool alt : 1;  // Alternate form ('#').
+  bool localized : 1;
+  detail::fill_t<Char> fill;
+
+  constexpr format_specs()
+      : width(0),
+        precision(-1),
+        type(presentation_type::none),
+        align(align::none),
+        sign(sign::none),
+        alt(false),
+        localized(false) {}
+};
+
+namespace detail {
+
+enum class arg_id_kind { none, index, name };
+
+// An argument reference.
+template <typename Char> struct arg_ref {
+  FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
+
+  FMT_CONSTEXPR explicit arg_ref(int index)
+      : kind(arg_id_kind::index), val(index) {}
+  FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
+      : kind(arg_id_kind::name), val(name) {}
+
+  FMT_CONSTEXPR auto operator=(int idx) -> arg_ref& {
+    kind = arg_id_kind::index;
+    val.index = idx;
+    return *this;
+  }
+
+  arg_id_kind kind;
+  union value {
+    FMT_CONSTEXPR value(int idx = 0) : index(idx) {}
+    FMT_CONSTEXPR value(basic_string_view<Char> n) : name(n) {}
+
+    int index;
+    basic_string_view<Char> name;
+  } val;
+};
+
+// Format specifiers with width and precision resolved at formatting rather
+// than parsing time to allow reusing the same parsed specifiers with
+// different sets of arguments (precompilation of format strings).
+template <typename Char = char>
+struct dynamic_format_specs : format_specs<Char> {
+  arg_ref<Char> width_ref;
+  arg_ref<Char> precision_ref;
 };
 
-template <typename Container> struct is_contiguous : std::false_type {};
+// Converts a character to ASCII. Returns '\0' on conversion failure.
+template <typename Char, FMT_ENABLE_IF(std::is_integral<Char>::value)>
+constexpr auto to_ascii(Char c) -> char {
+  return c <= 0xff ? static_cast<char>(c) : '\0';
+}
+template <typename Char, FMT_ENABLE_IF(std::is_enum<Char>::value)>
+constexpr auto to_ascii(Char c) -> char {
+  return c <= 0xff ? static_cast<char>(c) : '\0';
+}
 
+// Returns the number of code units in a code point or 1 on error.
 template <typename Char>
-struct is_contiguous<std::basic_string<Char>> : std::true_type {};
+FMT_CONSTEXPR auto code_point_length(const Char* begin) -> int {
+  if (const_check(sizeof(Char) != 1)) return 1;
+  auto c = static_cast<unsigned char>(*begin);
+  return static_cast<int>((0x3a55000000000000ull >> (2 * (c >> 3))) & 0x3) + 1;
+}
+
+// Return the result via the out param to workaround gcc bug 77539.
+template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
+FMT_CONSTEXPR auto find(Ptr first, Ptr last, T value, Ptr& out) -> bool {
+  for (out = first; out != last; ++out) {
+    if (*out == value) return true;
+  }
+  return false;
+}
 
+template <>
+inline auto find<false, char>(const char* first, const char* last, char value,
+                              const char*& out) -> bool {
+  out = static_cast<const char*>(
+      std::memchr(first, value, to_unsigned(last - first)));
+  return out != nullptr;
+}
+
+// Parses the range [begin, end) as an unsigned integer. This function assumes
+// that the range is non-empty and the first character is a digit.
 template <typename Char>
-struct is_contiguous<internal::buffer<Char>> : std::true_type {};
+FMT_CONSTEXPR auto parse_nonnegative_int(const Char*& begin, const Char* end,
+                                         int error_value) noexcept -> int {
+  FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
+  unsigned value = 0, prev = 0;
+  auto p = begin;
+  do {
+    prev = value;
+    value = value * 10 + unsigned(*p - '0');
+    ++p;
+  } while (p != end && '0' <= *p && *p <= '9');
+  auto num_digits = p - begin;
+  begin = p;
+  if (num_digits <= std::numeric_limits<int>::digits10)
+    return static_cast<int>(value);
+  // Check for overflow.
+  const unsigned max = to_unsigned((std::numeric_limits<int>::max)());
+  return num_digits == std::numeric_limits<int>::digits10 + 1 &&
+                 prev * 10ull + unsigned(p[-1] - '0') <= max
+             ? static_cast<int>(value)
+             : error_value;
+}
 
-namespace internal {
+FMT_CONSTEXPR inline auto parse_align(char c) -> align_t {
+  switch (c) {
+  case '<':
+    return align::left;
+  case '>':
+    return align::right;
+  case '^':
+    return align::center;
+  }
+  return align::none;
+}
 
-template <typename OutputIt>
-struct is_contiguous_back_insert_iterator : std::false_type {};
-template <typename Container>
-struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
-    : is_contiguous<Container> {};
+template <typename Char> constexpr auto is_name_start(Char c) -> bool {
+  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '_';
+}
 
-template <typename Char> struct named_arg_base {
-  basic_string_view<Char> name;
+template <typename Char, typename Handler>
+FMT_CONSTEXPR auto do_parse_arg_id(const Char* begin, const Char* end,
+                                   Handler&& handler) -> const Char* {
+  Char c = *begin;
+  if (c >= '0' && c <= '9') {
+    int index = 0;
+    constexpr int max = (std::numeric_limits<int>::max)();
+    if (c != '0')
+      index = parse_nonnegative_int(begin, end, max);
+    else
+      ++begin;
+    if (begin == end || (*begin != '}' && *begin != ':'))
+      throw_format_error("invalid format string");
+    else
+      handler.on_index(index);
+    return begin;
+  }
+  if (!is_name_start(c)) {
+    throw_format_error("invalid format string");
+    return begin;
+  }
+  auto it = begin;
+  do {
+    ++it;
+  } while (it != end && (is_name_start(*it) || ('0' <= *it && *it <= '9')));
+  handler.on_name({begin, to_unsigned(it - begin)});
+  return it;
+}
 
-  // Serialized value<context>.
-  mutable char data[sizeof(basic_format_arg<buffer_context<Char>>)];
+template <typename Char, typename Handler>
+FMT_CONSTEXPR FMT_INLINE auto parse_arg_id(const Char* begin, const Char* end,
+                                           Handler&& handler) -> const Char* {
+  FMT_ASSERT(begin != end, "");
+  Char c = *begin;
+  if (c != '}' && c != ':') return do_parse_arg_id(begin, end, handler);
+  handler.on_auto();
+  return begin;
+}
 
-  named_arg_base(basic_string_view<Char> nm) : name(nm) {}
+template <typename Char> struct dynamic_spec_id_handler {
+  basic_format_parse_context<Char>& ctx;
+  arg_ref<Char>& ref;
 
-  template <typename Context> basic_format_arg<Context> deserialize() const {
-    basic_format_arg<Context> arg;
-    std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
-    return arg;
+  FMT_CONSTEXPR void on_auto() {
+    int id = ctx.next_arg_id();
+    ref = arg_ref<Char>(id);
+    ctx.check_dynamic_spec(id);
+  }
+  FMT_CONSTEXPR void on_index(int id) {
+    ref = arg_ref<Char>(id);
+    ctx.check_arg_id(id);
+    ctx.check_dynamic_spec(id);
+  }
+  FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
+    ref = arg_ref<Char>(id);
+    ctx.check_arg_id(id);
   }
 };
 
-struct view {};
+// Parses [integer | "{" [arg_id] "}"].
+template <typename Char>
+FMT_CONSTEXPR auto parse_dynamic_spec(const Char* begin, const Char* end,
+                                      int& value, arg_ref<Char>& ref,
+                                      basic_format_parse_context<Char>& ctx)
+    -> const Char* {
+  FMT_ASSERT(begin != end, "");
+  if ('0' <= *begin && *begin <= '9') {
+    int val = parse_nonnegative_int(begin, end, -1);
+    if (val != -1)
+      value = val;
+    else
+      throw_format_error("number is too big");
+  } else if (*begin == '{') {
+    ++begin;
+    auto handler = dynamic_spec_id_handler<Char>{ctx, ref};
+    if (begin != end) begin = parse_arg_id(begin, end, handler);
+    if (begin != end && *begin == '}') return ++begin;
+    throw_format_error("invalid format string");
+  }
+  return begin;
+}
 
-template <typename T, typename Char>
-struct named_arg : view, named_arg_base<Char> {
-  const T& value;
+template <typename Char>
+FMT_CONSTEXPR auto parse_precision(const Char* begin, const Char* end,
+                                   int& value, arg_ref<Char>& ref,
+                                   basic_format_parse_context<Char>& ctx)
+    -> const Char* {
+  ++begin;
+  if (begin == end || *begin == '}') {
+    throw_format_error("invalid precision");
+    return begin;
+  }
+  return parse_dynamic_spec(begin, end, value, ref, ctx);
+}
+
+enum class state { start, align, sign, hash, zero, width, precision, locale };
+
+// Parses standard format specifiers.
+template <typename Char>
+FMT_CONSTEXPR FMT_INLINE auto parse_format_specs(
+    const Char* begin, const Char* end, dynamic_format_specs<Char>& specs,
+    basic_format_parse_context<Char>& ctx, type arg_type) -> const Char* {
+  auto c = '\0';
+  if (end - begin > 1) {
+    auto next = to_ascii(begin[1]);
+    c = parse_align(next) == align::none ? to_ascii(*begin) : '\0';
+  } else {
+    if (begin == end) return begin;
+    c = to_ascii(*begin);
+  }
+
+  struct {
+    state current_state = state::start;
+    FMT_CONSTEXPR void operator()(state s, bool valid = true) {
+      if (current_state >= s || !valid)
+        throw_format_error("invalid format specifier");
+      current_state = s;
+    }
+  } enter_state;
+
+  using pres = presentation_type;
+  constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
+  struct {
+    const Char*& begin;
+    dynamic_format_specs<Char>& specs;
+    type arg_type;
+
+    FMT_CONSTEXPR auto operator()(pres pres_type, int set) -> const Char* {
+      if (!in(arg_type, set)) {
+        if (arg_type == type::none_type) return begin;
+        throw_format_error("invalid format specifier");
+      }
+      specs.type = pres_type;
+      return begin + 1;
+    }
+  } parse_presentation_type{begin, specs, arg_type};
+
+  for (;;) {
+    switch (c) {
+    case '<':
+    case '>':
+    case '^':
+      enter_state(state::align);
+      specs.align = parse_align(c);
+      ++begin;
+      break;
+    case '+':
+    case '-':
+    case ' ':
+      if (arg_type == type::none_type) return begin;
+      enter_state(state::sign, in(arg_type, sint_set | float_set));
+      switch (c) {
+      case '+':
+        specs.sign = sign::plus;
+        break;
+      case '-':
+        specs.sign = sign::minus;
+        break;
+      case ' ':
+        specs.sign = sign::space;
+        break;
+      }
+      ++begin;
+      break;
+    case '#':
+      if (arg_type == type::none_type) return begin;
+      enter_state(state::hash, is_arithmetic_type(arg_type));
+      specs.alt = true;
+      ++begin;
+      break;
+    case '0':
+      enter_state(state::zero);
+      if (!is_arithmetic_type(arg_type)) {
+        if (arg_type == type::none_type) return begin;
+        throw_format_error("format specifier requires numeric argument");
+      }
+      if (specs.align == align::none) {
+        // Ignore 0 if align is specified for compatibility with std::format.
+        specs.align = align::numeric;
+        specs.fill[0] = Char('0');
+      }
+      ++begin;
+      break;
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+    case '{':
+      enter_state(state::width);
+      begin = parse_dynamic_spec(begin, end, specs.width, specs.width_ref, ctx);
+      break;
+    case '.':
+      if (arg_type == type::none_type) return begin;
+      enter_state(state::precision,
+                  in(arg_type, float_set | string_set | cstring_set));
+      begin = parse_precision(begin, end, specs.precision, specs.precision_ref,
+                              ctx);
+      break;
+    case 'L':
+      if (arg_type == type::none_type) return begin;
+      enter_state(state::locale, is_arithmetic_type(arg_type));
+      specs.localized = true;
+      ++begin;
+      break;
+    case 'd':
+      return parse_presentation_type(pres::dec, integral_set);
+    case 'o':
+      return parse_presentation_type(pres::oct, integral_set);
+    case 'x':
+      return parse_presentation_type(pres::hex_lower, integral_set);
+    case 'X':
+      return parse_presentation_type(pres::hex_upper, integral_set);
+    case 'b':
+      return parse_presentation_type(pres::bin_lower, integral_set);
+    case 'B':
+      return parse_presentation_type(pres::bin_upper, integral_set);
+    case 'a':
+      return parse_presentation_type(pres::hexfloat_lower, float_set);
+    case 'A':
+      return parse_presentation_type(pres::hexfloat_upper, float_set);
+    case 'e':
+      return parse_presentation_type(pres::exp_lower, float_set);
+    case 'E':
+      return parse_presentation_type(pres::exp_upper, float_set);
+    case 'f':
+      return parse_presentation_type(pres::fixed_lower, float_set);
+    case 'F':
+      return parse_presentation_type(pres::fixed_upper, float_set);
+    case 'g':
+      return parse_presentation_type(pres::general_lower, float_set);
+    case 'G':
+      return parse_presentation_type(pres::general_upper, float_set);
+    case 'c':
+      if (arg_type == type::bool_type)
+        throw_format_error("invalid format specifier");
+      return parse_presentation_type(pres::chr, integral_set);
+    case 's':
+      return parse_presentation_type(pres::string,
+                                     bool_set | string_set | cstring_set);
+    case 'p':
+      return parse_presentation_type(pres::pointer, pointer_set | cstring_set);
+    case '?':
+      return parse_presentation_type(pres::debug,
+                                     char_set | string_set | cstring_set);
+    case '}':
+      return begin;
+    default: {
+      if (*begin == '}') return begin;
+      // Parse fill and alignment.
+      auto fill_end = begin + code_point_length(begin);
+      if (end - fill_end <= 0) {
+        throw_format_error("invalid format specifier");
+        return begin;
+      }
+      if (*begin == '{') {
+        throw_format_error("invalid fill character '{'");
+        return begin;
+      }
+      auto align = parse_align(to_ascii(*fill_end));
+      enter_state(state::align, align != align::none);
+      specs.fill = {begin, to_unsigned(fill_end - begin)};
+      specs.align = align;
+      begin = fill_end + 1;
+    }
+    }
+    if (begin == end) return begin;
+    c = to_ascii(*begin);
+  }
+}
+
+template <typename Char, typename Handler>
+FMT_CONSTEXPR auto parse_replacement_field(const Char* begin, const Char* end,
+                                           Handler&& handler) -> const Char* {
+  struct id_adapter {
+    Handler& handler;
+    int arg_id;
+
+    FMT_CONSTEXPR void on_auto() { arg_id = handler.on_arg_id(); }
+    FMT_CONSTEXPR void on_index(int id) { arg_id = handler.on_arg_id(id); }
+    FMT_CONSTEXPR void on_name(basic_string_view<Char> id) {
+      arg_id = handler.on_arg_id(id);
+    }
+  };
+
+  ++begin;
+  if (begin == end) return handler.on_error("invalid format string"), end;
+  if (*begin == '}') {
+    handler.on_replacement_field(handler.on_arg_id(), begin);
+  } else if (*begin == '{') {
+    handler.on_text(begin, begin + 1);
+  } else {
+    auto adapter = id_adapter{handler, 0};
+    begin = parse_arg_id(begin, end, adapter);
+    Char c = begin != end ? *begin : Char();
+    if (c == '}') {
+      handler.on_replacement_field(adapter.arg_id, begin);
+    } else if (c == ':') {
+      begin = handler.on_format_specs(adapter.arg_id, begin + 1, end);
+      if (begin == end || *begin != '}')
+        return handler.on_error("unknown format specifier"), end;
+    } else {
+      return handler.on_error("missing '}' in format string"), end;
+    }
+  }
+  return begin + 1;
+}
+
+template <bool IS_CONSTEXPR, typename Char, typename Handler>
+FMT_CONSTEXPR FMT_INLINE void parse_format_string(
+    basic_string_view<Char> format_str, Handler&& handler) {
+  auto begin = format_str.data();
+  auto end = begin + format_str.size();
+  if (end - begin < 32) {
+    // Use a simple loop instead of memchr for small strings.
+    const Char* p = begin;
+    while (p != end) {
+      auto c = *p++;
+      if (c == '{') {
+        handler.on_text(begin, p - 1);
+        begin = p = parse_replacement_field(p - 1, end, handler);
+      } else if (c == '}') {
+        if (p == end || *p != '}')
+          return handler.on_error("unmatched '}' in format string");
+        handler.on_text(begin, p);
+        begin = ++p;
+      }
+    }
+    handler.on_text(begin, end);
+    return;
+  }
+  struct writer {
+    FMT_CONSTEXPR void operator()(const Char* from, const Char* to) {
+      if (from == to) return;
+      for (;;) {
+        const Char* p = nullptr;
+        if (!find<IS_CONSTEXPR>(from, to, Char('}'), p))
+          return handler_.on_text(from, to);
+        ++p;
+        if (p == to || *p != '}')
+          return handler_.on_error("unmatched '}' in format string");
+        handler_.on_text(from, p);
+        from = p + 1;
+      }
+    }
+    Handler& handler_;
+  } write = {handler};
+  while (begin != end) {
+    // Doing two passes with memchr (one for '{' and another for '}') is up to
+    // 2.5x faster than the naive one-pass implementation on big format strings.
+    const Char* p = begin;
+    if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, Char('{'), p))
+      return write(begin, end);
+    write(begin, p);
+    begin = parse_replacement_field(p, end, handler);
+  }
+}
 
-  named_arg(basic_string_view<Char> name, const T& val)
-      : named_arg_base<Char>(name), value(val) {}
+template <typename T, bool = is_named_arg<T>::value> struct strip_named_arg {
+  using type = T;
+};
+template <typename T> struct strip_named_arg<T, true> {
+  using type = remove_cvref_t<decltype(T::value)>;
 };
 
-template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
-inline void check_format_string(const S&) {
-#if defined(FMT_ENFORCE_COMPILE_STRING)
-  static_assert(is_compile_string<S>::value,
-                "FMT_ENFORCE_COMPILE_STRING requires all format strings to "
-                "utilize FMT_STRING() or fmt().");
+template <typename T, typename ParseContext>
+FMT_CONSTEXPR auto parse_format_specs(ParseContext& ctx)
+    -> decltype(ctx.begin()) {
+  using char_type = typename ParseContext::char_type;
+  using context = buffer_context<char_type>;
+  using mapped_type = conditional_t<
+      mapped_type_constant<T, context>::value != type::custom_type,
+      decltype(arg_mapper<context>().map(std::declval<const T&>())),
+      typename strip_named_arg<T>::type>;
+#if defined(__cpp_if_constexpr)
+  if constexpr (std::is_default_constructible<
+                    formatter<mapped_type, char_type>>::value) {
+    return formatter<mapped_type, char_type>().parse(ctx);
+  } else {
+    type_is_unformattable_for<T, char_type> _;
+    return ctx.begin();
+  }
+#else
+  return formatter<mapped_type, char_type>().parse(ctx);
 #endif
 }
-template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
-void check_format_string(S);
 
-template <bool...> struct bool_pack;
-template <bool... Args>
-using all_true =
-    std::is_same<bool_pack<Args..., true>, bool_pack<true, Args...>>;
+// Checks char specs and returns true iff the presentation type is char-like.
+template <typename Char>
+FMT_CONSTEXPR auto check_char_specs(const format_specs<Char>& specs) -> bool {
+  if (specs.type != presentation_type::none &&
+      specs.type != presentation_type::chr &&
+      specs.type != presentation_type::debug) {
+    return false;
+  }
+  if (specs.align == align::numeric || specs.sign != sign::none || specs.alt)
+    throw_format_error("invalid format specifier for char");
+  return true;
+}
+
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <int N, typename T, typename... Args, typename Char>
+constexpr auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
+  if constexpr (is_statically_named_arg<T>()) {
+    if (name == T::name) return N;
+  }
+  if constexpr (sizeof...(Args) > 0)
+    return get_arg_index_by_name<N + 1, Args...>(name);
+  (void)name;  // Workaround an MSVC bug about "unused" parameter.
+  return -1;
+}
+#endif
 
-template <typename... Args, typename S, typename Char = char_t<S>>
-inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
-make_args_checked(const S& format_str,
-                  const remove_reference_t<Args>&... args) {
-  static_assert(
-      all_true<(!std::is_base_of<view, remove_reference_t<Args>>::value ||
-                !std::is_reference<Args>::value)...>::value,
-      "passing views as lvalues is disallowed");
-  check_format_string<Args...>(format_str);
-  return {args...};
+template <typename... Args, typename Char>
+FMT_CONSTEXPR auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+  if constexpr (sizeof...(Args) > 0)
+    return get_arg_index_by_name<0, Args...>(name);
+#endif
+  (void)name;
+  return -1;
 }
 
-template <typename Char>
-std::basic_string<Char> vformat(
-    basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args);
+template <typename Char, typename... Args> class format_string_checker {
+ private:
+  using parse_context_type = compile_parse_context<Char>;
+  static constexpr int num_args = sizeof...(Args);
 
-template <typename Char>
-typename buffer_context<Char>::iterator vformat_to(
-    buffer<Char>& buf, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args);
+  // Format specifier parsing function.
+  // In the future basic_format_parse_context will replace compile_parse_context
+  // here and will use is_constant_evaluated and downcasting to access the data
+  // needed for compile-time checks: https://godbolt.org/z/GvWzcTjh1.
+  using parse_func = const Char* (*)(parse_context_type&);
+
+  type types_[num_args > 0 ? static_cast<size_t>(num_args) : 1];
+  parse_context_type context_;
+  parse_func parse_funcs_[num_args > 0 ? static_cast<size_t>(num_args) : 1];
+
+ public:
+  explicit FMT_CONSTEXPR format_string_checker(basic_string_view<Char> fmt)
+      : types_{mapped_type_constant<Args, buffer_context<Char>>::value...},
+        context_(fmt, num_args, types_),
+        parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
+
+  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
 
-template <typename Char, typename Args,
-          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
-inline void vprint_mojibake(std::FILE*, basic_string_view<Char>, const Args&) {}
+  FMT_CONSTEXPR auto on_arg_id() -> int { return context_.next_arg_id(); }
+  FMT_CONSTEXPR auto on_arg_id(int id) -> int {
+    return context_.check_arg_id(id), id;
+  }
+  FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+    auto index = get_arg_index_by_name<Args...>(id);
+    if (index < 0) on_error("named argument is not found");
+    return index;
+#else
+    (void)id;
+    on_error("compile-time checks for named arguments require C++20 support");
+    return 0;
+#endif
+  }
+
+  FMT_CONSTEXPR void on_replacement_field(int id, const Char* begin) {
+    on_format_specs(id, begin, begin);  // Call parse() on empty specs.
+  }
+
+  FMT_CONSTEXPR auto on_format_specs(int id, const Char* begin, const Char*)
+      -> const Char* {
+    context_.advance_to(begin);
+    // id >= 0 check is a workaround for gcc 10 bug (#2065).
+    return id >= 0 && id < num_args ? parse_funcs_[id](context_) : begin;
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    throw_format_error(message);
+  }
+};
+
+// Reports a compile-time error if S is not a valid format string.
+template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
+FMT_INLINE void check_format_string(const S&) {
+#ifdef FMT_ENFORCE_COMPILE_STRING
+  static_assert(is_compile_string<S>::value,
+                "FMT_ENFORCE_COMPILE_STRING requires all format strings to use "
+                "FMT_STRING.");
+#endif
+}
+template <typename... Args, typename S,
+          FMT_ENABLE_IF(is_compile_string<S>::value)>
+void check_format_string(S format_str) {
+  using char_t = typename S::char_type;
+  FMT_CONSTEXPR auto s = basic_string_view<char_t>(format_str);
+  using checker = format_string_checker<char_t, remove_cvref_t<Args>...>;
+  FMT_CONSTEXPR bool error = (parse_format_string<true>(s, checker(s)), true);
+  ignore_unused(error);
+}
+
+template <typename Char = char> struct vformat_args {
+  using type = basic_format_args<
+      basic_format_context<std::back_insert_iterator<buffer<Char>>, Char>>;
+};
+template <> struct vformat_args<char> {
+  using type = format_args;
+};
+
+// Use vformat_args and avoid type_identity to keep symbols short.
+template <typename Char>
+void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
+                typename vformat_args<Char>::type args, locale_ref loc = {});
 
 FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
 #ifndef _WIN32
 inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
 #endif
-}  // namespace internal
+}  // namespace detail
+
+FMT_BEGIN_EXPORT
+
+// A formatter specialization for natively supported types.
+template <typename T, typename Char>
+struct formatter<T, Char,
+                 enable_if_t<detail::type_constant<T, Char>::value !=
+                             detail::type::custom_type>> {
+ private:
+  detail::dynamic_format_specs<Char> specs_;
+
+ public:
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const Char* {
+    auto type = detail::type_constant<T, Char>::value;
+    auto end =
+        detail::parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx, type);
+    if (type == detail::type::char_type) detail::check_char_specs(specs_);
+    return end;
+  }
+
+  template <detail::type U = detail::type_constant<T, Char>::value,
+            FMT_ENABLE_IF(U == detail::type::string_type ||
+                          U == detail::type::cstring_type ||
+                          U == detail::type::char_type)>
+  FMT_CONSTEXPR void set_debug_format(bool set = true) {
+    specs_.type = set ? presentation_type::debug : presentation_type::none;
+  }
+
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const T& val, FormatContext& ctx) const
+      -> decltype(ctx.out());
+};
+
+template <typename Char = char> struct runtime_format_string {
+  basic_string_view<Char> str;
+};
+
+/** A compile-time format string. */
+template <typename Char, typename... Args> class basic_format_string {
+ private:
+  basic_string_view<Char> str_;
+
+ public:
+  template <typename S,
+            FMT_ENABLE_IF(
+                std::is_convertible<const S&, basic_string_view<Char>>::value)>
+  FMT_CONSTEVAL FMT_INLINE basic_format_string(const S& s) : str_(s) {
+    static_assert(
+        detail::count<
+            (std::is_base_of<detail::view, remove_reference_t<Args>>::value &&
+             std::is_reference<Args>::value)...>() == 0,
+        "passing views as lvalues is disallowed");
+#ifdef FMT_HAS_CONSTEVAL
+    if constexpr (detail::count_named_args<Args...>() ==
+                  detail::count_statically_named_args<Args...>()) {
+      using checker =
+          detail::format_string_checker<Char, remove_cvref_t<Args>...>;
+      detail::parse_format_string<true>(str_, checker(s));
+    }
+#else
+    detail::check_format_string<Args...>(s);
+#endif
+  }
+  basic_format_string(runtime_format_string<Char> fmt) : str_(fmt.str) {}
+
+  FMT_INLINE operator basic_string_view<Char>() const { return str_; }
+  FMT_INLINE auto get() const -> basic_string_view<Char> { return str_; }
+};
 
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+// Workaround broken conversion on older gcc.
+template <typename...> using format_string = string_view;
+inline auto runtime(string_view s) -> string_view { return s; }
+#else
+template <typename... Args>
+using format_string = basic_format_string<char, type_identity_t<Args>...>;
 /**
   \rst
-  Returns a named argument to be used in a formatting function. It should only
-  be used in a call to a formatting function.
+  Creates a runtime format string.
 
   **Example**::
 
-    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+    // Check format string at runtime instead of compile-time.
+    fmt::print(fmt::runtime("{:d}"), "I am not a number");
   \endrst
  */
-template <typename S, typename T, typename Char = char_t<S>>
-inline internal::named_arg<T, Char> arg(const S& name, const T& arg) {
-  static_assert(internal::is_string<S>::value, "");
-  return {name, arg};
-}
+inline auto runtime(string_view s) -> runtime_format_string<> { return {{s}}; }
+#endif
+
+FMT_API auto vformat(string_view fmt, format_args args) -> std::string;
 
-// Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
-template <typename S, typename T, typename Char>
-void arg(S, internal::named_arg<T, Char>) = delete;
+/**
+  \rst
+  Formats ``args`` according to specifications in ``fmt`` and returns the result
+  as a string.
+
+  **Example**::
+
+    #include <fmt/core.h>
+    std::string message = fmt::format("The answer is {}.", 42);
+  \endrst
+*/
+template <typename... T>
+FMT_NODISCARD FMT_INLINE auto format(format_string<T...> fmt, T&&... args)
+    -> std::string {
+  return vformat(fmt, fmt::make_format_args(args...));
+}
 
 /** Formats a string and writes the output to ``out``. */
-// GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
-// vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
-template <typename OutputIt, typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(
-              internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
-OutputIt vformat_to(
-    OutputIt out, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using container = remove_reference_t<decltype(internal::get_container(out))>;
-  internal::container_buffer<container> buf((internal::get_container(out)));
-  internal::vformat_to(buf, to_string_view(format_str), args);
-  return out;
+template <typename OutputIt,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+auto vformat_to(OutputIt out, string_view fmt, format_args args) -> OutputIt {
+  auto&& buf = detail::get_buffer<char>(out);
+  detail::vformat_to(buf, fmt, args, {});
+  return detail::get_iterator(buf, out);
 }
 
-template <typename Container, typename S, typename... Args,
-          FMT_ENABLE_IF(
-              is_contiguous<Container>::value&& internal::is_string<S>::value)>
-inline std::back_insert_iterator<Container> format_to(
-    std::back_insert_iterator<Container> out, const S& format_str,
-    Args&&... args) {
-  return vformat_to(out, to_string_view(format_str),
-                    internal::make_args_checked<Args...>(format_str, args...));
+/**
+ \rst
+ Formats ``args`` according to specifications in ``fmt``, writes the result to
+ the output iterator ``out`` and returns the iterator past the end of the output
+ range. `format_to` does not append a terminating null character.
+
+ **Example**::
+
+   auto out = std::vector<char>();
+   fmt::format_to(std::back_inserter(out), "{}", 42);
+ \endrst
+ */
+template <typename OutputIt, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+FMT_INLINE auto format_to(OutputIt out, format_string<T...> fmt, T&&... args)
+    -> OutputIt {
+  return vformat_to(out, fmt, fmt::make_format_args(args...));
 }
 
-template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
-    const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat(to_string_view(format_str), args);
+template <typename OutputIt> struct format_to_n_result {
+  /** Iterator past the end of the output range. */
+  OutputIt out;
+  /** Total (not truncated) output size. */
+  size_t size;
+};
+
+template <typename OutputIt, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+auto vformat_to_n(OutputIt out, size_t n, string_view fmt, format_args args)
+    -> format_to_n_result<OutputIt> {
+  using traits = detail::fixed_buffer_traits;
+  auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
+  detail::vformat_to(buf, fmt, args, {});
+  return {buf.out(), buf.count()};
 }
 
 /**
   \rst
-  Formats arguments and returns the result as a string.
-
-  **Example**::
-
-    #include <fmt/core.h>
-    std::string message = fmt::format("The answer is {}", 42);
+  Formats ``args`` according to specifications in ``fmt``, writes up to ``n``
+  characters of the result to the output iterator ``out`` and returns the total
+  (not truncated) output size and the iterator past the end of the output range.
+  `format_to_n` does not append a terminating null character.
   \endrst
-*/
-// Pass char_t as a default template parameter instead of using
-// std::basic_string<char_t<S>> to reduce the symbol size.
-template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const S& format_str, Args&&... args) {
-  return internal::vformat(
-      to_string_view(format_str),
-      internal::make_args_checked<Args...>(format_str, args...));
+ */
+template <typename OutputIt, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+FMT_INLINE auto format_to_n(OutputIt out, size_t n, format_string<T...> fmt,
+                            T&&... args) -> format_to_n_result<OutputIt> {
+  return vformat_to_n(out, n, fmt, fmt::make_format_args(args...));
 }
 
-FMT_API void vprint(string_view, format_args);
-FMT_API void vprint(std::FILE*, string_view, format_args);
+/** Returns the number of chars in the output of ``format(fmt, args...)``. */
+template <typename... T>
+FMT_NODISCARD FMT_INLINE auto formatted_size(format_string<T...> fmt,
+                                             T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<>();
+  detail::vformat_to<char>(buf, fmt, fmt::make_format_args(args...), {});
+  return buf.count();
+}
+
+FMT_API void vprint(string_view fmt, format_args args);
+FMT_API void vprint(std::FILE* f, string_view fmt, format_args args);
 
 /**
   \rst
-  Formats ``args`` according to specifications in ``format_str`` and writes the
-  output to the file ``f``. Strings are assumed to be Unicode-encoded unless the
-  ``FMT_UNICODE`` macro is set to 0.
+  Formats ``args`` according to specifications in ``fmt`` and writes the output
+  to ``stdout``.
 
   **Example**::
 
-    fmt::print(stderr, "Don't {}!", "panic");
+    fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
   \endrst
  */
-template <typename S, typename... Args, typename Char = char_t<S>>
-inline void print(std::FILE* f, const S& format_str, Args&&... args) {
-  return internal::is_unicode<Char>()
-             ? vprint(f, to_string_view(format_str),
-                      internal::make_args_checked<Args...>(format_str, args...))
-             : internal::vprint_mojibake(
-                   f, to_string_view(format_str),
-                   internal::make_args_checked<Args...>(format_str, args...));
+template <typename... T>
+FMT_INLINE void print(format_string<T...> fmt, T&&... args) {
+  const auto& vargs = fmt::make_format_args(args...);
+  return detail::is_utf8() ? vprint(fmt, vargs)
+                           : detail::vprint_mojibake(stdout, fmt, vargs);
 }
 
 /**
   \rst
-  Formats ``args`` according to specifications in ``format_str`` and writes
-  the output to ``stdout``. Strings are assumed to be Unicode-encoded unless
-  the ``FMT_UNICODE`` macro is set to 0.
+  Formats ``args`` according to specifications in ``fmt`` and writes the
+  output to the file ``f``.
 
   **Example**::
 
-    fmt::print("Elapsed time: {0:.2f} seconds", 1.23);
+    fmt::print(stderr, "Don't {}!", "panic");
   \endrst
  */
-template <typename S, typename... Args, typename Char = char_t<S>>
-inline void print(const S& format_str, Args&&... args) {
-  return internal::is_unicode<Char>()
-             ? vprint(to_string_view(format_str),
-                      internal::make_args_checked<Args...>(format_str, args...))
-             : internal::vprint_mojibake(
-                   stdout, to_string_view(format_str),
-                   internal::make_args_checked<Args...>(format_str, args...));
+template <typename... T>
+FMT_INLINE void print(std::FILE* f, format_string<T...> fmt, T&&... args) {
+  const auto& vargs = fmt::make_format_args(args...);
+  return detail::is_utf8() ? vprint(f, fmt, vargs)
+                           : detail::vprint_mojibake(f, fmt, vargs);
+}
+
+/**
+  Formats ``args`` according to specifications in ``fmt`` and writes the
+  output to the file ``f`` followed by a newline.
+ */
+template <typename... T>
+FMT_INLINE void println(std::FILE* f, format_string<T...> fmt, T&&... args) {
+  return fmt::print(f, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+/**
+  Formats ``args`` according to specifications in ``fmt`` and writes the output
+  to ``stdout`` followed by a newline.
+ */
+template <typename... T>
+FMT_INLINE void println(format_string<T...> fmt, T&&... args) {
+  return fmt::println(stdout, fmt, std::forward<T>(args)...);
 }
+
+FMT_END_EXPORT
+FMT_GCC_PRAGMA("GCC pop_options")
 FMT_END_NAMESPACE
 
+#ifdef FMT_HEADER_ONLY
+#  include "format.h"
+#endif
 #endif  // FMT_CORE_H_
diff --git a/contrib/fmt/include/fmt/format-inl.h b/contrib/fmt/include/fmt/format-inl.h
index f632714d81e..efac5d1f88f 100644
--- a/contrib/fmt/include/fmt/format-inl.h
+++ b/contrib/fmt/include/fmt/format-inl.h
@@ -8,1298 +8,1393 @@
 #ifndef FMT_FORMAT_INL_H_
 #define FMT_FORMAT_INL_H_
 
-#include <cassert>
-#include <cctype>
+#include <algorithm>
+#include <cerrno>  // errno
 #include <climits>
 #include <cmath>
-#include <cstdarg>
-#include <cstring>  // for std::memmove
-#include <cwchar>
+#include <exception>
 
-#include "format.h"
-#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 #  include <locale>
 #endif
 
-#ifdef _WIN32
-#  include <io.h>
-#  include <windows.h>
-#endif
-
-#ifdef _MSC_VER
-#  pragma warning(push)
-#  pragma warning(disable : 4702)  // unreachable code
+#if defined(_WIN32) && !defined(FMT_WINDOWS_NO_WCHAR)
+#  include <io.h>  // _isatty
 #endif
 
-// Dummy implementations of strerror_r and strerror_s called if corresponding
-// system functions are not available.
-inline fmt::internal::null<> strerror_r(int, char*, ...) { return {}; }
-inline fmt::internal::null<> strerror_s(char*, std::size_t, ...) { return {}; }
+#include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
-  print(stderr, "{}:{}: assertion failed: {}", file, line, message);
-  std::abort();
+  // Use unchecked std::fprintf to avoid triggering another assertion when
+  // writing to stderr fails
+  std::fprintf(stderr, "%s:%d: assertion failed: %s", file, line, message);
+  // Chosen instead of std::abort to satisfy Clang in CUDA mode during device
+  // code pass.
+  std::terminate();
 }
 
-#ifndef _MSC_VER
-#  define FMT_SNPRINTF snprintf
-#else  // _MSC_VER
-inline int fmt_snprintf(char* buffer, size_t size, const char* format, ...) {
-  va_list args;
-  va_start(args, format);
-  int result = vsnprintf_s(buffer, size, _TRUNCATE, format, args);
-  va_end(args);
-  return result;
-}
-#  define FMT_SNPRINTF fmt_snprintf
-#endif  // _MSC_VER
-
-// A portable thread-safe version of strerror.
-// Sets buffer to point to a string describing the error code.
-// This can be either a pointer to a string stored in buffer,
-// or a pointer to some static immutable string.
-// Returns one of the following values:
-//   0      - success
-//   ERANGE - buffer is not large enough to store the error message
-//   other  - failure
-// Buffer should be at least of size 1.
-FMT_FUNC int safe_strerror(int error_code, char*& buffer,
-                           std::size_t buffer_size) FMT_NOEXCEPT {
-  FMT_ASSERT(buffer != nullptr && buffer_size != 0, "invalid buffer");
-
-  class dispatcher {
-   private:
-    int error_code_;
-    char*& buffer_;
-    std::size_t buffer_size_;
-
-    // A noop assignment operator to avoid bogus warnings.
-    void operator=(const dispatcher&) {}
-
-    // Handle the result of XSI-compliant version of strerror_r.
-    int handle(int result) {
-      // glibc versions before 2.13 return result in errno.
-      return result == -1 ? errno : result;
-    }
-
-    // Handle the result of GNU-specific version of strerror_r.
-    FMT_MAYBE_UNUSED
-    int handle(char* message) {
-      // If the buffer is full then the message is probably truncated.
-      if (message == buffer_ && strlen(buffer_) == buffer_size_ - 1)
-        return ERANGE;
-      buffer_ = message;
-      return 0;
-    }
-
-    // Handle the case when strerror_r is not available.
-    FMT_MAYBE_UNUSED
-    int handle(internal::null<>) {
-      return fallback(strerror_s(buffer_, buffer_size_, error_code_));
-    }
-
-    // Fallback to strerror_s when strerror_r is not available.
-    FMT_MAYBE_UNUSED
-    int fallback(int result) {
-      // If the buffer is full then the message is probably truncated.
-      return result == 0 && strlen(buffer_) == buffer_size_ - 1 ? ERANGE
-                                                                : result;
-    }
-
-#if !FMT_MSC_VER
-    // Fallback to strerror if strerror_r and strerror_s are not available.
-    int fallback(internal::null<>) {
-      errno = 0;
-      buffer_ = strerror(error_code_);
-      return errno;
-    }
-#endif
-
-   public:
-    dispatcher(int err_code, char*& buf, std::size_t buf_size)
-        : error_code_(err_code), buffer_(buf), buffer_size_(buf_size) {}
-
-    int run() { return handle(strerror_r(error_code_, buffer_, buffer_size_)); }
-  };
-  return dispatcher(error_code, buffer, buffer_size).run();
+FMT_FUNC void throw_format_error(const char* message) {
+  FMT_THROW(format_error(message));
 }
 
-FMT_FUNC void format_error_code(internal::buffer<char>& out, int error_code,
-                                string_view message) FMT_NOEXCEPT {
+FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
+                                string_view message) noexcept {
   // Report error code making sure that the output fits into
   // inline_buffer_size to avoid dynamic memory allocation and potential
   // bad_alloc.
-  out.resize(0);
+  out.try_resize(0);
   static const char SEP[] = ": ";
   static const char ERROR_STR[] = "error ";
   // Subtract 2 to account for terminating null characters in SEP and ERROR_STR.
-  std::size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
+  size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
   auto abs_value = static_cast<uint32_or_64_or_128_t<int>>(error_code);
-  if (internal::is_negative(error_code)) {
+  if (detail::is_negative(error_code)) {
     abs_value = 0 - abs_value;
     ++error_code_size;
   }
-  error_code_size += internal::to_unsigned(internal::count_digits(abs_value));
-  internal::writer w(out);
-  if (message.size() <= inline_buffer_size - error_code_size) {
-    w.write(message);
-    w.write(SEP);
-  }
-  w.write(ERROR_STR);
-  w.write(error_code);
-  assert(out.size() <= inline_buffer_size);
+  error_code_size += detail::to_unsigned(detail::count_digits(abs_value));
+  auto it = buffer_appender<char>(out);
+  if (message.size() <= inline_buffer_size - error_code_size)
+    fmt::format_to(it, FMT_STRING("{}{}"), message, SEP);
+  fmt::format_to(it, FMT_STRING("{}{}"), ERROR_STR, error_code);
+  FMT_ASSERT(out.size() <= inline_buffer_size, "");
 }
 
 FMT_FUNC void report_error(format_func func, int error_code,
-                           string_view message) FMT_NOEXCEPT {
+                           const char* message) noexcept {
   memory_buffer full_message;
   func(full_message, error_code, message);
   // Don't use fwrite_fully because the latter may throw.
-  (void)std::fwrite(full_message.data(), full_message.size(), 1, stderr);
-  std::fputc('\n', stderr);
+  if (std::fwrite(full_message.data(), full_message.size(), 1, stderr) > 0)
+    std::fputc('\n', stderr);
 }
 
 // A wrapper around fwrite that throws on error.
-FMT_FUNC void fwrite_fully(const void* ptr, size_t size, size_t count,
-                           FILE* stream) {
-  size_t written = std::fwrite(ptr, size, count, stream);
-  if (written < count) FMT_THROW(system_error(errno, "cannot write to file"));
+inline void fwrite_fully(const void* ptr, size_t count, FILE* stream) {
+  size_t written = std::fwrite(ptr, 1, count, stream);
+  if (written < count)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
 }
-}  // namespace internal
-
-#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-namespace internal {
 
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 template <typename Locale>
 locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
   static_assert(std::is_same<Locale, std::locale>::value, "");
 }
 
-template <typename Locale> Locale locale_ref::get() const {
+template <typename Locale> auto locale_ref::get() const -> Locale {
   static_assert(std::is_same<Locale, std::locale>::value, "");
   return locale_ ? *static_cast<const std::locale*>(locale_) : std::locale();
 }
 
-template <typename Char> FMT_FUNC std::string grouping_impl(locale_ref loc) {
-  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>()).grouping();
-}
-template <typename Char> FMT_FUNC Char thousands_sep_impl(locale_ref loc) {
-  return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
-      .thousands_sep();
+template <typename Char>
+FMT_FUNC auto thousands_sep_impl(locale_ref loc) -> thousands_sep_result<Char> {
+  auto& facet = std::use_facet<std::numpunct<Char>>(loc.get<std::locale>());
+  auto grouping = facet.grouping();
+  auto thousands_sep = grouping.empty() ? Char() : facet.thousands_sep();
+  return {std::move(grouping), thousands_sep};
 }
-template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref loc) {
+template <typename Char>
+FMT_FUNC auto decimal_point_impl(locale_ref loc) -> Char {
   return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
       .decimal_point();
 }
-}  // namespace internal
 #else
 template <typename Char>
-FMT_FUNC std::string internal::grouping_impl(locale_ref) {
-  return "\03";
-}
-template <typename Char>
-FMT_FUNC Char internal::thousands_sep_impl(locale_ref) {
-  return FMT_STATIC_THOUSANDS_SEPARATOR;
+FMT_FUNC auto thousands_sep_impl(locale_ref) -> thousands_sep_result<Char> {
+  return {"\03", FMT_STATIC_THOUSANDS_SEPARATOR};
 }
-template <typename Char>
-FMT_FUNC Char internal::decimal_point_impl(locale_ref) {
+template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref) {
   return '.';
 }
 #endif
 
-FMT_API FMT_FUNC format_error::~format_error() FMT_NOEXCEPT = default;
-FMT_API FMT_FUNC system_error::~system_error() FMT_NOEXCEPT = default;
-
-FMT_FUNC void system_error::init(int err_code, string_view format_str,
-                                 format_args args) {
-  error_code_ = err_code;
-  memory_buffer buffer;
-  format_system_error(buffer, err_code, vformat(format_str, args));
-  std::runtime_error& base = *this;
-  base = std::runtime_error(to_string(buffer));
+FMT_FUNC auto write_loc(appender out, loc_value value,
+                        const format_specs<>& specs, locale_ref loc) -> bool {
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+  auto locale = loc.get<std::locale>();
+  // We cannot use the num_put<char> facet because it may produce output in
+  // a wrong encoding.
+  using facet = format_facet<std::locale>;
+  if (std::has_facet<facet>(locale))
+    return std::use_facet<facet>(locale).put(out, value, specs);
+  return facet(locale).put(out, value, specs);
+#endif
+  return false;
 }
+}  // namespace detail
 
-namespace internal {
+template <typename Locale> typename Locale::id format_facet<Locale>::id;
 
-template <> FMT_FUNC int count_digits<4>(internal::fallback_uintptr n) {
-  // fallback_uintptr is always stored in little endian.
-  int i = static_cast<int>(sizeof(void*)) - 1;
-  while (i > 0 && n.value[i] == 0) --i;
-  auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
-  return i >= 0 ? i * char_digits + count_digits<4, unsigned>(n.value[i]) : 1;
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+template <typename Locale> format_facet<Locale>::format_facet(Locale& loc) {
+  auto& numpunct = std::use_facet<std::numpunct<char>>(loc);
+  grouping_ = numpunct.grouping();
+  if (!grouping_.empty()) separator_ = std::string(1, numpunct.thousands_sep());
 }
 
-template <typename T>
-const char basic_data<T>::digits[] =
-    "0001020304050607080910111213141516171819"
-    "2021222324252627282930313233343536373839"
-    "4041424344454647484950515253545556575859"
-    "6061626364656667686970717273747576777879"
-    "8081828384858687888990919293949596979899";
-
-template <typename T>
-const char basic_data<T>::hex_digits[] = "0123456789abcdef";
-
-#define FMT_POWERS_OF_10(factor)                                             \
-  factor * 10, (factor)*100, (factor)*1000, (factor)*10000, (factor)*100000, \
-      (factor)*1000000, (factor)*10000000, (factor)*100000000,               \
-      (factor)*1000000000
-
-template <typename T>
-const uint64_t basic_data<T>::powers_of_10_64[] = {
-    1, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
-    10000000000000000000ULL};
-
-template <typename T>
-const uint32_t basic_data<T>::zero_or_powers_of_10_32[] = {0,
-                                                           FMT_POWERS_OF_10(1)};
-
-template <typename T>
-const uint64_t basic_data<T>::zero_or_powers_of_10_64[] = {
-    0, FMT_POWERS_OF_10(1), FMT_POWERS_OF_10(1000000000ULL),
-    10000000000000000000ULL};
-
-// Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
-// These are generated by support/compute-powers.py.
-template <typename T>
-const uint64_t basic_data<T>::pow10_significands[] = {
-    0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
-    0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
-    0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
-    0x8dd01fad907ffc3c, 0xd3515c2831559a83, 0x9d71ac8fada6c9b5,
-    0xea9c227723ee8bcb, 0xaecc49914078536d, 0x823c12795db6ce57,
-    0xc21094364dfb5637, 0x9096ea6f3848984f, 0xd77485cb25823ac7,
-    0xa086cfcd97bf97f4, 0xef340a98172aace5, 0xb23867fb2a35b28e,
-    0x84c8d4dfd2c63f3b, 0xc5dd44271ad3cdba, 0x936b9fcebb25c996,
-    0xdbac6c247d62a584, 0xa3ab66580d5fdaf6, 0xf3e2f893dec3f126,
-    0xb5b5ada8aaff80b8, 0x87625f056c7c4a8b, 0xc9bcff6034c13053,
-    0x964e858c91ba2655, 0xdff9772470297ebd, 0xa6dfbd9fb8e5b88f,
-    0xf8a95fcf88747d94, 0xb94470938fa89bcf, 0x8a08f0f8bf0f156b,
-    0xcdb02555653131b6, 0x993fe2c6d07b7fac, 0xe45c10c42a2b3b06,
-    0xaa242499697392d3, 0xfd87b5f28300ca0e, 0xbce5086492111aeb,
-    0x8cbccc096f5088cc, 0xd1b71758e219652c, 0x9c40000000000000,
-    0xe8d4a51000000000, 0xad78ebc5ac620000, 0x813f3978f8940984,
-    0xc097ce7bc90715b3, 0x8f7e32ce7bea5c70, 0xd5d238a4abe98068,
-    0x9f4f2726179a2245, 0xed63a231d4c4fb27, 0xb0de65388cc8ada8,
-    0x83c7088e1aab65db, 0xc45d1df942711d9a, 0x924d692ca61be758,
-    0xda01ee641a708dea, 0xa26da3999aef774a, 0xf209787bb47d6b85,
-    0xb454e4a179dd1877, 0x865b86925b9bc5c2, 0xc83553c5c8965d3d,
-    0x952ab45cfa97a0b3, 0xde469fbd99a05fe3, 0xa59bc234db398c25,
-    0xf6c69a72a3989f5c, 0xb7dcbf5354e9bece, 0x88fcf317f22241e2,
-    0xcc20ce9bd35c78a5, 0x98165af37b2153df, 0xe2a0b5dc971f303a,
-    0xa8d9d1535ce3b396, 0xfb9b7cd9a4a7443c, 0xbb764c4ca7a44410,
-    0x8bab8eefb6409c1a, 0xd01fef10a657842c, 0x9b10a4e5e9913129,
-    0xe7109bfba19c0c9d, 0xac2820d9623bf429, 0x80444b5e7aa7cf85,
-    0xbf21e44003acdd2d, 0x8e679c2f5e44ff8f, 0xd433179d9c8cb841,
-    0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9, 0xaf87023b9bf0ee6b,
-};
-
-// Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
-// to significands above.
-template <typename T>
-const int16_t basic_data<T>::pow10_exponents[] = {
-    -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
-    -927,  -901,  -874,  -847,  -821,  -794,  -768,  -741,  -715,  -688, -661,
-    -635,  -608,  -582,  -555,  -529,  -502,  -475,  -449,  -422,  -396, -369,
-    -343,  -316,  -289,  -263,  -236,  -210,  -183,  -157,  -130,  -103, -77,
-    -50,   -24,   3,     30,    56,    83,    109,   136,   162,   189,  216,
-    242,   269,   295,   322,   348,   375,   402,   428,   455,   481,  508,
-    534,   561,   588,   614,   641,   667,   694,   720,   747,   774,  800,
-    827,   853,   880,   907,   933,   960,   986,   1013,  1039,  1066};
-
-template <typename T>
-const char basic_data<T>::foreground_color[] = "\x1b[38;2;";
-template <typename T>
-const char basic_data<T>::background_color[] = "\x1b[48;2;";
-template <typename T> const char basic_data<T>::reset_color[] = "\x1b[0m";
-template <typename T> const wchar_t basic_data<T>::wreset_color[] = L"\x1b[0m";
-template <typename T> const char basic_data<T>::signs[] = {0, '-', '+', ' '};
-
-template <typename T> struct bits {
-  static FMT_CONSTEXPR_DECL const int value =
-      static_cast<int>(sizeof(T) * std::numeric_limits<unsigned char>::digits);
-};
-
-class fp;
-template <int SHIFT = 0> fp normalize(fp value);
+template <>
+FMT_API FMT_FUNC auto format_facet<std::locale>::do_put(
+    appender out, loc_value val, const format_specs<>& specs) const -> bool {
+  return val.visit(
+      detail::loc_writer<>{out, specs, separator_, grouping_, decimal_point_});
+}
+#endif
 
-// Lower (upper) boundary is a value half way between a floating-point value
-// and its predecessor (successor). Boundaries have the same exponent as the
-// value so only significands are stored.
-struct boundaries {
-  uint64_t lower;
-  uint64_t upper;
-};
+FMT_FUNC auto vsystem_error(int error_code, string_view fmt, format_args args)
+    -> std::system_error {
+  auto ec = std::error_code(error_code, std::generic_category());
+  return std::system_error(ec, vformat(fmt, args));
+}
 
-// A handmade floating-point number f * pow(2, e).
-class fp {
- private:
-  using significand_type = uint64_t;
-
- public:
-  significand_type f;
-  int e;
-
-  // All sizes are in bits.
-  // Subtract 1 to account for an implicit most significant bit in the
-  // normalized form.
-  static FMT_CONSTEXPR_DECL const int double_significand_size =
-      std::numeric_limits<double>::digits - 1;
-  static FMT_CONSTEXPR_DECL const uint64_t implicit_bit =
-      1ULL << double_significand_size;
-  static FMT_CONSTEXPR_DECL const int significand_size =
-      bits<significand_type>::value;
-
-  fp() : f(0), e(0) {}
-  fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
-
-  // Constructs fp from an IEEE754 double. It is a template to prevent compile
-  // errors on platforms where double is not IEEE754.
-  template <typename Double> explicit fp(Double d) { assign(d); }
-
-  // Assigns d to this and return true iff predecessor is closer than successor.
-  template <typename Double, FMT_ENABLE_IF(sizeof(Double) == sizeof(uint64_t))>
-  bool assign(Double d) {
-    // Assume double is in the format [sign][exponent][significand].
-    using limits = std::numeric_limits<Double>;
-    const int exponent_size =
-        bits<Double>::value - double_significand_size - 1;  // -1 for sign
-    const uint64_t significand_mask = implicit_bit - 1;
-    const uint64_t exponent_mask = (~0ULL >> 1) & ~significand_mask;
-    const int exponent_bias = (1 << exponent_size) - limits::max_exponent - 1;
-    auto u = bit_cast<uint64_t>(d);
-    f = u & significand_mask;
-    int biased_e =
-        static_cast<int>((u & exponent_mask) >> double_significand_size);
-    // Predecessor is closer if d is a normalized power of 2 (f == 0) other than
-    // the smallest normalized number (biased_e > 1).
-    bool is_predecessor_closer = f == 0 && biased_e > 1;
-    if (biased_e != 0)
-      f += implicit_bit;
-    else
-      biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
-    e = biased_e - exponent_bias - double_significand_size;
-    return is_predecessor_closer;
-  }
+namespace detail {
 
-  template <typename Double, FMT_ENABLE_IF(sizeof(Double) != sizeof(uint64_t))>
-  bool assign(Double) {
-    *this = fp();
-    return false;
-  }
+template <typename F>
+inline auto operator==(basic_fp<F> x, basic_fp<F> y) -> bool {
+  return x.f == y.f && x.e == y.e;
+}
 
-  // Assigns d to this together with computing lower and upper boundaries,
-  // where a boundary is a value half way between the number and its predecessor
-  // (lower) or successor (upper). The upper boundary is normalized and lower
-  // has the same exponent but may be not normalized.
-  template <typename Double> boundaries assign_with_boundaries(Double d) {
-    bool is_lower_closer = assign(d);
-    fp lower =
-        is_lower_closer ? fp((f << 2) - 1, e - 2) : fp((f << 1) - 1, e - 1);
-    // 1 in normalize accounts for the exponent shift above.
-    fp upper = normalize<1>(fp((f << 1) + 1, e - 1));
-    lower.f <<= lower.e - upper.e;
-    return boundaries{lower.f, upper.f};
-  }
+// Compilers should be able to optimize this into the ror instruction.
+FMT_CONSTEXPR inline auto rotr(uint32_t n, uint32_t r) noexcept -> uint32_t {
+  r &= 31;
+  return (n >> r) | (n << (32 - r));
+}
+FMT_CONSTEXPR inline auto rotr(uint64_t n, uint32_t r) noexcept -> uint64_t {
+  r &= 63;
+  return (n >> r) | (n << (64 - r));
+}
 
-  template <typename Double> boundaries assign_float_with_boundaries(Double d) {
-    assign(d);
-    constexpr int min_normal_e = std::numeric_limits<float>::min_exponent -
-                                 std::numeric_limits<double>::digits;
-    significand_type half_ulp = 1 << (std::numeric_limits<double>::digits -
-                                      std::numeric_limits<float>::digits - 1);
-    if (min_normal_e > e) half_ulp <<= min_normal_e - e;
-    fp upper = normalize<0>(fp(f + half_ulp, e));
-    fp lower = fp(
-        f - (half_ulp >> ((f == implicit_bit && e > min_normal_e) ? 1 : 0)), e);
-    lower.f <<= lower.e - upper.e;
-    return boundaries{lower.f, upper.f};
-  }
-};
+// Implementation of Dragonbox algorithm: https://github.com/jk-jeon/dragonbox.
+namespace dragonbox {
+// Computes upper 64 bits of multiplication of a 32-bit unsigned integer and a
+// 64-bit unsigned integer.
+inline auto umul96_upper64(uint32_t x, uint64_t y) noexcept -> uint64_t {
+  return umul128_upper64(static_cast<uint64_t>(x) << 32, y);
+}
 
-// Normalizes the value converted from double and multiplied by (1 << SHIFT).
-template <int SHIFT> fp normalize(fp value) {
-  // Handle subnormals.
-  const auto shifted_implicit_bit = fp::implicit_bit << SHIFT;
-  while ((value.f & shifted_implicit_bit) == 0) {
-    value.f <<= 1;
-    --value.e;
-  }
-  // Subtract 1 to account for hidden bit.
-  const auto offset =
-      fp::significand_size - fp::double_significand_size - SHIFT - 1;
-  value.f <<= offset;
-  value.e -= offset;
-  return value;
+// Computes lower 128 bits of multiplication of a 64-bit unsigned integer and a
+// 128-bit unsigned integer.
+inline auto umul192_lower128(uint64_t x, uint128_fallback y) noexcept
+    -> uint128_fallback {
+  uint64_t high = x * y.high();
+  uint128_fallback high_low = umul128(x, y.low());
+  return {high + high_low.high(), high_low.low()};
 }
 
-inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
+// Computes lower 64 bits of multiplication of a 32-bit unsigned integer and a
+// 64-bit unsigned integer.
+inline auto umul96_lower64(uint32_t x, uint64_t y) noexcept -> uint64_t {
+  return x * y;
+}
 
-// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
-inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
-#if FMT_USE_INT128
-  auto product = static_cast<__uint128_t>(lhs) * rhs;
-  auto f = static_cast<uint64_t>(product >> 64);
-  return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
-#else
-  // Multiply 32-bit parts of significands.
-  uint64_t mask = (1ULL << 32) - 1;
-  uint64_t a = lhs >> 32, b = lhs & mask;
-  uint64_t c = rhs >> 32, d = rhs & mask;
-  uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
-  // Compute mid 64-bit of result and round.
-  uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
-  return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
-#endif
+// Various fast log computations.
+inline auto floor_log10_pow2_minus_log10_4_over_3(int e) noexcept -> int {
+  FMT_ASSERT(e <= 2936 && e >= -2985, "too large exponent");
+  return (e * 631305 - 261663) >> 21;
 }
 
-inline fp operator*(fp x, fp y) { return {multiply(x.f, y.f), x.e + y.e + 64}; }
-
-// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
-// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
-inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
-  const int64_t one_over_log2_10 = 0x4d104d42;  // round(pow(2, 32) / log2(10))
-  int index = static_cast<int>(
-      ((min_exponent + fp::significand_size - 1) * one_over_log2_10 +
-       ((int64_t(1) << 32) - 1))  // ceil
-      >> 32                       // arithmetic shift
-  );
-  // Decimal exponent of the first (smallest) cached power of 10.
-  const int first_dec_exp = -348;
-  // Difference between 2 consecutive decimal exponents in cached powers of 10.
-  const int dec_exp_step = 8;
-  index = (index - first_dec_exp - 1) / dec_exp_step + 1;
-  pow10_exponent = first_dec_exp + index * dec_exp_step;
-  return {data::pow10_significands[index], data::pow10_exponents[index]};
+FMT_INLINE_VARIABLE constexpr struct {
+  uint32_t divisor;
+  int shift_amount;
+} div_small_pow10_infos[] = {{10, 16}, {100, 16}};
+
+// Replaces n by floor(n / pow(10, N)) returning true if and only if n is
+// divisible by pow(10, N).
+// Precondition: n <= pow(10, N + 1).
+template <int N>
+auto check_divisibility_and_divide_by_pow10(uint32_t& n) noexcept -> bool {
+  // The numbers below are chosen such that:
+  //   1. floor(n/d) = floor(nm / 2^k) where d=10 or d=100,
+  //   2. nm mod 2^k < m if and only if n is divisible by d,
+  // where m is magic_number, k is shift_amount
+  // and d is divisor.
+  //
+  // Item 1 is a common technique of replacing division by a constant with
+  // multiplication, see e.g. "Division by Invariant Integers Using
+  // Multiplication" by Granlund and Montgomery (1994). magic_number (m) is set
+  // to ceil(2^k/d) for large enough k.
+  // The idea for item 2 originates from Schubfach.
+  constexpr auto info = div_small_pow10_infos[N - 1];
+  FMT_ASSERT(n <= info.divisor * 10, "n is too large");
+  constexpr uint32_t magic_number =
+      (1u << info.shift_amount) / info.divisor + 1;
+  n *= magic_number;
+  const uint32_t comparison_mask = (1u << info.shift_amount) - 1;
+  bool result = (n & comparison_mask) < magic_number;
+  n >>= info.shift_amount;
+  return result;
 }
 
-// A simple accumulator to hold the sums of terms in bigint::square if uint128_t
-// is not available.
-struct accumulator {
-  uint64_t lower;
-  uint64_t upper;
+// Computes floor(n / pow(10, N)) for small n and N.
+// Precondition: n <= pow(10, N + 1).
+template <int N> auto small_division_by_pow10(uint32_t n) noexcept -> uint32_t {
+  constexpr auto info = div_small_pow10_infos[N - 1];
+  FMT_ASSERT(n <= info.divisor * 10, "n is too large");
+  constexpr uint32_t magic_number =
+      (1u << info.shift_amount) / info.divisor + 1;
+  return (n * magic_number) >> info.shift_amount;
+}
 
-  accumulator() : lower(0), upper(0) {}
-  explicit operator uint32_t() const { return static_cast<uint32_t>(lower); }
+// Computes floor(n / 10^(kappa + 1)) (float)
+inline auto divide_by_10_to_kappa_plus_1(uint32_t n) noexcept -> uint32_t {
+  // 1374389535 = ceil(2^37/100)
+  return static_cast<uint32_t>((static_cast<uint64_t>(n) * 1374389535) >> 37);
+}
+// Computes floor(n / 10^(kappa + 1)) (double)
+inline auto divide_by_10_to_kappa_plus_1(uint64_t n) noexcept -> uint64_t {
+  // 2361183241434822607 = ceil(2^(64+7)/1000)
+  return umul128_upper64(n, 2361183241434822607ull) >> 7;
+}
 
-  void operator+=(uint64_t n) {
-    lower += n;
-    if (lower < n) ++upper;
-  }
-  void operator>>=(int shift) {
-    assert(shift == 32);
-    (void)shift;
-    lower = (upper << 32) | (lower >> 32);
-    upper >>= 32;
+// Various subroutines using pow10 cache
+template <typename T> struct cache_accessor;
+
+template <> struct cache_accessor<float> {
+  using carrier_uint = float_info<float>::carrier_uint;
+  using cache_entry_type = uint64_t;
+
+  static auto get_cached_power(int k) noexcept -> uint64_t {
+    FMT_ASSERT(k >= float_info<float>::min_k && k <= float_info<float>::max_k,
+               "k is out of range");
+    static constexpr const uint64_t pow10_significands[] = {
+        0x81ceb32c4b43fcf5, 0xa2425ff75e14fc32, 0xcad2f7f5359a3b3f,
+        0xfd87b5f28300ca0e, 0x9e74d1b791e07e49, 0xc612062576589ddb,
+        0xf79687aed3eec552, 0x9abe14cd44753b53, 0xc16d9a0095928a28,
+        0xf1c90080baf72cb2, 0x971da05074da7bef, 0xbce5086492111aeb,
+        0xec1e4a7db69561a6, 0x9392ee8e921d5d08, 0xb877aa3236a4b44a,
+        0xe69594bec44de15c, 0x901d7cf73ab0acda, 0xb424dc35095cd810,
+        0xe12e13424bb40e14, 0x8cbccc096f5088cc, 0xafebff0bcb24aaff,
+        0xdbe6fecebdedd5bf, 0x89705f4136b4a598, 0xabcc77118461cefd,
+        0xd6bf94d5e57a42bd, 0x8637bd05af6c69b6, 0xa7c5ac471b478424,
+        0xd1b71758e219652c, 0x83126e978d4fdf3c, 0xa3d70a3d70a3d70b,
+        0xcccccccccccccccd, 0x8000000000000000, 0xa000000000000000,
+        0xc800000000000000, 0xfa00000000000000, 0x9c40000000000000,
+        0xc350000000000000, 0xf424000000000000, 0x9896800000000000,
+        0xbebc200000000000, 0xee6b280000000000, 0x9502f90000000000,
+        0xba43b74000000000, 0xe8d4a51000000000, 0x9184e72a00000000,
+        0xb5e620f480000000, 0xe35fa931a0000000, 0x8e1bc9bf04000000,
+        0xb1a2bc2ec5000000, 0xde0b6b3a76400000, 0x8ac7230489e80000,
+        0xad78ebc5ac620000, 0xd8d726b7177a8000, 0x878678326eac9000,
+        0xa968163f0a57b400, 0xd3c21bcecceda100, 0x84595161401484a0,
+        0xa56fa5b99019a5c8, 0xcecb8f27f4200f3a, 0x813f3978f8940985,
+        0xa18f07d736b90be6, 0xc9f2c9cd04674edf, 0xfc6f7c4045812297,
+        0x9dc5ada82b70b59e, 0xc5371912364ce306, 0xf684df56c3e01bc7,
+        0x9a130b963a6c115d, 0xc097ce7bc90715b4, 0xf0bdc21abb48db21,
+        0x96769950b50d88f5, 0xbc143fa4e250eb32, 0xeb194f8e1ae525fe,
+        0x92efd1b8d0cf37bf, 0xb7abc627050305ae, 0xe596b7b0c643c71a,
+        0x8f7e32ce7bea5c70, 0xb35dbf821ae4f38c, 0xe0352f62a19e306f};
+    return pow10_significands[k - float_info<float>::min_k];
   }
-};
-
-class bigint {
- private:
-  // A bigint is stored as an array of bigits (big digits), with bigit at index
-  // 0 being the least significant one.
-  using bigit = uint32_t;
-  using double_bigit = uint64_t;
-  enum { bigits_capacity = 32 };
-  basic_memory_buffer<bigit, bigits_capacity> bigits_;
-  int exp_;
-
-  bigit operator[](int index) const { return bigits_[to_unsigned(index)]; }
-  bigit& operator[](int index) { return bigits_[to_unsigned(index)]; }
-
-  static FMT_CONSTEXPR_DECL const int bigit_bits = bits<bigit>::value;
 
-  friend struct formatter<bigint>;
+  struct compute_mul_result {
+    carrier_uint result;
+    bool is_integer;
+  };
+  struct compute_mul_parity_result {
+    bool parity;
+    bool is_integer;
+  };
 
-  void subtract_bigits(int index, bigit other, bigit& borrow) {
-    auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
-    (*this)[index] = static_cast<bigit>(result);
-    borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
+  static auto compute_mul(carrier_uint u,
+                          const cache_entry_type& cache) noexcept
+      -> compute_mul_result {
+    auto r = umul96_upper64(u, cache);
+    return {static_cast<carrier_uint>(r >> 32),
+            static_cast<carrier_uint>(r) == 0};
   }
 
-  void remove_leading_zeros() {
-    int num_bigits = static_cast<int>(bigits_.size()) - 1;
-    while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
-    bigits_.resize(to_unsigned(num_bigits + 1));
+  static auto compute_delta(const cache_entry_type& cache, int beta) noexcept
+      -> uint32_t {
+    return static_cast<uint32_t>(cache >> (64 - 1 - beta));
   }
 
-  // Computes *this -= other assuming aligned bigints and *this >= other.
-  void subtract_aligned(const bigint& other) {
-    FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
-    FMT_ASSERT(compare(*this, other) >= 0, "");
-    bigit borrow = 0;
-    int i = other.exp_ - exp_;
-    for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j) {
-      subtract_bigits(i, other.bigits_[j], borrow);
-    }
-    while (borrow > 0) subtract_bigits(i, 0, borrow);
-    remove_leading_zeros();
+  static auto compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta) noexcept
+      -> compute_mul_parity_result {
+    FMT_ASSERT(beta >= 1, "");
+    FMT_ASSERT(beta < 64, "");
+
+    auto r = umul96_lower64(two_f, cache);
+    return {((r >> (64 - beta)) & 1) != 0,
+            static_cast<uint32_t>(r >> (32 - beta)) == 0};
   }
 
-  void multiply(uint32_t value) {
-    const double_bigit wide_value = value;
-    bigit carry = 0;
-    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
-      double_bigit result = bigits_[i] * wide_value + carry;
-      bigits_[i] = static_cast<bigit>(result);
-      carry = static_cast<bigit>(result >> bigit_bits);
-    }
-    if (carry != 0) bigits_.push_back(carry);
+  static auto compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return static_cast<carrier_uint>(
+        (cache - (cache >> (num_significand_bits<float>() + 2))) >>
+        (64 - num_significand_bits<float>() - 1 - beta));
   }
 
-  void multiply(uint64_t value) {
-    const bigit mask = ~bigit(0);
-    const double_bigit lower = value & mask;
-    const double_bigit upper = value >> bigit_bits;
-    double_bigit carry = 0;
-    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
-      double_bigit result = bigits_[i] * lower + (carry & mask);
-      carry =
-          bigits_[i] * upper + (result >> bigit_bits) + (carry >> bigit_bits);
-      bigits_[i] = static_cast<bigit>(result);
-    }
-    while (carry != 0) {
-      bigits_.push_back(carry & mask);
-      carry >>= bigit_bits;
-    }
+  static auto compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return static_cast<carrier_uint>(
+        (cache + (cache >> (num_significand_bits<float>() + 1))) >>
+        (64 - num_significand_bits<float>() - 1 - beta));
   }
 
- public:
-  bigint() : exp_(0) {}
-  explicit bigint(uint64_t n) { assign(n); }
-  ~bigint() { assert(bigits_.capacity() <= bigits_capacity); }
+  static auto compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return (static_cast<carrier_uint>(
+                cache >> (64 - num_significand_bits<float>() - 2 - beta)) +
+            1) /
+           2;
+  }
+};
 
-  bigint(const bigint&) = delete;
-  void operator=(const bigint&) = delete;
+template <> struct cache_accessor<double> {
+  using carrier_uint = float_info<double>::carrier_uint;
+  using cache_entry_type = uint128_fallback;
+
+  static auto get_cached_power(int k) noexcept -> uint128_fallback {
+    FMT_ASSERT(k >= float_info<double>::min_k && k <= float_info<double>::max_k,
+               "k is out of range");
+
+    static constexpr const uint128_fallback pow10_significands[] = {
+#if FMT_USE_FULL_CACHE_DRAGONBOX
+      {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
+      {0x9faacf3df73609b1, 0x77b191618c54e9ad},
+      {0xc795830d75038c1d, 0xd59df5b9ef6a2418},
+      {0xf97ae3d0d2446f25, 0x4b0573286b44ad1e},
+      {0x9becce62836ac577, 0x4ee367f9430aec33},
+      {0xc2e801fb244576d5, 0x229c41f793cda740},
+      {0xf3a20279ed56d48a, 0x6b43527578c11110},
+      {0x9845418c345644d6, 0x830a13896b78aaaa},
+      {0xbe5691ef416bd60c, 0x23cc986bc656d554},
+      {0xedec366b11c6cb8f, 0x2cbfbe86b7ec8aa9},
+      {0x94b3a202eb1c3f39, 0x7bf7d71432f3d6aa},
+      {0xb9e08a83a5e34f07, 0xdaf5ccd93fb0cc54},
+      {0xe858ad248f5c22c9, 0xd1b3400f8f9cff69},
+      {0x91376c36d99995be, 0x23100809b9c21fa2},
+      {0xb58547448ffffb2d, 0xabd40a0c2832a78b},
+      {0xe2e69915b3fff9f9, 0x16c90c8f323f516d},
+      {0x8dd01fad907ffc3b, 0xae3da7d97f6792e4},
+      {0xb1442798f49ffb4a, 0x99cd11cfdf41779d},
+      {0xdd95317f31c7fa1d, 0x40405643d711d584},
+      {0x8a7d3eef7f1cfc52, 0x482835ea666b2573},
+      {0xad1c8eab5ee43b66, 0xda3243650005eed0},
+      {0xd863b256369d4a40, 0x90bed43e40076a83},
+      {0x873e4f75e2224e68, 0x5a7744a6e804a292},
+      {0xa90de3535aaae202, 0x711515d0a205cb37},
+      {0xd3515c2831559a83, 0x0d5a5b44ca873e04},
+      {0x8412d9991ed58091, 0xe858790afe9486c3},
+      {0xa5178fff668ae0b6, 0x626e974dbe39a873},
+      {0xce5d73ff402d98e3, 0xfb0a3d212dc81290},
+      {0x80fa687f881c7f8e, 0x7ce66634bc9d0b9a},
+      {0xa139029f6a239f72, 0x1c1fffc1ebc44e81},
+      {0xc987434744ac874e, 0xa327ffb266b56221},
+      {0xfbe9141915d7a922, 0x4bf1ff9f0062baa9},
+      {0x9d71ac8fada6c9b5, 0x6f773fc3603db4aa},
+      {0xc4ce17b399107c22, 0xcb550fb4384d21d4},
+      {0xf6019da07f549b2b, 0x7e2a53a146606a49},
+      {0x99c102844f94e0fb, 0x2eda7444cbfc426e},
+      {0xc0314325637a1939, 0xfa911155fefb5309},
+      {0xf03d93eebc589f88, 0x793555ab7eba27cb},
+      {0x96267c7535b763b5, 0x4bc1558b2f3458df},
+      {0xbbb01b9283253ca2, 0x9eb1aaedfb016f17},
+      {0xea9c227723ee8bcb, 0x465e15a979c1cadd},
+      {0x92a1958a7675175f, 0x0bfacd89ec191eca},
+      {0xb749faed14125d36, 0xcef980ec671f667c},
+      {0xe51c79a85916f484, 0x82b7e12780e7401b},
+      {0x8f31cc0937ae58d2, 0xd1b2ecb8b0908811},
+      {0xb2fe3f0b8599ef07, 0x861fa7e6dcb4aa16},
+      {0xdfbdcece67006ac9, 0x67a791e093e1d49b},
+      {0x8bd6a141006042bd, 0xe0c8bb2c5c6d24e1},
+      {0xaecc49914078536d, 0x58fae9f773886e19},
+      {0xda7f5bf590966848, 0xaf39a475506a899f},
+      {0x888f99797a5e012d, 0x6d8406c952429604},
+      {0xaab37fd7d8f58178, 0xc8e5087ba6d33b84},
+      {0xd5605fcdcf32e1d6, 0xfb1e4a9a90880a65},
+      {0x855c3be0a17fcd26, 0x5cf2eea09a550680},
+      {0xa6b34ad8c9dfc06f, 0xf42faa48c0ea481f},
+      {0xd0601d8efc57b08b, 0xf13b94daf124da27},
+      {0x823c12795db6ce57, 0x76c53d08d6b70859},
+      {0xa2cb1717b52481ed, 0x54768c4b0c64ca6f},
+      {0xcb7ddcdda26da268, 0xa9942f5dcf7dfd0a},
+      {0xfe5d54150b090b02, 0xd3f93b35435d7c4d},
+      {0x9efa548d26e5a6e1, 0xc47bc5014a1a6db0},
+      {0xc6b8e9b0709f109a, 0x359ab6419ca1091c},
+      {0xf867241c8cc6d4c0, 0xc30163d203c94b63},
+      {0x9b407691d7fc44f8, 0x79e0de63425dcf1e},
+      {0xc21094364dfb5636, 0x985915fc12f542e5},
+      {0xf294b943e17a2bc4, 0x3e6f5b7b17b2939e},
+      {0x979cf3ca6cec5b5a, 0xa705992ceecf9c43},
+      {0xbd8430bd08277231, 0x50c6ff782a838354},
+      {0xece53cec4a314ebd, 0xa4f8bf5635246429},
+      {0x940f4613ae5ed136, 0x871b7795e136be9a},
+      {0xb913179899f68584, 0x28e2557b59846e40},
+      {0xe757dd7ec07426e5, 0x331aeada2fe589d0},
+      {0x9096ea6f3848984f, 0x3ff0d2c85def7622},
+      {0xb4bca50b065abe63, 0x0fed077a756b53aa},
+      {0xe1ebce4dc7f16dfb, 0xd3e8495912c62895},
+      {0x8d3360f09cf6e4bd, 0x64712dd7abbbd95d},
+      {0xb080392cc4349dec, 0xbd8d794d96aacfb4},
+      {0xdca04777f541c567, 0xecf0d7a0fc5583a1},
+      {0x89e42caaf9491b60, 0xf41686c49db57245},
+      {0xac5d37d5b79b6239, 0x311c2875c522ced6},
+      {0xd77485cb25823ac7, 0x7d633293366b828c},
+      {0x86a8d39ef77164bc, 0xae5dff9c02033198},
+      {0xa8530886b54dbdeb, 0xd9f57f830283fdfd},
+      {0xd267caa862a12d66, 0xd072df63c324fd7c},
+      {0x8380dea93da4bc60, 0x4247cb9e59f71e6e},
+      {0xa46116538d0deb78, 0x52d9be85f074e609},
+      {0xcd795be870516656, 0x67902e276c921f8c},
+      {0x806bd9714632dff6, 0x00ba1cd8a3db53b7},
+      {0xa086cfcd97bf97f3, 0x80e8a40eccd228a5},
+      {0xc8a883c0fdaf7df0, 0x6122cd128006b2ce},
+      {0xfad2a4b13d1b5d6c, 0x796b805720085f82},
+      {0x9cc3a6eec6311a63, 0xcbe3303674053bb1},
+      {0xc3f490aa77bd60fc, 0xbedbfc4411068a9d},
+      {0xf4f1b4d515acb93b, 0xee92fb5515482d45},
+      {0x991711052d8bf3c5, 0x751bdd152d4d1c4b},
+      {0xbf5cd54678eef0b6, 0xd262d45a78a0635e},
+      {0xef340a98172aace4, 0x86fb897116c87c35},
+      {0x9580869f0e7aac0e, 0xd45d35e6ae3d4da1},
+      {0xbae0a846d2195712, 0x8974836059cca10a},
+      {0xe998d258869facd7, 0x2bd1a438703fc94c},
+      {0x91ff83775423cc06, 0x7b6306a34627ddd0},
+      {0xb67f6455292cbf08, 0x1a3bc84c17b1d543},
+      {0xe41f3d6a7377eeca, 0x20caba5f1d9e4a94},
+      {0x8e938662882af53e, 0x547eb47b7282ee9d},
+      {0xb23867fb2a35b28d, 0xe99e619a4f23aa44},
+      {0xdec681f9f4c31f31, 0x6405fa00e2ec94d5},
+      {0x8b3c113c38f9f37e, 0xde83bc408dd3dd05},
+      {0xae0b158b4738705e, 0x9624ab50b148d446},
+      {0xd98ddaee19068c76, 0x3badd624dd9b0958},
+      {0x87f8a8d4cfa417c9, 0xe54ca5d70a80e5d7},
+      {0xa9f6d30a038d1dbc, 0x5e9fcf4ccd211f4d},
+      {0xd47487cc8470652b, 0x7647c32000696720},
+      {0x84c8d4dfd2c63f3b, 0x29ecd9f40041e074},
+      {0xa5fb0a17c777cf09, 0xf468107100525891},
+      {0xcf79cc9db955c2cc, 0x7182148d4066eeb5},
+      {0x81ac1fe293d599bf, 0xc6f14cd848405531},
+      {0xa21727db38cb002f, 0xb8ada00e5a506a7d},
+      {0xca9cf1d206fdc03b, 0xa6d90811f0e4851d},
+      {0xfd442e4688bd304a, 0x908f4a166d1da664},
+      {0x9e4a9cec15763e2e, 0x9a598e4e043287ff},
+      {0xc5dd44271ad3cdba, 0x40eff1e1853f29fe},
+      {0xf7549530e188c128, 0xd12bee59e68ef47d},
+      {0x9a94dd3e8cf578b9, 0x82bb74f8301958cf},
+      {0xc13a148e3032d6e7, 0xe36a52363c1faf02},
+      {0xf18899b1bc3f8ca1, 0xdc44e6c3cb279ac2},
+      {0x96f5600f15a7b7e5, 0x29ab103a5ef8c0ba},
+      {0xbcb2b812db11a5de, 0x7415d448f6b6f0e8},
+      {0xebdf661791d60f56, 0x111b495b3464ad22},
+      {0x936b9fcebb25c995, 0xcab10dd900beec35},
+      {0xb84687c269ef3bfb, 0x3d5d514f40eea743},
+      {0xe65829b3046b0afa, 0x0cb4a5a3112a5113},
+      {0x8ff71a0fe2c2e6dc, 0x47f0e785eaba72ac},
+      {0xb3f4e093db73a093, 0x59ed216765690f57},
+      {0xe0f218b8d25088b8, 0x306869c13ec3532d},
+      {0x8c974f7383725573, 0x1e414218c73a13fc},
+      {0xafbd2350644eeacf, 0xe5d1929ef90898fb},
+      {0xdbac6c247d62a583, 0xdf45f746b74abf3a},
+      {0x894bc396ce5da772, 0x6b8bba8c328eb784},
+      {0xab9eb47c81f5114f, 0x066ea92f3f326565},
+      {0xd686619ba27255a2, 0xc80a537b0efefebe},
+      {0x8613fd0145877585, 0xbd06742ce95f5f37},
+      {0xa798fc4196e952e7, 0x2c48113823b73705},
+      {0xd17f3b51fca3a7a0, 0xf75a15862ca504c6},
+      {0x82ef85133de648c4, 0x9a984d73dbe722fc},
+      {0xa3ab66580d5fdaf5, 0xc13e60d0d2e0ebbb},
+      {0xcc963fee10b7d1b3, 0x318df905079926a9},
+      {0xffbbcfe994e5c61f, 0xfdf17746497f7053},
+      {0x9fd561f1fd0f9bd3, 0xfeb6ea8bedefa634},
+      {0xc7caba6e7c5382c8, 0xfe64a52ee96b8fc1},
+      {0xf9bd690a1b68637b, 0x3dfdce7aa3c673b1},
+      {0x9c1661a651213e2d, 0x06bea10ca65c084f},
+      {0xc31bfa0fe5698db8, 0x486e494fcff30a63},
+      {0xf3e2f893dec3f126, 0x5a89dba3c3efccfb},
+      {0x986ddb5c6b3a76b7, 0xf89629465a75e01d},
+      {0xbe89523386091465, 0xf6bbb397f1135824},
+      {0xee2ba6c0678b597f, 0x746aa07ded582e2d},
+      {0x94db483840b717ef, 0xa8c2a44eb4571cdd},
+      {0xba121a4650e4ddeb, 0x92f34d62616ce414},
+      {0xe896a0d7e51e1566, 0x77b020baf9c81d18},
+      {0x915e2486ef32cd60, 0x0ace1474dc1d122f},
+      {0xb5b5ada8aaff80b8, 0x0d819992132456bb},
+      {0xe3231912d5bf60e6, 0x10e1fff697ed6c6a},
+      {0x8df5efabc5979c8f, 0xca8d3ffa1ef463c2},
+      {0xb1736b96b6fd83b3, 0xbd308ff8a6b17cb3},
+      {0xddd0467c64bce4a0, 0xac7cb3f6d05ddbdf},
+      {0x8aa22c0dbef60ee4, 0x6bcdf07a423aa96c},
+      {0xad4ab7112eb3929d, 0x86c16c98d2c953c7},
+      {0xd89d64d57a607744, 0xe871c7bf077ba8b8},
+      {0x87625f056c7c4a8b, 0x11471cd764ad4973},
+      {0xa93af6c6c79b5d2d, 0xd598e40d3dd89bd0},
+      {0xd389b47879823479, 0x4aff1d108d4ec2c4},
+      {0x843610cb4bf160cb, 0xcedf722a585139bb},
+      {0xa54394fe1eedb8fe, 0xc2974eb4ee658829},
+      {0xce947a3da6a9273e, 0x733d226229feea33},
+      {0x811ccc668829b887, 0x0806357d5a3f5260},
+      {0xa163ff802a3426a8, 0xca07c2dcb0cf26f8},
+      {0xc9bcff6034c13052, 0xfc89b393dd02f0b6},
+      {0xfc2c3f3841f17c67, 0xbbac2078d443ace3},
+      {0x9d9ba7832936edc0, 0xd54b944b84aa4c0e},
+      {0xc5029163f384a931, 0x0a9e795e65d4df12},
+      {0xf64335bcf065d37d, 0x4d4617b5ff4a16d6},
+      {0x99ea0196163fa42e, 0x504bced1bf8e4e46},
+      {0xc06481fb9bcf8d39, 0xe45ec2862f71e1d7},
+      {0xf07da27a82c37088, 0x5d767327bb4e5a4d},
+      {0x964e858c91ba2655, 0x3a6a07f8d510f870},
+      {0xbbe226efb628afea, 0x890489f70a55368c},
+      {0xeadab0aba3b2dbe5, 0x2b45ac74ccea842f},
+      {0x92c8ae6b464fc96f, 0x3b0b8bc90012929e},
+      {0xb77ada0617e3bbcb, 0x09ce6ebb40173745},
+      {0xe55990879ddcaabd, 0xcc420a6a101d0516},
+      {0x8f57fa54c2a9eab6, 0x9fa946824a12232e},
+      {0xb32df8e9f3546564, 0x47939822dc96abfa},
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+      {0x969eb7c47859e743, 0x9f644ae5a4b1b326},
+      {0xbc4665b596706114, 0x873d5d9f0dde1fef},
+      {0xeb57ff22fc0c7959, 0xa90cb506d155a7eb},
+      {0x9316ff75dd87cbd8, 0x09a7f12442d588f3},
+      {0xb7dcbf5354e9bece, 0x0c11ed6d538aeb30},
+      {0xe5d3ef282a242e81, 0x8f1668c8a86da5fb},
+      {0x8fa475791a569d10, 0xf96e017d694487bd},
+      {0xb38d92d760ec4455, 0x37c981dcc395a9ad},
+      {0xe070f78d3927556a, 0x85bbe253f47b1418},
+      {0x8c469ab843b89562, 0x93956d7478ccec8f},
+      {0xaf58416654a6babb, 0x387ac8d1970027b3},
+      {0xdb2e51bfe9d0696a, 0x06997b05fcc0319f},
+      {0x88fcf317f22241e2, 0x441fece3bdf81f04},
+      {0xab3c2fddeeaad25a, 0xd527e81cad7626c4},
+      {0xd60b3bd56a5586f1, 0x8a71e223d8d3b075},
+      {0x85c7056562757456, 0xf6872d5667844e4a},
+      {0xa738c6bebb12d16c, 0xb428f8ac016561dc},
+      {0xd106f86e69d785c7, 0xe13336d701beba53},
+      {0x82a45b450226b39c, 0xecc0024661173474},
+      {0xa34d721642b06084, 0x27f002d7f95d0191},
+      {0xcc20ce9bd35c78a5, 0x31ec038df7b441f5},
+      {0xff290242c83396ce, 0x7e67047175a15272},
+      {0x9f79a169bd203e41, 0x0f0062c6e984d387},
+      {0xc75809c42c684dd1, 0x52c07b78a3e60869},
+      {0xf92e0c3537826145, 0xa7709a56ccdf8a83},
+      {0x9bbcc7a142b17ccb, 0x88a66076400bb692},
+      {0xc2abf989935ddbfe, 0x6acff893d00ea436},
+      {0xf356f7ebf83552fe, 0x0583f6b8c4124d44},
+      {0x98165af37b2153de, 0xc3727a337a8b704b},
+      {0xbe1bf1b059e9a8d6, 0x744f18c0592e4c5d},
+      {0xeda2ee1c7064130c, 0x1162def06f79df74},
+      {0x9485d4d1c63e8be7, 0x8addcb5645ac2ba9},
+      {0xb9a74a0637ce2ee1, 0x6d953e2bd7173693},
+      {0xe8111c87c5c1ba99, 0xc8fa8db6ccdd0438},
+      {0x910ab1d4db9914a0, 0x1d9c9892400a22a3},
+      {0xb54d5e4a127f59c8, 0x2503beb6d00cab4c},
+      {0xe2a0b5dc971f303a, 0x2e44ae64840fd61e},
+      {0x8da471a9de737e24, 0x5ceaecfed289e5d3},
+      {0xb10d8e1456105dad, 0x7425a83e872c5f48},
+      {0xdd50f1996b947518, 0xd12f124e28f7771a},
+      {0x8a5296ffe33cc92f, 0x82bd6b70d99aaa70},
+      {0xace73cbfdc0bfb7b, 0x636cc64d1001550c},
+      {0xd8210befd30efa5a, 0x3c47f7e05401aa4f},
+      {0x8714a775e3e95c78, 0x65acfaec34810a72},
+      {0xa8d9d1535ce3b396, 0x7f1839a741a14d0e},
+      {0xd31045a8341ca07c, 0x1ede48111209a051},
+      {0x83ea2b892091e44d, 0x934aed0aab460433},
+      {0xa4e4b66b68b65d60, 0xf81da84d56178540},
+      {0xce1de40642e3f4b9, 0x36251260ab9d668f},
+      {0x80d2ae83e9ce78f3, 0xc1d72b7c6b42601a},
+      {0xa1075a24e4421730, 0xb24cf65b8612f820},
+      {0xc94930ae1d529cfc, 0xdee033f26797b628},
+      {0xfb9b7cd9a4a7443c, 0x169840ef017da3b2},
+      {0x9d412e0806e88aa5, 0x8e1f289560ee864f},
+      {0xc491798a08a2ad4e, 0xf1a6f2bab92a27e3},
+      {0xf5b5d7ec8acb58a2, 0xae10af696774b1dc},
+      {0x9991a6f3d6bf1765, 0xacca6da1e0a8ef2a},
+      {0xbff610b0cc6edd3f, 0x17fd090a58d32af4},
+      {0xeff394dcff8a948e, 0xddfc4b4cef07f5b1},
+      {0x95f83d0a1fb69cd9, 0x4abdaf101564f98f},
+      {0xbb764c4ca7a4440f, 0x9d6d1ad41abe37f2},
+      {0xea53df5fd18d5513, 0x84c86189216dc5ee},
+      {0x92746b9be2f8552c, 0x32fd3cf5b4e49bb5},
+      {0xb7118682dbb66a77, 0x3fbc8c33221dc2a2},
+      {0xe4d5e82392a40515, 0x0fabaf3feaa5334b},
+      {0x8f05b1163ba6832d, 0x29cb4d87f2a7400f},
+      {0xb2c71d5bca9023f8, 0x743e20e9ef511013},
+      {0xdf78e4b2bd342cf6, 0x914da9246b255417},
+      {0x8bab8eefb6409c1a, 0x1ad089b6c2f7548f},
+      {0xae9672aba3d0c320, 0xa184ac2473b529b2},
+      {0xda3c0f568cc4f3e8, 0xc9e5d72d90a2741f},
+      {0x8865899617fb1871, 0x7e2fa67c7a658893},
+      {0xaa7eebfb9df9de8d, 0xddbb901b98feeab8},
+      {0xd51ea6fa85785631, 0x552a74227f3ea566},
+      {0x8533285c936b35de, 0xd53a88958f872760},
+      {0xa67ff273b8460356, 0x8a892abaf368f138},
+      {0xd01fef10a657842c, 0x2d2b7569b0432d86},
+      {0x8213f56a67f6b29b, 0x9c3b29620e29fc74},
+      {0xa298f2c501f45f42, 0x8349f3ba91b47b90},
+      {0xcb3f2f7642717713, 0x241c70a936219a74},
+      {0xfe0efb53d30dd4d7, 0xed238cd383aa0111},
+      {0x9ec95d1463e8a506, 0xf4363804324a40ab},
+      {0xc67bb4597ce2ce48, 0xb143c6053edcd0d6},
+      {0xf81aa16fdc1b81da, 0xdd94b7868e94050b},
+      {0x9b10a4e5e9913128, 0xca7cf2b4191c8327},
+      {0xc1d4ce1f63f57d72, 0xfd1c2f611f63a3f1},
+      {0xf24a01a73cf2dccf, 0xbc633b39673c8ced},
+      {0x976e41088617ca01, 0xd5be0503e085d814},
+      {0xbd49d14aa79dbc82, 0x4b2d8644d8a74e19},
+      {0xec9c459d51852ba2, 0xddf8e7d60ed1219f},
+      {0x93e1ab8252f33b45, 0xcabb90e5c942b504},
+      {0xb8da1662e7b00a17, 0x3d6a751f3b936244},
+      {0xe7109bfba19c0c9d, 0x0cc512670a783ad5},
+      {0x906a617d450187e2, 0x27fb2b80668b24c6},
+      {0xb484f9dc9641e9da, 0xb1f9f660802dedf7},
+      {0xe1a63853bbd26451, 0x5e7873f8a0396974},
+      {0x8d07e33455637eb2, 0xdb0b487b6423e1e9},
+      {0xb049dc016abc5e5f, 0x91ce1a9a3d2cda63},
+      {0xdc5c5301c56b75f7, 0x7641a140cc7810fc},
+      {0x89b9b3e11b6329ba, 0xa9e904c87fcb0a9e},
+      {0xac2820d9623bf429, 0x546345fa9fbdcd45},
+      {0xd732290fbacaf133, 0xa97c177947ad4096},
+      {0x867f59a9d4bed6c0, 0x49ed8eabcccc485e},
+      {0xa81f301449ee8c70, 0x5c68f256bfff5a75},
+      {0xd226fc195c6a2f8c, 0x73832eec6fff3112},
+      {0x83585d8fd9c25db7, 0xc831fd53c5ff7eac},
+      {0xa42e74f3d032f525, 0xba3e7ca8b77f5e56},
+      {0xcd3a1230c43fb26f, 0x28ce1bd2e55f35ec},
+      {0x80444b5e7aa7cf85, 0x7980d163cf5b81b4},
+      {0xa0555e361951c366, 0xd7e105bcc3326220},
+      {0xc86ab5c39fa63440, 0x8dd9472bf3fefaa8},
+      {0xfa856334878fc150, 0xb14f98f6f0feb952},
+      {0x9c935e00d4b9d8d2, 0x6ed1bf9a569f33d4},
+      {0xc3b8358109e84f07, 0x0a862f80ec4700c9},
+      {0xf4a642e14c6262c8, 0xcd27bb612758c0fb},
+      {0x98e7e9cccfbd7dbd, 0x8038d51cb897789d},
+      {0xbf21e44003acdd2c, 0xe0470a63e6bd56c4},
+      {0xeeea5d5004981478, 0x1858ccfce06cac75},
+      {0x95527a5202df0ccb, 0x0f37801e0c43ebc9},
+      {0xbaa718e68396cffd, 0xd30560258f54e6bb},
+      {0xe950df20247c83fd, 0x47c6b82ef32a206a},
+      {0x91d28b7416cdd27e, 0x4cdc331d57fa5442},
+      {0xb6472e511c81471d, 0xe0133fe4adf8e953},
+      {0xe3d8f9e563a198e5, 0x58180fddd97723a7},
+      {0x8e679c2f5e44ff8f, 0x570f09eaa7ea7649},
+      {0xb201833b35d63f73, 0x2cd2cc6551e513db},
+      {0xde81e40a034bcf4f, 0xf8077f7ea65e58d2},
+      {0x8b112e86420f6191, 0xfb04afaf27faf783},
+      {0xadd57a27d29339f6, 0x79c5db9af1f9b564},
+      {0xd94ad8b1c7380874, 0x18375281ae7822bd},
+      {0x87cec76f1c830548, 0x8f2293910d0b15b6},
+      {0xa9c2794ae3a3c69a, 0xb2eb3875504ddb23},
+      {0xd433179d9c8cb841, 0x5fa60692a46151ec},
+      {0x849feec281d7f328, 0xdbc7c41ba6bcd334},
+      {0xa5c7ea73224deff3, 0x12b9b522906c0801},
+      {0xcf39e50feae16bef, 0xd768226b34870a01},
+      {0x81842f29f2cce375, 0xe6a1158300d46641},
+      {0xa1e53af46f801c53, 0x60495ae3c1097fd1},
+      {0xca5e89b18b602368, 0x385bb19cb14bdfc5},
+      {0xfcf62c1dee382c42, 0x46729e03dd9ed7b6},
+      {0x9e19db92b4e31ba9, 0x6c07a2c26a8346d2},
+      {0xc5a05277621be293, 0xc7098b7305241886},
+      {0xf70867153aa2db38, 0xb8cbee4fc66d1ea8},
+      {0x9a65406d44a5c903, 0x737f74f1dc043329},
+      {0xc0fe908895cf3b44, 0x505f522e53053ff3},
+      {0xf13e34aabb430a15, 0x647726b9e7c68ff0},
+      {0x96c6e0eab509e64d, 0x5eca783430dc19f6},
+      {0xbc789925624c5fe0, 0xb67d16413d132073},
+      {0xeb96bf6ebadf77d8, 0xe41c5bd18c57e890},
+      {0x933e37a534cbaae7, 0x8e91b962f7b6f15a},
+      {0xb80dc58e81fe95a1, 0x723627bbb5a4adb1},
+      {0xe61136f2227e3b09, 0xcec3b1aaa30dd91d},
+      {0x8fcac257558ee4e6, 0x213a4f0aa5e8a7b2},
+      {0xb3bd72ed2af29e1f, 0xa988e2cd4f62d19e},
+      {0xe0accfa875af45a7, 0x93eb1b80a33b8606},
+      {0x8c6c01c9498d8b88, 0xbc72f130660533c4},
+      {0xaf87023b9bf0ee6a, 0xeb8fad7c7f8680b5},
+      {0xdb68c2ca82ed2a05, 0xa67398db9f6820e2},
+#else
+      {0xff77b1fcbebcdc4f, 0x25e8e89c13bb0f7b},
+      {0xce5d73ff402d98e3, 0xfb0a3d212dc81290},
+      {0xa6b34ad8c9dfc06f, 0xf42faa48c0ea481f},
+      {0x86a8d39ef77164bc, 0xae5dff9c02033198},
+      {0xd98ddaee19068c76, 0x3badd624dd9b0958},
+      {0xafbd2350644eeacf, 0xe5d1929ef90898fb},
+      {0x8df5efabc5979c8f, 0xca8d3ffa1ef463c2},
+      {0xe55990879ddcaabd, 0xcc420a6a101d0516},
+      {0xb94470938fa89bce, 0xf808e40e8d5b3e6a},
+      {0x95a8637627989aad, 0xdde7001379a44aa9},
+      {0xf1c90080baf72cb1, 0x5324c68b12dd6339},
+      {0xc350000000000000, 0x0000000000000000},
+      {0x9dc5ada82b70b59d, 0xf020000000000000},
+      {0xfee50b7025c36a08, 0x02f236d04753d5b5},
+      {0xcde6fd5e09abcf26, 0xed4c0226b55e6f87},
+      {0xa6539930bf6bff45, 0x84db8346b786151d},
+      {0x865b86925b9bc5c2, 0x0b8a2392ba45a9b3},
+      {0xd910f7ff28069da4, 0x1b2ba1518094da05},
+      {0xaf58416654a6babb, 0x387ac8d1970027b3},
+      {0x8da471a9de737e24, 0x5ceaecfed289e5d3},
+      {0xe4d5e82392a40515, 0x0fabaf3feaa5334b},
+      {0xb8da1662e7b00a17, 0x3d6a751f3b936244},
+      {0x95527a5202df0ccb, 0x0f37801e0c43ebc9},
+      {0xf13e34aabb430a15, 0x647726b9e7c68ff0}
+#endif
+    };
 
-  void assign(const bigint& other) {
-    bigits_.resize(other.bigits_.size());
-    auto data = other.bigits_.data();
-    std::copy(data, data + other.bigits_.size(), bigits_.data());
-    exp_ = other.exp_;
+#if FMT_USE_FULL_CACHE_DRAGONBOX
+    return pow10_significands[k - float_info<double>::min_k];
+#else
+    static constexpr const uint64_t powers_of_5_64[] = {
+        0x0000000000000001, 0x0000000000000005, 0x0000000000000019,
+        0x000000000000007d, 0x0000000000000271, 0x0000000000000c35,
+        0x0000000000003d09, 0x000000000001312d, 0x000000000005f5e1,
+        0x00000000001dcd65, 0x00000000009502f9, 0x0000000002e90edd,
+        0x000000000e8d4a51, 0x0000000048c27395, 0x000000016bcc41e9,
+        0x000000071afd498d, 0x0000002386f26fc1, 0x000000b1a2bc2ec5,
+        0x000003782dace9d9, 0x00001158e460913d, 0x000056bc75e2d631,
+        0x0001b1ae4d6e2ef5, 0x000878678326eac9, 0x002a5a058fc295ed,
+        0x00d3c21bcecceda1, 0x0422ca8b0a00a425, 0x14adf4b7320334b9};
+
+    static const int compression_ratio = 27;
+
+    // Compute base index.
+    int cache_index = (k - float_info<double>::min_k) / compression_ratio;
+    int kb = cache_index * compression_ratio + float_info<double>::min_k;
+    int offset = k - kb;
+
+    // Get base cache.
+    uint128_fallback base_cache = pow10_significands[cache_index];
+    if (offset == 0) return base_cache;
+
+    // Compute the required amount of bit-shift.
+    int alpha = floor_log2_pow10(kb + offset) - floor_log2_pow10(kb) - offset;
+    FMT_ASSERT(alpha > 0 && alpha < 64, "shifting error detected");
+
+    // Try to recover the real cache.
+    uint64_t pow5 = powers_of_5_64[offset];
+    uint128_fallback recovered_cache = umul128(base_cache.high(), pow5);
+    uint128_fallback middle_low = umul128(base_cache.low(), pow5);
+
+    recovered_cache += middle_low.high();
+
+    uint64_t high_to_middle = recovered_cache.high() << (64 - alpha);
+    uint64_t middle_to_low = recovered_cache.low() << (64 - alpha);
+
+    recovered_cache =
+        uint128_fallback{(recovered_cache.low() >> alpha) | high_to_middle,
+                         ((middle_low.low() >> alpha) | middle_to_low)};
+    FMT_ASSERT(recovered_cache.low() + 1 != 0, "");
+    return {recovered_cache.high(), recovered_cache.low() + 1};
+#endif
   }
 
-  void assign(uint64_t n) {
-    size_t num_bigits = 0;
-    do {
-      bigits_[num_bigits++] = n & ~bigit(0);
-      n >>= bigit_bits;
-    } while (n != 0);
-    bigits_.resize(num_bigits);
-    exp_ = 0;
-  }
+  struct compute_mul_result {
+    carrier_uint result;
+    bool is_integer;
+  };
+  struct compute_mul_parity_result {
+    bool parity;
+    bool is_integer;
+  };
 
-  int num_bigits() const { return static_cast<int>(bigits_.size()) + exp_; }
-
-  bigint& operator<<=(int shift) {
-    assert(shift >= 0);
-    exp_ += shift / bigit_bits;
-    shift %= bigit_bits;
-    if (shift == 0) return *this;
-    bigit carry = 0;
-    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
-      bigit c = bigits_[i] >> (bigit_bits - shift);
-      bigits_[i] = (bigits_[i] << shift) + carry;
-      carry = c;
-    }
-    if (carry != 0) bigits_.push_back(carry);
-    return *this;
+  static auto compute_mul(carrier_uint u,
+                          const cache_entry_type& cache) noexcept
+      -> compute_mul_result {
+    auto r = umul192_upper128(u, cache);
+    return {r.high(), r.low() == 0};
   }
 
-  template <typename Int> bigint& operator*=(Int value) {
-    FMT_ASSERT(value > 0, "");
-    multiply(uint32_or_64_or_128_t<Int>(value));
-    return *this;
+  static auto compute_delta(cache_entry_type const& cache, int beta) noexcept
+      -> uint32_t {
+    return static_cast<uint32_t>(cache.high() >> (64 - 1 - beta));
   }
 
-  friend int compare(const bigint& lhs, const bigint& rhs) {
-    int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
-    if (num_lhs_bigits != num_rhs_bigits)
-      return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
-    int i = static_cast<int>(lhs.bigits_.size()) - 1;
-    int j = static_cast<int>(rhs.bigits_.size()) - 1;
-    int end = i - j;
-    if (end < 0) end = 0;
-    for (; i >= end; --i, --j) {
-      bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
-      if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
-    }
-    if (i != j) return i > j ? 1 : -1;
-    return 0;
-  }
+  static auto compute_mul_parity(carrier_uint two_f,
+                                 const cache_entry_type& cache,
+                                 int beta) noexcept
+      -> compute_mul_parity_result {
+    FMT_ASSERT(beta >= 1, "");
+    FMT_ASSERT(beta < 64, "");
 
-  // Returns compare(lhs1 + lhs2, rhs).
-  friend int add_compare(const bigint& lhs1, const bigint& lhs2,
-                         const bigint& rhs) {
-    int max_lhs_bigits = (std::max)(lhs1.num_bigits(), lhs2.num_bigits());
-    int num_rhs_bigits = rhs.num_bigits();
-    if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
-    if (max_lhs_bigits > num_rhs_bigits) return 1;
-    auto get_bigit = [](const bigint& n, int i) -> bigit {
-      return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
-    };
-    double_bigit borrow = 0;
-    int min_exp = (std::min)((std::min)(lhs1.exp_, lhs2.exp_), rhs.exp_);
-    for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
-      double_bigit sum =
-          static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
-      bigit rhs_bigit = get_bigit(rhs, i);
-      if (sum > rhs_bigit + borrow) return 1;
-      borrow = rhs_bigit + borrow - sum;
-      if (borrow > 1) return -1;
-      borrow <<= bigit_bits;
-    }
-    return borrow != 0 ? -1 : 0;
+    auto r = umul192_lower128(two_f, cache);
+    return {((r.high() >> (64 - beta)) & 1) != 0,
+            ((r.high() << beta) | (r.low() >> (64 - beta))) == 0};
   }
 
-  // Assigns pow(10, exp) to this bigint.
-  void assign_pow10(int exp) {
-    assert(exp >= 0);
-    if (exp == 0) return assign(1);
-    // Find the top bit.
-    int bitmask = 1;
-    while (exp >= bitmask) bitmask <<= 1;
-    bitmask >>= 1;
-    // pow(10, exp) = pow(5, exp) * pow(2, exp). First compute pow(5, exp) by
-    // repeated squaring and multiplication.
-    assign(5);
-    bitmask >>= 1;
-    while (bitmask != 0) {
-      square();
-      if ((exp & bitmask) != 0) *this *= 5;
-      bitmask >>= 1;
-    }
-    *this <<= exp;  // Multiply by pow(2, exp) by shifting.
+  static auto compute_left_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return (cache.high() -
+            (cache.high() >> (num_significand_bits<double>() + 2))) >>
+           (64 - num_significand_bits<double>() - 1 - beta);
   }
 
-  void square() {
-    basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
-    int num_bigits = static_cast<int>(bigits_.size());
-    int num_result_bigits = 2 * num_bigits;
-    bigits_.resize(to_unsigned(num_result_bigits));
-    using accumulator_t = conditional_t<FMT_USE_INT128, uint128_t, accumulator>;
-    auto sum = accumulator_t();
-    for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
-      // Compute bigit at position bigit_index of the result by adding
-      // cross-product terms n[i] * n[j] such that i + j == bigit_index.
-      for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
-        // Most terms are multiplied twice which can be optimized in the future.
-        sum += static_cast<double_bigit>(n[i]) * n[j];
-      }
-      (*this)[bigit_index] = static_cast<bigit>(sum);
-      sum >>= bits<bigit>::value;  // Compute the carry.
-    }
-    // Do the same for the top half.
-    for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
-         ++bigit_index) {
-      for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
-        sum += static_cast<double_bigit>(n[i++]) * n[j--];
-      (*this)[bigit_index] = static_cast<bigit>(sum);
-      sum >>= bits<bigit>::value;
-    }
-    --num_result_bigits;
-    remove_leading_zeros();
-    exp_ *= 2;
+  static auto compute_right_endpoint_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return (cache.high() +
+            (cache.high() >> (num_significand_bits<double>() + 1))) >>
+           (64 - num_significand_bits<double>() - 1 - beta);
   }
 
-  // Divides this bignum by divisor, assigning the remainder to this and
-  // returning the quotient.
-  int divmod_assign(const bigint& divisor) {
-    FMT_ASSERT(this != &divisor, "");
-    if (compare(*this, divisor) < 0) return 0;
-    int num_bigits = static_cast<int>(bigits_.size());
-    FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
-    int exp_difference = exp_ - divisor.exp_;
-    if (exp_difference > 0) {
-      // Align bigints by adding trailing zeros to simplify subtraction.
-      bigits_.resize(to_unsigned(num_bigits + exp_difference));
-      for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
-        bigits_[j] = bigits_[i];
-      std::uninitialized_fill_n(bigits_.data(), exp_difference, 0);
-      exp_ -= exp_difference;
-    }
-    int quotient = 0;
-    do {
-      subtract_aligned(divisor);
-      ++quotient;
-    } while (compare(*this, divisor) >= 0);
-    return quotient;
+  static auto compute_round_up_for_shorter_interval_case(
+      const cache_entry_type& cache, int beta) noexcept -> carrier_uint {
+    return ((cache.high() >> (64 - num_significand_bits<double>() - 2 - beta)) +
+            1) /
+           2;
   }
 };
 
-enum class round_direction { unknown, up, down };
-
-// Given the divisor (normally a power of 10), the remainder = v % divisor for
-// some number v and the error, returns whether v should be rounded up, down, or
-// whether the rounding direction can't be determined due to error.
-// error should be less than divisor / 2.
-inline round_direction get_round_direction(uint64_t divisor, uint64_t remainder,
-                                           uint64_t error) {
-  FMT_ASSERT(remainder < divisor, "");  // divisor - remainder won't overflow.
-  FMT_ASSERT(error < divisor, "");      // divisor - error won't overflow.
-  FMT_ASSERT(error < divisor - error, "");  // error * 2 won't overflow.
-  // Round down if (remainder + error) * 2 <= divisor.
-  if (remainder <= divisor - remainder && error * 2 <= divisor - remainder * 2)
-    return round_direction::down;
-  // Round up if (remainder - error) * 2 >= divisor.
-  if (remainder >= error &&
-      remainder - error >= divisor - (remainder - error)) {
-    return round_direction::up;
-  }
-  return round_direction::unknown;
+FMT_FUNC auto get_cached_power(int k) noexcept -> uint128_fallback {
+  return cache_accessor<double>::get_cached_power(k);
 }
 
-namespace digits {
-enum result {
-  more,  // Generate more digits.
-  done,  // Done generating digits.
-  error  // Digit generation cancelled due to an error.
-};
-}
-
-// A version of count_digits optimized for grisu_gen_digits.
-inline int grisu_count_digits(uint32_t n) {
-  if (n < 10) return 1;
-  if (n < 100) return 2;
-  if (n < 1000) return 3;
-  if (n < 10000) return 4;
-  if (n < 100000) return 5;
-  if (n < 1000000) return 6;
-  if (n < 10000000) return 7;
-  if (n < 100000000) return 8;
-  if (n < 1000000000) return 9;
-  return 10;
+// Various integer checks
+template <typename T>
+auto is_left_endpoint_integer_shorter_interval(int exponent) noexcept -> bool {
+  const int case_shorter_interval_left_endpoint_lower_threshold = 2;
+  const int case_shorter_interval_left_endpoint_upper_threshold = 3;
+  return exponent >= case_shorter_interval_left_endpoint_lower_threshold &&
+         exponent <= case_shorter_interval_left_endpoint_upper_threshold;
 }
 
-// Generates output using the Grisu digit-gen algorithm.
-// error: the size of the region (lower, upper) outside of which numbers
-// definitely do not round to value (Delta in Grisu3).
-template <typename Handler>
-FMT_ALWAYS_INLINE digits::result grisu_gen_digits(fp value, uint64_t error,
-                                                  int& exp, Handler& handler) {
-  const fp one(1ULL << -value.e, value.e);
-  // The integral part of scaled value (p1 in Grisu) = value / one. It cannot be
-  // zero because it contains a product of two 64-bit numbers with MSB set (due
-  // to normalization) - 1, shifted right by at most 60 bits.
-  auto integral = static_cast<uint32_t>(value.f >> -one.e);
-  FMT_ASSERT(integral != 0, "");
-  FMT_ASSERT(integral == value.f >> -one.e, "");
-  // The fractional part of scaled value (p2 in Grisu) c = value % one.
-  uint64_t fractional = value.f & (one.f - 1);
-  exp = grisu_count_digits(integral);  // kappa in Grisu.
-  // Divide by 10 to prevent overflow.
-  auto result = handler.on_start(data::powers_of_10_64[exp - 1] << -one.e,
-                                 value.f / 10, error * 10, exp);
-  if (result != digits::more) return result;
-  // Generate digits for the integral part. This can produce up to 10 digits.
-  do {
-    uint32_t digit = 0;
-    auto divmod_integral = [&](uint32_t divisor) {
-      digit = integral / divisor;
-      integral %= divisor;
-    };
-    // This optimization by Milo Yip reduces the number of integer divisions by
-    // one per iteration.
-    switch (exp) {
-    case 10:
-      divmod_integral(1000000000);
-      break;
-    case 9:
-      divmod_integral(100000000);
-      break;
-    case 8:
-      divmod_integral(10000000);
-      break;
-    case 7:
-      divmod_integral(1000000);
-      break;
-    case 6:
-      divmod_integral(100000);
-      break;
-    case 5:
-      divmod_integral(10000);
-      break;
-    case 4:
-      divmod_integral(1000);
-      break;
-    case 3:
-      divmod_integral(100);
-      break;
-    case 2:
-      divmod_integral(10);
-      break;
-    case 1:
-      digit = integral;
-      integral = 0;
-      break;
-    default:
-      FMT_ASSERT(false, "invalid number of digits");
-    }
-    --exp;
-    uint64_t remainder =
-        (static_cast<uint64_t>(integral) << -one.e) + fractional;
-    result = handler.on_digit(static_cast<char>('0' + digit),
-                              data::powers_of_10_64[exp] << -one.e, remainder,
-                              error, exp, true);
-    if (result != digits::more) return result;
-  } while (exp > 0);
-  // Generate digits for the fractional part.
-  for (;;) {
-    fractional *= 10;
-    error *= 10;
-    char digit =
-        static_cast<char>('0' + static_cast<char>(fractional >> -one.e));
-    fractional &= one.f - 1;
-    --exp;
-    result = handler.on_digit(digit, one.f, fractional, error, exp, false);
-    if (result != digits::more) return result;
+// Remove trailing zeros from n and return the number of zeros removed (float)
+FMT_INLINE int remove_trailing_zeros(uint32_t& n, int s = 0) noexcept {
+  FMT_ASSERT(n != 0, "");
+  // Modular inverse of 5 (mod 2^32): (mod_inv_5 * 5) mod 2^32 = 1.
+  constexpr uint32_t mod_inv_5 = 0xcccccccd;
+  constexpr uint32_t mod_inv_25 = 0xc28f5c29;  // = mod_inv_5 * mod_inv_5
+
+  while (true) {
+    auto q = rotr(n * mod_inv_25, 2);
+    if (q > max_value<uint32_t>() / 100) break;
+    n = q;
+    s += 2;
   }
-}
-
-// The fixed precision digit handler.
-struct fixed_handler {
-  char* buf;
-  int size;
-  int precision;
-  int exp10;
-  bool fixed;
-
-  digits::result on_start(uint64_t divisor, uint64_t remainder, uint64_t error,
-                          int& exp) {
-    // Non-fixed formats require at least one digit and no precision adjustment.
-    if (!fixed) return digits::more;
-    // Adjust fixed precision by exponent because it is relative to decimal
-    // point.
-    precision += exp + exp10;
-    // Check if precision is satisfied just by leading zeros, e.g.
-    // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
-    if (precision > 0) return digits::more;
-    if (precision < 0) return digits::done;
-    auto dir = get_round_direction(divisor, remainder, error);
-    if (dir == round_direction::unknown) return digits::error;
-    buf[size++] = dir == round_direction::up ? '1' : '0';
-    return digits::done;
+  auto q = rotr(n * mod_inv_5, 1);
+  if (q <= max_value<uint32_t>() / 10) {
+    n = q;
+    s |= 1;
   }
+  return s;
+}
 
-  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
-                          uint64_t error, int, bool integral) {
-    FMT_ASSERT(remainder < divisor, "");
-    buf[size++] = digit;
-    if (size < precision) return digits::more;
-    if (!integral) {
-      // Check if error * 2 < divisor with overflow prevention.
-      // The check is not needed for the integral part because error = 1
-      // and divisor > (1 << 32) there.
-      if (error >= divisor || error >= divisor - error) return digits::error;
-    } else {
-      FMT_ASSERT(error == 1 && divisor > 2, "");
-    }
-    auto dir = get_round_direction(divisor, remainder, error);
-    if (dir != round_direction::up)
-      return dir == round_direction::down ? digits::done : digits::error;
-    ++buf[size - 1];
-    for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
-      buf[i] = '0';
-      ++buf[i - 1];
-    }
-    if (buf[0] > '9') {
-      buf[0] = '1';
-      buf[size++] = '0';
-    }
-    return digits::done;
+// Removes trailing zeros and returns the number of zeros removed (double)
+FMT_INLINE int remove_trailing_zeros(uint64_t& n) noexcept {
+  FMT_ASSERT(n != 0, "");
+
+  // This magic number is ceil(2^90 / 10^8).
+  constexpr uint64_t magic_number = 12379400392853802749ull;
+  auto nm = umul128(n, magic_number);
+
+  // Is n is divisible by 10^8?
+  if ((nm.high() & ((1ull << (90 - 64)) - 1)) == 0 && nm.low() < magic_number) {
+    // If yes, work with the quotient...
+    auto n32 = static_cast<uint32_t>(nm.high() >> (90 - 64));
+    // ... and use the 32 bit variant of the function
+    int s = remove_trailing_zeros(n32, 8);
+    n = n32;
+    return s;
   }
-};
 
-// The shortest representation digit handler.
-struct grisu_shortest_handler {
-  char* buf;
-  int size;
-  // Distance between scaled value and upper bound (wp_W in Grisu3).
-  uint64_t diff;
+  // If n is not divisible by 10^8, work with n itself.
+  constexpr uint64_t mod_inv_5 = 0xcccccccccccccccd;
+  constexpr uint64_t mod_inv_25 = 0x8f5c28f5c28f5c29;  // mod_inv_5 * mod_inv_5
 
-  digits::result on_start(uint64_t, uint64_t, uint64_t, int&) {
-    return digits::more;
+  int s = 0;
+  while (true) {
+    auto q = rotr(n * mod_inv_25, 2);
+    if (q > max_value<uint64_t>() / 100) break;
+    n = q;
+    s += 2;
   }
-
-  // Decrement the generated number approaching value from above.
-  void round(uint64_t d, uint64_t divisor, uint64_t& remainder,
-             uint64_t error) {
-    while (
-        remainder < d && error - remainder >= divisor &&
-        (remainder + divisor < d || d - remainder >= remainder + divisor - d)) {
-      --buf[size - 1];
-      remainder += divisor;
-    }
+  auto q = rotr(n * mod_inv_5, 1);
+  if (q <= max_value<uint64_t>() / 10) {
+    n = q;
+    s |= 1;
   }
 
-  // Implements Grisu's round_weed.
-  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
-                          uint64_t error, int exp, bool integral) {
-    buf[size++] = digit;
-    if (remainder >= error) return digits::more;
-    uint64_t unit = integral ? 1 : data::powers_of_10_64[-exp];
-    uint64_t up = (diff - 1) * unit;  // wp_Wup
-    round(up, divisor, remainder, error);
-    uint64_t down = (diff + 1) * unit;  // wp_Wdown
-    if (remainder < down && error - remainder >= divisor &&
-        (remainder + divisor < down ||
-         down - remainder > remainder + divisor - down)) {
-      return digits::error;
-    }
-    return 2 * unit <= remainder && remainder <= error - 4 * unit
-               ? digits::done
-               : digits::error;
-  }
-};
-
-// Formats value using a variation of the Fixed-Precision Positive
-// Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
-// https://fmt.dev/p372-steele.pdf.
-template <typename Double>
-void fallback_format(Double d, buffer<char>& buf, int& exp10) {
-  bigint numerator;    // 2 * R in (FPP)^2.
-  bigint denominator;  // 2 * S in (FPP)^2.
-  // lower and upper are differences between value and corresponding boundaries.
-  bigint lower;             // (M^- in (FPP)^2).
-  bigint upper_store;       // upper's value if different from lower.
-  bigint* upper = nullptr;  // (M^+ in (FPP)^2).
-  fp value;
-  // Shift numerator and denominator by an extra bit or two (if lower boundary
-  // is closer) to make lower and upper integers. This eliminates multiplication
-  // by 2 during later computations.
-  // TODO: handle float
-  int shift = value.assign(d) ? 2 : 1;
-  uint64_t significand = value.f << shift;
-  if (value.e >= 0) {
-    numerator.assign(significand);
-    numerator <<= value.e;
-    lower.assign(1);
-    lower <<= value.e;
-    if (shift != 1) {
-      upper_store.assign(1);
-      upper_store <<= value.e + 1;
-      upper = &upper_store;
-    }
-    denominator.assign_pow10(exp10);
-    denominator <<= 1;
-  } else if (exp10 < 0) {
-    numerator.assign_pow10(-exp10);
-    lower.assign(numerator);
-    if (shift != 1) {
-      upper_store.assign(numerator);
-      upper_store <<= 1;
-      upper = &upper_store;
-    }
-    numerator *= significand;
-    denominator.assign(1);
-    denominator <<= shift - value.e;
-  } else {
-    numerator.assign(significand);
-    denominator.assign_pow10(exp10);
-    denominator <<= shift - value.e;
-    lower.assign(1);
-    if (shift != 1) {
-      upper_store.assign(1ULL << 1);
-      upper = &upper_store;
-    }
-  }
-  if (!upper) upper = &lower;
-  // Invariant: value == (numerator / denominator) * pow(10, exp10).
-  bool even = (value.f & 1) == 0;
-  int num_digits = 0;
-  char* data = buf.data();
-  for (;;) {
-    int digit = numerator.divmod_assign(denominator);
-    bool low = compare(numerator, lower) - even < 0;  // numerator <[=] lower.
-    // numerator + upper >[=] pow10:
-    bool high = add_compare(numerator, *upper, denominator) + even > 0;
-    data[num_digits++] = static_cast<char>('0' + digit);
-    if (low || high) {
-      if (!low) {
-        ++data[num_digits - 1];
-      } else if (high) {
-        int result = add_compare(numerator, numerator, denominator);
-        // Round half to even.
-        if (result > 0 || (result == 0 && (digit % 2) != 0))
-          ++data[num_digits - 1];
-      }
-      buf.resize(to_unsigned(num_digits));
-      exp10 -= num_digits - 1;
-      return;
-    }
-    numerator *= 10;
-    lower *= 10;
-    if (upper != &lower) *upper *= 10;
-  }
+  return s;
 }
 
-// Formats value using the Grisu algorithm
-// (https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf)
-// if T is a IEEE754 binary32 or binary64 and snprintf otherwise.
+// The main algorithm for shorter interval case
 template <typename T>
-int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
-  static_assert(!std::is_same<T, float>::value, "");
-  FMT_ASSERT(value >= 0, "value is negative");
-
-  const bool fixed = specs.format == float_format::fixed;
-  if (value <= 0) {  // <= instead of == to silence a warning.
-    if (precision <= 0 || !fixed) {
-      buf.push_back('0');
-      return 0;
-    }
-    buf.resize(to_unsigned(precision));
-    std::uninitialized_fill_n(buf.data(), precision, '0');
-    return -precision;
+FMT_INLINE decimal_fp<T> shorter_interval_case(int exponent) noexcept {
+  decimal_fp<T> ret_value;
+  // Compute k and beta
+  const int minus_k = floor_log10_pow2_minus_log10_4_over_3(exponent);
+  const int beta = exponent + floor_log2_pow10(-minus_k);
+
+  // Compute xi and zi
+  using cache_entry_type = typename cache_accessor<T>::cache_entry_type;
+  const cache_entry_type cache = cache_accessor<T>::get_cached_power(-minus_k);
+
+  auto xi = cache_accessor<T>::compute_left_endpoint_for_shorter_interval_case(
+      cache, beta);
+  auto zi = cache_accessor<T>::compute_right_endpoint_for_shorter_interval_case(
+      cache, beta);
+
+  // If the left endpoint is not an integer, increase it
+  if (!is_left_endpoint_integer_shorter_interval<T>(exponent)) ++xi;
+
+  // Try bigger divisor
+  ret_value.significand = zi / 10;
+
+  // If succeed, remove trailing zeros if necessary and return
+  if (ret_value.significand * 10 >= xi) {
+    ret_value.exponent = minus_k + 1;
+    ret_value.exponent += remove_trailing_zeros(ret_value.significand);
+    return ret_value;
   }
 
-  if (!specs.use_grisu) return snprintf_float(value, precision, specs, buf);
-
-  int exp = 0;
-  const int min_exp = -60;  // alpha in Grisu.
-  int cached_exp10 = 0;     // K in Grisu.
-  if (precision < 0) {
-    fp fp_value;
-    auto boundaries = specs.binary32
-                          ? fp_value.assign_float_with_boundaries(value)
-                          : fp_value.assign_with_boundaries(value);
-    fp_value = normalize(fp_value);
-    // Find a cached power of 10 such that multiplying value by it will bring
-    // the exponent in the range [min_exp, -32].
-    const fp cached_pow = get_cached_power(
-        min_exp - (fp_value.e + fp::significand_size), cached_exp10);
-    // Multiply value and boundaries by the cached power of 10.
-    fp_value = fp_value * cached_pow;
-    boundaries.lower = multiply(boundaries.lower, cached_pow.f);
-    boundaries.upper = multiply(boundaries.upper, cached_pow.f);
-    assert(min_exp <= fp_value.e && fp_value.e <= -32);
-    --boundaries.lower;  // \tilde{M}^- - 1 ulp -> M^-_{\downarrow}.
-    ++boundaries.upper;  // \tilde{M}^+ + 1 ulp -> M^+_{\uparrow}.
-    // Numbers outside of (lower, upper) definitely do not round to value.
-    grisu_shortest_handler handler{buf.data(), 0,
-                                   boundaries.upper - fp_value.f};
-    auto result =
-        grisu_gen_digits(fp(boundaries.upper, fp_value.e),
-                         boundaries.upper - boundaries.lower, exp, handler);
-    if (result == digits::error) {
-      exp += handler.size - cached_exp10 - 1;
-      fallback_format(value, buf, exp);
-      return exp;
-    }
-    buf.resize(to_unsigned(handler.size));
-  } else {
-    if (precision > 17) return snprintf_float(value, precision, specs, buf);
-    fp normalized = normalize(fp(value));
-    const auto cached_pow = get_cached_power(
-        min_exp - (normalized.e + fp::significand_size), cached_exp10);
-    normalized = normalized * cached_pow;
-    fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
-    if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error)
-      return snprintf_float(value, precision, specs, buf);
-    int num_digits = handler.size;
-    if (!fixed) {
-      // Remove trailing zeros.
-      while (num_digits > 0 && buf[num_digits - 1] == '0') {
-        --num_digits;
-        ++exp;
-      }
-    }
-    buf.resize(to_unsigned(num_digits));
+  // Otherwise, compute the round-up of y
+  ret_value.significand =
+      cache_accessor<T>::compute_round_up_for_shorter_interval_case(cache,
+                                                                    beta);
+  ret_value.exponent = minus_k;
+
+  // When tie occurs, choose one of them according to the rule
+  if (exponent >= float_info<T>::shorter_interval_tie_lower_threshold &&
+      exponent <= float_info<T>::shorter_interval_tie_upper_threshold) {
+    ret_value.significand = ret_value.significand % 2 == 0
+                                ? ret_value.significand
+                                : ret_value.significand - 1;
+  } else if (ret_value.significand < xi) {
+    ++ret_value.significand;
   }
-  return exp - cached_exp10;
+  return ret_value;
 }
 
-template <typename T>
-int snprintf_float(T value, int precision, float_specs specs,
-                   buffer<char>& buf) {
-  // Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
-  FMT_ASSERT(buf.capacity() > buf.size(), "empty buffer");
-  static_assert(!std::is_same<T, float>::value, "");
-
-  // Subtract 1 to account for the difference in precision since we use %e for
-  // both general and exponent format.
-  if (specs.format == float_format::general ||
-      specs.format == float_format::exp)
-    precision = (precision >= 0 ? precision : 6) - 1;
-
-  // Build the format string.
-  enum { max_format_size = 7 };  // Ths longest format is "%#.*Le".
-  char format[max_format_size];
-  char* format_ptr = format;
-  *format_ptr++ = '%';
-  if (specs.showpoint && specs.format == float_format::hex) *format_ptr++ = '#';
-  if (precision >= 0) {
-    *format_ptr++ = '.';
-    *format_ptr++ = '*';
+template <typename T> auto to_decimal(T x) noexcept -> decimal_fp<T> {
+  // Step 1: integer promotion & Schubfach multiplier calculation.
+
+  using carrier_uint = typename float_info<T>::carrier_uint;
+  using cache_entry_type = typename cache_accessor<T>::cache_entry_type;
+  auto br = bit_cast<carrier_uint>(x);
+
+  // Extract significand bits and exponent bits.
+  const carrier_uint significand_mask =
+      (static_cast<carrier_uint>(1) << num_significand_bits<T>()) - 1;
+  carrier_uint significand = (br & significand_mask);
+  int exponent =
+      static_cast<int>((br & exponent_mask<T>()) >> num_significand_bits<T>());
+
+  if (exponent != 0) {  // Check if normal.
+    exponent -= exponent_bias<T>() + num_significand_bits<T>();
+
+    // Shorter interval case; proceed like Schubfach.
+    // In fact, when exponent == 1 and significand == 0, the interval is
+    // regular. However, it can be shown that the end-results are anyway same.
+    if (significand == 0) return shorter_interval_case<T>(exponent);
+
+    significand |= (static_cast<carrier_uint>(1) << num_significand_bits<T>());
+  } else {
+    // Subnormal case; the interval is always regular.
+    if (significand == 0) return {0, 0};
+    exponent =
+        std::numeric_limits<T>::min_exponent - num_significand_bits<T>() - 1;
   }
-  if (std::is_same<T, long double>()) *format_ptr++ = 'L';
-  *format_ptr++ = specs.format != float_format::hex
-                      ? (specs.format == float_format::fixed ? 'f' : 'e')
-                      : (specs.upper ? 'A' : 'a');
-  *format_ptr = '\0';
-
-  // Format using snprintf.
-  auto offset = buf.size();
-  for (;;) {
-    auto begin = buf.data() + offset;
-    auto capacity = buf.capacity() - offset;
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-    if (precision > 100000)
-      throw std::runtime_error(
-          "fuzz mode - avoid large allocation inside snprintf");
-#endif
-    // Suppress the warning about a nonliteral format string.
-    // Cannot use auto becase of a bug in MinGW (#1532).
-    int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
-    int result = precision >= 0
-                     ? snprintf_ptr(begin, capacity, format, precision, value)
-                     : snprintf_ptr(begin, capacity, format, value);
-    if (result < 0) {
-      buf.reserve(buf.capacity() + 1);  // The buffer will grow exponentially.
-      continue;
-    }
-    auto size = to_unsigned(result);
-    // Size equal to capacity means that the last character was truncated.
-    if (size >= capacity) {
-      buf.reserve(size + offset + 1);  // Add 1 for the terminating '\0'.
-      continue;
-    }
-    auto is_digit = [](char c) { return c >= '0' && c <= '9'; };
-    if (specs.format == float_format::fixed) {
-      if (precision == 0) {
-        buf.resize(size);
-        return 0;
-      }
-      // Find and remove the decimal point.
-      auto end = begin + size, p = end;
-      do {
-        --p;
-      } while (is_digit(*p));
-      int fraction_size = static_cast<int>(end - p - 1);
-      std::memmove(p, p + 1, to_unsigned(fraction_size));
-      buf.resize(size - 1);
-      return -fraction_size;
-    }
-    if (specs.format == float_format::hex) {
-      buf.resize(size + offset);
-      return 0;
-    }
-    // Find and parse the exponent.
-    auto end = begin + size, exp_pos = end;
-    do {
-      --exp_pos;
-    } while (*exp_pos != 'e');
-    char sign = exp_pos[1];
-    assert(sign == '+' || sign == '-');
-    int exp = 0;
-    auto p = exp_pos + 2;  // Skip 'e' and sign.
-    do {
-      assert(is_digit(*p));
-      exp = exp * 10 + (*p++ - '0');
-    } while (p != end);
-    if (sign == '-') exp = -exp;
-    int fraction_size = 0;
-    if (exp_pos != begin + 1) {
-      // Remove trailing zeros.
-      auto fraction_end = exp_pos - 1;
-      while (*fraction_end == '0') --fraction_end;
-      // Move the fractional part left to get rid of the decimal point.
-      fraction_size = static_cast<int>(fraction_end - begin - 1);
-      std::memmove(begin + 1, begin + 2, to_unsigned(fraction_size));
+
+  const bool include_left_endpoint = (significand % 2 == 0);
+  const bool include_right_endpoint = include_left_endpoint;
+
+  // Compute k and beta.
+  const int minus_k = floor_log10_pow2(exponent) - float_info<T>::kappa;
+  const cache_entry_type cache = cache_accessor<T>::get_cached_power(-minus_k);
+  const int beta = exponent + floor_log2_pow10(-minus_k);
+
+  // Compute zi and deltai.
+  // 10^kappa <= deltai < 10^(kappa + 1)
+  const uint32_t deltai = cache_accessor<T>::compute_delta(cache, beta);
+  const carrier_uint two_fc = significand << 1;
+
+  // For the case of binary32, the result of integer check is not correct for
+  // 29711844 * 2^-82
+  // = 6.1442653300000000008655037797566933477355632930994033813476... * 10^-18
+  // and 29711844 * 2^-81
+  // = 1.2288530660000000001731007559513386695471126586198806762695... * 10^-17,
+  // and they are the unique counterexamples. However, since 29711844 is even,
+  // this does not cause any problem for the endpoints calculations; it can only
+  // cause a problem when we need to perform integer check for the center.
+  // Fortunately, with these inputs, that branch is never executed, so we are
+  // fine.
+  const typename cache_accessor<T>::compute_mul_result z_mul =
+      cache_accessor<T>::compute_mul((two_fc | 1) << beta, cache);
+
+  // Step 2: Try larger divisor; remove trailing zeros if necessary.
+
+  // Using an upper bound on zi, we might be able to optimize the division
+  // better than the compiler; we are computing zi / big_divisor here.
+  decimal_fp<T> ret_value;
+  ret_value.significand = divide_by_10_to_kappa_plus_1(z_mul.result);
+  uint32_t r = static_cast<uint32_t>(z_mul.result - float_info<T>::big_divisor *
+                                                        ret_value.significand);
+
+  if (r < deltai) {
+    // Exclude the right endpoint if necessary.
+    if (r == 0 && (z_mul.is_integer & !include_right_endpoint)) {
+      --ret_value.significand;
+      r = float_info<T>::big_divisor;
+      goto small_divisor_case_label;
     }
-    buf.resize(to_unsigned(fraction_size) + offset + 1);
-    return exp - fraction_size;
-  }
-}
+  } else if (r > deltai) {
+    goto small_divisor_case_label;
+  } else {
+    // r == deltai; compare fractional parts.
+    const typename cache_accessor<T>::compute_mul_parity_result x_mul =
+        cache_accessor<T>::compute_mul_parity(two_fc - 1, cache, beta);
 
-// A public domain branchless UTF-8 decoder by Christopher Wellons:
-// https://github.com/skeeto/branchless-utf8
-/* Decode the next character, c, from buf, reporting errors in e.
- *
- * Since this is a branchless decoder, four bytes will be read from the
- * buffer regardless of the actual length of the next character. This
- * means the buffer _must_ have at least three bytes of zero padding
- * following the end of the data stream.
- *
- * Errors are reported in e, which will be non-zero if the parsed
- * character was somehow invalid: invalid byte sequence, non-canonical
- * encoding, or a surrogate half.
- *
- * The function returns a pointer to the next character. When an error
- * occurs, this pointer will be a guess that depends on the particular
- * error, but it will always advance at least one byte.
- */
-FMT_FUNC const char* utf8_decode(const char* buf, uint32_t* c, int* e) {
-  static const char lengths[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-                                 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,
-                                 0, 0, 2, 2, 2, 2, 3, 3, 4, 0};
-  static const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
-  static const uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
-  static const int shiftc[] = {0, 18, 12, 6, 0};
-  static const int shifte[] = {0, 6, 4, 2, 0};
-
-  auto s = reinterpret_cast<const unsigned char*>(buf);
-  int len = lengths[s[0] >> 3];
-
-  // Compute the pointer to the next character early so that the next
-  // iteration can start working on the next character. Neither Clang
-  // nor GCC figure out this reordering on their own.
-  const char* next = buf + len + !len;
-
-  // Assume a four-byte character and load four bytes. Unused bits are
-  // shifted out.
-  *c = uint32_t(s[0] & masks[len]) << 18;
-  *c |= uint32_t(s[1] & 0x3f) << 12;
-  *c |= uint32_t(s[2] & 0x3f) << 6;
-  *c |= uint32_t(s[3] & 0x3f) << 0;
-  *c >>= shiftc[len];
-
-  // Accumulate the various error conditions.
-  *e = (*c < mins[len]) << 6;       // non-canonical encoding
-  *e |= ((*c >> 11) == 0x1b) << 7;  // surrogate half?
-  *e |= (*c > 0x10FFFF) << 8;       // out of range?
-  *e |= (s[1] & 0xc0) >> 2;
-  *e |= (s[2] & 0xc0) >> 4;
-  *e |= (s[3]) >> 6;
-  *e ^= 0x2a;  // top two bits of each tail byte correct?
-  *e >>= shifte[len];
-
-  return next;
+    if (!(x_mul.parity | (x_mul.is_integer & include_left_endpoint)))
+      goto small_divisor_case_label;
+  }
+  ret_value.exponent = minus_k + float_info<T>::kappa + 1;
+
+  // We may need to remove trailing zeros.
+  ret_value.exponent += remove_trailing_zeros(ret_value.significand);
+  return ret_value;
+
+  // Step 3: Find the significand with the smaller divisor.
+
+small_divisor_case_label:
+  ret_value.significand *= 10;
+  ret_value.exponent = minus_k + float_info<T>::kappa;
+
+  uint32_t dist = r - (deltai / 2) + (float_info<T>::small_divisor / 2);
+  const bool approx_y_parity =
+      ((dist ^ (float_info<T>::small_divisor / 2)) & 1) != 0;
+
+  // Is dist divisible by 10^kappa?
+  const bool divisible_by_small_divisor =
+      check_divisibility_and_divide_by_pow10<float_info<T>::kappa>(dist);
+
+  // Add dist / 10^kappa to the significand.
+  ret_value.significand += dist;
+
+  if (!divisible_by_small_divisor) return ret_value;
+
+  // Check z^(f) >= epsilon^(f).
+  // We have either yi == zi - epsiloni or yi == (zi - epsiloni) - 1,
+  // where yi == zi - epsiloni if and only if z^(f) >= epsilon^(f).
+  // Since there are only 2 possibilities, we only need to care about the
+  // parity. Also, zi and r should have the same parity since the divisor
+  // is an even number.
+  const auto y_mul = cache_accessor<T>::compute_mul_parity(two_fc, cache, beta);
+
+  // If z^(f) >= epsilon^(f), we might have a tie when z^(f) == epsilon^(f),
+  // or equivalently, when y is an integer.
+  if (y_mul.parity != approx_y_parity)
+    --ret_value.significand;
+  else if (y_mul.is_integer & (ret_value.significand % 2 != 0))
+    --ret_value.significand;
+  return ret_value;
 }
-}  // namespace internal
+}  // namespace dragonbox
+}  // namespace detail
 
-template <> struct formatter<internal::bigint> {
-  format_parse_context::iterator parse(format_parse_context& ctx) {
+template <> struct formatter<detail::bigint> {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx)
+      -> format_parse_context::iterator {
     return ctx.begin();
   }
 
-  format_context::iterator format(const internal::bigint& n,
-                                  format_context& ctx) {
+  auto format(const detail::bigint& n, format_context& ctx) const
+      -> format_context::iterator {
     auto out = ctx.out();
     bool first = true;
     for (auto i = n.bigits_.size(); i > 0; --i) {
       auto value = n.bigits_[i - 1u];
       if (first) {
-        out = format_to(out, "{:x}", value);
+        out = fmt::format_to(out, FMT_STRING("{:x}"), value);
         first = false;
         continue;
       }
-      out = format_to(out, "{:08x}", value);
+      out = fmt::format_to(out, FMT_STRING("{:08x}"), value);
     }
     if (n.exp_ > 0)
-      out = format_to(out, "p{}", n.exp_ * internal::bigint::bigit_bits);
+      out = fmt::format_to(out, FMT_STRING("p{}"),
+                           n.exp_ * detail::bigint::bigit_bits);
     return out;
   }
 };
 
-FMT_FUNC internal::utf8_to_utf16::utf8_to_utf16(string_view s) {
-  auto transcode = [this](const char* p) {
-    auto cp = uint32_t();
-    auto error = 0;
-    p = utf8_decode(p, &cp, &error);
-    if (error != 0) FMT_THROW(std::runtime_error("invalid utf8"));
+FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
+  for_each_codepoint(s, [this](uint32_t cp, string_view) {
+    if (cp == invalid_code_point) FMT_THROW(std::runtime_error("invalid utf8"));
     if (cp <= 0xFFFF) {
       buffer_.push_back(static_cast<wchar_t>(cp));
     } else {
@@ -1307,97 +1402,277 @@ FMT_FUNC internal::utf8_to_utf16::utf8_to_utf16(string_view s) {
       buffer_.push_back(static_cast<wchar_t>(0xD800 + (cp >> 10)));
       buffer_.push_back(static_cast<wchar_t>(0xDC00 + (cp & 0x3FF)));
     }
-    return p;
-  };
-  auto p = s.data();
-  const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
-  if (s.size() >= block_size) {
-    for (auto end = p + s.size() - block_size + 1; p < end;) p = transcode(p);
-  }
-  if (auto num_chars_left = s.data() + s.size() - p) {
-    char buf[2 * block_size - 1] = {};
-    memcpy(buf, p, to_unsigned(num_chars_left));
-    p = buf;
-    do {
-      p = transcode(p);
-    } while (p - buf < num_chars_left);
-  }
+    return true;
+  });
   buffer_.push_back(0);
 }
 
-FMT_FUNC void format_system_error(internal::buffer<char>& out, int error_code,
-                                  string_view message) FMT_NOEXCEPT {
+FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
+                                  const char* message) noexcept {
   FMT_TRY {
-    memory_buffer buf;
-    buf.resize(inline_buffer_size);
-    for (;;) {
-      char* system_message = &buf[0];
-      int result =
-          internal::safe_strerror(error_code, system_message, buf.size());
-      if (result == 0) {
-        internal::writer w(out);
-        w.write(message);
-        w.write(": ");
-        w.write(system_message);
-        return;
-      }
-      if (result != ERANGE)
-        break;  // Can't get error message, report error code instead.
-      buf.resize(buf.size() * 2);
-    }
+    auto ec = std::error_code(error_code, std::generic_category());
+    write(std::back_inserter(out), std::system_error(ec, message).what());
+    return;
   }
   FMT_CATCH(...) {}
   format_error_code(out, error_code, message);
 }
 
-FMT_FUNC void internal::error_handler::on_error(const char* message) {
-  FMT_THROW(format_error(message));
-}
-
 FMT_FUNC void report_system_error(int error_code,
-                                  fmt::string_view message) FMT_NOEXCEPT {
+                                  const char* message) noexcept {
   report_error(format_system_error, error_code, message);
 }
 
-FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
-  memory_buffer buffer;
-  internal::vformat_to(buffer, format_str,
-                       basic_format_args<buffer_context<char>>(args));
+FMT_FUNC auto vformat(string_view fmt, format_args args) -> std::string {
+  // Don't optimize the "{}" case to keep the binary size small and because it
+  // can be better optimized in fmt::format anyway.
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt, args);
+  return to_string(buffer);
+}
+
+namespace detail {
+#if !defined(_WIN32) || defined(FMT_WINDOWS_NO_WCHAR)
+FMT_FUNC auto write_console(int, string_view) -> bool { return false; }
+FMT_FUNC auto write_console(std::FILE*, string_view) -> bool { return false; }
+#else
+using dword = conditional_t<sizeof(long) == 4, unsigned long, unsigned>;
+extern "C" __declspec(dllimport) int __stdcall WriteConsoleW(  //
+    void*, const void*, dword, dword*, void*);
+
+FMT_FUNC bool write_console(int fd, string_view text) {
+  auto u16 = utf8_to_utf16(text);
+  return WriteConsoleW(reinterpret_cast<void*>(_get_osfhandle(fd)), u16.c_str(),
+                       static_cast<dword>(u16.size()), nullptr, nullptr) != 0;
+}
+
+FMT_FUNC auto write_console(std::FILE* f, string_view text) -> bool {
+  return write_console(_fileno(f), text);
+}
+#endif
+
 #ifdef _WIN32
-  auto fd = _fileno(f);
+// Print assuming legacy (non-Unicode) encoding.
+FMT_FUNC void vprint_mojibake(std::FILE* f, string_view fmt, format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt, args);
+  fwrite_fully(buffer.data(), buffer.size(), f);
+}
+#endif
+
+FMT_FUNC void print(std::FILE* f, string_view text) {
+#ifdef _WIN32
+  int fd = _fileno(f);
   if (_isatty(fd)) {
-    internal::utf8_to_utf16 u16(string_view(buffer.data(), buffer.size()));
-    auto written = DWORD();
-    if (!WriteConsoleW(reinterpret_cast<HANDLE>(_get_osfhandle(fd)),
-                       u16.c_str(), static_cast<DWORD>(u16.size()), &written,
-                       nullptr)) {
-      FMT_THROW(format_error("failed to write to console"));
-    }
-    return;
+    std::fflush(f);
+    if (write_console(fd, text)) return;
   }
 #endif
-  internal::fwrite_fully(buffer.data(), 1, buffer.size(), f);
+  fwrite_fully(text.data(), text.size(), f);
 }
+}  // namespace detail
 
-#ifdef _WIN32
-// Print assuming legacy (non-Unicode) encoding.
-FMT_FUNC void internal::vprint_mojibake(std::FILE* f, string_view format_str,
-                                        format_args args) {
-  memory_buffer buffer;
-  internal::vformat_to(buffer, format_str,
-                       basic_format_args<buffer_context<char>>(args));
-  fwrite_fully(buffer.data(), 1, buffer.size(), f);
+FMT_FUNC void vprint(std::FILE* f, string_view fmt, format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, fmt, args);
+  detail::print(f, {buffer.data(), buffer.size()});
 }
-#endif
 
-FMT_FUNC void vprint(string_view format_str, format_args args) {
-  vprint(stdout, format_str, args);
+FMT_FUNC void vprint(string_view fmt, format_args args) {
+  vprint(stdout, fmt, args);
 }
 
-FMT_END_NAMESPACE
+namespace detail {
 
-#ifdef _MSC_VER
-#  pragma warning(pop)
-#endif
+struct singleton {
+  unsigned char upper;
+  unsigned char lower_count;
+};
+
+inline auto is_printable(uint16_t x, const singleton* singletons,
+                         size_t singletons_size,
+                         const unsigned char* singleton_lowers,
+                         const unsigned char* normal, size_t normal_size)
+    -> bool {
+  auto upper = x >> 8;
+  auto lower_start = 0;
+  for (size_t i = 0; i < singletons_size; ++i) {
+    auto s = singletons[i];
+    auto lower_end = lower_start + s.lower_count;
+    if (upper < s.upper) break;
+    if (upper == s.upper) {
+      for (auto j = lower_start; j < lower_end; ++j) {
+        if (singleton_lowers[j] == (x & 0xff)) return false;
+      }
+    }
+    lower_start = lower_end;
+  }
+
+  auto xsigned = static_cast<int>(x);
+  auto current = true;
+  for (size_t i = 0; i < normal_size; ++i) {
+    auto v = static_cast<int>(normal[i]);
+    auto len = (v & 0x80) != 0 ? (v & 0x7f) << 8 | normal[++i] : v;
+    xsigned -= len;
+    if (xsigned < 0) break;
+    current = !current;
+  }
+  return current;
+}
+
+// This code is generated by support/printable.py.
+FMT_FUNC auto is_printable(uint32_t cp) -> bool {
+  static constexpr singleton singletons0[] = {
+      {0x00, 1},  {0x03, 5},  {0x05, 6},  {0x06, 3},  {0x07, 6},  {0x08, 8},
+      {0x09, 17}, {0x0a, 28}, {0x0b, 25}, {0x0c, 20}, {0x0d, 16}, {0x0e, 13},
+      {0x0f, 4},  {0x10, 3},  {0x12, 18}, {0x13, 9},  {0x16, 1},  {0x17, 5},
+      {0x18, 2},  {0x19, 3},  {0x1a, 7},  {0x1c, 2},  {0x1d, 1},  {0x1f, 22},
+      {0x20, 3},  {0x2b, 3},  {0x2c, 2},  {0x2d, 11}, {0x2e, 1},  {0x30, 3},
+      {0x31, 2},  {0x32, 1},  {0xa7, 2},  {0xa9, 2},  {0xaa, 4},  {0xab, 8},
+      {0xfa, 2},  {0xfb, 5},  {0xfd, 4},  {0xfe, 3},  {0xff, 9},
+  };
+  static constexpr unsigned char singletons0_lower[] = {
+      0xad, 0x78, 0x79, 0x8b, 0x8d, 0xa2, 0x30, 0x57, 0x58, 0x8b, 0x8c, 0x90,
+      0x1c, 0x1d, 0xdd, 0x0e, 0x0f, 0x4b, 0x4c, 0xfb, 0xfc, 0x2e, 0x2f, 0x3f,
+      0x5c, 0x5d, 0x5f, 0xb5, 0xe2, 0x84, 0x8d, 0x8e, 0x91, 0x92, 0xa9, 0xb1,
+      0xba, 0xbb, 0xc5, 0xc6, 0xc9, 0xca, 0xde, 0xe4, 0xe5, 0xff, 0x00, 0x04,
+      0x11, 0x12, 0x29, 0x31, 0x34, 0x37, 0x3a, 0x3b, 0x3d, 0x49, 0x4a, 0x5d,
+      0x84, 0x8e, 0x92, 0xa9, 0xb1, 0xb4, 0xba, 0xbb, 0xc6, 0xca, 0xce, 0xcf,
+      0xe4, 0xe5, 0x00, 0x04, 0x0d, 0x0e, 0x11, 0x12, 0x29, 0x31, 0x34, 0x3a,
+      0x3b, 0x45, 0x46, 0x49, 0x4a, 0x5e, 0x64, 0x65, 0x84, 0x91, 0x9b, 0x9d,
+      0xc9, 0xce, 0xcf, 0x0d, 0x11, 0x29, 0x45, 0x49, 0x57, 0x64, 0x65, 0x8d,
+      0x91, 0xa9, 0xb4, 0xba, 0xbb, 0xc5, 0xc9, 0xdf, 0xe4, 0xe5, 0xf0, 0x0d,
+      0x11, 0x45, 0x49, 0x64, 0x65, 0x80, 0x84, 0xb2, 0xbc, 0xbe, 0xbf, 0xd5,
+      0xd7, 0xf0, 0xf1, 0x83, 0x85, 0x8b, 0xa4, 0xa6, 0xbe, 0xbf, 0xc5, 0xc7,
+      0xce, 0xcf, 0xda, 0xdb, 0x48, 0x98, 0xbd, 0xcd, 0xc6, 0xce, 0xcf, 0x49,
+      0x4e, 0x4f, 0x57, 0x59, 0x5e, 0x5f, 0x89, 0x8e, 0x8f, 0xb1, 0xb6, 0xb7,
+      0xbf, 0xc1, 0xc6, 0xc7, 0xd7, 0x11, 0x16, 0x17, 0x5b, 0x5c, 0xf6, 0xf7,
+      0xfe, 0xff, 0x80, 0x0d, 0x6d, 0x71, 0xde, 0xdf, 0x0e, 0x0f, 0x1f, 0x6e,
+      0x6f, 0x1c, 0x1d, 0x5f, 0x7d, 0x7e, 0xae, 0xaf, 0xbb, 0xbc, 0xfa, 0x16,
+      0x17, 0x1e, 0x1f, 0x46, 0x47, 0x4e, 0x4f, 0x58, 0x5a, 0x5c, 0x5e, 0x7e,
+      0x7f, 0xb5, 0xc5, 0xd4, 0xd5, 0xdc, 0xf0, 0xf1, 0xf5, 0x72, 0x73, 0x8f,
+      0x74, 0x75, 0x96, 0x2f, 0x5f, 0x26, 0x2e, 0x2f, 0xa7, 0xaf, 0xb7, 0xbf,
+      0xc7, 0xcf, 0xd7, 0xdf, 0x9a, 0x40, 0x97, 0x98, 0x30, 0x8f, 0x1f, 0xc0,
+      0xc1, 0xce, 0xff, 0x4e, 0x4f, 0x5a, 0x5b, 0x07, 0x08, 0x0f, 0x10, 0x27,
+      0x2f, 0xee, 0xef, 0x6e, 0x6f, 0x37, 0x3d, 0x3f, 0x42, 0x45, 0x90, 0x91,
+      0xfe, 0xff, 0x53, 0x67, 0x75, 0xc8, 0xc9, 0xd0, 0xd1, 0xd8, 0xd9, 0xe7,
+      0xfe, 0xff,
+  };
+  static constexpr singleton singletons1[] = {
+      {0x00, 6},  {0x01, 1}, {0x03, 1},  {0x04, 2}, {0x08, 8},  {0x09, 2},
+      {0x0a, 5},  {0x0b, 2}, {0x0e, 4},  {0x10, 1}, {0x11, 2},  {0x12, 5},
+      {0x13, 17}, {0x14, 1}, {0x15, 2},  {0x17, 2}, {0x19, 13}, {0x1c, 5},
+      {0x1d, 8},  {0x24, 1}, {0x6a, 3},  {0x6b, 2}, {0xbc, 2},  {0xd1, 2},
+      {0xd4, 12}, {0xd5, 9}, {0xd6, 2},  {0xd7, 2}, {0xda, 1},  {0xe0, 5},
+      {0xe1, 2},  {0xe8, 2}, {0xee, 32}, {0xf0, 4}, {0xf8, 2},  {0xf9, 2},
+      {0xfa, 2},  {0xfb, 1},
+  };
+  static constexpr unsigned char singletons1_lower[] = {
+      0x0c, 0x27, 0x3b, 0x3e, 0x4e, 0x4f, 0x8f, 0x9e, 0x9e, 0x9f, 0x06, 0x07,
+      0x09, 0x36, 0x3d, 0x3e, 0x56, 0xf3, 0xd0, 0xd1, 0x04, 0x14, 0x18, 0x36,
+      0x37, 0x56, 0x57, 0x7f, 0xaa, 0xae, 0xaf, 0xbd, 0x35, 0xe0, 0x12, 0x87,
+      0x89, 0x8e, 0x9e, 0x04, 0x0d, 0x0e, 0x11, 0x12, 0x29, 0x31, 0x34, 0x3a,
+      0x45, 0x46, 0x49, 0x4a, 0x4e, 0x4f, 0x64, 0x65, 0x5c, 0xb6, 0xb7, 0x1b,
+      0x1c, 0x07, 0x08, 0x0a, 0x0b, 0x14, 0x17, 0x36, 0x39, 0x3a, 0xa8, 0xa9,
+      0xd8, 0xd9, 0x09, 0x37, 0x90, 0x91, 0xa8, 0x07, 0x0a, 0x3b, 0x3e, 0x66,
+      0x69, 0x8f, 0x92, 0x6f, 0x5f, 0xee, 0xef, 0x5a, 0x62, 0x9a, 0x9b, 0x27,
+      0x28, 0x55, 0x9d, 0xa0, 0xa1, 0xa3, 0xa4, 0xa7, 0xa8, 0xad, 0xba, 0xbc,
+      0xc4, 0x06, 0x0b, 0x0c, 0x15, 0x1d, 0x3a, 0x3f, 0x45, 0x51, 0xa6, 0xa7,
+      0xcc, 0xcd, 0xa0, 0x07, 0x19, 0x1a, 0x22, 0x25, 0x3e, 0x3f, 0xc5, 0xc6,
+      0x04, 0x20, 0x23, 0x25, 0x26, 0x28, 0x33, 0x38, 0x3a, 0x48, 0x4a, 0x4c,
+      0x50, 0x53, 0x55, 0x56, 0x58, 0x5a, 0x5c, 0x5e, 0x60, 0x63, 0x65, 0x66,
+      0x6b, 0x73, 0x78, 0x7d, 0x7f, 0x8a, 0xa4, 0xaa, 0xaf, 0xb0, 0xc0, 0xd0,
+      0xae, 0xaf, 0x79, 0xcc, 0x6e, 0x6f, 0x93,
+  };
+  static constexpr unsigned char normal0[] = {
+      0x00, 0x20, 0x5f, 0x22, 0x82, 0xdf, 0x04, 0x82, 0x44, 0x08, 0x1b, 0x04,
+      0x06, 0x11, 0x81, 0xac, 0x0e, 0x80, 0xab, 0x35, 0x28, 0x0b, 0x80, 0xe0,
+      0x03, 0x19, 0x08, 0x01, 0x04, 0x2f, 0x04, 0x34, 0x04, 0x07, 0x03, 0x01,
+      0x07, 0x06, 0x07, 0x11, 0x0a, 0x50, 0x0f, 0x12, 0x07, 0x55, 0x07, 0x03,
+      0x04, 0x1c, 0x0a, 0x09, 0x03, 0x08, 0x03, 0x07, 0x03, 0x02, 0x03, 0x03,
+      0x03, 0x0c, 0x04, 0x05, 0x03, 0x0b, 0x06, 0x01, 0x0e, 0x15, 0x05, 0x3a,
+      0x03, 0x11, 0x07, 0x06, 0x05, 0x10, 0x07, 0x57, 0x07, 0x02, 0x07, 0x15,
+      0x0d, 0x50, 0x04, 0x43, 0x03, 0x2d, 0x03, 0x01, 0x04, 0x11, 0x06, 0x0f,
+      0x0c, 0x3a, 0x04, 0x1d, 0x25, 0x5f, 0x20, 0x6d, 0x04, 0x6a, 0x25, 0x80,
+      0xc8, 0x05, 0x82, 0xb0, 0x03, 0x1a, 0x06, 0x82, 0xfd, 0x03, 0x59, 0x07,
+      0x15, 0x0b, 0x17, 0x09, 0x14, 0x0c, 0x14, 0x0c, 0x6a, 0x06, 0x0a, 0x06,
+      0x1a, 0x06, 0x59, 0x07, 0x2b, 0x05, 0x46, 0x0a, 0x2c, 0x04, 0x0c, 0x04,
+      0x01, 0x03, 0x31, 0x0b, 0x2c, 0x04, 0x1a, 0x06, 0x0b, 0x03, 0x80, 0xac,
+      0x06, 0x0a, 0x06, 0x21, 0x3f, 0x4c, 0x04, 0x2d, 0x03, 0x74, 0x08, 0x3c,
+      0x03, 0x0f, 0x03, 0x3c, 0x07, 0x38, 0x08, 0x2b, 0x05, 0x82, 0xff, 0x11,
+      0x18, 0x08, 0x2f, 0x11, 0x2d, 0x03, 0x20, 0x10, 0x21, 0x0f, 0x80, 0x8c,
+      0x04, 0x82, 0x97, 0x19, 0x0b, 0x15, 0x88, 0x94, 0x05, 0x2f, 0x05, 0x3b,
+      0x07, 0x02, 0x0e, 0x18, 0x09, 0x80, 0xb3, 0x2d, 0x74, 0x0c, 0x80, 0xd6,
+      0x1a, 0x0c, 0x05, 0x80, 0xff, 0x05, 0x80, 0xdf, 0x0c, 0xee, 0x0d, 0x03,
+      0x84, 0x8d, 0x03, 0x37, 0x09, 0x81, 0x5c, 0x14, 0x80, 0xb8, 0x08, 0x80,
+      0xcb, 0x2a, 0x38, 0x03, 0x0a, 0x06, 0x38, 0x08, 0x46, 0x08, 0x0c, 0x06,
+      0x74, 0x0b, 0x1e, 0x03, 0x5a, 0x04, 0x59, 0x09, 0x80, 0x83, 0x18, 0x1c,
+      0x0a, 0x16, 0x09, 0x4c, 0x04, 0x80, 0x8a, 0x06, 0xab, 0xa4, 0x0c, 0x17,
+      0x04, 0x31, 0xa1, 0x04, 0x81, 0xda, 0x26, 0x07, 0x0c, 0x05, 0x05, 0x80,
+      0xa5, 0x11, 0x81, 0x6d, 0x10, 0x78, 0x28, 0x2a, 0x06, 0x4c, 0x04, 0x80,
+      0x8d, 0x04, 0x80, 0xbe, 0x03, 0x1b, 0x03, 0x0f, 0x0d,
+  };
+  static constexpr unsigned char normal1[] = {
+      0x5e, 0x22, 0x7b, 0x05, 0x03, 0x04, 0x2d, 0x03, 0x66, 0x03, 0x01, 0x2f,
+      0x2e, 0x80, 0x82, 0x1d, 0x03, 0x31, 0x0f, 0x1c, 0x04, 0x24, 0x09, 0x1e,
+      0x05, 0x2b, 0x05, 0x44, 0x04, 0x0e, 0x2a, 0x80, 0xaa, 0x06, 0x24, 0x04,
+      0x24, 0x04, 0x28, 0x08, 0x34, 0x0b, 0x01, 0x80, 0x90, 0x81, 0x37, 0x09,
+      0x16, 0x0a, 0x08, 0x80, 0x98, 0x39, 0x03, 0x63, 0x08, 0x09, 0x30, 0x16,
+      0x05, 0x21, 0x03, 0x1b, 0x05, 0x01, 0x40, 0x38, 0x04, 0x4b, 0x05, 0x2f,
+      0x04, 0x0a, 0x07, 0x09, 0x07, 0x40, 0x20, 0x27, 0x04, 0x0c, 0x09, 0x36,
+      0x03, 0x3a, 0x05, 0x1a, 0x07, 0x04, 0x0c, 0x07, 0x50, 0x49, 0x37, 0x33,
+      0x0d, 0x33, 0x07, 0x2e, 0x08, 0x0a, 0x81, 0x26, 0x52, 0x4e, 0x28, 0x08,
+      0x2a, 0x56, 0x1c, 0x14, 0x17, 0x09, 0x4e, 0x04, 0x1e, 0x0f, 0x43, 0x0e,
+      0x19, 0x07, 0x0a, 0x06, 0x48, 0x08, 0x27, 0x09, 0x75, 0x0b, 0x3f, 0x41,
+      0x2a, 0x06, 0x3b, 0x05, 0x0a, 0x06, 0x51, 0x06, 0x01, 0x05, 0x10, 0x03,
+      0x05, 0x80, 0x8b, 0x62, 0x1e, 0x48, 0x08, 0x0a, 0x80, 0xa6, 0x5e, 0x22,
+      0x45, 0x0b, 0x0a, 0x06, 0x0d, 0x13, 0x39, 0x07, 0x0a, 0x36, 0x2c, 0x04,
+      0x10, 0x80, 0xc0, 0x3c, 0x64, 0x53, 0x0c, 0x48, 0x09, 0x0a, 0x46, 0x45,
+      0x1b, 0x48, 0x08, 0x53, 0x1d, 0x39, 0x81, 0x07, 0x46, 0x0a, 0x1d, 0x03,
+      0x47, 0x49, 0x37, 0x03, 0x0e, 0x08, 0x0a, 0x06, 0x39, 0x07, 0x0a, 0x81,
+      0x36, 0x19, 0x80, 0xb7, 0x01, 0x0f, 0x32, 0x0d, 0x83, 0x9b, 0x66, 0x75,
+      0x0b, 0x80, 0xc4, 0x8a, 0xbc, 0x84, 0x2f, 0x8f, 0xd1, 0x82, 0x47, 0xa1,
+      0xb9, 0x82, 0x39, 0x07, 0x2a, 0x04, 0x02, 0x60, 0x26, 0x0a, 0x46, 0x0a,
+      0x28, 0x05, 0x13, 0x82, 0xb0, 0x5b, 0x65, 0x4b, 0x04, 0x39, 0x07, 0x11,
+      0x40, 0x05, 0x0b, 0x02, 0x0e, 0x97, 0xf8, 0x08, 0x84, 0xd6, 0x2a, 0x09,
+      0xa2, 0xf7, 0x81, 0x1f, 0x31, 0x03, 0x11, 0x04, 0x08, 0x81, 0x8c, 0x89,
+      0x04, 0x6b, 0x05, 0x0d, 0x03, 0x09, 0x07, 0x10, 0x93, 0x60, 0x80, 0xf6,
+      0x0a, 0x73, 0x08, 0x6e, 0x17, 0x46, 0x80, 0x9a, 0x14, 0x0c, 0x57, 0x09,
+      0x19, 0x80, 0x87, 0x81, 0x47, 0x03, 0x85, 0x42, 0x0f, 0x15, 0x85, 0x50,
+      0x2b, 0x80, 0xd5, 0x2d, 0x03, 0x1a, 0x04, 0x02, 0x81, 0x70, 0x3a, 0x05,
+      0x01, 0x85, 0x00, 0x80, 0xd7, 0x29, 0x4c, 0x04, 0x0a, 0x04, 0x02, 0x83,
+      0x11, 0x44, 0x4c, 0x3d, 0x80, 0xc2, 0x3c, 0x06, 0x01, 0x04, 0x55, 0x05,
+      0x1b, 0x34, 0x02, 0x81, 0x0e, 0x2c, 0x04, 0x64, 0x0c, 0x56, 0x0a, 0x80,
+      0xae, 0x38, 0x1d, 0x0d, 0x2c, 0x04, 0x09, 0x07, 0x02, 0x0e, 0x06, 0x80,
+      0x9a, 0x83, 0xd8, 0x08, 0x0d, 0x03, 0x0d, 0x03, 0x74, 0x0c, 0x59, 0x07,
+      0x0c, 0x14, 0x0c, 0x04, 0x38, 0x08, 0x0a, 0x06, 0x28, 0x08, 0x22, 0x4e,
+      0x81, 0x54, 0x0c, 0x15, 0x03, 0x03, 0x05, 0x07, 0x09, 0x19, 0x07, 0x07,
+      0x09, 0x03, 0x0d, 0x07, 0x29, 0x80, 0xcb, 0x25, 0x0a, 0x84, 0x06,
+  };
+  auto lower = static_cast<uint16_t>(cp);
+  if (cp < 0x10000) {
+    return is_printable(lower, singletons0,
+                        sizeof(singletons0) / sizeof(*singletons0),
+                        singletons0_lower, normal0, sizeof(normal0));
+  }
+  if (cp < 0x20000) {
+    return is_printable(lower, singletons1,
+                        sizeof(singletons1) / sizeof(*singletons1),
+                        singletons1_lower, normal1, sizeof(normal1));
+  }
+  if (0x2a6de <= cp && cp < 0x2a700) return false;
+  if (0x2b735 <= cp && cp < 0x2b740) return false;
+  if (0x2b81e <= cp && cp < 0x2b820) return false;
+  if (0x2cea2 <= cp && cp < 0x2ceb0) return false;
+  if (0x2ebe1 <= cp && cp < 0x2f800) return false;
+  if (0x2fa1e <= cp && cp < 0x30000) return false;
+  if (0x3134b <= cp && cp < 0xe0100) return false;
+  if (0xe01f0 <= cp && cp < 0x110000) return false;
+  return cp < 0x110000;
+}
+
+}  // namespace detail
+
+FMT_END_NAMESPACE
 
 #endif  // FMT_FORMAT_INL_H_
diff --git a/contrib/fmt/include/fmt/format.h b/contrib/fmt/include/fmt/format.h
index 4e96539fa2a..7637c8a0d06 100644
--- a/contrib/fmt/include/fmt/format.h
+++ b/contrib/fmt/include/fmt/format.h
@@ -1,64 +1,103 @@
 /*
- Formatting library for C++
-
- Copyright (c) 2012 - present, Victor Zverovich
-
- Permission is hereby granted, free of charge, to any person obtaining
- a copy of this software and associated documentation files (the
- "Software"), to deal in the Software without restriction, including
- without limitation the rights to use, copy, modify, merge, publish,
- distribute, sublicense, and/or sell copies of the Software, and to
- permit persons to whom the Software is furnished to do so, subject to
- the following conditions:
-
- The above copyright notice and this permission notice shall be
- included in all copies or substantial portions of the Software.
-
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
- MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
- NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
- LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
- OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
- --- Optional exception to the license ---
-
- As an exception, if, as a result of your compiling your source code, portions
- of this Software are embedded into a machine-executable object form of such
- source code, you may redistribute such embedded portions in such object form
- without including the above copyright and permission notices.
+  Formatting library for C++
+
+  Copyright (c) 2012 - present, Victor Zverovich
+
+  Permission is hereby granted, free of charge, to any person obtaining
+  a copy of this software and associated documentation files (the
+  "Software"), to deal in the Software without restriction, including
+  without limitation the rights to use, copy, modify, merge, publish,
+  distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so, subject to
+  the following conditions:
+
+  The above copyright notice and this permission notice shall be
+  included in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+  --- Optional exception to the license ---
+
+  As an exception, if, as a result of your compiling your source code, portions
+  of this Software are embedded into a machine-executable object form of such
+  source code, you may redistribute such embedded portions in such object form
+  without including the above copyright and permission notices.
  */
 
 #ifndef FMT_FORMAT_H_
 #define FMT_FORMAT_H_
 
-#include <algorithm>
-#include <cerrno>
-#include <cmath>
-#include <cstdint>
-#include <limits>
-#include <memory>
-#include <stdexcept>
+#include <cmath>             // std::signbit
+#include <cstdint>           // uint32_t
+#include <cstring>           // std::memcpy
+#include <initializer_list>  // std::initializer_list
+#include <limits>            // std::numeric_limits
+#include <memory>            // std::uninitialized_copy
+#include <stdexcept>         // std::runtime_error
+#include <system_error>      // std::system_error
+
+#ifdef __cpp_lib_bit_cast
+#  include <bit>  // std::bit_cast
+#endif
 
 #include "core.h"
 
-#ifdef FMT_DEPRECATED_INCLUDE_OS
-#  include "os.h"
+#if defined __cpp_inline_variables && __cpp_inline_variables >= 201606L
+#  define FMT_INLINE_VARIABLE inline
+#else
+#  define FMT_INLINE_VARIABLE
 #endif
 
-#ifdef __INTEL_COMPILER
-#  define FMT_ICC_VERSION __INTEL_COMPILER
-#elif defined(__ICL)
-#  define FMT_ICC_VERSION __ICL
+#if FMT_HAS_CPP17_ATTRIBUTE(fallthrough)
+#  define FMT_FALLTHROUGH [[fallthrough]]
+#elif defined(__clang__)
+#  define FMT_FALLTHROUGH [[clang::fallthrough]]
+#elif FMT_GCC_VERSION >= 700 && \
+    (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 520)
+#  define FMT_FALLTHROUGH [[gnu::fallthrough]]
 #else
-#  define FMT_ICC_VERSION 0
+#  define FMT_FALLTHROUGH
+#endif
+
+#ifndef FMT_DEPRECATED
+#  if FMT_HAS_CPP14_ATTRIBUTE(deprecated) || FMT_MSC_VERSION >= 1900
+#    define FMT_DEPRECATED [[deprecated]]
+#  else
+#    if (defined(__GNUC__) && !defined(__LCC__)) || defined(__clang__)
+#      define FMT_DEPRECATED __attribute__((deprecated))
+#    elif FMT_MSC_VERSION
+#      define FMT_DEPRECATED __declspec(deprecated)
+#    else
+#      define FMT_DEPRECATED /* deprecated */
+#    endif
+#  endif
+#endif
+
+#ifndef FMT_NO_UNIQUE_ADDRESS
+#  if FMT_CPLUSPLUS >= 202002L
+#    if FMT_HAS_CPP_ATTRIBUTE(no_unique_address)
+#      define FMT_NO_UNIQUE_ADDRESS [[no_unique_address]]
+// VS2019 v16.10 and later except clang-cl (https://reviews.llvm.org/D110485)
+#    elif (FMT_MSC_VERSION >= 1929) && !FMT_CLANG_VERSION
+#      define FMT_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#    endif
+#  endif
+#endif
+#ifndef FMT_NO_UNIQUE_ADDRESS
+#  define FMT_NO_UNIQUE_ADDRESS
 #endif
 
-#ifdef __NVCC__
-#  define FMT_CUDA_VERSION (__CUDACC_VER_MAJOR__ * 100 + __CUDACC_VER_MINOR__)
+// Visibility when compiled as a shared library/object.
+#if defined(FMT_LIB_EXPORT) || defined(FMT_SHARED)
+#  define FMT_SO_VISIBILITY(value) FMT_VISIBILITY(value)
 #else
-#  define FMT_CUDA_VERSION 0
+#  define FMT_SO_VISIBILITY(value)
 #endif
 
 #ifdef __has_builtin
@@ -73,44 +112,26 @@
 #  define FMT_NOINLINE
 #endif
 
-#if __cplusplus == 201103L || __cplusplus == 201402L
-#  if defined(__clang__)
-#    define FMT_FALLTHROUGH [[clang::fallthrough]]
-#  elif FMT_GCC_VERSION >= 700 && !defined(__PGI)
-#    define FMT_FALLTHROUGH [[gnu::fallthrough]]
-#  else
-#    define FMT_FALLTHROUGH
-#  endif
-#elif FMT_HAS_CPP17_ATTRIBUTE(fallthrough) || \
-    (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
-#  define FMT_FALLTHROUGH [[fallthrough]]
-#else
-#  define FMT_FALLTHROUGH
-#endif
-
 #ifndef FMT_THROW
 #  if FMT_EXCEPTIONS
-#    if FMT_MSC_VER || FMT_NVCC
+#    if FMT_MSC_VERSION || defined(__NVCC__)
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 template <typename Exception> inline void do_throw(const Exception& x) {
   // Silence unreachable code warnings in MSVC and NVCC because these
   // are nearly impossible to fix in a generic code.
   volatile bool b = true;
   if (b) throw x;
 }
-}  // namespace internal
+}  // namespace detail
 FMT_END_NAMESPACE
-#      define FMT_THROW(x) internal::do_throw(x)
+#      define FMT_THROW(x) detail::do_throw(x)
 #    else
 #      define FMT_THROW(x) throw x
 #    endif
 #  else
-#    define FMT_THROW(x)              \
-      do {                            \
-        static_cast<void>(sizeof(x)); \
-        FMT_ASSERT(false, "");        \
-      } while (false)
+#    define FMT_THROW(x) \
+      ::fmt::detail::assert_fail(__FILE__, __LINE__, (x).what())
 #  endif
 #endif
 
@@ -122,476 +143,715 @@ FMT_END_NAMESPACE
 #  define FMT_CATCH(x) if (false)
 #endif
 
-#ifndef FMT_USE_USER_DEFINED_LITERALS
-// For Intel and NVIDIA compilers both they and the system gcc/msc support UDLs.
-#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 ||      \
-       FMT_MSC_VER >= 1900) &&                                              \
-      (!(FMT_ICC_VERSION || FMT_CUDA_VERSION) || FMT_ICC_VERSION >= 1500 || \
-       FMT_CUDA_VERSION >= 700)
-#    define FMT_USE_USER_DEFINED_LITERALS 1
+#ifndef FMT_MAYBE_UNUSED
+#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
+#    define FMT_MAYBE_UNUSED [[maybe_unused]]
 #  else
-#    define FMT_USE_USER_DEFINED_LITERALS 0
+#    define FMT_MAYBE_UNUSED
 #  endif
 #endif
 
-#ifndef FMT_USE_UDL_TEMPLATE
-// EDG front end based compilers (icc, nvcc) and GCC < 6.4 do not propertly
-// support UDL templates and GCC >= 9 warns about them.
-#  if FMT_USE_USER_DEFINED_LITERALS && FMT_ICC_VERSION == 0 && \
-      FMT_CUDA_VERSION == 0 &&                                 \
-      ((FMT_GCC_VERSION >= 604 && FMT_GCC_VERSION <= 900 &&    \
-        __cplusplus >= 201402L) ||                             \
-       FMT_CLANG_VERSION >= 304)
-#    define FMT_USE_UDL_TEMPLATE 1
+#ifndef FMT_USE_USER_DEFINED_LITERALS
+// EDG based compilers (Intel, NVIDIA, Elbrus, etc), GCC and MSVC support UDLs.
+//
+// GCC before 4.9 requires a space in `operator"" _a` which is invalid in later
+// compiler versions.
+#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 409 || \
+       FMT_MSC_VERSION >= 1900) &&                                     \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= /* UDL feature */ 480)
+#    define FMT_USE_USER_DEFINED_LITERALS 1
 #  else
-#    define FMT_USE_UDL_TEMPLATE 0
+#    define FMT_USE_USER_DEFINED_LITERALS 0
 #  endif
 #endif
 
-#ifndef FMT_USE_FLOAT
-#  define FMT_USE_FLOAT 1
+// Defining FMT_REDUCE_INT_INSTANTIATIONS to 1, will reduce the number of
+// integer formatter template instantiations to just one by only using the
+// largest integer type. This results in a reduction in binary size but will
+// cause a decrease in integer formatting performance.
+#if !defined(FMT_REDUCE_INT_INSTANTIATIONS)
+#  define FMT_REDUCE_INT_INSTANTIATIONS 0
 #endif
 
-#ifndef FMT_USE_DOUBLE
-#  define FMT_USE_DOUBLE 1
+// __builtin_clz is broken in clang with Microsoft CodeGen:
+// https://github.com/fmtlib/fmt/issues/519.
+#if !FMT_MSC_VERSION
+#  if FMT_HAS_BUILTIN(__builtin_clz) || FMT_GCC_VERSION || FMT_ICC_VERSION
+#    define FMT_BUILTIN_CLZ(n) __builtin_clz(n)
+#  endif
+#  if FMT_HAS_BUILTIN(__builtin_clzll) || FMT_GCC_VERSION || FMT_ICC_VERSION
+#    define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
+#  endif
 #endif
 
-#ifndef FMT_USE_LONG_DOUBLE
-#  define FMT_USE_LONG_DOUBLE 1
+// __builtin_ctz is broken in Intel Compiler Classic on Windows:
+// https://github.com/fmtlib/fmt/issues/2510.
+#ifndef __ICL
+#  if FMT_HAS_BUILTIN(__builtin_ctz) || FMT_GCC_VERSION || FMT_ICC_VERSION || \
+      defined(__NVCOMPILER)
+#    define FMT_BUILTIN_CTZ(n) __builtin_ctz(n)
+#  endif
+#  if FMT_HAS_BUILTIN(__builtin_ctzll) || FMT_GCC_VERSION || \
+      FMT_ICC_VERSION || defined(__NVCOMPILER)
+#    define FMT_BUILTIN_CTZLL(n) __builtin_ctzll(n)
+#  endif
 #endif
 
-// __builtin_clz is broken in clang with Microsoft CodeGen:
-// https://github.com/fmtlib/fmt/issues/519
-#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clz)) && !FMT_MSC_VER
-#  define FMT_BUILTIN_CLZ(n) __builtin_clz(n)
-#endif
-#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clzll)) && !FMT_MSC_VER
-#  define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
+#if FMT_MSC_VERSION
+#  include <intrin.h>  // _BitScanReverse[64], _BitScanForward[64], _umul128
 #endif
 
 // Some compilers masquerade as both MSVC and GCC-likes or otherwise support
 // __builtin_clz and __builtin_clzll, so only define FMT_BUILTIN_CLZ using the
 // MSVC intrinsics if the clz and clzll builtins are not available.
-#if FMT_MSC_VER && !defined(FMT_BUILTIN_CLZLL) && !defined(_MANAGED)
-#  include <intrin.h>  // _BitScanReverse, _BitScanReverse64
-
+#if FMT_MSC_VERSION && !defined(FMT_BUILTIN_CLZLL) && \
+    !defined(FMT_BUILTIN_CTZLL)
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 // Avoid Clang with Microsoft CodeGen's -Wunknown-pragmas warning.
-#  ifndef __clang__
+#  if !defined(__clang__)
+#    pragma intrinsic(_BitScanForward)
 #    pragma intrinsic(_BitScanReverse)
+#    if defined(_WIN64)
+#      pragma intrinsic(_BitScanForward64)
+#      pragma intrinsic(_BitScanReverse64)
+#    endif
 #  endif
-inline uint32_t clz(uint32_t x) {
+
+inline auto clz(uint32_t x) -> int {
   unsigned long r = 0;
   _BitScanReverse(&r, x);
-
   FMT_ASSERT(x != 0, "");
   // Static analysis complains about using uninitialized data
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
-  return 31 - r;
+  FMT_MSC_WARNING(suppress : 6102)
+  return 31 ^ static_cast<int>(r);
 }
-#  define FMT_BUILTIN_CLZ(n) internal::clz(n)
-
-#  if defined(_WIN64) && !defined(__clang__)
-#    pragma intrinsic(_BitScanReverse64)
-#  endif
+#  define FMT_BUILTIN_CLZ(n) detail::clz(n)
 
-inline uint32_t clzll(uint64_t x) {
+inline auto clzll(uint64_t x) -> int {
   unsigned long r = 0;
 #  ifdef _WIN64
   _BitScanReverse64(&r, x);
 #  else
   // Scan the high 32 bits.
-  if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32))) return 63 - (r + 32);
-
+  if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32)))
+    return 63 ^ static_cast<int>(r + 32);
   // Scan the low 32 bits.
   _BitScanReverse(&r, static_cast<uint32_t>(x));
 #  endif
+  FMT_ASSERT(x != 0, "");
+  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
+  return 63 ^ static_cast<int>(r);
+}
+#  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
 
+inline auto ctz(uint32_t x) -> int {
+  unsigned long r = 0;
+  _BitScanForward(&r, x);
   FMT_ASSERT(x != 0, "");
-  // Static analysis complains about using uninitialized data
-  // "r", but the only way that can happen is if "x" is 0,
-  // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
-  return 63 - r;
+  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
+  return static_cast<int>(r);
+}
+#  define FMT_BUILTIN_CTZ(n) detail::ctz(n)
+
+inline auto ctzll(uint64_t x) -> int {
+  unsigned long r = 0;
+  FMT_ASSERT(x != 0, "");
+  FMT_MSC_WARNING(suppress : 6102)  // Suppress a bogus static analysis warning.
+#  ifdef _WIN64
+  _BitScanForward64(&r, x);
+#  else
+  // Scan the low 32 bits.
+  if (_BitScanForward(&r, static_cast<uint32_t>(x))) return static_cast<int>(r);
+  // Scan the high 32 bits.
+  _BitScanForward(&r, static_cast<uint32_t>(x >> 32));
+  r += 32;
+#  endif
+  return static_cast<int>(r);
 }
-#  define FMT_BUILTIN_CLZLL(n) internal::clzll(n)
-}  // namespace internal
+#  define FMT_BUILTIN_CTZLL(n) detail::ctzll(n)
+}  // namespace detail
 FMT_END_NAMESPACE
 #endif
 
-// Enable the deprecated numeric alignment.
-#ifndef FMT_NUMERIC_ALIGN
-#  define FMT_NUMERIC_ALIGN 1
-#endif
+FMT_BEGIN_NAMESPACE
+namespace detail {
 
-// Enable the deprecated percent specifier.
-#ifndef FMT_DEPRECATED_PERCENT
-#  define FMT_DEPRECATED_PERCENT 0
+FMT_CONSTEXPR inline void abort_fuzzing_if(bool condition) {
+  ignore_unused(condition);
+#ifdef FMT_FUZZ
+  if (condition) throw std::runtime_error("fuzzing limit reached");
 #endif
+}
 
-FMT_BEGIN_NAMESPACE
-namespace internal {
+template <typename CharT, CharT... C> struct string_literal {
+  static constexpr CharT value[sizeof...(C)] = {C...};
+  constexpr operator basic_string_view<CharT>() const {
+    return {value, sizeof...(C)};
+  }
+};
+
+#if FMT_CPLUSPLUS < 201703L
+template <typename CharT, CharT... C>
+constexpr CharT string_literal<CharT, C...>::value[sizeof...(C)];
+#endif
 
-// An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
-// undefined behavior (e.g. due to type aliasing).
-// Example: uint64_t d = bit_cast<uint64_t>(2.718);
-template <typename Dest, typename Source>
-inline Dest bit_cast(const Source& source) {
-  static_assert(sizeof(Dest) == sizeof(Source), "size mismatch");
-  Dest dest;
-  std::memcpy(&dest, &source, sizeof(dest));
-  return dest;
+// Implementation of std::bit_cast for pre-C++20.
+template <typename To, typename From, FMT_ENABLE_IF(sizeof(To) == sizeof(From))>
+FMT_CONSTEXPR20 auto bit_cast(const From& from) -> To {
+#ifdef __cpp_lib_bit_cast
+  if (is_constant_evaluated()) return std::bit_cast<To>(from);
+#endif
+  auto to = To();
+  // The cast suppresses a bogus -Wclass-memaccess on GCC.
+  std::memcpy(static_cast<void*>(&to), &from, sizeof(to));
+  return to;
 }
 
-inline bool is_big_endian() {
-  const auto u = 1u;
+inline auto is_big_endian() -> bool {
+#ifdef _WIN32
+  return false;
+#elif defined(__BIG_ENDIAN__)
+  return true;
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__)
+  return __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__;
+#else
   struct bytes {
-    char data[sizeof(u)];
+    char data[sizeof(int)];
   };
-  return bit_cast<bytes>(u).data[0] == 0;
+  return bit_cast<bytes>(1).data[0] == 0;
+#endif
 }
 
-// A fallback implementation of uintptr_t for systems that lack it.
-struct fallback_uintptr {
-  unsigned char value[sizeof(void*)];
+class uint128_fallback {
+ private:
+  uint64_t lo_, hi_;
 
-  fallback_uintptr() = default;
-  explicit fallback_uintptr(const void* p) {
-    *this = bit_cast<fallback_uintptr>(p);
-    if (is_big_endian()) {
-      for (size_t i = 0, j = sizeof(void*) - 1; i < j; ++i, --j)
-        std::swap(value[i], value[j]);
+ public:
+  constexpr uint128_fallback(uint64_t hi, uint64_t lo) : lo_(lo), hi_(hi) {}
+  constexpr uint128_fallback(uint64_t value = 0) : lo_(value), hi_(0) {}
+
+  constexpr auto high() const noexcept -> uint64_t { return hi_; }
+  constexpr auto low() const noexcept -> uint64_t { return lo_; }
+
+  template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+  constexpr explicit operator T() const {
+    return static_cast<T>(lo_);
+  }
+
+  friend constexpr auto operator==(const uint128_fallback& lhs,
+                                   const uint128_fallback& rhs) -> bool {
+    return lhs.hi_ == rhs.hi_ && lhs.lo_ == rhs.lo_;
+  }
+  friend constexpr auto operator!=(const uint128_fallback& lhs,
+                                   const uint128_fallback& rhs) -> bool {
+    return !(lhs == rhs);
+  }
+  friend constexpr auto operator>(const uint128_fallback& lhs,
+                                  const uint128_fallback& rhs) -> bool {
+    return lhs.hi_ != rhs.hi_ ? lhs.hi_ > rhs.hi_ : lhs.lo_ > rhs.lo_;
+  }
+  friend constexpr auto operator|(const uint128_fallback& lhs,
+                                  const uint128_fallback& rhs)
+      -> uint128_fallback {
+    return {lhs.hi_ | rhs.hi_, lhs.lo_ | rhs.lo_};
+  }
+  friend constexpr auto operator&(const uint128_fallback& lhs,
+                                  const uint128_fallback& rhs)
+      -> uint128_fallback {
+    return {lhs.hi_ & rhs.hi_, lhs.lo_ & rhs.lo_};
+  }
+  friend constexpr auto operator~(const uint128_fallback& n)
+      -> uint128_fallback {
+    return {~n.hi_, ~n.lo_};
+  }
+  friend auto operator+(const uint128_fallback& lhs,
+                        const uint128_fallback& rhs) -> uint128_fallback {
+    auto result = uint128_fallback(lhs);
+    result += rhs;
+    return result;
+  }
+  friend auto operator*(const uint128_fallback& lhs, uint32_t rhs)
+      -> uint128_fallback {
+    FMT_ASSERT(lhs.hi_ == 0, "");
+    uint64_t hi = (lhs.lo_ >> 32) * rhs;
+    uint64_t lo = (lhs.lo_ & ~uint32_t()) * rhs;
+    uint64_t new_lo = (hi << 32) + lo;
+    return {(hi >> 32) + (new_lo < lo ? 1 : 0), new_lo};
+  }
+  friend auto operator-(const uint128_fallback& lhs, uint64_t rhs)
+      -> uint128_fallback {
+    return {lhs.hi_ - (lhs.lo_ < rhs ? 1 : 0), lhs.lo_ - rhs};
+  }
+  FMT_CONSTEXPR auto operator>>(int shift) const -> uint128_fallback {
+    if (shift == 64) return {0, hi_};
+    if (shift > 64) return uint128_fallback(0, hi_) >> (shift - 64);
+    return {hi_ >> shift, (hi_ << (64 - shift)) | (lo_ >> shift)};
+  }
+  FMT_CONSTEXPR auto operator<<(int shift) const -> uint128_fallback {
+    if (shift == 64) return {lo_, 0};
+    if (shift > 64) return uint128_fallback(lo_, 0) << (shift - 64);
+    return {hi_ << shift | (lo_ >> (64 - shift)), (lo_ << shift)};
+  }
+  FMT_CONSTEXPR auto operator>>=(int shift) -> uint128_fallback& {
+    return *this = *this >> shift;
+  }
+  FMT_CONSTEXPR void operator+=(uint128_fallback n) {
+    uint64_t new_lo = lo_ + n.lo_;
+    uint64_t new_hi = hi_ + n.hi_ + (new_lo < lo_ ? 1 : 0);
+    FMT_ASSERT(new_hi >= hi_, "");
+    lo_ = new_lo;
+    hi_ = new_hi;
+  }
+  FMT_CONSTEXPR void operator&=(uint128_fallback n) {
+    lo_ &= n.lo_;
+    hi_ &= n.hi_;
+  }
+
+  FMT_CONSTEXPR20 auto operator+=(uint64_t n) noexcept -> uint128_fallback& {
+    if (is_constant_evaluated()) {
+      lo_ += n;
+      hi_ += (lo_ < n ? 1 : 0);
+      return *this;
     }
+#if FMT_HAS_BUILTIN(__builtin_addcll) && !defined(__ibmxl__)
+    unsigned long long carry;
+    lo_ = __builtin_addcll(lo_, n, 0, &carry);
+    hi_ += carry;
+#elif FMT_HAS_BUILTIN(__builtin_ia32_addcarryx_u64) && !defined(__ibmxl__)
+    unsigned long long result;
+    auto carry = __builtin_ia32_addcarryx_u64(0, lo_, n, &result);
+    lo_ = result;
+    hi_ += carry;
+#elif defined(_MSC_VER) && defined(_M_X64)
+    auto carry = _addcarry_u64(0, lo_, n, &lo_);
+    _addcarry_u64(carry, hi_, 0, &hi_);
+#else
+    lo_ += n;
+    hi_ += (lo_ < n ? 1 : 0);
+#endif
+    return *this;
   }
 };
+
+using uint128_t = conditional_t<FMT_USE_INT128, uint128_opt, uint128_fallback>;
+
 #ifdef UINTPTR_MAX
 using uintptr_t = ::uintptr_t;
-inline uintptr_t to_uintptr(const void* p) { return bit_cast<uintptr_t>(p); }
 #else
-using uintptr_t = fallback_uintptr;
-inline fallback_uintptr to_uintptr(const void* p) {
-  return fallback_uintptr(p);
-}
+using uintptr_t = uint128_t;
 #endif
 
 // Returns the largest possible value for type T. Same as
 // std::numeric_limits<T>::max() but shorter and not affected by the max macro.
-template <typename T> constexpr T max_value() {
+template <typename T> constexpr auto max_value() -> T {
   return (std::numeric_limits<T>::max)();
 }
-template <typename T> constexpr int num_bits() {
+template <typename T> constexpr auto num_bits() -> int {
   return std::numeric_limits<T>::digits;
 }
-template <> constexpr int num_bits<fallback_uintptr>() {
-  return static_cast<int>(sizeof(void*) *
-                          std::numeric_limits<unsigned char>::digits);
+// std::numeric_limits<T>::digits may return 0 for 128-bit ints.
+template <> constexpr auto num_bits<int128_opt>() -> int { return 128; }
+template <> constexpr auto num_bits<uint128_t>() -> int { return 128; }
+
+// A heterogeneous bit_cast used for converting 96-bit long double to uint128_t
+// and 128-bit pointers to uint128_fallback.
+template <typename To, typename From, FMT_ENABLE_IF(sizeof(To) > sizeof(From))>
+inline auto bit_cast(const From& from) -> To {
+  constexpr auto size = static_cast<int>(sizeof(From) / sizeof(unsigned));
+  struct data_t {
+    unsigned value[static_cast<unsigned>(size)];
+  } data = bit_cast<data_t>(from);
+  auto result = To();
+  if (const_check(is_big_endian())) {
+    for (int i = 0; i < size; ++i)
+      result = (result << num_bits<unsigned>()) | data.value[i];
+  } else {
+    for (int i = size - 1; i >= 0; --i)
+      result = (result << num_bits<unsigned>()) | data.value[i];
+  }
+  return result;
 }
 
-// An approximation of iterator_t for pre-C++20 systems.
-template <typename T>
-using iterator_t = decltype(std::begin(std::declval<T&>()));
-
-// Detect the iterator category of *any* given type in a SFINAE-friendly way.
-// Unfortunately, older implementations of std::iterator_traits are not safe
-// for use in a SFINAE-context.
-template <typename It, typename Enable = void>
-struct iterator_category : std::false_type {};
-
-template <typename T> struct iterator_category<T*> {
-  using type = std::random_access_iterator_tag;
-};
+template <typename UInt>
+FMT_CONSTEXPR20 inline auto countl_zero_fallback(UInt n) -> int {
+  int lz = 0;
+  constexpr UInt msb_mask = static_cast<UInt>(1) << (num_bits<UInt>() - 1);
+  for (; (n & msb_mask) == 0; n <<= 1) lz++;
+  return lz;
+}
 
-template <typename It>
-struct iterator_category<It, void_t<typename It::iterator_category>> {
-  using type = typename It::iterator_category;
-};
+FMT_CONSTEXPR20 inline auto countl_zero(uint32_t n) -> int {
+#ifdef FMT_BUILTIN_CLZ
+  if (!is_constant_evaluated()) return FMT_BUILTIN_CLZ(n);
+#endif
+  return countl_zero_fallback(n);
+}
 
-// Detect if *any* given type models the OutputIterator concept.
-template <typename It> class is_output_iterator {
-  // Check for mutability because all iterator categories derived from
-  // std::input_iterator_tag *may* also meet the requirements of an
-  // OutputIterator, thereby falling into the category of 'mutable iterators'
-  // [iterator.requirements.general] clause 4. The compiler reveals this
-  // property only at the point of *actually dereferencing* the iterator!
-  template <typename U>
-  static decltype(*(std::declval<U>())) test(std::input_iterator_tag);
-  template <typename U> static char& test(std::output_iterator_tag);
-  template <typename U> static const char& test(...);
+FMT_CONSTEXPR20 inline auto countl_zero(uint64_t n) -> int {
+#ifdef FMT_BUILTIN_CLZLL
+  if (!is_constant_evaluated()) return FMT_BUILTIN_CLZLL(n);
+#endif
+  return countl_zero_fallback(n);
+}
 
-  using type = decltype(test<It>(typename iterator_category<It>::type{}));
+FMT_INLINE void assume(bool condition) {
+  (void)condition;
+#if FMT_HAS_BUILTIN(__builtin_assume) && !FMT_ICC_VERSION
+  __builtin_assume(condition);
+#elif FMT_GCC_VERSION
+  if (!condition) __builtin_unreachable();
+#endif
+}
 
- public:
-  enum { value = !std::is_const<remove_reference_t<type>>::value };
-};
+// An approximation of iterator_t for pre-C++20 systems.
+template <typename T>
+using iterator_t = decltype(std::begin(std::declval<T&>()));
+template <typename T> using sentinel_t = decltype(std::end(std::declval<T&>()));
 
 // A workaround for std::string not having mutable data() until C++17.
-template <typename Char> inline Char* get_data(std::basic_string<Char>& s) {
+template <typename Char>
+inline auto get_data(std::basic_string<Char>& s) -> Char* {
   return &s[0];
 }
 template <typename Container>
-inline typename Container::value_type* get_data(Container& c) {
+inline auto get_data(Container& c) -> typename Container::value_type* {
   return c.data();
 }
 
-#if defined(_SECURE_SCL) && _SECURE_SCL
-// Make a checked iterator to avoid MSVC warnings.
-template <typename T> using checked_ptr = stdext::checked_array_iterator<T*>;
-template <typename T> checked_ptr<T> make_checked(T* p, std::size_t size) {
-  return {p, size};
-}
-#else
-template <typename T> using checked_ptr = T*;
-template <typename T> inline T* make_checked(T* p, std::size_t) { return p; }
-#endif
-
+// Attempts to reserve space for n extra characters in the output range.
+// Returns a pointer to the reserved range or a reference to it.
 template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
-inline checked_ptr<typename Container::value_type> reserve(
-    std::back_insert_iterator<Container>& it, std::size_t n) {
+#if FMT_CLANG_VERSION >= 307 && !FMT_ICC_VERSION
+__attribute__((no_sanitize("undefined")))
+#endif
+inline auto
+reserve(std::back_insert_iterator<Container> it, size_t n) ->
+    typename Container::value_type* {
   Container& c = get_container(it);
-  std::size_t size = c.size();
+  size_t size = c.size();
   c.resize(size + n);
-  return make_checked(get_data(c) + size, n);
+  return get_data(c) + size;
 }
 
-template <typename Iterator>
-inline Iterator& reserve(Iterator& it, std::size_t) {
+template <typename T>
+inline auto reserve(buffer_appender<T> it, size_t n) -> buffer_appender<T> {
+  buffer<T>& buf = get_container(it);
+  buf.try_reserve(buf.size() + n);
   return it;
 }
 
-// An output iterator that counts the number of objects written to it and
-// discards them.
-class counting_iterator {
- private:
-  std::size_t count_;
-
- public:
-  using iterator_category = std::output_iterator_tag;
-  using difference_type = std::ptrdiff_t;
-  using pointer = void;
-  using reference = void;
-  using _Unchecked_type = counting_iterator;  // Mark iterator as checked.
+template <typename Iterator>
+constexpr auto reserve(Iterator& it, size_t) -> Iterator& {
+  return it;
+}
 
-  struct value_type {
-    template <typename T> void operator=(const T&) {}
-  };
+template <typename OutputIt>
+using reserve_iterator =
+    remove_reference_t<decltype(reserve(std::declval<OutputIt&>(), 0))>;
 
-  counting_iterator() : count_(0) {}
+template <typename T, typename OutputIt>
+constexpr auto to_pointer(OutputIt, size_t) -> T* {
+  return nullptr;
+}
+template <typename T> auto to_pointer(buffer_appender<T> it, size_t n) -> T* {
+  buffer<T>& buf = get_container(it);
+  auto size = buf.size();
+  if (buf.capacity() < size + n) return nullptr;
+  buf.try_resize(size + n);
+  return buf.data() + size;
+}
 
-  std::size_t count() const { return count_; }
+template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
+inline auto base_iterator(std::back_insert_iterator<Container> it,
+                          typename Container::value_type*)
+    -> std::back_insert_iterator<Container> {
+  return it;
+}
 
-  counting_iterator& operator++() {
-    ++count_;
-    return *this;
-  }
+template <typename Iterator>
+constexpr auto base_iterator(Iterator, Iterator it) -> Iterator {
+  return it;
+}
 
-  counting_iterator operator++(int) {
-    auto it = *this;
-    ++*this;
-    return it;
+// <algorithm> is spectacularly slow to compile in C++20 so use a simple fill_n
+// instead (#1998).
+template <typename OutputIt, typename Size, typename T>
+FMT_CONSTEXPR auto fill_n(OutputIt out, Size count, const T& value)
+    -> OutputIt {
+  for (Size i = 0; i < count; ++i) *out++ = value;
+  return out;
+}
+template <typename T, typename Size>
+FMT_CONSTEXPR20 auto fill_n(T* out, Size count, char value) -> T* {
+  if (is_constant_evaluated()) {
+    return fill_n<T*, Size, T>(out, count, value);
   }
+  std::memset(out, value, to_unsigned(count));
+  return out + count;
+}
 
-  value_type operator*() const { return {}; }
-};
-
-template <typename OutputIt> class truncating_iterator_base {
- protected:
-  OutputIt out_;
-  std::size_t limit_;
-  std::size_t count_;
-
-  truncating_iterator_base(OutputIt out, std::size_t limit)
-      : out_(out), limit_(limit), count_(0) {}
-
- public:
-  using iterator_category = std::output_iterator_tag;
-  using value_type = typename std::iterator_traits<OutputIt>::value_type;
-  using difference_type = void;
-  using pointer = void;
-  using reference = void;
-  using _Unchecked_type =
-      truncating_iterator_base;  // Mark iterator as checked.
-
-  OutputIt base() const { return out_; }
-  std::size_t count() const { return count_; }
-};
-
-// An output iterator that truncates the output and counts the number of objects
-// written to it.
-template <typename OutputIt,
-          typename Enable = typename std::is_void<
-              typename std::iterator_traits<OutputIt>::value_type>::type>
-class truncating_iterator;
-
-template <typename OutputIt>
-class truncating_iterator<OutputIt, std::false_type>
-    : public truncating_iterator_base<OutputIt> {
-  mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;
-
- public:
-  using value_type = typename truncating_iterator_base<OutputIt>::value_type;
-
-  truncating_iterator(OutputIt out, std::size_t limit)
-      : truncating_iterator_base<OutputIt>(out, limit) {}
+#ifdef __cpp_char8_t
+using char8_type = char8_t;
+#else
+enum char8_type : unsigned char {};
+#endif
 
-  truncating_iterator& operator++() {
-    if (this->count_++ < this->limit_) ++this->out_;
-    return *this;
-  }
+template <typename OutChar, typename InputIt, typename OutputIt>
+FMT_CONSTEXPR FMT_NOINLINE auto copy_str_noinline(InputIt begin, InputIt end,
+                                                  OutputIt out) -> OutputIt {
+  return copy_str<OutChar>(begin, end, out);
+}
 
-  truncating_iterator operator++(int) {
-    auto it = *this;
-    ++*this;
-    return it;
-  }
+// A public domain branchless UTF-8 decoder by Christopher Wellons:
+// https://github.com/skeeto/branchless-utf8
+/* Decode the next character, c, from s, reporting errors in e.
+ *
+ * Since this is a branchless decoder, four bytes will be read from the
+ * buffer regardless of the actual length of the next character. This
+ * means the buffer _must_ have at least three bytes of zero padding
+ * following the end of the data stream.
+ *
+ * Errors are reported in e, which will be non-zero if the parsed
+ * character was somehow invalid: invalid byte sequence, non-canonical
+ * encoding, or a surrogate half.
+ *
+ * The function returns a pointer to the next character. When an error
+ * occurs, this pointer will be a guess that depends on the particular
+ * error, but it will always advance at least one byte.
+ */
+FMT_CONSTEXPR inline auto utf8_decode(const char* s, uint32_t* c, int* e)
+    -> const char* {
+  constexpr const int masks[] = {0x00, 0x7f, 0x1f, 0x0f, 0x07};
+  constexpr const uint32_t mins[] = {4194304, 0, 128, 2048, 65536};
+  constexpr const int shiftc[] = {0, 18, 12, 6, 0};
+  constexpr const int shifte[] = {0, 6, 4, 2, 0};
+
+  int len = "\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\1\0\0\0\0\0\0\0\0\2\2\2\2\3\3\4"
+      [static_cast<unsigned char>(*s) >> 3];
+  // Compute the pointer to the next character early so that the next
+  // iteration can start working on the next character. Neither Clang
+  // nor GCC figure out this reordering on their own.
+  const char* next = s + len + !len;
+
+  using uchar = unsigned char;
+
+  // Assume a four-byte character and load four bytes. Unused bits are
+  // shifted out.
+  *c = uint32_t(uchar(s[0]) & masks[len]) << 18;
+  *c |= uint32_t(uchar(s[1]) & 0x3f) << 12;
+  *c |= uint32_t(uchar(s[2]) & 0x3f) << 6;
+  *c |= uint32_t(uchar(s[3]) & 0x3f) << 0;
+  *c >>= shiftc[len];
+
+  // Accumulate the various error conditions.
+  *e = (*c < mins[len]) << 6;       // non-canonical encoding
+  *e |= ((*c >> 11) == 0x1b) << 7;  // surrogate half?
+  *e |= (*c > 0x10FFFF) << 8;       // out of range?
+  *e |= (uchar(s[1]) & 0xc0) >> 2;
+  *e |= (uchar(s[2]) & 0xc0) >> 4;
+  *e |= uchar(s[3]) >> 6;
+  *e ^= 0x2a;  // top two bits of each tail byte correct?
+  *e >>= shifte[len];
+
+  return next;
+}
 
-  value_type& operator*() const {
-    return this->count_ < this->limit_ ? *this->out_ : blackhole_;
+constexpr FMT_INLINE_VARIABLE uint32_t invalid_code_point = ~uint32_t();
+
+// Invokes f(cp, sv) for every code point cp in s with sv being the string view
+// corresponding to the code point. cp is invalid_code_point on error.
+template <typename F>
+FMT_CONSTEXPR void for_each_codepoint(string_view s, F f) {
+  auto decode = [f](const char* buf_ptr, const char* ptr) {
+    auto cp = uint32_t();
+    auto error = 0;
+    auto end = utf8_decode(buf_ptr, &cp, &error);
+    bool result = f(error ? invalid_code_point : cp,
+                    string_view(ptr, error ? 1 : to_unsigned(end - buf_ptr)));
+    return result ? (error ? buf_ptr + 1 : end) : nullptr;
+  };
+  auto p = s.data();
+  const size_t block_size = 4;  // utf8_decode always reads blocks of 4 chars.
+  if (s.size() >= block_size) {
+    for (auto end = p + s.size() - block_size + 1; p < end;) {
+      p = decode(p, p);
+      if (!p) return;
+    }
   }
-};
-
-template <typename OutputIt>
-class truncating_iterator<OutputIt, std::true_type>
-    : public truncating_iterator_base<OutputIt> {
- public:
-  truncating_iterator(OutputIt out, std::size_t limit)
-      : truncating_iterator_base<OutputIt>(out, limit) {}
-
-  template <typename T> truncating_iterator& operator=(T val) {
-    if (this->count_++ < this->limit_) *this->out_++ = val;
-    return *this;
+  if (auto num_chars_left = s.data() + s.size() - p) {
+    char buf[2 * block_size - 1] = {};
+    copy_str<char>(p, p + num_chars_left, buf);
+    const char* buf_ptr = buf;
+    do {
+      auto end = decode(buf_ptr, p);
+      if (!end) return;
+      p += end - buf_ptr;
+      buf_ptr = end;
+    } while (buf_ptr - buf < num_chars_left);
   }
-
-  truncating_iterator& operator++() { return *this; }
-  truncating_iterator& operator++(int) { return *this; }
-  truncating_iterator& operator*() { return *this; }
-};
-
-// A range with the specified output iterator and value type.
-template <typename OutputIt, typename T = typename OutputIt::value_type>
-class output_range {
- private:
-  OutputIt it_;
-
- public:
-  using value_type = T;
-  using iterator = OutputIt;
-  struct sentinel {};
-
-  explicit output_range(OutputIt it) : it_(it) {}
-  OutputIt begin() const { return it_; }
-  sentinel end() const { return {}; }  // Sentinel is not used yet.
-};
+}
 
 template <typename Char>
-inline size_t count_code_points(basic_string_view<Char> s) {
+inline auto compute_width(basic_string_view<Char> s) -> size_t {
   return s.size();
 }
 
-// Counts the number of code points in a UTF-8 string.
-inline size_t count_code_points(basic_string_view<char> s) {
-  const char* data = s.data();
+// Computes approximate display width of a UTF-8 string.
+FMT_CONSTEXPR inline auto compute_width(string_view s) -> size_t {
   size_t num_code_points = 0;
-  for (size_t i = 0, size = s.size(); i != size; ++i) {
-    if ((data[i] & 0xc0) != 0x80) ++num_code_points;
-  }
+  // It is not a lambda for compatibility with C++14.
+  struct count_code_points {
+    size_t* count;
+    FMT_CONSTEXPR auto operator()(uint32_t cp, string_view) const -> bool {
+      *count += detail::to_unsigned(
+          1 +
+          (cp >= 0x1100 &&
+           (cp <= 0x115f ||  // Hangul Jamo init. consonants
+            cp == 0x2329 ||  // LEFT-POINTING ANGLE BRACKET
+            cp == 0x232a ||  // RIGHT-POINTING ANGLE BRACKET
+            // CJK ... Yi except IDEOGRAPHIC HALF FILL SPACE:
+            (cp >= 0x2e80 && cp <= 0xa4cf && cp != 0x303f) ||
+            (cp >= 0xac00 && cp <= 0xd7a3) ||    // Hangul Syllables
+            (cp >= 0xf900 && cp <= 0xfaff) ||    // CJK Compatibility Ideographs
+            (cp >= 0xfe10 && cp <= 0xfe19) ||    // Vertical Forms
+            (cp >= 0xfe30 && cp <= 0xfe6f) ||    // CJK Compatibility Forms
+            (cp >= 0xff00 && cp <= 0xff60) ||    // Fullwidth Forms
+            (cp >= 0xffe0 && cp <= 0xffe6) ||    // Fullwidth Forms
+            (cp >= 0x20000 && cp <= 0x2fffd) ||  // CJK
+            (cp >= 0x30000 && cp <= 0x3fffd) ||
+            // Miscellaneous Symbols and Pictographs + Emoticons:
+            (cp >= 0x1f300 && cp <= 0x1f64f) ||
+            // Supplemental Symbols and Pictographs:
+            (cp >= 0x1f900 && cp <= 0x1f9ff))));
+      return true;
+    }
+  };
+  // We could avoid branches by using utf8_decode directly.
+  for_each_codepoint(s, count_code_points{&num_code_points});
   return num_code_points;
 }
 
-inline size_t count_code_points(basic_string_view<char8_type> s) {
-  return count_code_points(basic_string_view<char>(
-      reinterpret_cast<const char*>(s.data()), s.size()));
+inline auto compute_width(basic_string_view<char8_type> s) -> size_t {
+  return compute_width(
+      string_view(reinterpret_cast<const char*>(s.data()), s.size()));
 }
 
 template <typename Char>
-inline size_t code_point_index(basic_string_view<Char> s, size_t n) {
+inline auto code_point_index(basic_string_view<Char> s, size_t n) -> size_t {
   size_t size = s.size();
   return n < size ? n : size;
 }
 
 // Calculates the index of the nth code point in a UTF-8 string.
-inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {
-  const char8_type* data = s.data();
-  size_t num_code_points = 0;
-  for (size_t i = 0, size = s.size(); i != size; ++i) {
-    if ((data[i] & 0xc0) != 0x80 && ++num_code_points > n) {
-      return i;
+inline auto code_point_index(string_view s, size_t n) -> size_t {
+  size_t result = s.size();
+  const char* begin = s.begin();
+  for_each_codepoint(s, [begin, &n, &result](uint32_t, string_view sv) {
+    if (n != 0) {
+      --n;
+      return true;
     }
-  }
-  return s.size();
+    result = to_unsigned(sv.begin() - begin);
+    return false;
+  });
+  return result;
 }
 
-inline char8_type to_char8_t(char c) { return static_cast<char8_type>(c); }
+inline auto code_point_index(basic_string_view<char8_type> s, size_t n)
+    -> size_t {
+  return code_point_index(
+      string_view(reinterpret_cast<const char*>(s.data()), s.size()), n);
+}
 
-template <typename InputIt, typename OutChar>
-using needs_conversion = bool_constant<
-    std::is_same<typename std::iterator_traits<InputIt>::value_type,
-                 char>::value &&
-    std::is_same<OutChar, char8_type>::value>;
+template <typename T> struct is_integral : std::is_integral<T> {};
+template <> struct is_integral<int128_opt> : std::true_type {};
+template <> struct is_integral<uint128_t> : std::true_type {};
 
-template <typename OutChar, typename InputIt, typename OutputIt,
-          FMT_ENABLE_IF(!needs_conversion<InputIt, OutChar>::value)>
-OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
-  return std::copy(begin, end, it);
-}
+template <typename T>
+using is_signed =
+    std::integral_constant<bool, std::numeric_limits<T>::is_signed ||
+                                     std::is_same<T, int128_opt>::value>;
 
-template <typename OutChar, typename InputIt, typename OutputIt,
-          FMT_ENABLE_IF(needs_conversion<InputIt, OutChar>::value)>
-OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
-  return std::transform(begin, end, it, to_char8_t);
-}
+template <typename T>
+using is_integer =
+    bool_constant<is_integral<T>::value && !std::is_same<T, bool>::value &&
+                  !std::is_same<T, char>::value &&
+                  !std::is_same<T, wchar_t>::value>;
 
-#ifndef FMT_USE_GRISU
-#  define FMT_USE_GRISU 1
+#ifndef FMT_USE_FLOAT
+#  define FMT_USE_FLOAT 1
+#endif
+#ifndef FMT_USE_DOUBLE
+#  define FMT_USE_DOUBLE 1
+#endif
+#ifndef FMT_USE_LONG_DOUBLE
+#  define FMT_USE_LONG_DOUBLE 1
 #endif
 
-template <typename T> constexpr bool use_grisu() {
-  return FMT_USE_GRISU && std::numeric_limits<double>::is_iec559 &&
-         sizeof(T) <= sizeof(double);
-}
+#ifndef FMT_USE_FLOAT128
+#  ifdef __clang__
+// Clang emulates GCC, so it has to appear early.
+#    if FMT_HAS_INCLUDE(<quadmath.h>)
+#      define FMT_USE_FLOAT128 1
+#    endif
+#  elif defined(__GNUC__)
+// GNU C++:
+#    if defined(_GLIBCXX_USE_FLOAT128) && !defined(__STRICT_ANSI__)
+#      define FMT_USE_FLOAT128 1
+#    endif
+#  endif
+#  ifndef FMT_USE_FLOAT128
+#    define FMT_USE_FLOAT128 0
+#  endif
+#endif
+
+#if FMT_USE_FLOAT128
+using float128 = __float128;
+#else
+using float128 = void;
+#endif
+template <typename T> using is_float128 = std::is_same<T, float128>;
+
+template <typename T>
+using is_floating_point =
+    bool_constant<std::is_floating_point<T>::value || is_float128<T>::value>;
+
+template <typename T, bool = std::is_floating_point<T>::value>
+struct is_fast_float : bool_constant<std::numeric_limits<T>::is_iec559 &&
+                                     sizeof(T) <= sizeof(double)> {};
+template <typename T> struct is_fast_float<T, false> : std::false_type {};
+
+template <typename T>
+using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
+
+#ifndef FMT_USE_FULL_CACHE_DRAGONBOX
+#  define FMT_USE_FULL_CACHE_DRAGONBOX 0
+#endif
 
 template <typename T>
 template <typename U>
 void buffer<T>::append(const U* begin, const U* end) {
-  std::size_t new_size = size_ + to_unsigned(end - begin);
-  reserve(new_size);
-  std::uninitialized_copy(begin, end, make_checked(ptr_, capacity_) + size_);
-  size_ = new_size;
+  while (begin != end) {
+    auto count = to_unsigned(end - begin);
+    try_reserve(size_ + count);
+    auto free_cap = capacity_ - size_;
+    if (free_cap < count) count = free_cap;
+    std::uninitialized_copy_n(begin, count, ptr_ + size_);
+    size_ += count;
+    begin += count;
+  }
 }
-}  // namespace internal
 
-// A range with an iterator appending to a buffer.
+template <typename T, typename Enable = void>
+struct is_locale : std::false_type {};
 template <typename T>
-class buffer_range : public internal::output_range<
-                         std::back_insert_iterator<internal::buffer<T>>, T> {
- public:
-  using iterator = std::back_insert_iterator<internal::buffer<T>>;
-  using internal::output_range<iterator, T>::output_range;
-  buffer_range(internal::buffer<T>& buf)
-      : internal::output_range<iterator, T>(std::back_inserter(buf)) {}
-};
-
-class FMT_DEPRECATED u8string_view
-    : public basic_string_view<internal::char8_type> {
- public:
-  u8string_view(const char* s)
-      : basic_string_view<internal::char8_type>(
-            reinterpret_cast<const internal::char8_type*>(s)) {}
-  u8string_view(const char* s, size_t count) FMT_NOEXCEPT
-      : basic_string_view<internal::char8_type>(
-            reinterpret_cast<const internal::char8_type*>(s), count) {}
-};
+struct is_locale<T, void_t<decltype(T::classic())>> : std::true_type {};
+}  // namespace detail
 
-#if FMT_USE_USER_DEFINED_LITERALS
-inline namespace literals {
-FMT_DEPRECATED inline basic_string_view<internal::char8_type> operator"" _u(
-    const char* s, std::size_t n) {
-  return {reinterpret_cast<const internal::char8_type*>(s), n};
-}
-}  // namespace literals
-#endif
+FMT_BEGIN_EXPORT
 
 // The number of characters to store in the basic_memory_buffer object itself
 // to avoid dynamic memory allocation.
@@ -602,20 +862,12 @@ enum { inline_buffer_size = 500 };
   A dynamically growing memory buffer for trivially copyable/constructible types
   with the first ``SIZE`` elements stored in the object itself.
 
-  You can use one of the following type aliases for common character types:
-
-  +----------------+------------------------------+
-  | Type           | Definition                   |
-  +================+==============================+
-  | memory_buffer  | basic_memory_buffer<char>    |
-  +----------------+------------------------------+
-  | wmemory_buffer | basic_memory_buffer<wchar_t> |
-  +----------------+------------------------------+
+  You can use the ``memory_buffer`` type alias for ``char`` instead.
 
   **Example**::
 
-     fmt::memory_buffer out;
-     format_to(out, "The answer is {}.", 42);
+     auto out = fmt::memory_buffer();
+     fmt::format_to(std::back_inserter(out), "The answer is {}.", 42);
 
   This will append the following output to the ``out`` object:
 
@@ -626,47 +878,72 @@ enum { inline_buffer_size = 500 };
   The output can be converted to an ``std::string`` with ``to_string(out)``.
   \endrst
  */
-template <typename T, std::size_t SIZE = inline_buffer_size,
+template <typename T, size_t SIZE = inline_buffer_size,
           typename Allocator = std::allocator<T>>
-class basic_memory_buffer : private Allocator, public internal::buffer<T> {
+class basic_memory_buffer final : public detail::buffer<T> {
  private:
   T store_[SIZE];
 
+  // Don't inherit from Allocator to avoid generating type_info for it.
+  FMT_NO_UNIQUE_ADDRESS Allocator alloc_;
+
   // Deallocate memory allocated by the buffer.
-  void deallocate() {
+  FMT_CONSTEXPR20 void deallocate() {
     T* data = this->data();
-    if (data != store_) Allocator::deallocate(data, this->capacity());
+    if (data != store_) alloc_.deallocate(data, this->capacity());
   }
 
  protected:
-  void grow(std::size_t size) FMT_OVERRIDE;
+  FMT_CONSTEXPR20 void grow(size_t size) override {
+    detail::abort_fuzzing_if(size > 5000);
+    const size_t max_size = std::allocator_traits<Allocator>::max_size(alloc_);
+    size_t old_capacity = this->capacity();
+    size_t new_capacity = old_capacity + old_capacity / 2;
+    if (size > new_capacity)
+      new_capacity = size;
+    else if (new_capacity > max_size)
+      new_capacity = size > max_size ? size : max_size;
+    T* old_data = this->data();
+    T* new_data =
+        std::allocator_traits<Allocator>::allocate(alloc_, new_capacity);
+    // Suppress a bogus -Wstringop-overflow in gcc 13.1 (#3481).
+    detail::assume(this->size() <= new_capacity);
+    // The following code doesn't throw, so the raw pointer above doesn't leak.
+    std::uninitialized_copy_n(old_data, this->size(), new_data);
+    this->set(new_data, new_capacity);
+    // deallocate must not throw according to the standard, but even if it does,
+    // the buffer already uses the new storage and will deallocate it in
+    // destructor.
+    if (old_data != store_) alloc_.deallocate(old_data, old_capacity);
+  }
 
  public:
   using value_type = T;
   using const_reference = const T&;
 
-  explicit basic_memory_buffer(const Allocator& alloc = Allocator())
-      : Allocator(alloc) {
+  FMT_CONSTEXPR20 explicit basic_memory_buffer(
+      const Allocator& alloc = Allocator())
+      : alloc_(alloc) {
     this->set(store_, SIZE);
+    if (detail::is_constant_evaluated()) detail::fill_n(store_, SIZE, T());
   }
-  ~basic_memory_buffer() FMT_OVERRIDE { deallocate(); }
+  FMT_CONSTEXPR20 ~basic_memory_buffer() { deallocate(); }
 
  private:
   // Move data from other to this buffer.
-  void move(basic_memory_buffer& other) {
-    Allocator &this_alloc = *this, &other_alloc = other;
-    this_alloc = std::move(other_alloc);
+  FMT_CONSTEXPR20 void move(basic_memory_buffer& other) {
+    alloc_ = std::move(other.alloc_);
     T* data = other.data();
-    std::size_t size = other.size(), capacity = other.capacity();
+    size_t size = other.size(), capacity = other.capacity();
     if (data == other.store_) {
       this->set(store_, capacity);
-      std::uninitialized_copy(other.store_, other.store_ + size,
-                              internal::make_checked(store_, capacity));
+      detail::copy_str<T>(other.store_, other.store_ + size, store_);
     } else {
       this->set(data, capacity);
       // Set pointer to the inline array so that delete is not called
       // when deallocating.
       other.set(other.store_, 0);
+      other.clear();
     }
     this->resize(size);
   }
@@ -678,14 +955,16 @@ class basic_memory_buffer : private Allocator, public internal::buffer<T> {
     of the other object to it.
     \endrst
    */
-  basic_memory_buffer(basic_memory_buffer&& other) FMT_NOEXCEPT { move(other); }
+  FMT_CONSTEXPR20 basic_memory_buffer(basic_memory_buffer&& other) noexcept {
+    move(other);
+  }
 
   /**
     \rst
     Moves the content of the other ``basic_memory_buffer`` object to this one.
     \endrst
    */
-  basic_memory_buffer& operator=(basic_memory_buffer&& other) FMT_NOEXCEPT {
+  auto operator=(basic_memory_buffer&& other) noexcept -> basic_memory_buffer& {
     FMT_ASSERT(this != &other, "");
     deallocate();
     move(other);
@@ -693,106 +972,176 @@ class basic_memory_buffer : private Allocator, public internal::buffer<T> {
   }
 
   // Returns a copy of the allocator associated with this buffer.
-  Allocator get_allocator() const { return *this; }
-};
+  auto get_allocator() const -> Allocator { return alloc_; }
 
-template <typename T, std::size_t SIZE, typename Allocator>
-void basic_memory_buffer<T, SIZE, Allocator>::grow(std::size_t size) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-  if (size > 1000) throw std::runtime_error("fuzz mode - won't grow that much");
-#endif
-  std::size_t old_capacity = this->capacity();
-  std::size_t new_capacity = old_capacity + old_capacity / 2;
-  if (size > new_capacity) new_capacity = size;
-  T* old_data = this->data();
-  T* new_data = std::allocator_traits<Allocator>::allocate(*this, new_capacity);
-  // The following code doesn't throw, so the raw pointer above doesn't leak.
-  std::uninitialized_copy(old_data, old_data + this->size(),
-                          internal::make_checked(new_data, new_capacity));
-  this->set(new_data, new_capacity);
-  // deallocate must not throw according to the standard, but even if it does,
-  // the buffer already uses the new storage and will deallocate it in
-  // destructor.
-  if (old_data != store_) Allocator::deallocate(old_data, old_capacity);
-}
+  /**
+    Resizes the buffer to contain *count* elements. If T is a POD type new
+    elements may not be initialized.
+   */
+  FMT_CONSTEXPR20 void resize(size_t count) { this->try_resize(count); }
+
+  /** Increases the buffer capacity to *new_capacity*. */
+  void reserve(size_t new_capacity) { this->try_reserve(new_capacity); }
+
+  using detail::buffer<T>::append;
+  template <typename ContiguousRange>
+  void append(const ContiguousRange& range) {
+    append(range.data(), range.data() + range.size());
+  }
+};
 
 using memory_buffer = basic_memory_buffer<char>;
-using wmemory_buffer = basic_memory_buffer<wchar_t>;
 
-/** A formatting error such as invalid format string. */
-FMT_CLASS_API
-class FMT_API format_error : public std::runtime_error {
+template <typename T, size_t SIZE, typename Allocator>
+struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+};
+
+FMT_END_EXPORT
+namespace detail {
+FMT_API auto write_console(int fd, string_view text) -> bool;
+FMT_API auto write_console(std::FILE* f, string_view text) -> bool;
+FMT_API void print(std::FILE*, string_view);
+}  // namespace detail
+
+FMT_BEGIN_EXPORT
+
+// Suppress a misleading warning in older versions of clang.
+#if FMT_CLANG_VERSION
+#  pragma clang diagnostic ignored "-Wweak-vtables"
+#endif
+
+/** An error reported from a formatting function. */
+class FMT_SO_VISIBILITY("default") format_error : public std::runtime_error {
+ public:
+  using std::runtime_error::runtime_error;
+};
+
+namespace detail_exported {
+#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <typename Char, size_t N> struct fixed_string {
+  constexpr fixed_string(const Char (&str)[N]) {
+    detail::copy_str<Char, const Char*, Char*>(static_cast<const Char*>(str),
+                                               str + N, data);
+  }
+  Char data[N] = {};
+};
+#endif
+
+// Converts a compile-time string to basic_string_view.
+template <typename Char, size_t N>
+constexpr auto compile_string_to_view(const Char (&s)[N])
+    -> basic_string_view<Char> {
+  // Remove trailing NUL character if needed. Won't be present if this is used
+  // with a raw character array (i.e. not defined as a string).
+  return {s, N - (std::char_traits<Char>::to_int_type(s[N - 1]) == 0 ? 1 : 0)};
+}
+template <typename Char>
+constexpr auto compile_string_to_view(detail::std_string_view<Char> s)
+    -> basic_string_view<Char> {
+  return {s.data(), s.size()};
+}
+}  // namespace detail_exported
+
+class loc_value {
+ private:
+  basic_format_arg<format_context> value_;
+
+ public:
+  template <typename T, FMT_ENABLE_IF(!detail::is_float128<T>::value)>
+  loc_value(T value) : value_(detail::make_arg<format_context>(value)) {}
+
+  template <typename T, FMT_ENABLE_IF(detail::is_float128<T>::value)>
+  loc_value(T) {}
+
+  template <typename Visitor> auto visit(Visitor&& vis) -> decltype(vis(0)) {
+    return visit_format_arg(vis, value_);
+  }
+};
+
+// A locale facet that formats values in UTF-8.
+// It is parameterized on the locale to avoid the heavy <locale> include.
+template <typename Locale> class format_facet : public Locale::facet {
+ private:
+  std::string separator_;
+  std::string grouping_;
+  std::string decimal_point_;
+
+ protected:
+  virtual auto do_put(appender out, loc_value val,
+                      const format_specs<>& specs) const -> bool;
+
  public:
-  explicit format_error(const char* message) : std::runtime_error(message) {}
-  explicit format_error(const std::string& message)
-      : std::runtime_error(message) {}
-  format_error(const format_error&) = default;
-  format_error& operator=(const format_error&) = default;
-  format_error(format_error&&) = default;
-  format_error& operator=(format_error&&) = default;
-  ~format_error() FMT_NOEXCEPT FMT_OVERRIDE;
+  static FMT_API typename Locale::id id;
+
+  explicit format_facet(Locale& loc);
+  explicit format_facet(string_view sep = "",
+                        std::initializer_list<unsigned char> g = {3},
+                        std::string decimal_point = ".")
+      : separator_(sep.data(), sep.size()),
+        grouping_(g.begin(), g.end()),
+        decimal_point_(decimal_point) {}
+
+  auto put(appender out, loc_value val, const format_specs<>& specs) const
+      -> bool {
+    return do_put(out, val, specs);
+  }
 };
 
-namespace internal {
+namespace detail {
 
 // Returns true if value is negative, false otherwise.
 // Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
-template <typename T, FMT_ENABLE_IF(std::numeric_limits<T>::is_signed)>
-FMT_CONSTEXPR bool is_negative(T value) {
+template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
+constexpr auto is_negative(T value) -> bool {
   return value < 0;
 }
-template <typename T, FMT_ENABLE_IF(!std::numeric_limits<T>::is_signed)>
-FMT_CONSTEXPR bool is_negative(T) {
+template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
+constexpr auto is_negative(T) -> bool {
   return false;
 }
 
-template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-FMT_CONSTEXPR bool is_supported_floating_point(T) {
-  return (std::is_same<T, float>::value && FMT_USE_FLOAT) ||
-         (std::is_same<T, double>::value && FMT_USE_DOUBLE) ||
-         (std::is_same<T, long double>::value && FMT_USE_LONG_DOUBLE);
+template <typename T>
+FMT_CONSTEXPR auto is_supported_floating_point(T) -> bool {
+  if (std::is_same<T, float>()) return FMT_USE_FLOAT;
+  if (std::is_same<T, double>()) return FMT_USE_DOUBLE;
+  if (std::is_same<T, long double>()) return FMT_USE_LONG_DOUBLE;
+  return true;
 }
 
 // Smallest of uint32_t, uint64_t, uint128_t that is large enough to
-// represent all values of T.
+// represent all values of an integral type T.
 template <typename T>
-using uint32_or_64_or_128_t = conditional_t<
-    std::numeric_limits<T>::digits <= 32, uint32_t,
-    conditional_t<std::numeric_limits<T>::digits <= 64, uint64_t, uint128_t>>;
-
-// Static data is placed in this class template for the header-only config.
-template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
-  static const uint64_t powers_of_10_64[];
-  static const uint32_t zero_or_powers_of_10_32[];
-  static const uint64_t zero_or_powers_of_10_64[];
-  static const uint64_t pow10_significands[];
-  static const int16_t pow10_exponents[];
-  static const char digits[];
-  static const char hex_digits[];
-  static const char foreground_color[];
-  static const char background_color[];
-  static const char reset_color[5];
-  static const wchar_t wreset_color[5];
-  static const char signs[];
-};
-
-FMT_EXTERN template struct basic_data<void>;
-
-// This is a struct rather than an alias to avoid shadowing warnings in gcc.
-struct data : basic_data<> {};
+using uint32_or_64_or_128_t =
+    conditional_t<num_bits<T>() <= 32 && !FMT_REDUCE_INT_INSTANTIATIONS,
+                  uint32_t,
+                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
+template <typename T>
+using uint64_or_128_t = conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>;
+
+#define FMT_POWERS_OF_10(factor)                                  \
+  factor * 10, (factor) * 100, (factor) * 1000, (factor) * 10000, \
+      (factor) * 100000, (factor) * 1000000, (factor) * 10000000, \
+      (factor) * 100000000, (factor) * 1000000000
+
+// Converts value in the range [0, 100) to a string.
+constexpr auto digits2(size_t value) -> const char* {
+  // GCC generates slightly better code when value is pointer-size.
+  return &"0001020304050607080910111213141516171819"
+         "2021222324252627282930313233343536373839"
+         "4041424344454647484950515253545556575859"
+         "6061626364656667686970717273747576777879"
+         "8081828384858687888990919293949596979899"[value * 2];
+}
 
-#ifdef FMT_BUILTIN_CLZLL
-// Returns the number of decimal digits in n. Leading zeros are not counted
-// except for n == 0 in which case count_digits returns 1.
-inline int count_digits(uint64_t n) {
-  // Based on http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
-  // and the benchmark https://github.com/localvoid/cxx-benchmark-count-digits.
-  int t = (64 - FMT_BUILTIN_CLZLL(n | 1)) * 1233 >> 12;
-  return t - (n < data::zero_or_powers_of_10_64[t]) + 1;
+// Sign is a template parameter to workaround a bug in gcc 4.8.
+template <typename Char, typename Sign> constexpr auto sign(Sign s) -> Char {
+#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 604
+  static_assert(std::is_same<Sign, sign_t>::value, "");
+#endif
+  return static_cast<Char>("\0-+ "[s]);
 }
-#else
-// Fallback version of count_digits used when __builtin_clz is not available.
-inline int count_digits(uint64_t n) {
+
+template <typename T> FMT_CONSTEXPR auto count_digits_fallback(T n) -> int {
   int count = 1;
   for (;;) {
     // Integer division is slow so do it for a group of four digits instead
@@ -806,279 +1155,445 @@ inline int count_digits(uint64_t n) {
     count += 4;
   }
 }
-#endif
-
 #if FMT_USE_INT128
-inline int count_digits(uint128_t n) {
-  int count = 1;
-  for (;;) {
-    // Integer division is slow so do it for a group of four digits instead
-    // of for every digit. The idea comes from the talk by Alexandrescu
-    // "Three Optimization Tips for C++". See speed-test for a comparison.
-    if (n < 10) return count;
-    if (n < 100) return count + 1;
-    if (n < 1000) return count + 2;
-    if (n < 10000) return count + 3;
-    n /= 10000U;
-    count += 4;
-  }
+FMT_CONSTEXPR inline auto count_digits(uint128_opt n) -> int {
+  return count_digits_fallback(n);
 }
 #endif
 
-// Counts the number of digits in n. BITS = log2(radix).
-template <unsigned BITS, typename UInt> inline int count_digits(UInt n) {
-  int num_digits = 0;
-  do {
-    ++num_digits;
-  } while ((n >>= BITS) != 0);
-  return num_digits;
+#ifdef FMT_BUILTIN_CLZLL
+// It is a separate function rather than a part of count_digits to workaround
+// the lack of static constexpr in constexpr functions.
+inline auto do_count_digits(uint64_t n) -> int {
+  // This has comparable performance to the version by Kendall Willets
+  // (https://github.com/fmtlib/format-benchmark/blob/master/digits10)
+  // but uses smaller tables.
+  // Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
+  static constexpr uint8_t bsr2log10[] = {
+      1,  1,  1,  2,  2,  2,  3,  3,  3,  4,  4,  4,  4,  5,  5,  5,
+      6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9,  10, 10, 10,
+      10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
+      15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
+  auto t = bsr2log10[FMT_BUILTIN_CLZLL(n | 1) ^ 63];
+  static constexpr const uint64_t zero_or_powers_of_10[] = {
+      0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
+      10000000000000000000ULL};
+  return t - (n < zero_or_powers_of_10[t]);
 }
+#endif
 
-template <> int count_digits<4>(internal::fallback_uintptr n);
+// Returns the number of decimal digits in n. Leading zeros are not counted
+// except for n == 0 in which case count_digits returns 1.
+FMT_CONSTEXPR20 inline auto count_digits(uint64_t n) -> int {
+#ifdef FMT_BUILTIN_CLZLL
+  if (!is_constant_evaluated()) {
+    return do_count_digits(n);
+  }
+#endif
+  return count_digits_fallback(n);
+}
 
-#if FMT_GCC_VERSION || FMT_CLANG_VERSION
-#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
-#else
-#  define FMT_ALWAYS_INLINE
+// Counts the number of digits in n. BITS = log2(radix).
+template <int BITS, typename UInt>
+FMT_CONSTEXPR auto count_digits(UInt n) -> int {
+#ifdef FMT_BUILTIN_CLZ
+  if (!is_constant_evaluated() && num_bits<UInt>() == 32)
+    return (FMT_BUILTIN_CLZ(static_cast<uint32_t>(n) | 1) ^ 31) / BITS + 1;
 #endif
+  // Lambda avoids unreachable code warnings from NVHPC.
+  return [](UInt m) {
+    int num_digits = 0;
+    do {
+      ++num_digits;
+    } while ((m >>= BITS) != 0);
+    return num_digits;
+  }(n);
+}
 
 #ifdef FMT_BUILTIN_CLZ
-// Optional version of count_digits for better performance on 32-bit platforms.
-inline int count_digits(uint32_t n) {
-  int t = (32 - FMT_BUILTIN_CLZ(n | 1)) * 1233 >> 12;
-  return t - (n < data::zero_or_powers_of_10_32[t]) + 1;
+// It is a separate function rather than a part of count_digits to workaround
+// the lack of static constexpr in constexpr functions.
+FMT_INLINE auto do_count_digits(uint32_t n) -> int {
+// An optimization by Kendall Willets from https://bit.ly/3uOIQrB.
+// This increments the upper 32 bits (log10(T) - 1) when >= T is added.
+#  define FMT_INC(T) (((sizeof(#T) - 1ull) << 32) - T)
+  static constexpr uint64_t table[] = {
+      FMT_INC(0),          FMT_INC(0),          FMT_INC(0),           // 8
+      FMT_INC(10),         FMT_INC(10),         FMT_INC(10),          // 64
+      FMT_INC(100),        FMT_INC(100),        FMT_INC(100),         // 512
+      FMT_INC(1000),       FMT_INC(1000),       FMT_INC(1000),        // 4096
+      FMT_INC(10000),      FMT_INC(10000),      FMT_INC(10000),       // 32k
+      FMT_INC(100000),     FMT_INC(100000),     FMT_INC(100000),      // 256k
+      FMT_INC(1000000),    FMT_INC(1000000),    FMT_INC(1000000),     // 2048k
+      FMT_INC(10000000),   FMT_INC(10000000),   FMT_INC(10000000),    // 16M
+      FMT_INC(100000000),  FMT_INC(100000000),  FMT_INC(100000000),   // 128M
+      FMT_INC(1000000000), FMT_INC(1000000000), FMT_INC(1000000000),  // 1024M
+      FMT_INC(1000000000), FMT_INC(1000000000)                        // 4B
+  };
+  auto inc = table[FMT_BUILTIN_CLZ(n | 1) ^ 31];
+  return static_cast<int>((n + inc) >> 32);
 }
 #endif
 
-template <typename Char> FMT_API std::string grouping_impl(locale_ref loc);
-template <typename Char> inline std::string grouping(locale_ref loc) {
-  return grouping_impl<char>(loc);
+// Optional version of count_digits for better performance on 32-bit platforms.
+FMT_CONSTEXPR20 inline auto count_digits(uint32_t n) -> int {
+#ifdef FMT_BUILTIN_CLZ
+  if (!is_constant_evaluated()) {
+    return do_count_digits(n);
+  }
+#endif
+  return count_digits_fallback(n);
 }
-template <> inline std::string grouping<wchar_t>(locale_ref loc) {
-  return grouping_impl<wchar_t>(loc);
+
+template <typename Int> constexpr auto digits10() noexcept -> int {
+  return std::numeric_limits<Int>::digits10;
 }
+template <> constexpr auto digits10<int128_opt>() noexcept -> int { return 38; }
+template <> constexpr auto digits10<uint128_t>() noexcept -> int { return 38; }
+
+template <typename Char> struct thousands_sep_result {
+  std::string grouping;
+  Char thousands_sep;
+};
 
-template <typename Char> FMT_API Char thousands_sep_impl(locale_ref loc);
-template <typename Char> inline Char thousands_sep(locale_ref loc) {
-  return Char(thousands_sep_impl<char>(loc));
+template <typename Char>
+FMT_API auto thousands_sep_impl(locale_ref loc) -> thousands_sep_result<Char>;
+template <typename Char>
+inline auto thousands_sep(locale_ref loc) -> thousands_sep_result<Char> {
+  auto result = thousands_sep_impl<char>(loc);
+  return {result.grouping, Char(result.thousands_sep)};
 }
-template <> inline wchar_t thousands_sep(locale_ref loc) {
+template <>
+inline auto thousands_sep(locale_ref loc) -> thousands_sep_result<wchar_t> {
   return thousands_sep_impl<wchar_t>(loc);
 }
 
-template <typename Char> FMT_API Char decimal_point_impl(locale_ref loc);
-template <typename Char> inline Char decimal_point(locale_ref loc) {
+template <typename Char>
+FMT_API auto decimal_point_impl(locale_ref loc) -> Char;
+template <typename Char> inline auto decimal_point(locale_ref loc) -> Char {
   return Char(decimal_point_impl<char>(loc));
 }
-template <> inline wchar_t decimal_point(locale_ref loc) {
+template <> inline auto decimal_point(locale_ref loc) -> wchar_t {
   return decimal_point_impl<wchar_t>(loc);
 }
 
-// Formats a decimal unsigned integer value writing into buffer.
-// add_thousands_sep is called after writing each char to add a thousands
-// separator if necessary.
-template <typename UInt, typename Char, typename F>
-inline Char* format_decimal(Char* buffer, UInt value, int num_digits,
-                            F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
-  buffer += num_digits;
-  Char* end = buffer;
+// Compares two characters for equality.
+template <typename Char> auto equal2(const Char* lhs, const char* rhs) -> bool {
+  return lhs[0] == Char(rhs[0]) && lhs[1] == Char(rhs[1]);
+}
+inline auto equal2(const char* lhs, const char* rhs) -> bool {
+  return memcmp(lhs, rhs, 2) == 0;
+}
+
+// Copies two characters from src to dst.
+template <typename Char>
+FMT_CONSTEXPR20 FMT_INLINE void copy2(Char* dst, const char* src) {
+  if (!is_constant_evaluated() && sizeof(Char) == sizeof(char)) {
+    memcpy(dst, src, 2);
+    return;
+  }
+  *dst++ = static_cast<Char>(*src++);
+  *dst = static_cast<Char>(*src);
+}
+
+template <typename Iterator> struct format_decimal_result {
+  Iterator begin;
+  Iterator end;
+};
+
+// Formats a decimal unsigned integer value writing into out pointing to a
+// buffer of specified size. The caller must ensure that the buffer is large
+// enough.
+template <typename Char, typename UInt>
+FMT_CONSTEXPR20 auto format_decimal(Char* out, UInt value, int size)
+    -> format_decimal_result<Char*> {
+  FMT_ASSERT(size >= count_digits(value), "invalid digit count");
+  out += size;
+  Char* end = out;
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
     // "Three Optimization Tips for C++". See speed-test for a comparison.
-    auto index = static_cast<unsigned>((value % 100) * 2);
+    out -= 2;
+    copy2(out, digits2(static_cast<size_t>(value % 100)));
     value /= 100;
-    *--buffer = static_cast<Char>(data::digits[index + 1]);
-    add_thousands_sep(buffer);
-    *--buffer = static_cast<Char>(data::digits[index]);
-    add_thousands_sep(buffer);
   }
   if (value < 10) {
-    *--buffer = static_cast<Char>('0' + value);
-    return end;
+    *--out = static_cast<Char>('0' + value);
+    return {out, end};
   }
-  auto index = static_cast<unsigned>(value * 2);
-  *--buffer = static_cast<Char>(data::digits[index + 1]);
-  add_thousands_sep(buffer);
-  *--buffer = static_cast<Char>(data::digits[index]);
-  return end;
-}
-
-template <typename Int> constexpr int digits10() FMT_NOEXCEPT {
-  return std::numeric_limits<Int>::digits10;
+  out -= 2;
+  copy2(out, digits2(static_cast<size_t>(value)));
+  return {out, end};
 }
-template <> constexpr int digits10<int128_t>() FMT_NOEXCEPT { return 38; }
-template <> constexpr int digits10<uint128_t>() FMT_NOEXCEPT { return 38; }
 
-template <typename Char, typename UInt, typename Iterator, typename F>
-inline Iterator format_decimal(Iterator out, UInt value, int num_digits,
-                               F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
-  // Buffer should be large enough to hold all digits (<= digits10 + 1).
-  enum { max_size = digits10<UInt>() + 1 };
-  Char buffer[2 * max_size];
-  auto end = format_decimal(buffer, value, num_digits, add_thousands_sep);
-  return internal::copy_str<Char>(buffer, end, out);
-}
-
-template <typename Char, typename It, typename UInt>
-inline It format_decimal(It out, UInt value, int num_digits) {
-  return format_decimal<Char>(out, value, num_digits, [](Char*) {});
+template <typename Char, typename UInt, typename Iterator,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
+FMT_CONSTEXPR inline auto format_decimal(Iterator out, UInt value, int size)
+    -> format_decimal_result<Iterator> {
+  // Buffer is large enough to hold all digits (digits10 + 1).
+  Char buffer[digits10<UInt>() + 1] = {};
+  auto end = format_decimal(buffer, value, size).end;
+  return {out, detail::copy_str_noinline<Char>(buffer, end, out)};
 }
 
 template <unsigned BASE_BITS, typename Char, typename UInt>
-inline Char* format_uint(Char* buffer, UInt value, int num_digits,
-                         bool upper = false) {
+FMT_CONSTEXPR auto format_uint(Char* buffer, UInt value, int num_digits,
+                               bool upper = false) -> Char* {
   buffer += num_digits;
   Char* end = buffer;
   do {
-    const char* digits = upper ? "0123456789ABCDEF" : data::hex_digits;
-    unsigned digit = (value & ((1 << BASE_BITS) - 1));
+    const char* digits = upper ? "0123456789ABCDEF" : "0123456789abcdef";
+    unsigned digit = static_cast<unsigned>(value & ((1 << BASE_BITS) - 1));
     *--buffer = static_cast<Char>(BASE_BITS < 4 ? static_cast<char>('0' + digit)
                                                 : digits[digit]);
   } while ((value >>= BASE_BITS) != 0);
   return end;
 }
 
-template <unsigned BASE_BITS, typename Char>
-Char* format_uint(Char* buffer, internal::fallback_uintptr n, int num_digits,
-                  bool = false) {
-  auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
-  int start = (num_digits + char_digits - 1) / char_digits - 1;
-  if (int start_digits = num_digits % char_digits) {
-    unsigned value = n.value[start--];
-    buffer = format_uint<BASE_BITS>(buffer, value, start_digits);
-  }
-  for (; start >= 0; --start) {
-    unsigned value = n.value[start];
-    buffer += char_digits;
-    auto p = buffer;
-    for (int i = 0; i < char_digits; ++i) {
-      unsigned digit = (value & ((1 << BASE_BITS) - 1));
-      *--p = static_cast<Char>(data::hex_digits[digit]);
-      value >>= BASE_BITS;
-    }
-  }
-  return buffer;
-}
-
 template <unsigned BASE_BITS, typename Char, typename It, typename UInt>
-inline It format_uint(It out, UInt value, int num_digits, bool upper = false) {
+FMT_CONSTEXPR inline auto format_uint(It out, UInt value, int num_digits,
+                                      bool upper = false) -> It {
+  if (auto ptr = to_pointer<Char>(out, to_unsigned(num_digits))) {
+    format_uint<BASE_BITS>(ptr, value, num_digits, upper);
+    return out;
+  }
   // Buffer should be large enough to hold all digits (digits / BASE_BITS + 1).
-  char buffer[num_bits<UInt>() / BASE_BITS + 1];
+  char buffer[num_bits<UInt>() / BASE_BITS + 1] = {};
   format_uint<BASE_BITS>(buffer, value, num_digits, upper);
-  return internal::copy_str<Char>(buffer, buffer + num_digits, out);
+  return detail::copy_str_noinline<Char>(buffer, buffer + num_digits, out);
 }
 
 // A converter from UTF-8 to UTF-16.
 class utf8_to_utf16 {
  private:
-  wmemory_buffer buffer_;
+  basic_memory_buffer<wchar_t> buffer_;
 
  public:
   FMT_API explicit utf8_to_utf16(string_view s);
-  operator wstring_view() const { return {&buffer_[0], size()}; }
-  size_t size() const { return buffer_.size() - 1; }
-  const wchar_t* c_str() const { return &buffer_[0]; }
-  std::wstring str() const { return {&buffer_[0], size()}; }
+  operator basic_string_view<wchar_t>() const { return {&buffer_[0], size()}; }
+  auto size() const -> size_t { return buffer_.size() - 1; }
+  auto c_str() const -> const wchar_t* { return &buffer_[0]; }
+  auto str() const -> std::wstring { return {&buffer_[0], size()}; }
 };
 
-template <typename T = void> struct null {};
+enum class to_utf8_error_policy { abort, replace };
 
-// Workaround an array initialization issue in gcc 4.8.
-template <typename Char> struct fill_t {
+// A converter from UTF-16/UTF-32 (host endian) to UTF-8.
+template <typename WChar, typename Buffer = memory_buffer> class to_utf8 {
  private:
-  enum { max_size = 4 };
-  Char data_[max_size];
-  unsigned char size_;
+  Buffer buffer_;
 
  public:
-  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
-    auto size = s.size();
-    if (size > max_size) {
-      FMT_THROW(format_error("invalid fill"));
-      return;
+  to_utf8() {}
+  explicit to_utf8(basic_string_view<WChar> s,
+                   to_utf8_error_policy policy = to_utf8_error_policy::abort) {
+    static_assert(sizeof(WChar) == 2 || sizeof(WChar) == 4,
+                  "Expect utf16 or utf32");
+    if (!convert(s, policy))
+      FMT_THROW(std::runtime_error(sizeof(WChar) == 2 ? "invalid utf16"
+                                                      : "invalid utf32"));
+  }
+  operator string_view() const { return string_view(&buffer_[0], size()); }
+  auto size() const -> size_t { return buffer_.size() - 1; }
+  auto c_str() const -> const char* { return &buffer_[0]; }
+  auto str() const -> std::string { return std::string(&buffer_[0], size()); }
+
+  // Performs conversion returning a bool instead of throwing exception on
+  // conversion error. This method may still throw in case of memory allocation
+  // error.
+  auto convert(basic_string_view<WChar> s,
+               to_utf8_error_policy policy = to_utf8_error_policy::abort)
+      -> bool {
+    if (!convert(buffer_, s, policy)) return false;
+    buffer_.push_back(0);
+    return true;
+  }
+  static auto convert(Buffer& buf, basic_string_view<WChar> s,
+                      to_utf8_error_policy policy = to_utf8_error_policy::abort)
+      -> bool {
+    for (auto p = s.begin(); p != s.end(); ++p) {
+      uint32_t c = static_cast<uint32_t>(*p);
+      if (sizeof(WChar) == 2 && c >= 0xd800 && c <= 0xdfff) {
+        // Handle a surrogate pair.
+        ++p;
+        if (p == s.end() || (c & 0xfc00) != 0xd800 || (*p & 0xfc00) != 0xdc00) {
+          if (policy == to_utf8_error_policy::abort) return false;
+          buf.append(string_view("\xEF\xBF\xBD"));
+          --p;
+        } else {
+          c = (c << 10) + static_cast<uint32_t>(*p) - 0x35fdc00;
+        }
+      } else if (c < 0x80) {
+        buf.push_back(static_cast<char>(c));
+      } else if (c < 0x800) {
+        buf.push_back(static_cast<char>(0xc0 | (c >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+      } else if ((c >= 0x800 && c <= 0xd7ff) || (c >= 0xe000 && c <= 0xffff)) {
+        buf.push_back(static_cast<char>(0xe0 | (c >> 12)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+      } else if (c >= 0x10000 && c <= 0x10ffff) {
+        buf.push_back(static_cast<char>(0xf0 | (c >> 18)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0x3ffff) >> 12)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+      } else {
+        return false;
+      }
     }
-    for (size_t i = 0; i < size; ++i) data_[i] = s[i];
-    size_ = static_cast<unsigned char>(size);
+    return true;
   }
+};
 
-  size_t size() const { return size_; }
-  const Char* data() const { return data_; }
+// Computes 128-bit result of multiplication of two 64-bit unsigned integers.
+inline auto umul128(uint64_t x, uint64_t y) noexcept -> uint128_fallback {
+#if FMT_USE_INT128
+  auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
+  return {static_cast<uint64_t>(p >> 64), static_cast<uint64_t>(p)};
+#elif defined(_MSC_VER) && defined(_M_X64)
+  auto hi = uint64_t();
+  auto lo = _umul128(x, y, &hi);
+  return {hi, lo};
+#else
+  const uint64_t mask = static_cast<uint64_t>(max_value<uint32_t>());
 
-  FMT_CONSTEXPR Char& operator[](size_t index) { return data_[index]; }
-  FMT_CONSTEXPR const Char& operator[](size_t index) const {
-    return data_[index];
-  }
+  uint64_t a = x >> 32;
+  uint64_t b = x & mask;
+  uint64_t c = y >> 32;
+  uint64_t d = y & mask;
 
-  static FMT_CONSTEXPR fill_t<Char> make() {
-    auto fill = fill_t<Char>();
-    fill[0] = Char(' ');
-    fill.size_ = 1;
-    return fill;
-  }
-};
-}  // namespace internal
+  uint64_t ac = a * c;
+  uint64_t bc = b * c;
+  uint64_t ad = a * d;
+  uint64_t bd = b * d;
+
+  uint64_t intermediate = (bd >> 32) + (ad & mask) + (bc & mask);
+
+  return {ac + (intermediate >> 32) + (ad >> 32) + (bc >> 32),
+          (intermediate << 32) + (bd & mask)};
+#endif
+}
 
-// We cannot use enum classes as bit fields because of a gcc bug
-// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414.
-namespace align {
-enum type { none, left, right, center, numeric };
+namespace dragonbox {
+// Computes floor(log10(pow(2, e))) for e in [-2620, 2620] using the method from
+// https://fmt.dev/papers/Dragonbox.pdf#page=28, section 6.1.
+inline auto floor_log10_pow2(int e) noexcept -> int {
+  FMT_ASSERT(e <= 2620 && e >= -2620, "too large exponent");
+  static_assert((-1 >> 1) == -1, "right shift is not arithmetic");
+  return (e * 315653) >> 20;
 }
-using align_t = align::type;
 
-namespace sign {
-enum type { none, minus, plus, space };
+inline auto floor_log2_pow10(int e) noexcept -> int {
+  FMT_ASSERT(e <= 1233 && e >= -1233, "too large exponent");
+  return (e * 1741647) >> 19;
 }
-using sign_t = sign::type;
 
-// Format specifiers for built-in and string types.
-template <typename Char> struct basic_format_specs {
-  int width;
-  int precision;
-  char type;
-  align_t align : 4;
-  sign_t sign : 3;
-  bool alt : 1;  // Alternate form ('#').
-  internal::fill_t<Char> fill;
-
-  constexpr basic_format_specs()
-      : width(0),
-        precision(-1),
-        type(0),
-        align(align::none),
-        sign(sign::none),
-        alt(false),
-        fill(internal::fill_t<Char>::make()) {}
+// Computes upper 64 bits of multiplication of two 64-bit unsigned integers.
+inline auto umul128_upper64(uint64_t x, uint64_t y) noexcept -> uint64_t {
+#if FMT_USE_INT128
+  auto p = static_cast<uint128_opt>(x) * static_cast<uint128_opt>(y);
+  return static_cast<uint64_t>(p >> 64);
+#elif defined(_MSC_VER) && defined(_M_X64)
+  return __umulh(x, y);
+#else
+  return umul128(x, y).high();
+#endif
+}
+
+// Computes upper 128 bits of multiplication of a 64-bit unsigned integer and a
+// 128-bit unsigned integer.
+inline auto umul192_upper128(uint64_t x, uint128_fallback y) noexcept
+    -> uint128_fallback {
+  uint128_fallback r = umul128(x, y.high());
+  r += umul128_upper64(x, y.low());
+  return r;
+}
+
+FMT_API auto get_cached_power(int k) noexcept -> uint128_fallback;
+
+// Type-specific information that Dragonbox uses.
+template <typename T, typename Enable = void> struct float_info;
+
+template <> struct float_info<float> {
+  using carrier_uint = uint32_t;
+  static const int exponent_bits = 8;
+  static const int kappa = 1;
+  static const int big_divisor = 100;
+  static const int small_divisor = 10;
+  static const int min_k = -31;
+  static const int max_k = 46;
+  static const int shorter_interval_tie_lower_threshold = -35;
+  static const int shorter_interval_tie_upper_threshold = -35;
 };
 
-using format_specs = basic_format_specs<char>;
+template <> struct float_info<double> {
+  using carrier_uint = uint64_t;
+  static const int exponent_bits = 11;
+  static const int kappa = 2;
+  static const int big_divisor = 1000;
+  static const int small_divisor = 100;
+  static const int min_k = -292;
+  static const int max_k = 341;
+  static const int shorter_interval_tie_lower_threshold = -77;
+  static const int shorter_interval_tie_upper_threshold = -77;
+};
 
-namespace internal {
+// An 80- or 128-bit floating point number.
+template <typename T>
+struct float_info<T, enable_if_t<std::numeric_limits<T>::digits == 64 ||
+                                 std::numeric_limits<T>::digits == 113 ||
+                                 is_float128<T>::value>> {
+  using carrier_uint = detail::uint128_t;
+  static const int exponent_bits = 15;
+};
 
-// A floating-point presentation format.
-enum class float_format : unsigned char {
-  general,  // General: exponent notation or fixed point based on magnitude.
-  exp,      // Exponent notation with the default precision of 6, e.g. 1.2e-3.
-  fixed,    // Fixed point with the default precision of 6, e.g. 0.0012.
-  hex
+// A double-double floating point number.
+template <typename T>
+struct float_info<T, enable_if_t<is_double_double<T>::value>> {
+  using carrier_uint = detail::uint128_t;
 };
 
-struct float_specs {
-  int precision;
-  float_format format : 8;
-  sign_t sign : 8;
-  bool upper : 1;
-  bool locale : 1;
-  bool percent : 1;
-  bool binary32 : 1;
-  bool use_grisu : 1;
-  bool showpoint : 1;
+template <typename T> struct decimal_fp {
+  using significand_type = typename float_info<T>::carrier_uint;
+  significand_type significand;
+  int exponent;
 };
 
+template <typename T> FMT_API auto to_decimal(T x) noexcept -> decimal_fp<T>;
+}  // namespace dragonbox
+
+// Returns true iff Float has the implicit bit which is not stored.
+template <typename Float> constexpr auto has_implicit_bit() -> bool {
+  // An 80-bit FP number has a 64-bit significand an no implicit bit.
+  return std::numeric_limits<Float>::digits != 64;
+}
+
+// Returns the number of significand bits stored in Float. The implicit bit is
+// not counted since it is not stored.
+template <typename Float> constexpr auto num_significand_bits() -> int {
+  // std::numeric_limits may not support __float128.
+  return is_float128<Float>() ? 112
+                              : (std::numeric_limits<Float>::digits -
+                                 (has_implicit_bit<Float>() ? 1 : 0));
+}
+
+template <typename Float>
+constexpr auto exponent_mask() ->
+    typename dragonbox::float_info<Float>::carrier_uint {
+  using float_uint = typename dragonbox::float_info<Float>::carrier_uint;
+  return ((float_uint(1) << dragonbox::float_info<Float>::exponent_bits) - 1)
+         << num_significand_bits<Float>();
+}
+template <typename Float> constexpr auto exponent_bias() -> int {
+  // std::numeric_limits may not support __float128.
+  return is_float128<Float>() ? 16383
+                              : std::numeric_limits<Float>::max_exponent - 1;
+}
+
 // Writes the exponent exp in the form "[+-]d{2,3}" to buffer.
-template <typename Char, typename It> It write_exponent(int exp, It it) {
+template <typename Char, typename It>
+FMT_CONSTEXPR auto write_exponent(int exp, It it) -> It {
   FMT_ASSERT(-10000 < exp && exp < 10000, "exponent out of range");
   if (exp < 0) {
     *it++ = static_cast<Char>('-');
@@ -1087,1767 +1602,2369 @@ template <typename Char, typename It> It write_exponent(int exp, It it) {
     *it++ = static_cast<Char>('+');
   }
   if (exp >= 100) {
-    const char* top = data::digits + (exp / 100) * 2;
+    const char* top = digits2(to_unsigned(exp / 100));
     if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
     *it++ = static_cast<Char>(top[1]);
     exp %= 100;
   }
-  const char* d = data::digits + exp * 2;
+  const char* d = digits2(to_unsigned(exp));
   *it++ = static_cast<Char>(d[0]);
   *it++ = static_cast<Char>(d[1]);
   return it;
 }
 
-template <typename Char> class float_writer {
- private:
-  // The number is given as v = digits_ * pow(10, exp_).
-  const char* digits_;
-  int num_digits_;
-  int exp_;
-  size_t size_;
-  float_specs specs_;
-  Char decimal_point_;
-
-  template <typename It> It prettify(It it) const {
-    // pow(10, full_exp - 1) <= v <= pow(10, full_exp).
-    int full_exp = num_digits_ + exp_;
-    if (specs_.format == float_format::exp) {
-      // Insert a decimal point after the first digit and add an exponent.
-      *it++ = static_cast<Char>(*digits_);
-      int num_zeros = specs_.precision - num_digits_;
-      if (num_digits_ > 1 || specs_.showpoint) *it++ = decimal_point_;
-      it = copy_str<Char>(digits_ + 1, digits_ + num_digits_, it);
-      if (num_zeros > 0 && specs_.showpoint)
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      *it++ = static_cast<Char>(specs_.upper ? 'E' : 'e');
-      return write_exponent<Char>(full_exp - 1, it);
-    }
-    if (num_digits_ <= full_exp) {
-      // 1234e7 -> 12340000000[.0+]
-      it = copy_str<Char>(digits_, digits_ + num_digits_, it);
-      it = std::fill_n(it, full_exp - num_digits_, static_cast<Char>('0'));
-      if (specs_.showpoint || specs_.precision < 0) {
-        *it++ = decimal_point_;
-        int num_zeros = specs_.precision - full_exp;
-        if (num_zeros <= 0) {
-          if (specs_.format != float_format::fixed)
-            *it++ = static_cast<Char>('0');
-          return it;
-        }
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-        if (num_zeros > 1000)
-          throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
-#endif
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      }
-    } else if (full_exp > 0) {
-      // 1234e-2 -> 12.34[0+]
-      it = copy_str<Char>(digits_, digits_ + full_exp, it);
-      if (!specs_.showpoint) {
-        // Remove trailing zeros.
-        int num_digits = num_digits_;
-        while (num_digits > full_exp && digits_[num_digits - 1] == '0')
-          --num_digits;
-        if (num_digits != full_exp) *it++ = decimal_point_;
-        return copy_str<Char>(digits_ + full_exp, digits_ + num_digits, it);
-      }
-      *it++ = decimal_point_;
-      it = copy_str<Char>(digits_ + full_exp, digits_ + num_digits_, it);
-      if (specs_.precision > num_digits_) {
-        // Add trailing zeros.
-        int num_zeros = specs_.precision - num_digits_;
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-      }
-    } else {
-      // 1234e-6 -> 0.001234
-      *it++ = static_cast<Char>('0');
-      int num_zeros = -full_exp;
-      int num_digits = num_digits_;
-      if (num_digits == 0 && specs_.precision >= 0 &&
-          specs_.precision < num_zeros) {
-        num_zeros = specs_.precision;
-      }
-      // Remove trailing zeros.
-      if (!specs_.showpoint)
-        while (num_digits > 0 && digits_[num_digits - 1] == '0') --num_digits;
-      if (num_zeros != 0 || num_digits != 0 || specs_.showpoint) {
-        *it++ = decimal_point_;
-        it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
-        it = copy_str<Char>(digits_, digits_ + num_digits, it);
-      }
-    }
-    return it;
+// A floating-point number f * pow(2, e) where F is an unsigned type.
+template <typename F> struct basic_fp {
+  F f;
+  int e;
+
+  static constexpr const int num_significand_bits =
+      static_cast<int>(sizeof(F) * num_bits<unsigned char>());
+
+  constexpr basic_fp() : f(0), e(0) {}
+  constexpr basic_fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
+
+  // Constructs fp from an IEEE754 floating-point number.
+  template <typename Float> FMT_CONSTEXPR basic_fp(Float n) { assign(n); }
+
+  // Assigns n to this and return true iff predecessor is closer than successor.
+  template <typename Float, FMT_ENABLE_IF(!is_double_double<Float>::value)>
+  FMT_CONSTEXPR auto assign(Float n) -> bool {
+    static_assert(std::numeric_limits<Float>::digits <= 113, "unsupported FP");
+    // Assume Float is in the format [sign][exponent][significand].
+    using carrier_uint = typename dragonbox::float_info<Float>::carrier_uint;
+    const auto num_float_significand_bits =
+        detail::num_significand_bits<Float>();
+    const auto implicit_bit = carrier_uint(1) << num_float_significand_bits;
+    const auto significand_mask = implicit_bit - 1;
+    auto u = bit_cast<carrier_uint>(n);
+    f = static_cast<F>(u & significand_mask);
+    auto biased_e = static_cast<int>((u & exponent_mask<Float>()) >>
+                                     num_float_significand_bits);
+    // The predecessor is closer if n is a normalized power of 2 (f == 0)
+    // other than the smallest normalized number (biased_e > 1).
+    auto is_predecessor_closer = f == 0 && biased_e > 1;
+    if (biased_e == 0)
+      biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
+    else if (has_implicit_bit<Float>())
+      f += static_cast<F>(implicit_bit);
+    e = biased_e - exponent_bias<Float>() - num_float_significand_bits;
+    if (!has_implicit_bit<Float>()) ++e;
+    return is_predecessor_closer;
+  }
+
+  template <typename Float, FMT_ENABLE_IF(is_double_double<Float>::value)>
+  FMT_CONSTEXPR auto assign(Float n) -> bool {
+    static_assert(std::numeric_limits<double>::is_iec559, "unsupported FP");
+    return assign(static_cast<double>(n));
   }
+};
 
- public:
-  float_writer(const char* digits, int num_digits, int exp, float_specs specs,
-               Char decimal_point)
-      : digits_(digits),
-        num_digits_(num_digits),
-        exp_(exp),
-        specs_(specs),
-        decimal_point_(decimal_point) {
-    int full_exp = num_digits + exp - 1;
-    int precision = specs.precision > 0 ? specs.precision : 16;
-    if (specs_.format == float_format::general &&
-        !(full_exp >= -4 && full_exp < precision)) {
-      specs_.format = float_format::exp;
-    }
-    size_ = prettify(counting_iterator()).count();
-    size_ += specs.sign ? 1 : 0;
-  }
+using fp = basic_fp<unsigned long long>;
+
+// Normalizes the value converted from double and multiplied by (1 << SHIFT).
+template <int SHIFT = 0, typename F>
+FMT_CONSTEXPR auto normalize(basic_fp<F> value) -> basic_fp<F> {
+  // Handle subnormals.
+  const auto implicit_bit = F(1) << num_significand_bits<double>();
+  const auto shifted_implicit_bit = implicit_bit << SHIFT;
+  while ((value.f & shifted_implicit_bit) == 0) {
+    value.f <<= 1;
+    --value.e;
+  }
+  // Subtract 1 to account for hidden bit.
+  const auto offset = basic_fp<F>::num_significand_bits -
+                      num_significand_bits<double>() - SHIFT - 1;
+  value.f <<= offset;
+  value.e -= offset;
+  return value;
+}
 
-  size_t size() const { return size_; }
-  size_t width() const { return size(); }
+// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
+FMT_CONSTEXPR inline auto multiply(uint64_t lhs, uint64_t rhs) -> uint64_t {
+#if FMT_USE_INT128
+  auto product = static_cast<__uint128_t>(lhs) * rhs;
+  auto f = static_cast<uint64_t>(product >> 64);
+  return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
+#else
+  // Multiply 32-bit parts of significands.
+  uint64_t mask = (1ULL << 32) - 1;
+  uint64_t a = lhs >> 32, b = lhs & mask;
+  uint64_t c = rhs >> 32, d = rhs & mask;
+  uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
+  // Compute mid 64-bit of result and round.
+  uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
+  return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
+#endif
+}
 
-  template <typename It> void operator()(It&& it) {
-    if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
-    it = prettify(it);
-  }
-};
+FMT_CONSTEXPR inline auto operator*(fp x, fp y) -> fp {
+  return {multiply(x.f, y.f), x.e + y.e + 64};
+}
 
-template <typename T>
-int format_float(T value, int precision, float_specs specs, buffer<char>& buf);
+template <typename T, bool doublish = num_bits<T>() == num_bits<double>()>
+using convert_float_result =
+    conditional_t<std::is_same<T, float>::value || doublish, double, T>;
 
-// Formats a floating-point number with snprintf.
 template <typename T>
-int snprintf_float(T value, int precision, float_specs specs,
-                   buffer<char>& buf);
-
-template <typename T> T promote_float(T value) { return value; }
-inline double promote_float(float value) { return static_cast<double>(value); }
-
-template <typename Handler>
-FMT_CONSTEXPR void handle_int_type_spec(char spec, Handler&& handler) {
-  switch (spec) {
-  case 0:
-  case 'd':
-    handler.on_dec();
-    break;
-  case 'x':
-  case 'X':
-    handler.on_hex();
-    break;
-  case 'b':
-  case 'B':
-    handler.on_bin();
-    break;
-  case 'o':
-    handler.on_oct();
-    break;
-  case 'n':
-  case 'L':
-    handler.on_num();
-    break;
-  default:
-    handler.on_error();
-  }
+constexpr auto convert_float(T value) -> convert_float_result<T> {
+  return static_cast<convert_float_result<T>>(value);
 }
 
-template <typename ErrorHandler = error_handler, typename Char>
-FMT_CONSTEXPR float_specs parse_float_type_spec(
-    const basic_format_specs<Char>& specs, ErrorHandler&& eh = {}) {
-  auto result = float_specs();
-  result.showpoint = specs.alt;
-  switch (specs.type) {
-  case 0:
-    result.format = float_format::general;
-    result.showpoint |= specs.precision > 0;
-    break;
-  case 'G':
-    result.upper = true;
-    FMT_FALLTHROUGH;
-  case 'g':
-    result.format = float_format::general;
-    break;
-  case 'E':
-    result.upper = true;
-    FMT_FALLTHROUGH;
-  case 'e':
-    result.format = float_format::exp;
-    result.showpoint |= specs.precision != 0;
-    break;
-  case 'F':
-    result.upper = true;
-    FMT_FALLTHROUGH;
-  case 'f':
-    result.format = float_format::fixed;
-    result.showpoint |= specs.precision != 0;
-    break;
-#if FMT_DEPRECATED_PERCENT
-  case '%':
-    result.format = float_format::fixed;
-    result.percent = true;
-    break;
-#endif
-  case 'A':
-    result.upper = true;
-    FMT_FALLTHROUGH;
-  case 'a':
-    result.format = float_format::hex;
-    break;
-  case 'n':
-    result.locale = true;
-    break;
-  default:
-    eh.on_error("invalid type specifier");
-    break;
-  }
-  return result;
+template <typename OutputIt, typename Char>
+FMT_NOINLINE FMT_CONSTEXPR auto fill(OutputIt it, size_t n,
+                                     const fill_t<Char>& fill) -> OutputIt {
+  auto fill_size = fill.size();
+  if (fill_size == 1) return detail::fill_n(it, n, fill[0]);
+  auto data = fill.data();
+  for (size_t i = 0; i < n; ++i)
+    it = copy_str<Char>(data, data + fill_size, it);
+  return it;
 }
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR void handle_char_specs(const basic_format_specs<Char>* specs,
-                                     Handler&& handler) {
-  if (!specs) return handler.on_char();
-  if (specs->type && specs->type != 'c') return handler.on_int();
-  if (specs->align == align::numeric || specs->sign != sign::none || specs->alt)
-    handler.on_error("invalid format specifier for char");
-  handler.on_char();
+// Writes the output of f, padded according to format specifications in specs.
+// size: output size in code units.
+// width: output display width in (terminal) column positions.
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+FMT_CONSTEXPR auto write_padded(OutputIt out, const format_specs<Char>& specs,
+                                size_t size, size_t width, F&& f) -> OutputIt {
+  static_assert(align == align::left || align == align::right, "");
+  unsigned spec_width = to_unsigned(specs.width);
+  size_t padding = spec_width > width ? spec_width - width : 0;
+  // Shifts are encoded as string literals because static constexpr is not
+  // supported in constexpr functions.
+  auto* shifts = align == align::left ? "\x1f\x1f\x00\x01" : "\x00\x1f\x00\x01";
+  size_t left_padding = padding >> shifts[specs.align];
+  size_t right_padding = padding - left_padding;
+  auto it = reserve(out, size + padding * specs.fill.size());
+  if (left_padding != 0) it = fill(it, left_padding, specs.fill);
+  it = f(it);
+  if (right_padding != 0) it = fill(it, right_padding, specs.fill);
+  return base_iterator(out, it);
 }
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR void handle_cstring_type_spec(Char spec, Handler&& handler) {
-  if (spec == 0 || spec == 's')
-    handler.on_string();
-  else if (spec == 'p')
-    handler.on_pointer();
-  else
-    handler.on_error("invalid type specifier");
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+constexpr auto write_padded(OutputIt out, const format_specs<Char>& specs,
+                            size_t size, F&& f) -> OutputIt {
+  return write_padded<align>(out, specs, size, size, f);
 }
 
-template <typename Char, typename ErrorHandler>
-FMT_CONSTEXPR void check_string_type_spec(Char spec, ErrorHandler&& eh) {
-  if (spec != 0 && spec != 's') eh.on_error("invalid type specifier");
+template <align::type align = align::left, typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write_bytes(OutputIt out, string_view bytes,
+                               const format_specs<Char>& specs) -> OutputIt {
+  return write_padded<align>(
+      out, specs, bytes.size(), [bytes](reserve_iterator<OutputIt> it) {
+        const char* data = bytes.data();
+        return copy_str<Char>(data, data + bytes.size(), it);
+      });
 }
 
-template <typename Char, typename ErrorHandler>
-FMT_CONSTEXPR void check_pointer_type_spec(Char spec, ErrorHandler&& eh) {
-  if (spec != 0 && spec != 'p') eh.on_error("invalid type specifier");
+template <typename Char, typename OutputIt, typename UIntPtr>
+auto write_ptr(OutputIt out, UIntPtr value, const format_specs<Char>* specs)
+    -> OutputIt {
+  int num_digits = count_digits<4>(value);
+  auto size = to_unsigned(num_digits) + size_t(2);
+  auto write = [=](reserve_iterator<OutputIt> it) {
+    *it++ = static_cast<Char>('0');
+    *it++ = static_cast<Char>('x');
+    return format_uint<4, Char>(it, value, num_digits);
+  };
+  return specs ? write_padded<align::right>(out, *specs, size, write)
+               : base_iterator(out, write(reserve(out, size)));
 }
 
-template <typename ErrorHandler> class int_type_checker : private ErrorHandler {
- public:
-  FMT_CONSTEXPR explicit int_type_checker(ErrorHandler eh) : ErrorHandler(eh) {}
+// Returns true iff the code point cp is printable.
+FMT_API auto is_printable(uint32_t cp) -> bool;
 
-  FMT_CONSTEXPR void on_dec() {}
-  FMT_CONSTEXPR void on_hex() {}
-  FMT_CONSTEXPR void on_bin() {}
-  FMT_CONSTEXPR void on_oct() {}
-  FMT_CONSTEXPR void on_num() {}
+inline auto needs_escape(uint32_t cp) -> bool {
+  return cp < 0x20 || cp == 0x7f || cp == '"' || cp == '\\' ||
+         !is_printable(cp);
+}
 
-  FMT_CONSTEXPR void on_error() {
-    ErrorHandler::on_error("invalid type specifier");
-  }
+template <typename Char> struct find_escape_result {
+  const Char* begin;
+  const Char* end;
+  uint32_t cp;
 };
 
-template <typename ErrorHandler>
-class char_specs_checker : public ErrorHandler {
- private:
-  char type_;
+template <typename Char>
+using make_unsigned_char =
+    typename conditional_t<std::is_integral<Char>::value,
+                           std::make_unsigned<Char>,
+                           type_identity<uint32_t>>::type;
 
- public:
-  FMT_CONSTEXPR char_specs_checker(char type, ErrorHandler eh)
-      : ErrorHandler(eh), type_(type) {}
+template <typename Char>
+auto find_escape(const Char* begin, const Char* end)
+    -> find_escape_result<Char> {
+  for (; begin != end; ++begin) {
+    uint32_t cp = static_cast<make_unsigned_char<Char>>(*begin);
+    if (const_check(sizeof(Char) == 1) && cp >= 0x80) continue;
+    if (needs_escape(cp)) return {begin, begin + 1, cp};
+  }
+  return {begin, nullptr, 0};
+}
 
-  FMT_CONSTEXPR void on_int() {
-    handle_int_type_spec(type_, int_type_checker<ErrorHandler>(*this));
-  }
-  FMT_CONSTEXPR void on_char() {}
-};
+inline auto find_escape(const char* begin, const char* end)
+    -> find_escape_result<char> {
+  if (!is_utf8()) return find_escape<char>(begin, end);
+  auto result = find_escape_result<char>{end, nullptr, 0};
+  for_each_codepoint(string_view(begin, to_unsigned(end - begin)),
+                     [&](uint32_t cp, string_view sv) {
+                       if (needs_escape(cp)) {
+                         result = {sv.begin(), sv.end(), cp};
+                         return false;
+                       }
+                       return true;
+                     });
+  return result;
+}
 
-template <typename ErrorHandler>
-class cstring_type_checker : public ErrorHandler {
- public:
-  FMT_CONSTEXPR explicit cstring_type_checker(ErrorHandler eh)
-      : ErrorHandler(eh) {}
+#define FMT_STRING_IMPL(s, base, explicit)                                    \
+  [] {                                                                        \
+    /* Use the hidden visibility as a workaround for a GCC bug (#1973). */    \
+    /* Use a macro-like name to avoid shadowing warnings. */                  \
+    struct FMT_VISIBILITY("hidden") FMT_COMPILE_STRING : base {               \
+      using char_type FMT_MAYBE_UNUSED = fmt::remove_cvref_t<decltype(s[0])>; \
+      FMT_MAYBE_UNUSED FMT_CONSTEXPR explicit                                 \
+      operator fmt::basic_string_view<char_type>() const {                    \
+        return fmt::detail_exported::compile_string_to_view<char_type>(s);    \
+      }                                                                       \
+    };                                                                        \
+    return FMT_COMPILE_STRING();                                              \
+  }()
 
-  FMT_CONSTEXPR void on_string() {}
-  FMT_CONSTEXPR void on_pointer() {}
-};
+/**
+  \rst
+  Constructs a compile-time format string from a string literal *s*.
+
+  **Example**::
+
+    // A compile-time error because 'd' is an invalid specifier for strings.
+    std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
+  \endrst
+ */
+#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::detail::compile_string, )
+
+template <size_t width, typename Char, typename OutputIt>
+auto write_codepoint(OutputIt out, char prefix, uint32_t cp) -> OutputIt {
+  *out++ = static_cast<Char>('\\');
+  *out++ = static_cast<Char>(prefix);
+  Char buf[width];
+  fill_n(buf, width, static_cast<Char>('0'));
+  format_uint<4>(buf, cp, width);
+  return copy_str<Char>(buf, buf + width, out);
+}
 
-template <typename Context>
-void arg_map<Context>::init(const basic_format_args<Context>& args) {
-  if (map_) return;
-  map_ = new entry[internal::to_unsigned(args.max_size())];
-  if (args.is_packed()) {
-    for (int i = 0;; ++i) {
-      internal::type arg_type = args.type(i);
-      if (arg_type == internal::type::none_type) return;
-      if (arg_type == internal::type::named_arg_type)
-        push_back(args.values_[i]);
+template <typename OutputIt, typename Char>
+auto write_escaped_cp(OutputIt out, const find_escape_result<Char>& escape)
+    -> OutputIt {
+  auto c = static_cast<Char>(escape.cp);
+  switch (escape.cp) {
+  case '\n':
+    *out++ = static_cast<Char>('\\');
+    c = static_cast<Char>('n');
+    break;
+  case '\r':
+    *out++ = static_cast<Char>('\\');
+    c = static_cast<Char>('r');
+    break;
+  case '\t':
+    *out++ = static_cast<Char>('\\');
+    c = static_cast<Char>('t');
+    break;
+  case '"':
+    FMT_FALLTHROUGH;
+  case '\'':
+    FMT_FALLTHROUGH;
+  case '\\':
+    *out++ = static_cast<Char>('\\');
+    break;
+  default:
+    if (escape.cp < 0x100) {
+      return write_codepoint<2, Char>(out, 'x', escape.cp);
     }
+    if (escape.cp < 0x10000) {
+      return write_codepoint<4, Char>(out, 'u', escape.cp);
+    }
+    if (escape.cp < 0x110000) {
+      return write_codepoint<8, Char>(out, 'U', escape.cp);
+    }
+    for (Char escape_char : basic_string_view<Char>(
+             escape.begin, to_unsigned(escape.end - escape.begin))) {
+      out = write_codepoint<2, Char>(out, 'x',
+                                     static_cast<uint32_t>(escape_char) & 0xFF);
+    }
+    return out;
   }
-  for (int i = 0, n = args.max_size(); i < n; ++i) {
-    auto type = args.args_[i].type_;
-    if (type == internal::type::named_arg_type) push_back(args.args_[i].value_);
-  }
+  *out++ = c;
+  return out;
 }
 
-template <typename Char> struct nonfinite_writer {
-  sign_t sign;
-  const char* str;
-  static constexpr size_t str_size = 3;
-
-  size_t size() const { return str_size + (sign ? 1 : 0); }
-  size_t width() const { return size(); }
+template <typename Char, typename OutputIt>
+auto write_escaped_string(OutputIt out, basic_string_view<Char> str)
+    -> OutputIt {
+  *out++ = static_cast<Char>('"');
+  auto begin = str.begin(), end = str.end();
+  do {
+    auto escape = find_escape(begin, end);
+    out = copy_str<Char>(begin, escape.begin, out);
+    begin = escape.end;
+    if (!begin) break;
+    out = write_escaped_cp<OutputIt, Char>(out, escape);
+  } while (begin != end);
+  *out++ = static_cast<Char>('"');
+  return out;
+}
 
-  template <typename It> void operator()(It&& it) const {
-    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
-    it = copy_str<Char>(str, str + str_size, it);
+template <typename Char, typename OutputIt>
+auto write_escaped_char(OutputIt out, Char v) -> OutputIt {
+  Char v_array[1] = {v};
+  *out++ = static_cast<Char>('\'');
+  if ((needs_escape(static_cast<uint32_t>(v)) && v != static_cast<Char>('"')) ||
+      v == static_cast<Char>('\'')) {
+    out = write_escaped_cp(out,
+                           find_escape_result<Char>{v_array, v_array + 1,
+                                                    static_cast<uint32_t>(v)});
+  } else {
+    *out++ = v;
   }
-};
-
-template <typename OutputIt, typename Char>
-FMT_NOINLINE OutputIt fill(OutputIt it, size_t n, const fill_t<Char>& fill) {
-  auto fill_size = fill.size();
-  if (fill_size == 1) return std::fill_n(it, n, fill[0]);
-  for (size_t i = 0; i < n; ++i) it = std::copy_n(fill.data(), fill_size, it);
-  return it;
+  *out++ = static_cast<Char>('\'');
+  return out;
 }
 
-// This template provides operations for formatting and writing data into a
-// character range.
-template <typename Range> class basic_writer {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write_char(OutputIt out, Char value,
+                              const format_specs<Char>& specs) -> OutputIt {
+  bool is_debug = specs.type == presentation_type::debug;
+  return write_padded(out, specs, 1, [=](reserve_iterator<OutputIt> it) {
+    if (is_debug) return write_escaped_char(it, value);
+    *it++ = value;
+    return it;
+  });
+}
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, Char value,
+                         const format_specs<Char>& specs, locale_ref loc = {})
+    -> OutputIt {
+  // char is formatted as unsigned char for consistency across platforms.
+  using unsigned_type =
+      conditional_t<std::is_same<Char, char>::value, unsigned char, unsigned>;
+  return check_char_specs(specs)
+             ? write_char(out, value, specs)
+             : write(out, static_cast<unsigned_type>(value), specs, loc);
+}
 
- private:
-  iterator out_;  // Output iterator.
-  locale_ref locale_;
-
-  // Attempts to reserve space for n extra characters in the output range.
-  // Returns a pointer to the reserved range or a reference to out_.
-  auto reserve(std::size_t n) -> decltype(internal::reserve(out_, n)) {
-    return internal::reserve(out_, n);
-  }
-
-  template <typename F> struct padded_int_writer {
-    size_t size_;
-    string_view prefix;
-    char_type fill;
-    std::size_t padding;
-    F f;
-
-    size_t size() const { return size_; }
-    size_t width() const { return size_; }
-
-    template <typename It> void operator()(It&& it) const {
-      if (prefix.size() != 0)
-        it = copy_str<char_type>(prefix.begin(), prefix.end(), it);
-      it = std::fill_n(it, padding, fill);
-      f(it);
-    }
-  };
+// Data for write_int that doesn't depend on output iterator type. It is used to
+// avoid template code bloat.
+template <typename Char> struct write_int_data {
+  size_t size;
+  size_t padding;
 
-  // Writes an integer in the format
-  //   <left-padding><prefix><numeric-padding><digits><right-padding>
-  // where <digits> are written by f(it).
-  template <typename F>
-  void write_int(int num_digits, string_view prefix, format_specs specs, F f) {
-    std::size_t size = prefix.size() + to_unsigned(num_digits);
-    char_type fill = specs.fill[0];
-    std::size_t padding = 0;
+  FMT_CONSTEXPR write_int_data(int num_digits, unsigned prefix,
+                               const format_specs<Char>& specs)
+      : size((prefix >> 24) + to_unsigned(num_digits)), padding(0) {
     if (specs.align == align::numeric) {
-      auto unsiged_width = to_unsigned(specs.width);
-      if (unsiged_width > size) {
-        padding = unsiged_width - size;
-        size = unsiged_width;
+      auto width = to_unsigned(specs.width);
+      if (width > size) {
+        padding = width - size;
+        size = width;
       }
     } else if (specs.precision > num_digits) {
-      size = prefix.size() + to_unsigned(specs.precision);
+      size = (prefix >> 24) + to_unsigned(specs.precision);
       padding = to_unsigned(specs.precision - num_digits);
-      fill = static_cast<char_type>('0');
-    }
-    if (specs.align == align::none) specs.align = align::right;
-    write_padded(specs, padded_int_writer<F>{size, prefix, fill, padding, f});
-  }
-
-  // Writes a decimal integer.
-  template <typename Int> void write_decimal(Int value) {
-    auto abs_value = static_cast<uint32_or_64_or_128_t<Int>>(value);
-    bool negative = is_negative(value);
-    // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
-    if (negative) abs_value = ~abs_value + 1;
-    int num_digits = count_digits(abs_value);
-    auto&& it = reserve((negative ? 1 : 0) + static_cast<size_t>(num_digits));
-    if (negative) *it++ = static_cast<char_type>('-');
-    it = format_decimal<char_type>(it, abs_value, num_digits);
-  }
-
-  // The handle_int_type_spec handler that writes an integer.
-  template <typename Int, typename Specs> struct int_writer {
-    using unsigned_type = uint32_or_64_or_128_t<Int>;
-
-    basic_writer<Range>& writer;
-    const Specs& specs;
-    unsigned_type abs_value;
-    char prefix[4];
-    unsigned prefix_size;
-
-    string_view get_prefix() const { return string_view(prefix, prefix_size); }
-
-    int_writer(basic_writer<Range>& w, Int value, const Specs& s)
-        : writer(w),
-          specs(s),
-          abs_value(static_cast<unsigned_type>(value)),
-          prefix_size(0) {
-      if (is_negative(value)) {
-        prefix[0] = '-';
-        ++prefix_size;
-        abs_value = 0 - abs_value;
-      } else if (specs.sign != sign::none && specs.sign != sign::minus) {
-        prefix[0] = specs.sign == sign::plus ? '+' : ' ';
-        ++prefix_size;
-      }
-    }
-
-    struct dec_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = internal::format_decimal<char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_dec() {
-      int num_digits = count_digits(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       dec_writer{abs_value, num_digits});
-    }
-
-    struct hex_writer {
-      int_writer& self;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<4, char_type>(it, self.abs_value, num_digits,
-                                       self.specs.type != 'x');
-      }
-    };
-
-    void on_hex() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = specs.type;
-      }
-      int num_digits = count_digits<4>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       hex_writer{*this, num_digits});
-    }
-
-    template <int BITS> struct bin_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<BITS, char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_bin() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = static_cast<char>(specs.type);
-      }
-      int num_digits = count_digits<1>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<1>{abs_value, num_digits});
     }
+  }
+};
 
-    void on_oct() {
-      int num_digits = count_digits<3>(abs_value);
-      if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
-        // Octal prefix '0' is counted as a digit, so only add it if precision
-        // is not greater than the number of digits.
-        prefix[prefix_size++] = '0';
-      }
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<3>{abs_value, num_digits});
-    }
-
-    enum { sep_size = 1 };
-
-    struct num_writer {
-      unsigned_type abs_value;
-      int size;
-      const std::string& groups;
-      char_type sep;
-
-      template <typename It> void operator()(It&& it) const {
-        basic_string_view<char_type> s(&sep, sep_size);
-        // Index of a decimal digit with the least significant digit having
-        // index 0.
-        int digit_index = 0;
-        std::string::const_iterator group = groups.cbegin();
-        it = format_decimal<char_type>(
-            it, abs_value, size,
-            [this, s, &group, &digit_index](char_type*& buffer) {
-              if (*group <= 0 || ++digit_index % *group != 0 ||
-                  *group == max_value<char>())
-                return;
-              if (group + 1 != groups.cend()) {
-                digit_index = 0;
-                ++group;
-              }
-              buffer -= s.size();
-              std::uninitialized_copy(s.data(), s.data() + s.size(),
-                                      make_checked(buffer, s.size()));
-            });
-      }
-    };
-
-    void on_num() {
-      std::string groups = grouping<char_type>(writer.locale_);
-      if (groups.empty()) return on_dec();
-      auto sep = thousands_sep<char_type>(writer.locale_);
-      if (!sep) return on_dec();
-      int num_digits = count_digits(abs_value);
-      int size = num_digits;
-      std::string::const_iterator group = groups.cbegin();
-      while (group != groups.cend() && num_digits > *group && *group > 0 &&
-             *group != max_value<char>()) {
-        size += sep_size;
-        num_digits -= *group;
-        ++group;
-      }
-      if (group == groups.cend())
-        size += sep_size * ((num_digits - 1) / groups.back());
-      writer.write_int(size, get_prefix(), specs,
-                       num_writer{abs_value, size, groups, sep});
-    }
-
-    FMT_NORETURN void on_error() {
-      FMT_THROW(format_error("invalid type specifier"));
-    }
-  };
-
-  template <typename Char> struct str_writer {
-    const Char* s;
-    size_t size_;
-
-    size_t size() const { return size_; }
-    size_t width() const {
-      return count_code_points(basic_string_view<Char>(s, size_));
-    }
-
-    template <typename It> void operator()(It&& it) const {
-      it = copy_str<char_type>(s, s + size_, it);
-    }
-  };
-
-  struct bytes_writer {
-    string_view bytes;
-
-    size_t size() const { return bytes.size(); }
-    size_t width() const { return bytes.size(); }
-
-    template <typename It> void operator()(It&& it) const {
-      const char* data = bytes.data();
-      it = copy_str<char>(data, data + size(), it);
+// Writes an integer in the format
+//   <left-padding><prefix><numeric-padding><digits><right-padding>
+// where <digits> are written by write_digits(it).
+// prefix contains chars in three lower bytes and the size in the fourth byte.
+template <typename OutputIt, typename Char, typename W>
+FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, int num_digits,
+                                        unsigned prefix,
+                                        const format_specs<Char>& specs,
+                                        W write_digits) -> OutputIt {
+  // Slightly faster check for specs.width == 0 && specs.precision == -1.
+  if ((specs.width | (specs.precision + 1)) == 0) {
+    auto it = reserve(out, to_unsigned(num_digits) + (prefix >> 24));
+    if (prefix != 0) {
+      for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
+        *it++ = static_cast<Char>(p & 0xff);
     }
-  };
-
-  template <typename UIntPtr> struct pointer_writer {
-    UIntPtr value;
-    int num_digits;
+    return base_iterator(out, write_digits(it));
+  }
+  auto data = write_int_data<Char>(num_digits, prefix, specs);
+  return write_padded<align::right>(
+      out, specs, data.size, [=](reserve_iterator<OutputIt> it) {
+        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
+          *it++ = static_cast<Char>(p & 0xff);
+        it = detail::fill_n(it, data.padding, static_cast<Char>('0'));
+        return write_digits(it);
+      });
+}
 
-    size_t size() const { return to_unsigned(num_digits) + 2; }
-    size_t width() const { return size(); }
+template <typename Char> class digit_grouping {
+ private:
+  std::string grouping_;
+  std::basic_string<Char> thousands_sep_;
 
-    template <typename It> void operator()(It&& it) const {
-      *it++ = static_cast<char_type>('0');
-      *it++ = static_cast<char_type>('x');
-      it = format_uint<4, char_type>(it, value, num_digits);
-    }
+  struct next_state {
+    std::string::const_iterator group;
+    int pos;
   };
+  auto initial_state() const -> next_state { return {grouping_.begin(), 0}; }
 
- public:
-  explicit basic_writer(Range out, locale_ref loc = locale_ref())
-      : out_(out.begin()), locale_(loc) {}
-
-  iterator out() const { return out_; }
-
-  // Writes a value in the format
-  //   <left-padding><value><right-padding>
-  // where <value> is written by f(it).
-  template <typename F> void write_padded(const format_specs& specs, F&& f) {
-    // User-perceived width (in code points).
-    unsigned width = to_unsigned(specs.width);
-    size_t size = f.size();  // The number of code units.
-    size_t num_code_points = width != 0 ? f.width() : size;
-    if (width <= num_code_points) return f(reserve(size));
-    size_t padding = width - num_code_points;
-    size_t fill_size = specs.fill.size();
-    auto&& it = reserve(size + padding * fill_size);
-    if (specs.align == align::right) {
-      it = fill(it, padding, specs.fill);
-      f(it);
-    } else if (specs.align == align::center) {
-      std::size_t left_padding = padding / 2;
-      it = fill(it, left_padding, specs.fill);
-      f(it);
-      it = fill(it, padding - left_padding, specs.fill);
-    } else {
-      f(it);
-      it = fill(it, padding, specs.fill);
-    }
-  }
-
-  void write(int value) { write_decimal(value); }
-  void write(long value) { write_decimal(value); }
-  void write(long long value) { write_decimal(value); }
-
-  void write(unsigned value) { write_decimal(value); }
-  void write(unsigned long value) { write_decimal(value); }
-  void write(unsigned long long value) { write_decimal(value); }
-
-#if FMT_USE_INT128
-  void write(int128_t value) { write_decimal(value); }
-  void write(uint128_t value) { write_decimal(value); }
-#endif
-
-  template <typename T, typename Spec>
-  void write_int(T value, const Spec& spec) {
-    handle_int_type_spec(spec.type, int_writer<T, Spec>(*this, value, spec));
+  // Returns the next digit group separator position.
+  auto next(next_state& state) const -> int {
+    if (thousands_sep_.empty()) return max_value<int>();
+    if (state.group == grouping_.end()) return state.pos += grouping_.back();
+    if (*state.group <= 0 || *state.group == max_value<char>())
+      return max_value<int>();
+    state.pos += *state.group++;
+    return state.pos;
   }
 
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  void write(T value, format_specs specs = {}) {
-    if (const_check(!is_supported_floating_point(value))) {
-      return;
-    }
-    float_specs fspecs = parse_float_type_spec(specs);
-    fspecs.sign = specs.sign;
-    if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
-      fspecs.sign = sign::minus;
-      value = -value;
-    } else if (fspecs.sign == sign::minus) {
-      fspecs.sign = sign::none;
-    }
-
-    if (!std::isfinite(value)) {
-      auto str = std::isinf(value) ? (fspecs.upper ? "INF" : "inf")
-                                   : (fspecs.upper ? "NAN" : "nan");
-      return write_padded(specs, nonfinite_writer<char_type>{fspecs.sign, str});
+ public:
+  explicit digit_grouping(locale_ref loc, bool localized = true) {
+    if (!localized) return;
+    auto sep = thousands_sep<Char>(loc);
+    grouping_ = sep.grouping;
+    if (sep.thousands_sep) thousands_sep_.assign(1, sep.thousands_sep);
+  }
+  digit_grouping(std::string grouping, std::basic_string<Char> sep)
+      : grouping_(std::move(grouping)), thousands_sep_(std::move(sep)) {}
+
+  auto has_separator() const -> bool { return !thousands_sep_.empty(); }
+
+  auto count_separators(int num_digits) const -> int {
+    int count = 0;
+    auto state = initial_state();
+    while (num_digits > next(state)) ++count;
+    return count;
+  }
+
+  // Applies grouping to digits and write the output to out.
+  template <typename Out, typename C>
+  auto apply(Out out, basic_string_view<C> digits) const -> Out {
+    auto num_digits = static_cast<int>(digits.size());
+    auto separators = basic_memory_buffer<int>();
+    separators.push_back(0);
+    auto state = initial_state();
+    while (int i = next(state)) {
+      if (i >= num_digits) break;
+      separators.push_back(i);
     }
-
-    if (specs.align == align::none) {
-      specs.align = align::right;
-    } else if (specs.align == align::numeric) {
-      if (fspecs.sign) {
-        auto&& it = reserve(1);
-        *it++ = static_cast<char_type>(data::signs[fspecs.sign]);
-        fspecs.sign = sign::none;
-        if (specs.width != 0) --specs.width;
+    for (int i = 0, sep_index = static_cast<int>(separators.size() - 1);
+         i < num_digits; ++i) {
+      if (num_digits - i == separators[sep_index]) {
+        out =
+            copy_str<Char>(thousands_sep_.data(),
+                           thousands_sep_.data() + thousands_sep_.size(), out);
+        --sep_index;
       }
-      specs.align = align::right;
-    }
-
-    memory_buffer buffer;
-    if (fspecs.format == float_format::hex) {
-      if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
-      snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
-      write_padded(specs, str_writer<char>{buffer.data(), buffer.size()});
-      return;
-    }
-    int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
-    if (fspecs.format == float_format::exp) {
-      if (precision == max_value<int>())
-        FMT_THROW(format_error("number is too big"));
-      else
-        ++precision;
+      *out++ = static_cast<Char>(digits[to_unsigned(i)]);
     }
-    if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
-    fspecs.use_grisu = use_grisu<T>();
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) value *= 100;
-    int exp = format_float(promote_float(value), precision, fspecs, buffer);
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) {
-      buffer.push_back('%');
-      --exp;  // Adjust decimal place position.
-    }
-    fspecs.precision = precision;
-    char_type point = fspecs.locale ? decimal_point<char_type>(locale_)
-                                    : static_cast<char_type>('.');
-    write_padded(specs, float_writer<char_type>(buffer.data(),
-                                                static_cast<int>(buffer.size()),
-                                                exp, fspecs, point));
-  }
-
-  void write(char value) {
-    auto&& it = reserve(1);
-    *it++ = value;
+    return out;
   }
+};
 
-  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char_type>::value)>
-  void write(Char value) {
-    auto&& it = reserve(1);
-    *it++ = value;
-  }
+FMT_CONSTEXPR inline void prefix_append(unsigned& prefix, unsigned value) {
+  prefix |= prefix != 0 ? value << 8 : value;
+  prefix += (1u + (value > 0xff ? 1 : 0)) << 24;
+}
 
-  void write(string_view value) {
-    auto&& it = reserve(value.size());
-    it = copy_str<char_type>(value.begin(), value.end(), it);
-  }
-  void write(wstring_view value) {
-    static_assert(std::is_same<char_type, wchar_t>::value, "");
-    auto&& it = reserve(value.size());
-    it = std::copy(value.begin(), value.end(), it);
+// Writes a decimal integer with digit grouping.
+template <typename OutputIt, typename UInt, typename Char>
+auto write_int(OutputIt out, UInt value, unsigned prefix,
+               const format_specs<Char>& specs,
+               const digit_grouping<Char>& grouping) -> OutputIt {
+  static_assert(std::is_same<uint64_or_128_t<UInt>, UInt>::value, "");
+  int num_digits = 0;
+  auto buffer = memory_buffer();
+  switch (specs.type) {
+  case presentation_type::none:
+  case presentation_type::dec: {
+    num_digits = count_digits(value);
+    format_decimal<char>(appender(buffer), value, num_digits);
+    break;
   }
-
-  template <typename Char>
-  void write(const Char* s, std::size_t size, const format_specs& specs) {
-    write_padded(specs, str_writer<Char>{s, size});
+  case presentation_type::hex_lower:
+  case presentation_type::hex_upper: {
+    bool upper = specs.type == presentation_type::hex_upper;
+    if (specs.alt)
+      prefix_append(prefix, unsigned(upper ? 'X' : 'x') << 8 | '0');
+    num_digits = count_digits<4>(value);
+    format_uint<4, char>(appender(buffer), value, num_digits, upper);
+    break;
   }
-
-  template <typename Char>
-  void write(basic_string_view<Char> s, const format_specs& specs = {}) {
-    const Char* data = s.data();
-    std::size_t size = s.size();
-    if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
-      size = code_point_index(s, to_unsigned(specs.precision));
-    write(data, size, specs);
+  case presentation_type::bin_lower:
+  case presentation_type::bin_upper: {
+    bool upper = specs.type == presentation_type::bin_upper;
+    if (specs.alt)
+      prefix_append(prefix, unsigned(upper ? 'B' : 'b') << 8 | '0');
+    num_digits = count_digits<1>(value);
+    format_uint<1, char>(appender(buffer), value, num_digits);
+    break;
   }
-
-  void write_bytes(string_view bytes, const format_specs& specs) {
-    write_padded(specs, bytes_writer{bytes});
+  case presentation_type::oct: {
+    num_digits = count_digits<3>(value);
+    // Octal prefix '0' is counted as a digit, so only add it if precision
+    // is not greater than the number of digits.
+    if (specs.alt && specs.precision <= num_digits && value != 0)
+      prefix_append(prefix, '0');
+    format_uint<3, char>(appender(buffer), value, num_digits);
+    break;
   }
-
-  template <typename UIntPtr>
-  void write_pointer(UIntPtr value, const format_specs* specs) {
-    int num_digits = count_digits<4>(value);
-    auto pw = pointer_writer<UIntPtr>{value, num_digits};
-    if (!specs) return pw(reserve(to_unsigned(num_digits) + 2));
-    format_specs specs_copy = *specs;
-    if (specs_copy.align == align::none) specs_copy.align = align::right;
-    write_padded(specs_copy, pw);
+  case presentation_type::chr:
+    return write_char(out, static_cast<Char>(value), specs);
+  default:
+    throw_format_error("invalid format specifier");
   }
-};
-
-using writer = basic_writer<buffer_range<char>>;
 
-template <typename T> struct is_integral : std::is_integral<T> {};
-template <> struct is_integral<int128_t> : std::true_type {};
-template <> struct is_integral<uint128_t> : std::true_type {};
-
-template <typename Range, typename ErrorHandler = internal::error_handler>
-class arg_formatter_base {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
+  unsigned size = (prefix != 0 ? prefix >> 24 : 0) + to_unsigned(num_digits) +
+                  to_unsigned(grouping.count_separators(num_digits));
+  return write_padded<align::right>(
+      out, specs, size, size, [&](reserve_iterator<OutputIt> it) {
+        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
+          *it++ = static_cast<Char>(p & 0xff);
+        return grouping.apply(it, string_view(buffer.data(), buffer.size()));
+      });
+}
 
- private:
-  using writer_type = basic_writer<Range>;
-  writer_type writer_;
-  format_specs* specs_;
+// Writes a localized value.
+FMT_API auto write_loc(appender out, loc_value value,
+                       const format_specs<>& specs, locale_ref loc) -> bool;
+template <typename OutputIt, typename Char>
+inline auto write_loc(OutputIt, loc_value, const format_specs<Char>&,
+                      locale_ref) -> bool {
+  return false;
+}
 
-  struct char_writer {
-    char_type value;
+template <typename UInt> struct write_int_arg {
+  UInt abs_value;
+  unsigned prefix;
+};
 
-    size_t size() const { return 1; }
-    size_t width() const { return 1; }
+template <typename T>
+FMT_CONSTEXPR auto make_write_int_arg(T value, sign_t sign)
+    -> write_int_arg<uint32_or_64_or_128_t<T>> {
+  auto prefix = 0u;
+  auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
+  if (is_negative(value)) {
+    prefix = 0x01000000 | '-';
+    abs_value = 0 - abs_value;
+  } else {
+    constexpr const unsigned prefixes[4] = {0, 0, 0x1000000u | '+',
+                                            0x1000000u | ' '};
+    prefix = prefixes[sign];
+  }
+  return {abs_value, prefix};
+}
 
-    template <typename It> void operator()(It&& it) const { *it++ = value; }
-  };
+template <typename Char = char> struct loc_writer {
+  buffer_appender<Char> out;
+  const format_specs<Char>& specs;
+  std::basic_string<Char> sep;
+  std::string grouping;
+  std::basic_string<Char> decimal_point;
 
-  void write_char(char_type value) {
-    if (specs_)
-      writer_.write_padded(*specs_, char_writer{value});
-    else
-      writer_.write(value);
+  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
+  auto operator()(T value) -> bool {
+    auto arg = make_write_int_arg(value, specs.sign);
+    write_int(out, static_cast<uint64_or_128_t<T>>(arg.abs_value), arg.prefix,
+              specs, digit_grouping<Char>(grouping, sep));
+    return true;
   }
 
-  void write_pointer(const void* p) {
-    writer_.write_pointer(internal::to_uintptr(p), specs_);
+  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
+  auto operator()(T) -> bool {
+    return false;
   }
+};
 
- protected:
-  writer_type& writer() { return writer_; }
-  FMT_DEPRECATED format_specs* spec() { return specs_; }
-  format_specs* specs() { return specs_; }
-  iterator out() { return writer_.out(); }
-
-  void write(bool value) {
-    string_view sv(value ? "true" : "false");
-    specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
+template <typename Char, typename OutputIt, typename T>
+FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, write_int_arg<T> arg,
+                                        const format_specs<Char>& specs,
+                                        locale_ref) -> OutputIt {
+  static_assert(std::is_same<T, uint32_or_64_or_128_t<T>>::value, "");
+  auto abs_value = arg.abs_value;
+  auto prefix = arg.prefix;
+  switch (specs.type) {
+  case presentation_type::none:
+  case presentation_type::dec: {
+    auto num_digits = count_digits(abs_value);
+    return write_int(
+        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
+          return format_decimal<Char>(it, abs_value, num_digits).end;
+        });
+  }
+  case presentation_type::hex_lower:
+  case presentation_type::hex_upper: {
+    bool upper = specs.type == presentation_type::hex_upper;
+    if (specs.alt)
+      prefix_append(prefix, unsigned(upper ? 'X' : 'x') << 8 | '0');
+    int num_digits = count_digits<4>(abs_value);
+    return write_int(
+        out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
+          return format_uint<4, Char>(it, abs_value, num_digits, upper);
+        });
+  }
+  case presentation_type::bin_lower:
+  case presentation_type::bin_upper: {
+    bool upper = specs.type == presentation_type::bin_upper;
+    if (specs.alt)
+      prefix_append(prefix, unsigned(upper ? 'B' : 'b') << 8 | '0');
+    int num_digits = count_digits<1>(abs_value);
+    return write_int(out, num_digits, prefix, specs,
+                     [=](reserve_iterator<OutputIt> it) {
+                       return format_uint<1, Char>(it, abs_value, num_digits);
+                     });
+  }
+  case presentation_type::oct: {
+    int num_digits = count_digits<3>(abs_value);
+    // Octal prefix '0' is counted as a digit, so only add it if precision
+    // is not greater than the number of digits.
+    if (specs.alt && specs.precision <= num_digits && abs_value != 0)
+      prefix_append(prefix, '0');
+    return write_int(out, num_digits, prefix, specs,
+                     [=](reserve_iterator<OutputIt> it) {
+                       return format_uint<3, Char>(it, abs_value, num_digits);
+                     });
+  }
+  case presentation_type::chr:
+    return write_char(out, static_cast<Char>(abs_value), specs);
+  default:
+    throw_format_error("invalid format specifier");
   }
+  return out;
+}
+template <typename Char, typename OutputIt, typename T>
+FMT_CONSTEXPR FMT_NOINLINE auto write_int_noinline(
+    OutputIt out, write_int_arg<T> arg, const format_specs<Char>& specs,
+    locale_ref loc) -> OutputIt {
+  return write_int(out, arg, specs, loc);
+}
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        std::is_same<OutputIt, buffer_appender<Char>>::value)>
+FMT_CONSTEXPR FMT_INLINE auto write(OutputIt out, T value,
+                                    const format_specs<Char>& specs,
+                                    locale_ref loc) -> OutputIt {
+  if (specs.localized && write_loc(out, value, specs, loc)) return out;
+  return write_int_noinline(out, make_write_int_arg(value, specs.sign), specs,
+                            loc);
+}
+// An inlined version of write used in format string compilation.
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<OutputIt, buffer_appender<Char>>::value)>
+FMT_CONSTEXPR FMT_INLINE auto write(OutputIt out, T value,
+                                    const format_specs<Char>& specs,
+                                    locale_ref loc) -> OutputIt {
+  if (specs.localized && write_loc(out, value, specs, loc)) return out;
+  return write_int(out, make_write_int_arg(value, specs.sign), specs, loc);
+}
 
-  void write(const char_type* value) {
-    if (!value) {
-      FMT_THROW(format_error("string pointer is null"));
-    } else {
-      auto length = std::char_traits<char_type>::length(value);
-      basic_string_view<char_type> sv(value, length);
-      specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
-    }
-  }
+// An output iterator that counts the number of objects written to it and
+// discards them.
+class counting_iterator {
+ private:
+  size_t count_;
 
  public:
-  arg_formatter_base(Range r, format_specs* s, locale_ref loc)
-      : writer_(r, loc), specs_(s) {}
+  using iterator_category = std::output_iterator_tag;
+  using difference_type = std::ptrdiff_t;
+  using pointer = void;
+  using reference = void;
+  FMT_UNCHECKED_ITERATOR(counting_iterator);
 
-  iterator operator()(monostate) {
-    FMT_ASSERT(false, "invalid argument type");
-    return out();
-  }
+  struct value_type {
+    template <typename T> FMT_CONSTEXPR void operator=(const T&) {}
+  };
 
-  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
-  iterator operator()(T value) {
-    if (specs_)
-      writer_.write_int(value, *specs_);
-    else
-      writer_.write(value);
-    return out();
-  }
+  FMT_CONSTEXPR counting_iterator() : count_(0) {}
 
-  iterator operator()(char_type value) {
-    internal::handle_char_specs(
-        specs_, char_spec_handler(*this, static_cast<char_type>(value)));
-    return out();
-  }
+  FMT_CONSTEXPR auto count() const -> size_t { return count_; }
 
-  iterator operator()(bool value) {
-    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
-    write(value != 0);
-    return out();
+  FMT_CONSTEXPR auto operator++() -> counting_iterator& {
+    ++count_;
+    return *this;
   }
-
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value) {
-    if (const_check(is_supported_floating_point(value)))
-      writer_.write(value, specs_ ? *specs_ : format_specs());
-    else
-      FMT_ASSERT(false, "unsupported float argument type");
-    return out();
+  FMT_CONSTEXPR auto operator++(int) -> counting_iterator {
+    auto it = *this;
+    ++*this;
+    return it;
   }
 
-  struct char_spec_handler : ErrorHandler {
-    arg_formatter_base& formatter;
-    char_type value;
-
-    char_spec_handler(arg_formatter_base& f, char_type val)
-        : formatter(f), value(val) {}
-
-    void on_int() {
-      if (formatter.specs_)
-        formatter.writer_.write_int(value, *formatter.specs_);
-      else
-        formatter.writer_.write(value);
-    }
-    void on_char() { formatter.write_char(value); }
-  };
-
-  struct cstring_spec_handler : internal::error_handler {
-    arg_formatter_base& formatter;
-    const char_type* value;
-
-    cstring_spec_handler(arg_formatter_base& f, const char_type* val)
-        : formatter(f), value(val) {}
-
-    void on_string() { formatter.write(value); }
-    void on_pointer() { formatter.write_pointer(value); }
-  };
-
-  iterator operator()(const char_type* value) {
-    if (!specs_) return write(value), out();
-    internal::handle_cstring_type_spec(specs_->type,
-                                       cstring_spec_handler(*this, value));
-    return out();
+  FMT_CONSTEXPR friend auto operator+(counting_iterator it, difference_type n)
+      -> counting_iterator {
+    it.count_ += static_cast<size_t>(n);
+    return it;
   }
 
-  iterator operator()(basic_string_view<char_type> value) {
-    if (specs_) {
-      internal::check_string_type_spec(specs_->type, internal::error_handler());
-      writer_.write(value, *specs_);
-    } else {
-      writer_.write(value);
-    }
-    return out();
-  }
+  FMT_CONSTEXPR auto operator*() const -> value_type { return {}; }
+};
 
-  iterator operator()(const void* value) {
-    if (specs_)
-      check_pointer_type_spec(specs_->type, internal::error_handler());
-    write_pointer(value);
-    return out();
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> s,
+                         const format_specs<Char>& specs) -> OutputIt {
+  auto data = s.data();
+  auto size = s.size();
+  if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
+    size = code_point_index(s, to_unsigned(specs.precision));
+  bool is_debug = specs.type == presentation_type::debug;
+  size_t width = 0;
+  if (specs.width != 0) {
+    if (is_debug)
+      width = write_escaped_string(counting_iterator{}, s).count();
+    else
+      width = compute_width(basic_string_view<Char>(data, size));
   }
-};
+  return write_padded(out, specs, size, width,
+                      [=](reserve_iterator<OutputIt> it) {
+                        if (is_debug) return write_escaped_string(it, s);
+                        return copy_str<Char>(data, data + size, it);
+                      });
+}
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out,
+                         basic_string_view<type_identity_t<Char>> s,
+                         const format_specs<Char>& specs, locale_ref)
+    -> OutputIt {
+  return write(out, s, specs);
+}
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, const Char* s,
+                         const format_specs<Char>& specs, locale_ref)
+    -> OutputIt {
+  if (specs.type == presentation_type::pointer)
+    return write_ptr<Char>(out, bit_cast<uintptr_t>(s), &specs);
+  if (!s) throw_format_error("string pointer is null");
+  return write(out, basic_string_view<Char>(s), specs, {});
+}
 
-template <typename Char> FMT_CONSTEXPR bool is_name_start(Char c) {
-  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || '_' == c;
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<T, Char>::value)>
+FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
+  auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
+  bool negative = is_negative(value);
+  // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
+  if (negative) abs_value = ~abs_value + 1;
+  int num_digits = count_digits(abs_value);
+  auto size = (negative ? 1 : 0) + static_cast<size_t>(num_digits);
+  auto it = reserve(out, size);
+  if (auto ptr = to_pointer<Char>(it, size)) {
+    if (negative) *ptr++ = static_cast<Char>('-');
+    format_decimal<Char>(ptr, abs_value, num_digits);
+    return out;
+  }
+  if (negative) *it++ = static_cast<Char>('-');
+  it = format_decimal<Char>(it, abs_value, num_digits).end;
+  return base_iterator(out, it);
 }
 
-// Parses the range [begin, end) as an unsigned integer. This function assumes
-// that the range is non-empty and the first character is a digit.
-template <typename Char, typename ErrorHandler>
-FMT_CONSTEXPR int parse_nonnegative_int(const Char*& begin, const Char* end,
-                                        ErrorHandler&& eh) {
-  FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
-  unsigned value = 0;
-  // Convert to unsigned to prevent a warning.
-  constexpr unsigned max_int = max_value<int>();
-  unsigned big = max_int / 10;
-  do {
-    // Check for overflow.
-    if (value > big) {
-      value = max_int + 1;
+// DEPRECATED!
+template <typename Char>
+FMT_CONSTEXPR auto parse_align(const Char* begin, const Char* end,
+                               format_specs<Char>& specs) -> const Char* {
+  FMT_ASSERT(begin != end, "");
+  auto align = align::none;
+  auto p = begin + code_point_length(begin);
+  if (end - p <= 0) p = begin;
+  for (;;) {
+    switch (to_ascii(*p)) {
+    case '<':
+      align = align::left;
+      break;
+    case '>':
+      align = align::right;
+      break;
+    case '^':
+      align = align::center;
       break;
     }
-    value = value * 10 + unsigned(*begin - '0');
-    ++begin;
-  } while (begin != end && '0' <= *begin && *begin <= '9');
-  if (value > max_int) eh.on_error("number is too big");
-  return static_cast<int>(value);
-}
-
-template <typename Context> class custom_formatter {
- private:
-  using char_type = typename Context::char_type;
-
-  basic_format_parse_context<char_type>& parse_ctx_;
-  Context& ctx_;
-
- public:
-  explicit custom_formatter(basic_format_parse_context<char_type>& parse_ctx,
-                            Context& ctx)
-      : parse_ctx_(parse_ctx), ctx_(ctx) {}
-
-  bool operator()(typename basic_format_arg<Context>::handle h) const {
-    h.format(parse_ctx_, ctx_);
-    return true;
+    if (align != align::none) {
+      if (p != begin) {
+        auto c = *begin;
+        if (c == '}') return begin;
+        if (c == '{') {
+          throw_format_error("invalid fill character '{'");
+          return begin;
+        }
+        specs.fill = {begin, to_unsigned(p - begin)};
+        begin = p + 1;
+      } else {
+        ++begin;
+      }
+      break;
+    } else if (p == begin) {
+      break;
+    }
+    p = begin;
   }
+  specs.align = align;
+  return begin;
+}
 
-  template <typename T> bool operator()(T) const { return false; }
+// A floating-point presentation format.
+enum class float_format : unsigned char {
+  general,  // General: exponent notation or fixed point based on magnitude.
+  exp,      // Exponent notation with the default precision of 6, e.g. 1.2e-3.
+  fixed,    // Fixed point with the default precision of 6, e.g. 0.0012.
+  hex
 };
 
-template <typename T>
-using is_integer =
-    bool_constant<is_integral<T>::value && !std::is_same<T, bool>::value &&
-                  !std::is_same<T, char>::value &&
-                  !std::is_same<T, wchar_t>::value>;
-
-template <typename ErrorHandler> class width_checker {
- public:
-  explicit FMT_CONSTEXPR width_checker(ErrorHandler& eh) : handler_(eh) {}
-
-  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
-  FMT_CONSTEXPR unsigned long long operator()(T value) {
-    if (is_negative(value)) handler_.on_error("negative width");
-    return static_cast<unsigned long long>(value);
-  }
-
-  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
-  FMT_CONSTEXPR unsigned long long operator()(T) {
-    handler_.on_error("width is not integer");
-    return 0;
-  }
-
- private:
-  ErrorHandler& handler_;
+struct float_specs {
+  int precision;
+  float_format format : 8;
+  sign_t sign : 8;
+  bool upper : 1;
+  bool locale : 1;
+  bool binary32 : 1;
+  bool showpoint : 1;
 };
 
-template <typename ErrorHandler> class precision_checker {
- public:
-  explicit FMT_CONSTEXPR precision_checker(ErrorHandler& eh) : handler_(eh) {}
-
-  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
-  FMT_CONSTEXPR unsigned long long operator()(T value) {
-    if (is_negative(value)) handler_.on_error("negative precision");
-    return static_cast<unsigned long long>(value);
+template <typename Char>
+FMT_CONSTEXPR auto parse_float_type_spec(const format_specs<Char>& specs)
+    -> float_specs {
+  auto result = float_specs();
+  result.showpoint = specs.alt;
+  result.locale = specs.localized;
+  switch (specs.type) {
+  case presentation_type::none:
+    result.format = float_format::general;
+    break;
+  case presentation_type::general_upper:
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case presentation_type::general_lower:
+    result.format = float_format::general;
+    break;
+  case presentation_type::exp_upper:
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case presentation_type::exp_lower:
+    result.format = float_format::exp;
+    result.showpoint |= specs.precision != 0;
+    break;
+  case presentation_type::fixed_upper:
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case presentation_type::fixed_lower:
+    result.format = float_format::fixed;
+    result.showpoint |= specs.precision != 0;
+    break;
+  case presentation_type::hexfloat_upper:
+    result.upper = true;
+    FMT_FALLTHROUGH;
+  case presentation_type::hexfloat_lower:
+    result.format = float_format::hex;
+    break;
+  default:
+    throw_format_error("invalid format specifier");
+    break;
   }
+  return result;
+}
 
-  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
-  FMT_CONSTEXPR unsigned long long operator()(T) {
-    handler_.on_error("precision is not integer");
-    return 0;
-  }
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR20 auto write_nonfinite(OutputIt out, bool isnan,
+                                     format_specs<Char> specs,
+                                     const float_specs& fspecs) -> OutputIt {
+  auto str =
+      isnan ? (fspecs.upper ? "NAN" : "nan") : (fspecs.upper ? "INF" : "inf");
+  constexpr size_t str_size = 3;
+  auto sign = fspecs.sign;
+  auto size = str_size + (sign ? 1 : 0);
+  // Replace '0'-padding with space for non-finite values.
+  const bool is_zero_fill =
+      specs.fill.size() == 1 && *specs.fill.data() == static_cast<Char>('0');
+  if (is_zero_fill) specs.fill[0] = static_cast<Char>(' ');
+  return write_padded(out, specs, size, [=](reserve_iterator<OutputIt> it) {
+    if (sign) *it++ = detail::sign<Char>(sign);
+    return copy_str<Char>(str, str + str_size, it);
+  });
+}
 
- private:
-  ErrorHandler& handler_;
+// A decimal floating-point number significand * pow(10, exp).
+struct big_decimal_fp {
+  const char* significand;
+  int significand_size;
+  int exponent;
 };
 
-// A format specifier handler that sets fields in basic_format_specs.
-template <typename Char> class specs_setter {
- public:
-  explicit FMT_CONSTEXPR specs_setter(basic_format_specs<Char>& specs)
-      : specs_(specs) {}
+constexpr auto get_significand_size(const big_decimal_fp& f) -> int {
+  return f.significand_size;
+}
+template <typename T>
+inline auto get_significand_size(const dragonbox::decimal_fp<T>& f) -> int {
+  return count_digits(f.significand);
+}
 
-  FMT_CONSTEXPR specs_setter(const specs_setter& other)
-      : specs_(other.specs_) {}
+template <typename Char, typename OutputIt>
+constexpr auto write_significand(OutputIt out, const char* significand,
+                                 int significand_size) -> OutputIt {
+  return copy_str<Char>(significand, significand + significand_size, out);
+}
+template <typename Char, typename OutputIt, typename UInt>
+inline auto write_significand(OutputIt out, UInt significand,
+                              int significand_size) -> OutputIt {
+  return format_decimal<Char>(out, significand, significand_size).end;
+}
+template <typename Char, typename OutputIt, typename T, typename Grouping>
+FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
+                                       int significand_size, int exponent,
+                                       const Grouping& grouping) -> OutputIt {
+  if (!grouping.has_separator()) {
+    out = write_significand<Char>(out, significand, significand_size);
+    return detail::fill_n(out, exponent, static_cast<Char>('0'));
+  }
+  auto buffer = memory_buffer();
+  write_significand<char>(appender(buffer), significand, significand_size);
+  detail::fill_n(appender(buffer), exponent, '0');
+  return grouping.apply(out, string_view(buffer.data(), buffer.size()));
+}
 
-  FMT_CONSTEXPR void on_align(align_t align) { specs_.align = align; }
-  FMT_CONSTEXPR void on_fill(basic_string_view<Char> fill) {
-    specs_.fill = fill;
-  }
-  FMT_CONSTEXPR void on_plus() { specs_.sign = sign::plus; }
-  FMT_CONSTEXPR void on_minus() { specs_.sign = sign::minus; }
-  FMT_CONSTEXPR void on_space() { specs_.sign = sign::space; }
-  FMT_CONSTEXPR void on_hash() { specs_.alt = true; }
+template <typename Char, typename UInt,
+          FMT_ENABLE_IF(std::is_integral<UInt>::value)>
+inline auto write_significand(Char* out, UInt significand, int significand_size,
+                              int integral_size, Char decimal_point) -> Char* {
+  if (!decimal_point)
+    return format_decimal(out, significand, significand_size).end;
+  out += significand_size + 1;
+  Char* end = out;
+  int floating_size = significand_size - integral_size;
+  for (int i = floating_size / 2; i > 0; --i) {
+    out -= 2;
+    copy2(out, digits2(static_cast<std::size_t>(significand % 100)));
+    significand /= 100;
+  }
+  if (floating_size % 2 != 0) {
+    *--out = static_cast<Char>('0' + significand % 10);
+    significand /= 10;
+  }
+  *--out = decimal_point;
+  format_decimal(out - integral_size, significand, integral_size);
+  return end;
+}
 
-  FMT_CONSTEXPR void on_zero() {
-    specs_.align = align::numeric;
-    specs_.fill[0] = Char('0');
-  }
+template <typename OutputIt, typename UInt, typename Char,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<OutputIt>>::value)>
+inline auto write_significand(OutputIt out, UInt significand,
+                              int significand_size, int integral_size,
+                              Char decimal_point) -> OutputIt {
+  // Buffer is large enough to hold digits (digits10 + 1) and a decimal point.
+  Char buffer[digits10<UInt>() + 2];
+  auto end = write_significand(buffer, significand, significand_size,
+                               integral_size, decimal_point);
+  return detail::copy_str_noinline<Char>(buffer, end, out);
+}
 
-  FMT_CONSTEXPR void on_width(int width) { specs_.width = width; }
-  FMT_CONSTEXPR void on_precision(int precision) {
-    specs_.precision = precision;
-  }
-  FMT_CONSTEXPR void end_precision() {}
+template <typename OutputIt, typename Char>
+FMT_CONSTEXPR auto write_significand(OutputIt out, const char* significand,
+                                     int significand_size, int integral_size,
+                                     Char decimal_point) -> OutputIt {
+  out = detail::copy_str_noinline<Char>(significand,
+                                        significand + integral_size, out);
+  if (!decimal_point) return out;
+  *out++ = decimal_point;
+  return detail::copy_str_noinline<Char>(significand + integral_size,
+                                         significand + significand_size, out);
+}
 
-  FMT_CONSTEXPR void on_type(Char type) {
-    specs_.type = static_cast<char>(type);
-  }
+template <typename OutputIt, typename Char, typename T, typename Grouping>
+FMT_CONSTEXPR20 auto write_significand(OutputIt out, T significand,
+                                       int significand_size, int integral_size,
+                                       Char decimal_point,
+                                       const Grouping& grouping) -> OutputIt {
+  if (!grouping.has_separator()) {
+    return write_significand(out, significand, significand_size, integral_size,
+                             decimal_point);
+  }
+  auto buffer = basic_memory_buffer<Char>();
+  write_significand(buffer_appender<Char>(buffer), significand,
+                    significand_size, integral_size, decimal_point);
+  grouping.apply(
+      out, basic_string_view<Char>(buffer.data(), to_unsigned(integral_size)));
+  return detail::copy_str_noinline<Char>(buffer.data() + integral_size,
+                                         buffer.end(), out);
+}
 
- protected:
-  basic_format_specs<Char>& specs_;
-};
+template <typename OutputIt, typename DecimalFP, typename Char,
+          typename Grouping = digit_grouping<Char>>
+FMT_CONSTEXPR20 auto do_write_float(OutputIt out, const DecimalFP& f,
+                                    const format_specs<Char>& specs,
+                                    float_specs fspecs, locale_ref loc)
+    -> OutputIt {
+  auto significand = f.significand;
+  int significand_size = get_significand_size(f);
+  const Char zero = static_cast<Char>('0');
+  auto sign = fspecs.sign;
+  size_t size = to_unsigned(significand_size) + (sign ? 1 : 0);
+  using iterator = reserve_iterator<OutputIt>;
+
+  Char decimal_point =
+      fspecs.locale ? detail::decimal_point<Char>(loc) : static_cast<Char>('.');
+
+  int output_exp = f.exponent + significand_size - 1;
+  auto use_exp_format = [=]() {
+    if (fspecs.format == float_format::exp) return true;
+    if (fspecs.format != float_format::general) return false;
+    // Use the fixed notation if the exponent is in [exp_lower, exp_upper),
+    // e.g. 0.0001 instead of 1e-04. Otherwise use the exponent notation.
+    const int exp_lower = -4, exp_upper = 16;
+    return output_exp < exp_lower ||
+           output_exp >= (fspecs.precision > 0 ? fspecs.precision : exp_upper);
+  };
+  if (use_exp_format()) {
+    int num_zeros = 0;
+    if (fspecs.showpoint) {
+      num_zeros = fspecs.precision - significand_size;
+      if (num_zeros < 0) num_zeros = 0;
+      size += to_unsigned(num_zeros);
+    } else if (significand_size == 1) {
+      decimal_point = Char();
+    }
+    auto abs_output_exp = output_exp >= 0 ? output_exp : -output_exp;
+    int exp_digits = 2;
+    if (abs_output_exp >= 100) exp_digits = abs_output_exp >= 1000 ? 4 : 3;
+
+    size += to_unsigned((decimal_point ? 1 : 0) + 2 + exp_digits);
+    char exp_char = fspecs.upper ? 'E' : 'e';
+    auto write = [=](iterator it) {
+      if (sign) *it++ = detail::sign<Char>(sign);
+      // Insert a decimal point after the first digit and add an exponent.
+      it = write_significand(it, significand, significand_size, 1,
+                             decimal_point);
+      if (num_zeros > 0) it = detail::fill_n(it, num_zeros, zero);
+      *it++ = static_cast<Char>(exp_char);
+      return write_exponent<Char>(output_exp, it);
+    };
+    return specs.width > 0 ? write_padded<align::right>(out, specs, size, write)
+                           : base_iterator(out, write(reserve(out, size)));
+  }
+
+  int exp = f.exponent + significand_size;
+  if (f.exponent >= 0) {
+    // 1234e5 -> 123400000[.0+]
+    size += to_unsigned(f.exponent);
+    int num_zeros = fspecs.precision - exp;
+    abort_fuzzing_if(num_zeros > 5000);
+    if (fspecs.showpoint) {
+      ++size;
+      if (num_zeros <= 0 && fspecs.format != float_format::fixed) num_zeros = 0;
+      if (num_zeros > 0) size += to_unsigned(num_zeros);
+    }
+    auto grouping = Grouping(loc, fspecs.locale);
+    size += to_unsigned(grouping.count_separators(exp));
+    return write_padded<align::right>(out, specs, size, [&](iterator it) {
+      if (sign) *it++ = detail::sign<Char>(sign);
+      it = write_significand<Char>(it, significand, significand_size,
+                                   f.exponent, grouping);
+      if (!fspecs.showpoint) return it;
+      *it++ = decimal_point;
+      return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it;
+    });
+  } else if (exp > 0) {
+    // 1234e-2 -> 12.34[0+]
+    int num_zeros = fspecs.showpoint ? fspecs.precision - significand_size : 0;
+    size += 1 + to_unsigned(num_zeros > 0 ? num_zeros : 0);
+    auto grouping = Grouping(loc, fspecs.locale);
+    size += to_unsigned(grouping.count_separators(exp));
+    return write_padded<align::right>(out, specs, size, [&](iterator it) {
+      if (sign) *it++ = detail::sign<Char>(sign);
+      it = write_significand(it, significand, significand_size, exp,
+                             decimal_point, grouping);
+      return num_zeros > 0 ? detail::fill_n(it, num_zeros, zero) : it;
+    });
+  }
+  // 1234e-6 -> 0.001234
+  int num_zeros = -exp;
+  if (significand_size == 0 && fspecs.precision >= 0 &&
+      fspecs.precision < num_zeros) {
+    num_zeros = fspecs.precision;
+  }
+  bool pointy = num_zeros != 0 || significand_size != 0 || fspecs.showpoint;
+  size += 1 + (pointy ? 1 : 0) + to_unsigned(num_zeros);
+  return write_padded<align::right>(out, specs, size, [&](iterator it) {
+    if (sign) *it++ = detail::sign<Char>(sign);
+    *it++ = zero;
+    if (!pointy) return it;
+    *it++ = decimal_point;
+    it = detail::fill_n(it, num_zeros, zero);
+    return write_significand<Char>(it, significand, significand_size);
+  });
+}
 
-template <typename ErrorHandler> class numeric_specs_checker {
+template <typename Char> class fallback_digit_grouping {
  public:
-  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, internal::type arg_type)
-      : error_handler_(eh), arg_type_(arg_type) {}
+  constexpr fallback_digit_grouping(locale_ref, bool) {}
 
-  FMT_CONSTEXPR void require_numeric_argument() {
-    if (!is_arithmetic_type(arg_type_))
-      error_handler_.on_error("format specifier requires numeric argument");
-  }
+  constexpr auto has_separator() const -> bool { return false; }
 
-  FMT_CONSTEXPR void check_sign() {
-    require_numeric_argument();
-    if (is_integral_type(arg_type_) && arg_type_ != type::int_type &&
-        arg_type_ != type::long_long_type && arg_type_ != type::char_type) {
-      error_handler_.on_error("format specifier requires signed argument");
-    }
-  }
+  constexpr auto count_separators(int) const -> int { return 0; }
 
-  FMT_CONSTEXPR void check_precision() {
-    if (is_integral_type(arg_type_) || arg_type_ == type::pointer_type)
-      error_handler_.on_error("precision not allowed for this argument type");
+  template <typename Out, typename C>
+  constexpr auto apply(Out out, basic_string_view<C>) const -> Out {
+    return out;
   }
-
- private:
-  ErrorHandler& error_handler_;
-  internal::type arg_type_;
 };
 
-// A format specifier handler that checks if specifiers are consistent with the
-// argument type.
-template <typename Handler> class specs_checker : public Handler {
- public:
-  FMT_CONSTEXPR specs_checker(const Handler& handler, internal::type arg_type)
-      : Handler(handler), checker_(*this, arg_type) {}
-
-  FMT_CONSTEXPR specs_checker(const specs_checker& other)
-      : Handler(other), checker_(*this, other.arg_type_) {}
-
-  FMT_CONSTEXPR void on_align(align_t align) {
-    if (align == align::numeric) checker_.require_numeric_argument();
-    Handler::on_align(align);
-  }
-
-  FMT_CONSTEXPR void on_plus() {
-    checker_.check_sign();
-    Handler::on_plus();
+template <typename OutputIt, typename DecimalFP, typename Char>
+FMT_CONSTEXPR20 auto write_float(OutputIt out, const DecimalFP& f,
+                                 const format_specs<Char>& specs,
+                                 float_specs fspecs, locale_ref loc)
+    -> OutputIt {
+  if (is_constant_evaluated()) {
+    return do_write_float<OutputIt, DecimalFP, Char,
+                          fallback_digit_grouping<Char>>(out, f, specs, fspecs,
+                                                         loc);
+  } else {
+    return do_write_float(out, f, specs, fspecs, loc);
   }
+}
 
-  FMT_CONSTEXPR void on_minus() {
-    checker_.check_sign();
-    Handler::on_minus();
-  }
+template <typename T> constexpr auto isnan(T value) -> bool {
+  return !(value >= value);  // std::isnan doesn't support __float128.
+}
 
-  FMT_CONSTEXPR void on_space() {
-    checker_.check_sign();
-    Handler::on_space();
-  }
+template <typename T, typename Enable = void>
+struct has_isfinite : std::false_type {};
 
-  FMT_CONSTEXPR void on_hash() {
-    checker_.require_numeric_argument();
-    Handler::on_hash();
-  }
+template <typename T>
+struct has_isfinite<T, enable_if_t<sizeof(std::isfinite(T())) != 0>>
+    : std::true_type {};
+
+template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value&&
+                                        has_isfinite<T>::value)>
+FMT_CONSTEXPR20 auto isfinite(T value) -> bool {
+  constexpr T inf = T(std::numeric_limits<double>::infinity());
+  if (is_constant_evaluated())
+    return !detail::isnan(value) && value < inf && value > -inf;
+  return std::isfinite(value);
+}
+template <typename T, FMT_ENABLE_IF(!has_isfinite<T>::value)>
+FMT_CONSTEXPR auto isfinite(T value) -> bool {
+  T inf = T(std::numeric_limits<double>::infinity());
+  // std::isfinite doesn't support __float128.
+  return !detail::isnan(value) && value < inf && value > -inf;
+}
 
-  FMT_CONSTEXPR void on_zero() {
-    checker_.require_numeric_argument();
-    Handler::on_zero();
+template <typename T, FMT_ENABLE_IF(is_floating_point<T>::value)>
+FMT_INLINE FMT_CONSTEXPR bool signbit(T value) {
+  if (is_constant_evaluated()) {
+#ifdef __cpp_if_constexpr
+    if constexpr (std::numeric_limits<double>::is_iec559) {
+      auto bits = detail::bit_cast<uint64_t>(static_cast<double>(value));
+      return (bits >> (num_bits<uint64_t>() - 1)) != 0;
+    }
+#endif
   }
-
-  FMT_CONSTEXPR void end_precision() { checker_.check_precision(); }
-
- private:
-  numeric_specs_checker<Handler> checker_;
-};
-
-template <template <typename> class Handler, typename FormatArg,
-          typename ErrorHandler>
-FMT_CONSTEXPR int get_dynamic_spec(FormatArg arg, ErrorHandler eh) {
-  unsigned long long value = visit_format_arg(Handler<ErrorHandler>(eh), arg);
-  if (value > to_unsigned(max_value<int>())) eh.on_error("number is too big");
-  return static_cast<int>(value);
+  return std::signbit(static_cast<double>(value));
 }
 
-struct auto_id {};
-
-template <typename Context>
-FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, int id) {
-  auto arg = ctx.arg(id);
-  if (!arg) ctx.on_error("argument index out of range");
-  return arg;
+inline FMT_CONSTEXPR20 void adjust_precision(int& precision, int exp10) {
+  // Adjust fixed precision by exponent because it is relative to decimal
+  // point.
+  if (exp10 > 0 && precision > max_value<int>() - exp10)
+    FMT_THROW(format_error("number is too big"));
+  precision += exp10;
 }
 
-// The standard format specifier handler with checking.
-template <typename ParseContext, typename Context>
-class specs_handler : public specs_setter<typename Context::char_type> {
- public:
-  using char_type = typename Context::char_type;
-
-  FMT_CONSTEXPR specs_handler(basic_format_specs<char_type>& specs,
-                              ParseContext& parse_ctx, Context& ctx)
-      : specs_setter<char_type>(specs),
-        parse_context_(parse_ctx),
-        context_(ctx) {}
+class bigint {
+ private:
+  // A bigint is stored as an array of bigits (big digits), with bigit at index
+  // 0 being the least significant one.
+  using bigit = uint32_t;
+  using double_bigit = uint64_t;
+  enum { bigits_capacity = 32 };
+  basic_memory_buffer<bigit, bigits_capacity> bigits_;
+  int exp_;
 
-  template <typename Id> FMT_CONSTEXPR void on_dynamic_width(Id arg_id) {
-    this->specs_.width = get_dynamic_spec<width_checker>(
-        get_arg(arg_id), context_.error_handler());
+  FMT_CONSTEXPR20 auto operator[](int index) const -> bigit {
+    return bigits_[to_unsigned(index)];
   }
-
-  template <typename Id> FMT_CONSTEXPR void on_dynamic_precision(Id arg_id) {
-    this->specs_.precision = get_dynamic_spec<precision_checker>(
-        get_arg(arg_id), context_.error_handler());
+  FMT_CONSTEXPR20 auto operator[](int index) -> bigit& {
+    return bigits_[to_unsigned(index)];
   }
 
-  void on_error(const char* message) { context_.on_error(message); }
+  static constexpr const int bigit_bits = num_bits<bigit>();
 
- private:
-  // This is only needed for compatibility with gcc 4.4.
-  using format_arg = typename Context::format_arg;
+  friend struct formatter<bigint>;
 
-  FMT_CONSTEXPR format_arg get_arg(auto_id) {
-    return internal::get_arg(context_, parse_context_.next_arg_id());
+  FMT_CONSTEXPR20 void subtract_bigits(int index, bigit other, bigit& borrow) {
+    auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
+    (*this)[index] = static_cast<bigit>(result);
+    borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
   }
 
-  FMT_CONSTEXPR format_arg get_arg(int arg_id) {
-    parse_context_.check_arg_id(arg_id);
-    return internal::get_arg(context_, arg_id);
+  FMT_CONSTEXPR20 void remove_leading_zeros() {
+    int num_bigits = static_cast<int>(bigits_.size()) - 1;
+    while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
+    bigits_.resize(to_unsigned(num_bigits + 1));
   }
 
-  FMT_CONSTEXPR format_arg get_arg(basic_string_view<char_type> arg_id) {
-    parse_context_.check_arg_id(arg_id);
-    return context_.arg(arg_id);
+  // Computes *this -= other assuming aligned bigints and *this >= other.
+  FMT_CONSTEXPR20 void subtract_aligned(const bigint& other) {
+    FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
+    FMT_ASSERT(compare(*this, other) >= 0, "");
+    bigit borrow = 0;
+    int i = other.exp_ - exp_;
+    for (size_t j = 0, n = other.bigits_.size(); j != n; ++i, ++j)
+      subtract_bigits(i, other.bigits_[j], borrow);
+    while (borrow > 0) subtract_bigits(i, 0, borrow);
+    remove_leading_zeros();
   }
 
-  ParseContext& parse_context_;
-  Context& context_;
-};
-
-enum class arg_id_kind { none, index, name };
-
-// An argument reference.
-template <typename Char> struct arg_ref {
-  FMT_CONSTEXPR arg_ref() : kind(arg_id_kind::none), val() {}
-
-  FMT_CONSTEXPR explicit arg_ref(int index)
-      : kind(arg_id_kind::index), val(index) {}
-  FMT_CONSTEXPR explicit arg_ref(basic_string_view<Char> name)
-      : kind(arg_id_kind::name), val(name) {}
-
-  FMT_CONSTEXPR arg_ref& operator=(int idx) {
-    kind = arg_id_kind::index;
-    val.index = idx;
-    return *this;
+  FMT_CONSTEXPR20 void multiply(uint32_t value) {
+    const double_bigit wide_value = value;
+    bigit carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      double_bigit result = bigits_[i] * wide_value + carry;
+      bigits_[i] = static_cast<bigit>(result);
+      carry = static_cast<bigit>(result >> bigit_bits);
+    }
+    if (carry != 0) bigits_.push_back(carry);
+  }
+
+  template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
+                                         std::is_same<UInt, uint128_t>::value)>
+  FMT_CONSTEXPR20 void multiply(UInt value) {
+    using half_uint =
+        conditional_t<std::is_same<UInt, uint128_t>::value, uint64_t, uint32_t>;
+    const int shift = num_bits<half_uint>() - bigit_bits;
+    const UInt lower = static_cast<half_uint>(value);
+    const UInt upper = value >> num_bits<half_uint>();
+    UInt carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      UInt result = lower * bigits_[i] + static_cast<bigit>(carry);
+      carry = (upper * bigits_[i] << shift) + (result >> bigit_bits) +
+              (carry >> bigit_bits);
+      bigits_[i] = static_cast<bigit>(result);
+    }
+    while (carry != 0) {
+      bigits_.push_back(static_cast<bigit>(carry));
+      carry >>= bigit_bits;
+    }
   }
 
-  arg_id_kind kind;
-  union value {
-    FMT_CONSTEXPR value(int id = 0) : index{id} {}
-    FMT_CONSTEXPR value(basic_string_view<Char> n) : name(n) {}
-
-    int index;
-    basic_string_view<Char> name;
-  } val;
-};
-
-// Format specifiers with width and precision resolved at formatting rather
-// than parsing time to allow re-using the same parsed specifiers with
-// different sets of arguments (precompilation of format strings).
-template <typename Char>
-struct dynamic_format_specs : basic_format_specs<Char> {
-  arg_ref<Char> width_ref;
-  arg_ref<Char> precision_ref;
-};
+  template <typename UInt, FMT_ENABLE_IF(std::is_same<UInt, uint64_t>::value ||
+                                         std::is_same<UInt, uint128_t>::value)>
+  FMT_CONSTEXPR20 void assign(UInt n) {
+    size_t num_bigits = 0;
+    do {
+      bigits_[num_bigits++] = static_cast<bigit>(n);
+      n >>= bigit_bits;
+    } while (n != 0);
+    bigits_.resize(num_bigits);
+    exp_ = 0;
+  }
 
-// Format spec handler that saves references to arguments representing dynamic
-// width and precision to be resolved at formatting time.
-template <typename ParseContext>
-class dynamic_specs_handler
-    : public specs_setter<typename ParseContext::char_type> {
  public:
-  using char_type = typename ParseContext::char_type;
+  FMT_CONSTEXPR20 bigint() : exp_(0) {}
+  explicit bigint(uint64_t n) { assign(n); }
 
-  FMT_CONSTEXPR dynamic_specs_handler(dynamic_format_specs<char_type>& specs,
-                                      ParseContext& ctx)
-      : specs_setter<char_type>(specs), specs_(specs), context_(ctx) {}
+  bigint(const bigint&) = delete;
+  void operator=(const bigint&) = delete;
 
-  FMT_CONSTEXPR dynamic_specs_handler(const dynamic_specs_handler& other)
-      : specs_setter<char_type>(other),
-        specs_(other.specs_),
-        context_(other.context_) {}
-
-  template <typename Id> FMT_CONSTEXPR void on_dynamic_width(Id arg_id) {
-    specs_.width_ref = make_arg_ref(arg_id);
+  FMT_CONSTEXPR20 void assign(const bigint& other) {
+    auto size = other.bigits_.size();
+    bigits_.resize(size);
+    auto data = other.bigits_.data();
+    copy_str<bigit>(data, data + size, bigits_.data());
+    exp_ = other.exp_;
   }
 
-  template <typename Id> FMT_CONSTEXPR void on_dynamic_precision(Id arg_id) {
-    specs_.precision_ref = make_arg_ref(arg_id);
+  template <typename Int> FMT_CONSTEXPR20 void operator=(Int n) {
+    FMT_ASSERT(n > 0, "");
+    assign(uint64_or_128_t<Int>(n));
   }
 
-  FMT_CONSTEXPR void on_error(const char* message) {
-    context_.on_error(message);
+  FMT_CONSTEXPR20 auto num_bigits() const -> int {
+    return static_cast<int>(bigits_.size()) + exp_;
   }
 
- private:
-  using arg_ref_type = arg_ref<char_type>;
+  FMT_NOINLINE FMT_CONSTEXPR20 auto operator<<=(int shift) -> bigint& {
+    FMT_ASSERT(shift >= 0, "");
+    exp_ += shift / bigit_bits;
+    shift %= bigit_bits;
+    if (shift == 0) return *this;
+    bigit carry = 0;
+    for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
+      bigit c = bigits_[i] >> (bigit_bits - shift);
+      bigits_[i] = (bigits_[i] << shift) + carry;
+      carry = c;
+    }
+    if (carry != 0) bigits_.push_back(carry);
+    return *this;
+  }
 
-  FMT_CONSTEXPR arg_ref_type make_arg_ref(int arg_id) {
-    context_.check_arg_id(arg_id);
-    return arg_ref_type(arg_id);
+  template <typename Int>
+  FMT_CONSTEXPR20 auto operator*=(Int value) -> bigint& {
+    FMT_ASSERT(value > 0, "");
+    multiply(uint32_or_64_or_128_t<Int>(value));
+    return *this;
   }
 
-  FMT_CONSTEXPR arg_ref_type make_arg_ref(auto_id) {
-    return arg_ref_type(context_.next_arg_id());
+  friend FMT_CONSTEXPR20 auto compare(const bigint& lhs, const bigint& rhs)
+      -> int {
+    int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
+    if (num_lhs_bigits != num_rhs_bigits)
+      return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
+    int i = static_cast<int>(lhs.bigits_.size()) - 1;
+    int j = static_cast<int>(rhs.bigits_.size()) - 1;
+    int end = i - j;
+    if (end < 0) end = 0;
+    for (; i >= end; --i, --j) {
+      bigit lhs_bigit = lhs[i], rhs_bigit = rhs[j];
+      if (lhs_bigit != rhs_bigit) return lhs_bigit > rhs_bigit ? 1 : -1;
+    }
+    if (i != j) return i > j ? 1 : -1;
+    return 0;
   }
 
-  FMT_CONSTEXPR arg_ref_type make_arg_ref(basic_string_view<char_type> arg_id) {
-    context_.check_arg_id(arg_id);
-    basic_string_view<char_type> format_str(
-        context_.begin(), to_unsigned(context_.end() - context_.begin()));
-    return arg_ref_type(arg_id);
+  // Returns compare(lhs1 + lhs2, rhs).
+  friend FMT_CONSTEXPR20 auto add_compare(const bigint& lhs1,
+                                          const bigint& lhs2, const bigint& rhs)
+      -> int {
+    auto minimum = [](int a, int b) { return a < b ? a : b; };
+    auto maximum = [](int a, int b) { return a > b ? a : b; };
+    int max_lhs_bigits = maximum(lhs1.num_bigits(), lhs2.num_bigits());
+    int num_rhs_bigits = rhs.num_bigits();
+    if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
+    if (max_lhs_bigits > num_rhs_bigits) return 1;
+    auto get_bigit = [](const bigint& n, int i) -> bigit {
+      return i >= n.exp_ && i < n.num_bigits() ? n[i - n.exp_] : 0;
+    };
+    double_bigit borrow = 0;
+    int min_exp = minimum(minimum(lhs1.exp_, lhs2.exp_), rhs.exp_);
+    for (int i = num_rhs_bigits - 1; i >= min_exp; --i) {
+      double_bigit sum =
+          static_cast<double_bigit>(get_bigit(lhs1, i)) + get_bigit(lhs2, i);
+      bigit rhs_bigit = get_bigit(rhs, i);
+      if (sum > rhs_bigit + borrow) return 1;
+      borrow = rhs_bigit + borrow - sum;
+      if (borrow > 1) return -1;
+      borrow <<= bigit_bits;
+    }
+    return borrow != 0 ? -1 : 0;
+  }
+
+  // Assigns pow(10, exp) to this bigint.
+  FMT_CONSTEXPR20 void assign_pow10(int exp) {
+    FMT_ASSERT(exp >= 0, "");
+    if (exp == 0) return *this = 1;
+    // Find the top bit.
+    int bitmask = 1;
+    while (exp >= bitmask) bitmask <<= 1;
+    bitmask >>= 1;
+    // pow(10, exp) = pow(5, exp) * pow(2, exp). First compute pow(5, exp) by
+    // repeated squaring and multiplication.
+    *this = 5;
+    bitmask >>= 1;
+    while (bitmask != 0) {
+      square();
+      if ((exp & bitmask) != 0) *this *= 5;
+      bitmask >>= 1;
+    }
+    *this <<= exp;  // Multiply by pow(2, exp) by shifting.
+  }
+
+  FMT_CONSTEXPR20 void square() {
+    int num_bigits = static_cast<int>(bigits_.size());
+    int num_result_bigits = 2 * num_bigits;
+    basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
+    bigits_.resize(to_unsigned(num_result_bigits));
+    auto sum = uint128_t();
+    for (int bigit_index = 0; bigit_index < num_bigits; ++bigit_index) {
+      // Compute bigit at position bigit_index of the result by adding
+      // cross-product terms n[i] * n[j] such that i + j == bigit_index.
+      for (int i = 0, j = bigit_index; j >= 0; ++i, --j) {
+        // Most terms are multiplied twice which can be optimized in the future.
+        sum += static_cast<double_bigit>(n[i]) * n[j];
+      }
+      (*this)[bigit_index] = static_cast<bigit>(sum);
+      sum >>= num_bits<bigit>();  // Compute the carry.
+    }
+    // Do the same for the top half.
+    for (int bigit_index = num_bigits; bigit_index < num_result_bigits;
+         ++bigit_index) {
+      for (int j = num_bigits - 1, i = bigit_index - j; i < num_bigits;)
+        sum += static_cast<double_bigit>(n[i++]) * n[j--];
+      (*this)[bigit_index] = static_cast<bigit>(sum);
+      sum >>= num_bits<bigit>();
+    }
+    remove_leading_zeros();
+    exp_ *= 2;
+  }
+
+  // If this bigint has a bigger exponent than other, adds trailing zero to make
+  // exponents equal. This simplifies some operations such as subtraction.
+  FMT_CONSTEXPR20 void align(const bigint& other) {
+    int exp_difference = exp_ - other.exp_;
+    if (exp_difference <= 0) return;
+    int num_bigits = static_cast<int>(bigits_.size());
+    bigits_.resize(to_unsigned(num_bigits + exp_difference));
+    for (int i = num_bigits - 1, j = i + exp_difference; i >= 0; --i, --j)
+      bigits_[j] = bigits_[i];
+    std::uninitialized_fill_n(bigits_.data(), exp_difference, 0u);
+    exp_ -= exp_difference;
+  }
+
+  // Divides this bignum by divisor, assigning the remainder to this and
+  // returning the quotient.
+  FMT_CONSTEXPR20 auto divmod_assign(const bigint& divisor) -> int {
+    FMT_ASSERT(this != &divisor, "");
+    if (compare(*this, divisor) < 0) return 0;
+    FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
+    align(divisor);
+    int quotient = 0;
+    do {
+      subtract_aligned(divisor);
+      ++quotient;
+    } while (compare(*this, divisor) >= 0);
+    return quotient;
   }
+};
 
-  dynamic_format_specs<char_type>& specs_;
-  ParseContext& context_;
+// format_dragon flags.
+enum dragon {
+  predecessor_closer = 1,
+  fixup = 2,  // Run fixup to correct exp10 which can be off by one.
+  fixed = 4,
 };
 
-template <typename Char, typename IDHandler>
-FMT_CONSTEXPR const Char* parse_arg_id(const Char* begin, const Char* end,
-                                       IDHandler&& handler) {
-  FMT_ASSERT(begin != end, "");
-  Char c = *begin;
-  if (c == '}' || c == ':') {
-    handler();
-    return begin;
+// Formats a floating-point number using a variation of the Fixed-Precision
+// Positive Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
+// https://fmt.dev/papers/p372-steele.pdf.
+FMT_CONSTEXPR20 inline void format_dragon(basic_fp<uint128_t> value,
+                                          unsigned flags, int num_digits,
+                                          buffer<char>& buf, int& exp10) {
+  bigint numerator;    // 2 * R in (FPP)^2.
+  bigint denominator;  // 2 * S in (FPP)^2.
+  // lower and upper are differences between value and corresponding boundaries.
+  bigint lower;             // (M^- in (FPP)^2).
+  bigint upper_store;       // upper's value if different from lower.
+  bigint* upper = nullptr;  // (M^+ in (FPP)^2).
+  // Shift numerator and denominator by an extra bit or two (if lower boundary
+  // is closer) to make lower and upper integers. This eliminates multiplication
+  // by 2 during later computations.
+  bool is_predecessor_closer = (flags & dragon::predecessor_closer) != 0;
+  int shift = is_predecessor_closer ? 2 : 1;
+  if (value.e >= 0) {
+    numerator = value.f;
+    numerator <<= value.e + shift;
+    lower = 1;
+    lower <<= value.e;
+    if (is_predecessor_closer) {
+      upper_store = 1;
+      upper_store <<= value.e + 1;
+      upper = &upper_store;
+    }
+    denominator.assign_pow10(exp10);
+    denominator <<= shift;
+  } else if (exp10 < 0) {
+    numerator.assign_pow10(-exp10);
+    lower.assign(numerator);
+    if (is_predecessor_closer) {
+      upper_store.assign(numerator);
+      upper_store <<= 1;
+      upper = &upper_store;
+    }
+    numerator *= value.f;
+    numerator <<= shift;
+    denominator = 1;
+    denominator <<= shift - value.e;
+  } else {
+    numerator = value.f;
+    numerator <<= shift;
+    denominator.assign_pow10(exp10);
+    denominator <<= shift - value.e;
+    lower = 1;
+    if (is_predecessor_closer) {
+      upper_store = 1ULL << 1;
+      upper = &upper_store;
+    }
   }
-  if (c >= '0' && c <= '9') {
-    int index = 0;
-    if (c != '0')
-      index = parse_nonnegative_int(begin, end, handler);
-    else
-      ++begin;
-    if (begin == end || (*begin != '}' && *begin != ':'))
-      handler.on_error("invalid format string");
-    else
-      handler(index);
-    return begin;
+  int even = static_cast<int>((value.f & 1) == 0);
+  if (!upper) upper = &lower;
+  bool shortest = num_digits < 0;
+  if ((flags & dragon::fixup) != 0) {
+    if (add_compare(numerator, *upper, denominator) + even <= 0) {
+      --exp10;
+      numerator *= 10;
+      if (num_digits < 0) {
+        lower *= 10;
+        if (upper != &lower) *upper *= 10;
+      }
+    }
+    if ((flags & dragon::fixed) != 0) adjust_precision(num_digits, exp10 + 1);
+  }
+  // Invariant: value == (numerator / denominator) * pow(10, exp10).
+  if (shortest) {
+    // Generate the shortest representation.
+    num_digits = 0;
+    char* data = buf.data();
+    for (;;) {
+      int digit = numerator.divmod_assign(denominator);
+      bool low = compare(numerator, lower) - even < 0;  // numerator <[=] lower.
+      // numerator + upper >[=] pow10:
+      bool high = add_compare(numerator, *upper, denominator) + even > 0;
+      data[num_digits++] = static_cast<char>('0' + digit);
+      if (low || high) {
+        if (!low) {
+          ++data[num_digits - 1];
+        } else if (high) {
+          int result = add_compare(numerator, numerator, denominator);
+          // Round half to even.
+          if (result > 0 || (result == 0 && (digit % 2) != 0))
+            ++data[num_digits - 1];
+        }
+        buf.try_resize(to_unsigned(num_digits));
+        exp10 -= num_digits - 1;
+        return;
+      }
+      numerator *= 10;
+      lower *= 10;
+      if (upper != &lower) *upper *= 10;
+    }
   }
-  if (!is_name_start(c)) {
-    handler.on_error("invalid format string");
-    return begin;
+  // Generate the given number of digits.
+  exp10 -= num_digits - 1;
+  if (num_digits <= 0) {
+    denominator *= 10;
+    auto digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    buf.push_back(digit);
+    return;
+  }
+  buf.try_resize(to_unsigned(num_digits));
+  for (int i = 0; i < num_digits - 1; ++i) {
+    int digit = numerator.divmod_assign(denominator);
+    buf[i] = static_cast<char>('0' + digit);
+    numerator *= 10;
+  }
+  int digit = numerator.divmod_assign(denominator);
+  auto result = add_compare(numerator, numerator, denominator);
+  if (result > 0 || (result == 0 && (digit % 2) != 0)) {
+    if (digit == 9) {
+      const auto overflow = '0' + 10;
+      buf[num_digits - 1] = overflow;
+      // Propagate the carry.
+      for (int i = num_digits - 1; i > 0 && buf[i] == overflow; --i) {
+        buf[i] = '0';
+        ++buf[i - 1];
+      }
+      if (buf[0] == overflow) {
+        buf[0] = '1';
+        if ((flags & dragon::fixed) != 0)
+          buf.push_back('0');
+        else
+          ++exp10;
+      }
+      return;
+    }
+    ++digit;
   }
-  auto it = begin;
-  do {
-    ++it;
-  } while (it != end && (is_name_start(c = *it) || ('0' <= c && c <= '9')));
-  handler(basic_string_view<Char>(begin, to_unsigned(it - begin)));
-  return it;
+  buf[num_digits - 1] = static_cast<char>('0' + digit);
 }
 
-// Adapts SpecHandler to IDHandler API for dynamic width.
-template <typename SpecHandler, typename Char> struct width_adapter {
-  explicit FMT_CONSTEXPR width_adapter(SpecHandler& h) : handler(h) {}
+// Formats a floating-point number using the hexfloat format.
+template <typename Float, FMT_ENABLE_IF(!is_double_double<Float>::value)>
+FMT_CONSTEXPR20 void format_hexfloat(Float value, int precision,
+                                     float_specs specs, buffer<char>& buf) {
+  // float is passed as double to reduce the number of instantiations and to
+  // simplify implementation.
+  static_assert(!std::is_same<Float, float>::value, "");
+
+  using info = dragonbox::float_info<Float>;
+
+  // Assume Float is in the format [sign][exponent][significand].
+  using carrier_uint = typename info::carrier_uint;
+
+  constexpr auto num_float_significand_bits =
+      detail::num_significand_bits<Float>();
+
+  basic_fp<carrier_uint> f(value);
+  f.e += num_float_significand_bits;
+  if (!has_implicit_bit<Float>()) --f.e;
+
+  constexpr auto num_fraction_bits =
+      num_float_significand_bits + (has_implicit_bit<Float>() ? 1 : 0);
+  constexpr auto num_xdigits = (num_fraction_bits + 3) / 4;
+
+  constexpr auto leading_shift = ((num_xdigits - 1) * 4);
+  const auto leading_mask = carrier_uint(0xF) << leading_shift;
+  const auto leading_xdigit =
+      static_cast<uint32_t>((f.f & leading_mask) >> leading_shift);
+  if (leading_xdigit > 1) f.e -= (32 - countl_zero(leading_xdigit) - 1);
+
+  int print_xdigits = num_xdigits - 1;
+  if (precision >= 0 && print_xdigits > precision) {
+    const int shift = ((print_xdigits - precision - 1) * 4);
+    const auto mask = carrier_uint(0xF) << shift;
+    const auto v = static_cast<uint32_t>((f.f & mask) >> shift);
+
+    if (v >= 8) {
+      const auto inc = carrier_uint(1) << (shift + 4);
+      f.f += inc;
+      f.f &= ~(inc - 1);
+    }
 
-  FMT_CONSTEXPR void operator()() { handler.on_dynamic_width(auto_id()); }
-  FMT_CONSTEXPR void operator()(int id) { handler.on_dynamic_width(id); }
-  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
-    handler.on_dynamic_width(id);
-  }
+    // Check long double overflow
+    if (!has_implicit_bit<Float>()) {
+      const auto implicit_bit = carrier_uint(1) << num_float_significand_bits;
+      if ((f.f & implicit_bit) == implicit_bit) {
+        f.f >>= 4;
+        f.e += 4;
+      }
+    }
 
-  FMT_CONSTEXPR void on_error(const char* message) {
-    handler.on_error(message);
+    print_xdigits = precision;
   }
 
-  SpecHandler& handler;
-};
+  char xdigits[num_bits<carrier_uint>() / 4];
+  detail::fill_n(xdigits, sizeof(xdigits), '0');
+  format_uint<4>(xdigits, f.f, num_xdigits, specs.upper);
 
-// Adapts SpecHandler to IDHandler API for dynamic precision.
-template <typename SpecHandler, typename Char> struct precision_adapter {
-  explicit FMT_CONSTEXPR precision_adapter(SpecHandler& h) : handler(h) {}
+  // Remove zero tail
+  while (print_xdigits > 0 && xdigits[print_xdigits] == '0') --print_xdigits;
 
-  FMT_CONSTEXPR void operator()() { handler.on_dynamic_precision(auto_id()); }
-  FMT_CONSTEXPR void operator()(int id) { handler.on_dynamic_precision(id); }
-  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
-    handler.on_dynamic_precision(id);
-  }
+  buf.push_back('0');
+  buf.push_back(specs.upper ? 'X' : 'x');
+  buf.push_back(xdigits[0]);
+  if (specs.showpoint || print_xdigits > 0 || print_xdigits < precision)
+    buf.push_back('.');
+  buf.append(xdigits + 1, xdigits + 1 + print_xdigits);
+  for (; print_xdigits < precision; ++print_xdigits) buf.push_back('0');
 
-  FMT_CONSTEXPR void on_error(const char* message) {
-    handler.on_error(message);
+  buf.push_back(specs.upper ? 'P' : 'p');
+
+  uint32_t abs_e;
+  if (f.e < 0) {
+    buf.push_back('-');
+    abs_e = static_cast<uint32_t>(-f.e);
+  } else {
+    buf.push_back('+');
+    abs_e = static_cast<uint32_t>(f.e);
   }
+  format_decimal<char>(appender(buf), abs_e, detail::count_digits(abs_e));
+}
 
-  SpecHandler& handler;
-};
+template <typename Float, FMT_ENABLE_IF(is_double_double<Float>::value)>
+FMT_CONSTEXPR20 void format_hexfloat(Float value, int precision,
+                                     float_specs specs, buffer<char>& buf) {
+  format_hexfloat(static_cast<double>(value), precision, specs, buf);
+}
 
-template <typename Char>
-FMT_CONSTEXPR const Char* next_code_point(const Char* begin, const Char* end) {
-  if (const_check(sizeof(Char) != 1) || (*begin & 0x80) == 0) return begin + 1;
-  do {
-    ++begin;
-  } while (begin != end && (*begin & 0xc0) == 0x80);
-  return begin;
+constexpr auto fractional_part_rounding_thresholds(int index) -> uint32_t {
+  // For checking rounding thresholds.
+  // The kth entry is chosen to be the smallest integer such that the
+  // upper 32-bits of 10^(k+1) times it is strictly bigger than 5 * 10^k.
+  // It is equal to ceil(2^31 + 2^32/10^(k + 1)).
+  // These are stored in a string literal because we cannot have static arrays
+  // in constexpr functions and non-static ones are poorly optimized.
+  return U"\x9999999a\x828f5c29\x80418938\x80068db9\x8000a7c6\x800010c7"
+         U"\x800001ae\x8000002b"[index];
 }
 
-// Parses fill and alignment.
-template <typename Char, typename Handler>
-FMT_CONSTEXPR const Char* parse_align(const Char* begin, const Char* end,
-                                      Handler&& handler) {
-  FMT_ASSERT(begin != end, "");
-  auto align = align::none;
-  auto p = next_code_point(begin, end);
-  if (p == end) p = begin;
-  for (;;) {
-    switch (static_cast<char>(*p)) {
-    case '<':
-      align = align::left;
-      break;
-    case '>':
-      align = align::right;
-      break;
-#if FMT_NUMERIC_ALIGN
-    case '=':
-      align = align::numeric;
-      break;
-#endif
-    case '^':
-      align = align::center;
-      break;
+template <typename Float>
+FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
+                                  buffer<char>& buf) -> int {
+  // float is passed as double to reduce the number of instantiations.
+  static_assert(!std::is_same<Float, float>::value, "");
+  FMT_ASSERT(value >= 0, "value is negative");
+  auto converted_value = convert_float(value);
+
+  const bool fixed = specs.format == float_format::fixed;
+  if (value <= 0) {  // <= instead of == to silence a warning.
+    if (precision <= 0 || !fixed) {
+      buf.push_back('0');
+      return 0;
     }
-    if (align != align::none) {
-      if (p != begin) {
-        auto c = *begin;
-        if (c == '{')
-          return handler.on_error("invalid fill character '{'"), begin;
-        handler.on_fill(basic_string_view<Char>(begin, to_unsigned(p - begin)));
-        begin = p + 1;
-      } else
-        ++begin;
-      handler.on_align(align);
-      break;
-    } else if (p == begin) {
-      break;
+    buf.try_resize(to_unsigned(precision));
+    fill_n(buf.data(), precision, '0');
+    return -precision;
+  }
+
+  int exp = 0;
+  bool use_dragon = true;
+  unsigned dragon_flags = 0;
+  if (!is_fast_float<Float>() || is_constant_evaluated()) {
+    const auto inv_log2_10 = 0.3010299956639812;  // 1 / log2(10)
+    using info = dragonbox::float_info<decltype(converted_value)>;
+    const auto f = basic_fp<typename info::carrier_uint>(converted_value);
+    // Compute exp, an approximate power of 10, such that
+    //   10^(exp - 1) <= value < 10^exp or 10^exp <= value < 10^(exp + 1).
+    // This is based on log10(value) == log2(value) / log2(10) and approximation
+    // of log2(value) by e + num_fraction_bits idea from double-conversion.
+    auto e = (f.e + count_digits<1>(f.f) - 1) * inv_log2_10 - 1e-10;
+    exp = static_cast<int>(e);
+    if (e > exp) ++exp;  // Compute ceil.
+    dragon_flags = dragon::fixup;
+  } else if (precision < 0) {
+    // Use Dragonbox for the shortest format.
+    if (specs.binary32) {
+      auto dec = dragonbox::to_decimal(static_cast<float>(value));
+      write<char>(buffer_appender<char>(buf), dec.significand);
+      return dec.exponent;
+    }
+    auto dec = dragonbox::to_decimal(static_cast<double>(value));
+    write<char>(buffer_appender<char>(buf), dec.significand);
+    return dec.exponent;
+  } else {
+    // Extract significand bits and exponent bits.
+    using info = dragonbox::float_info<double>;
+    auto br = bit_cast<uint64_t>(static_cast<double>(value));
+
+    const uint64_t significand_mask =
+        (static_cast<uint64_t>(1) << num_significand_bits<double>()) - 1;
+    uint64_t significand = (br & significand_mask);
+    int exponent = static_cast<int>((br & exponent_mask<double>()) >>
+                                    num_significand_bits<double>());
+
+    if (exponent != 0) {  // Check if normal.
+      exponent -= exponent_bias<double>() + num_significand_bits<double>();
+      significand |=
+          (static_cast<uint64_t>(1) << num_significand_bits<double>());
+      significand <<= 1;
+    } else {
+      // Normalize subnormal inputs.
+      FMT_ASSERT(significand != 0, "zeros should not appear here");
+      int shift = countl_zero(significand);
+      FMT_ASSERT(shift >= num_bits<uint64_t>() - num_significand_bits<double>(),
+                 "");
+      shift -= (num_bits<uint64_t>() - num_significand_bits<double>() - 2);
+      exponent = (std::numeric_limits<double>::min_exponent -
+                  num_significand_bits<double>()) -
+                 shift;
+      significand <<= shift;
     }
-    p = begin;
-  }
-  return begin;
-}
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR const Char* parse_width(const Char* begin, const Char* end,
-                                      Handler&& handler) {
-  FMT_ASSERT(begin != end, "");
-  if ('0' <= *begin && *begin <= '9') {
-    handler.on_width(parse_nonnegative_int(begin, end, handler));
-  } else if (*begin == '{') {
-    ++begin;
-    if (begin != end)
-      begin = parse_arg_id(begin, end, width_adapter<Handler, Char>(handler));
-    if (begin == end || *begin != '}')
-      return handler.on_error("invalid format string"), begin;
-    ++begin;
-  }
-  return begin;
-}
+    // Compute the first several nonzero decimal significand digits.
+    // We call the number we get the first segment.
+    const int k = info::kappa - dragonbox::floor_log10_pow2(exponent);
+    exp = -k;
+    const int beta = exponent + dragonbox::floor_log2_pow10(k);
+    uint64_t first_segment;
+    bool has_more_segments;
+    int digits_in_the_first_segment;
+    {
+      const auto r = dragonbox::umul192_upper128(
+          significand << beta, dragonbox::get_cached_power(k));
+      first_segment = r.high();
+      has_more_segments = r.low() != 0;
+
+      // The first segment can have 18 ~ 19 digits.
+      if (first_segment >= 1000000000000000000ULL) {
+        digits_in_the_first_segment = 19;
+      } else {
+        // When it is of 18-digits, we align it to 19-digits by adding a bogus
+        // zero at the end.
+        digits_in_the_first_segment = 18;
+        first_segment *= 10;
+      }
+    }
+
+    // Compute the actual number of decimal digits to print.
+    if (fixed) adjust_precision(precision, exp + digits_in_the_first_segment);
+
+    // Use Dragon4 only when there might be not enough digits in the first
+    // segment.
+    if (digits_in_the_first_segment > precision) {
+      use_dragon = false;
+
+      if (precision <= 0) {
+        exp += digits_in_the_first_segment;
+
+        if (precision < 0) {
+          // Nothing to do, since all we have are just leading zeros.
+          buf.try_resize(0);
+        } else {
+          // We may need to round-up.
+          buf.try_resize(1);
+          if ((first_segment | static_cast<uint64_t>(has_more_segments)) >
+              5000000000000000000ULL) {
+            buf[0] = '1';
+          } else {
+            buf[0] = '0';
+          }
+        }
+      }  // precision <= 0
+      else {
+        exp += digits_in_the_first_segment - precision;
+
+        // When precision > 0, we divide the first segment into three
+        // subsegments, each with 9, 9, and 0 ~ 1 digits so that each fits
+        // in 32-bits which usually allows faster calculation than in
+        // 64-bits. Since some compiler (e.g. MSVC) doesn't know how to optimize
+        // division-by-constant for large 64-bit divisors, we do it here
+        // manually. The magic number 7922816251426433760 below is equal to
+        // ceil(2^(64+32) / 10^10).
+        const uint32_t first_subsegment = static_cast<uint32_t>(
+            dragonbox::umul128_upper64(first_segment, 7922816251426433760ULL) >>
+            32);
+        const uint64_t second_third_subsegments =
+            first_segment - first_subsegment * 10000000000ULL;
+
+        uint64_t prod;
+        uint32_t digits;
+        bool should_round_up;
+        int number_of_digits_to_print = precision > 9 ? 9 : precision;
+
+        // Print a 9-digits subsegment, either the first or the second.
+        auto print_subsegment = [&](uint32_t subsegment, char* buffer) {
+          int number_of_digits_printed = 0;
+
+          // If we want to print an odd number of digits from the subsegment,
+          if ((number_of_digits_to_print & 1) != 0) {
+            // Convert to 64-bit fixed-point fractional form with 1-digit
+            // integer part. The magic number 720575941 is a good enough
+            // approximation of 2^(32 + 24) / 10^8; see
+            // https://jk-jeon.github.io/posts/2022/12/fixed-precision-formatting/#fixed-length-case
+            // for details.
+            prod = ((subsegment * static_cast<uint64_t>(720575941)) >> 24) + 1;
+            digits = static_cast<uint32_t>(prod >> 32);
+            *buffer = static_cast<char>('0' + digits);
+            number_of_digits_printed++;
+          }
+          // If we want to print an even number of digits from the
+          // first_subsegment,
+          else {
+            // Convert to 64-bit fixed-point fractional form with 2-digits
+            // integer part. The magic number 450359963 is a good enough
+            // approximation of 2^(32 + 20) / 10^7; see
+            // https://jk-jeon.github.io/posts/2022/12/fixed-precision-formatting/#fixed-length-case
+            // for details.
+            prod = ((subsegment * static_cast<uint64_t>(450359963)) >> 20) + 1;
+            digits = static_cast<uint32_t>(prod >> 32);
+            copy2(buffer, digits2(digits));
+            number_of_digits_printed += 2;
+          }
+
+          // Print all digit pairs.
+          while (number_of_digits_printed < number_of_digits_to_print) {
+            prod = static_cast<uint32_t>(prod) * static_cast<uint64_t>(100);
+            digits = static_cast<uint32_t>(prod >> 32);
+            copy2(buffer + number_of_digits_printed, digits2(digits));
+            number_of_digits_printed += 2;
+          }
+        };
+
+        // Print first subsegment.
+        print_subsegment(first_subsegment, buf.data());
+
+        // Perform rounding if the first subsegment is the last subsegment to
+        // print.
+        if (precision <= 9) {
+          // Rounding inside the subsegment.
+          // We round-up if:
+          //  - either the fractional part is strictly larger than 1/2, or
+          //  - the fractional part is exactly 1/2 and the last digit is odd.
+          // We rely on the following observations:
+          //  - If fractional_part >= threshold, then the fractional part is
+          //    strictly larger than 1/2.
+          //  - If the MSB of fractional_part is set, then the fractional part
+          //    must be at least 1/2.
+          //  - When the MSB of fractional_part is set, either
+          //    second_third_subsegments being nonzero or has_more_segments
+          //    being true means there are further digits not printed, so the
+          //    fractional part is strictly larger than 1/2.
+          if (precision < 9) {
+            uint32_t fractional_part = static_cast<uint32_t>(prod);
+            should_round_up =
+                fractional_part >= fractional_part_rounding_thresholds(
+                                       8 - number_of_digits_to_print) ||
+                ((fractional_part >> 31) &
+                 ((digits & 1) | (second_third_subsegments != 0) |
+                  has_more_segments)) != 0;
+          }
+          // Rounding at the subsegment boundary.
+          // In this case, the fractional part is at least 1/2 if and only if
+          // second_third_subsegments >= 5000000000ULL, and is strictly larger
+          // than 1/2 if we further have either second_third_subsegments >
+          // 5000000000ULL or has_more_segments == true.
+          else {
+            should_round_up = second_third_subsegments > 5000000000ULL ||
+                              (second_third_subsegments == 5000000000ULL &&
+                               ((digits & 1) != 0 || has_more_segments));
+          }
+        }
+        // Otherwise, print the second subsegment.
+        else {
+          // Compilers are not aware of how to leverage the maximum value of
+          // second_third_subsegments to find out a better magic number which
+          // allows us to eliminate an additional shift. 1844674407370955162 =
+          // ceil(2^64/10) < ceil(2^64*(10^9/(10^10 - 1))).
+          const uint32_t second_subsegment =
+              static_cast<uint32_t>(dragonbox::umul128_upper64(
+                  second_third_subsegments, 1844674407370955162ULL));
+          const uint32_t third_subsegment =
+              static_cast<uint32_t>(second_third_subsegments) -
+              second_subsegment * 10;
+
+          number_of_digits_to_print = precision - 9;
+          print_subsegment(second_subsegment, buf.data() + 9);
+
+          // Rounding inside the subsegment.
+          if (precision < 18) {
+            // The condition third_subsegment != 0 implies that the segment was
+            // of 19 digits, so in this case the third segment should be
+            // consisting of a genuine digit from the input.
+            uint32_t fractional_part = static_cast<uint32_t>(prod);
+            should_round_up =
+                fractional_part >= fractional_part_rounding_thresholds(
+                                       8 - number_of_digits_to_print) ||
+                ((fractional_part >> 31) &
+                 ((digits & 1) | (third_subsegment != 0) |
+                  has_more_segments)) != 0;
+          }
+          // Rounding at the subsegment boundary.
+          else {
+            // In this case, the segment must be of 19 digits, thus
+            // the third subsegment should be consisting of a genuine digit from
+            // the input.
+            should_round_up = third_subsegment > 5 ||
+                              (third_subsegment == 5 &&
+                               ((digits & 1) != 0 || has_more_segments));
+          }
+        }
 
-template <typename Char, typename Handler>
-FMT_CONSTEXPR const Char* parse_precision(const Char* begin, const Char* end,
-                                          Handler&& handler) {
-  ++begin;
-  auto c = begin != end ? *begin : Char();
-  if ('0' <= c && c <= '9') {
-    handler.on_precision(parse_nonnegative_int(begin, end, handler));
-  } else if (c == '{') {
-    ++begin;
-    if (begin != end) {
-      begin =
-          parse_arg_id(begin, end, precision_adapter<Handler, Char>(handler));
+        // Round-up if necessary.
+        if (should_round_up) {
+          ++buf[precision - 1];
+          for (int i = precision - 1; i > 0 && buf[i] > '9'; --i) {
+            buf[i] = '0';
+            ++buf[i - 1];
+          }
+          if (buf[0] > '9') {
+            buf[0] = '1';
+            if (fixed)
+              buf[precision++] = '0';
+            else
+              ++exp;
+          }
+        }
+        buf.try_resize(to_unsigned(precision));
+      }
+    }  // if (digits_in_the_first_segment > precision)
+    else {
+      // Adjust the exponent for its use in Dragon4.
+      exp += digits_in_the_first_segment - 1;
     }
-    if (begin == end || *begin++ != '}')
-      return handler.on_error("invalid format string"), begin;
-  } else {
-    return handler.on_error("missing precision specifier"), begin;
   }
-  handler.end_precision();
-  return begin;
+  if (use_dragon) {
+    auto f = basic_fp<uint128_t>();
+    bool is_predecessor_closer = specs.binary32
+                                     ? f.assign(static_cast<float>(value))
+                                     : f.assign(converted_value);
+    if (is_predecessor_closer) dragon_flags |= dragon::predecessor_closer;
+    if (fixed) dragon_flags |= dragon::fixed;
+    // Limit precision to the maximum possible number of significant digits in
+    // an IEEE754 double because we don't need to generate zeros.
+    const int max_double_digits = 767;
+    if (precision > max_double_digits) precision = max_double_digits;
+    format_dragon(f, dragon_flags, precision, buf, exp);
+  }
+  if (!fixed && !specs.showpoint) {
+    // Remove trailing zeros.
+    auto num_digits = buf.size();
+    while (num_digits > 0 && buf[num_digits - 1] == '0') {
+      --num_digits;
+      ++exp;
+    }
+    buf.try_resize(num_digits);
+  }
+  return exp;
+}
+template <typename Char, typename OutputIt, typename T>
+FMT_CONSTEXPR20 auto write_float(OutputIt out, T value,
+                                 format_specs<Char> specs, locale_ref loc)
+    -> OutputIt {
+  float_specs fspecs = parse_float_type_spec(specs);
+  fspecs.sign = specs.sign;
+  if (detail::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  } else if (fspecs.sign == sign::minus) {
+    fspecs.sign = sign::none;
+  }
+
+  if (!detail::isfinite(value))
+    return write_nonfinite(out, detail::isnan(value), specs, fspecs);
+
+  if (specs.align == align::numeric && fspecs.sign) {
+    auto it = reserve(out, 1);
+    *it++ = detail::sign<Char>(fspecs.sign);
+    out = base_iterator(out, it);
+    fspecs.sign = sign::none;
+    if (specs.width != 0) --specs.width;
+  }
+
+  memory_buffer buffer;
+  if (fspecs.format == float_format::hex) {
+    if (fspecs.sign) buffer.push_back(detail::sign<char>(fspecs.sign));
+    format_hexfloat(convert_float(value), specs.precision, fspecs, buffer);
+    return write_bytes<align::right>(out, {buffer.data(), buffer.size()},
+                                     specs);
+  }
+  int precision = specs.precision >= 0 || specs.type == presentation_type::none
+                      ? specs.precision
+                      : 6;
+  if (fspecs.format == float_format::exp) {
+    if (precision == max_value<int>())
+      throw_format_error("number is too big");
+    else
+      ++precision;
+  } else if (fspecs.format != float_format::fixed && precision == 0) {
+    precision = 1;
+  }
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  int exp = format_float(convert_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  auto f = big_decimal_fp{buffer.data(), static_cast<int>(buffer.size()), exp};
+  return write_float(out, f, specs, fspecs, loc);
 }
 
-// Parses standard format specifiers and sends notifications about parsed
-// components to handler.
-template <typename Char, typename SpecHandler>
-FMT_CONSTEXPR const Char* parse_format_specs(const Char* begin, const Char* end,
-                                             SpecHandler&& handler) {
-  if (begin == end || *begin == '}') return begin;
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_floating_point<T>::value)>
+FMT_CONSTEXPR20 auto write(OutputIt out, T value, format_specs<Char> specs,
+                           locale_ref loc = {}) -> OutputIt {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  return specs.localized && write_loc(out, value, specs, loc)
+             ? out
+             : write_float(out, value, specs, loc);
+}
 
-  begin = parse_align(begin, end, handler);
-  if (begin == end) return begin;
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_fast_float<T>::value)>
+FMT_CONSTEXPR20 auto write(OutputIt out, T value) -> OutputIt {
+  if (is_constant_evaluated()) return write(out, value, format_specs<Char>());
+  if (const_check(!is_supported_floating_point(value))) return out;
 
-  // Parse sign.
-  switch (static_cast<char>(*begin)) {
-  case '+':
-    handler.on_plus();
-    ++begin;
-    break;
-  case '-':
-    handler.on_minus();
-    ++begin;
-    break;
-  case ' ':
-    handler.on_space();
-    ++begin;
-    break;
+  auto fspecs = float_specs();
+  if (detail::signbit(value)) {
+    fspecs.sign = sign::minus;
+    value = -value;
   }
-  if (begin == end) return begin;
 
-  if (*begin == '#') {
-    handler.on_hash();
-    if (++begin == end) return begin;
-  }
+  constexpr auto specs = format_specs<Char>();
+  using floaty = conditional_t<std::is_same<T, long double>::value, double, T>;
+  using floaty_uint = typename dragonbox::float_info<floaty>::carrier_uint;
+  floaty_uint mask = exponent_mask<floaty>();
+  if ((bit_cast<floaty_uint>(value) & mask) == mask)
+    return write_nonfinite(out, std::isnan(value), specs, fspecs);
 
-  // Parse zero flag.
-  if (*begin == '0') {
-    handler.on_zero();
-    if (++begin == end) return begin;
-  }
+  auto dec = dragonbox::to_decimal(static_cast<floaty>(value));
+  return write_float(out, dec, specs, fspecs, {});
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_floating_point<T>::value &&
+                        !is_fast_float<T>::value)>
+inline auto write(OutputIt out, T value) -> OutputIt {
+  return write(out, value, format_specs<Char>());
+}
 
-  begin = parse_width(begin, end, handler);
-  if (begin == end) return begin;
+template <typename Char, typename OutputIt>
+auto write(OutputIt out, monostate, format_specs<Char> = {}, locale_ref = {})
+    -> OutputIt {
+  FMT_ASSERT(false, "");
+  return out;
+}
 
-  // Parse precision.
-  if (*begin == '.') {
-    begin = parse_precision(begin, end, handler);
-  }
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, basic_string_view<Char> value)
+    -> OutputIt {
+  auto it = reserve(out, value.size());
+  it = copy_str_noinline<Char>(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
 
-  // Parse type.
-  if (begin != end && *begin != '}') handler.on_type(*begin++);
-  return begin;
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_string<T>::value)>
+constexpr auto write(OutputIt out, const T& value) -> OutputIt {
+  return write<Char>(out, to_string_view(value));
 }
 
-// Return the result via the out param to workaround gcc bug 77539.
-template <bool IS_CONSTEXPR, typename T, typename Ptr = const T*>
-FMT_CONSTEXPR bool find(Ptr first, Ptr last, T value, Ptr& out) {
-  for (out = first; out != last; ++out) {
-    if (*out == value) return true;
-  }
-  return false;
+// FMT_ENABLE_IF() condition separated to workaround an MSVC bug.
+template <
+    typename Char, typename OutputIt, typename T,
+    bool check =
+        std::is_enum<T>::value && !std::is_same<T, Char>::value &&
+        mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value !=
+            type::custom_type,
+    FMT_ENABLE_IF(check)>
+FMT_CONSTEXPR auto write(OutputIt out, T value) -> OutputIt {
+  return write<Char>(out, static_cast<underlying_t<T>>(value));
 }
 
-template <>
-inline bool find<false, char>(const char* first, const char* last, char value,
-                              const char*& out) {
-  out = static_cast<const char*>(
-      std::memchr(first, value, internal::to_unsigned(last - first)));
-  return out != nullptr;
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_same<T, bool>::value)>
+FMT_CONSTEXPR auto write(OutputIt out, T value,
+                         const format_specs<Char>& specs = {}, locale_ref = {})
+    -> OutputIt {
+  return specs.type != presentation_type::none &&
+                 specs.type != presentation_type::string
+             ? write(out, value ? 1 : 0, specs, {})
+             : write_bytes(out, value ? "true" : "false", specs);
 }
 
-template <typename Handler, typename Char> struct id_adapter {
-  FMT_CONSTEXPR void operator()() { handler.on_arg_id(); }
-  FMT_CONSTEXPR void operator()(int id) { handler.on_arg_id(id); }
-  FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
-    handler.on_arg_id(id);
-  }
-  FMT_CONSTEXPR void on_error(const char* message) {
-    handler.on_error(message);
-  }
-  Handler& handler;
-};
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR auto write(OutputIt out, Char value) -> OutputIt {
+  auto it = reserve(out, 1);
+  *it++ = value;
+  return base_iterator(out, it);
+}
 
-template <bool IS_CONSTEXPR, typename Char, typename Handler>
-FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
-                                       Handler&& handler) {
-  struct pfs_writer {
-    FMT_CONSTEXPR void operator()(const Char* begin, const Char* end) {
-      if (begin == end) return;
-      for (;;) {
-        const Char* p = nullptr;
-        if (!find<IS_CONSTEXPR>(begin, end, '}', p))
-          return handler_.on_text(begin, end);
-        ++p;
-        if (p == end || *p != '}')
-          return handler_.on_error("unmatched '}' in format string");
-        handler_.on_text(begin, p);
-        begin = p + 1;
-      }
-    }
-    Handler& handler_;
-  } write{handler};
-  auto begin = format_str.data();
-  auto end = begin + format_str.size();
-  while (begin != end) {
-    // Doing two passes with memchr (one for '{' and another for '}') is up to
-    // 2.5x faster than the naive one-pass implementation on big format strings.
-    const Char* p = begin;
-    if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, '{', p))
-      return write(begin, end);
-    write(begin, p);
-    ++p;
-    if (p == end) return handler.on_error("invalid format string");
-    if (static_cast<char>(*p) == '}') {
-      handler.on_arg_id();
-      handler.on_replacement_field(p);
-    } else if (*p == '{') {
-      handler.on_text(p, p + 1);
-    } else {
-      p = parse_arg_id(p, end, id_adapter<Handler, Char>{handler});
-      Char c = p != end ? *p : Char();
-      if (c == '}') {
-        handler.on_replacement_field(p);
-      } else if (c == ':') {
-        p = handler.on_format_specs(p + 1, end);
-        if (p == end || *p != '}')
-          return handler.on_error("unknown format specifier");
-      } else {
-        return handler.on_error("missing '}' in format string");
-      }
-    }
-    begin = p + 1;
-  }
+template <typename Char, typename OutputIt>
+FMT_CONSTEXPR_CHAR_TRAITS auto write(OutputIt out, const Char* value)
+    -> OutputIt {
+  if (value) return write(out, basic_string_view<Char>(value));
+  throw_format_error("string pointer is null");
+  return out;
 }
 
-template <typename T, typename ParseContext>
-FMT_CONSTEXPR const typename ParseContext::char_type* parse_format_specs(
-    ParseContext& ctx) {
-  using char_type = typename ParseContext::char_type;
-  using context = buffer_context<char_type>;
-  using mapped_type =
-      conditional_t<internal::mapped_type_constant<T, context>::value !=
-                        type::custom_type,
-                    decltype(arg_mapper<context>().map(std::declval<T>())), T>;
-  auto f = conditional_t<has_formatter<mapped_type, context>::value,
-                         formatter<mapped_type, char_type>,
-                         internal::fallback_formatter<T, char_type>>();
-  return f.parse(ctx);
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_same<T, void>::value)>
+auto write(OutputIt out, const T* value, const format_specs<Char>& specs = {},
+           locale_ref = {}) -> OutputIt {
+  return write_ptr<Char>(out, bit_cast<uintptr_t>(value), &specs);
 }
 
-template <typename Char, typename ErrorHandler, typename... Args>
-class format_string_checker {
- public:
-  explicit FMT_CONSTEXPR format_string_checker(
-      basic_string_view<Char> format_str, ErrorHandler eh)
-      : arg_id_(-1),
-        context_(format_str, eh),
-        parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
+// A write overload that handles implicit conversions.
+template <typename Char, typename OutputIt, typename T,
+          typename Context = basic_format_context<OutputIt, Char>>
+FMT_CONSTEXPR auto write(OutputIt out, const T& value) -> enable_if_t<
+    std::is_class<T>::value && !is_string<T>::value &&
+        !is_floating_point<T>::value && !std::is_same<T, Char>::value &&
+        !std::is_same<T, remove_cvref_t<decltype(arg_mapper<Context>().map(
+                             value))>>::value,
+    OutputIt> {
+  return write<Char>(out, arg_mapper<Context>().map(value));
+}
 
-  FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
+template <typename Char, typename OutputIt, typename T,
+          typename Context = basic_format_context<OutputIt, Char>>
+FMT_CONSTEXPR auto write(OutputIt out, const T& value)
+    -> enable_if_t<mapped_type_constant<T, Context>::value == type::custom_type,
+                   OutputIt> {
+  auto formatter = typename Context::template formatter_type<T>();
+  auto parse_ctx = typename Context::parse_context_type({});
+  formatter.parse(parse_ctx);
+  auto ctx = Context(out, {}, {});
+  return formatter.format(value, ctx);
+}
 
-  FMT_CONSTEXPR void on_arg_id() {
-    arg_id_ = context_.next_arg_id();
-    check_arg_id();
-  }
-  FMT_CONSTEXPR void on_arg_id(int id) {
-    arg_id_ = id;
-    context_.check_arg_id(id);
-    check_arg_id();
+// An argument visitor that formats the argument and writes it via the output
+// iterator. It's a class and not a generic lambda for compatibility with C++11.
+template <typename Char> struct default_arg_formatter {
+  using iterator = buffer_appender<Char>;
+  using context = buffer_context<Char>;
+
+  iterator out;
+  basic_format_args<context> args;
+  locale_ref loc;
+
+  template <typename T> auto operator()(T value) -> iterator {
+    return write<Char>(out, value);
   }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) {
-    on_error("compile-time checks don't support named arguments");
+  auto operator()(typename basic_format_arg<context>::handle h) -> iterator {
+    basic_format_parse_context<Char> parse_ctx({});
+    context format_ctx(out, args, loc);
+    h.format(parse_ctx, format_ctx);
+    return format_ctx.out();
   }
+};
 
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
+template <typename Char> struct arg_formatter {
+  using iterator = buffer_appender<Char>;
+  using context = buffer_context<Char>;
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin, const Char*) {
-    advance_to(context_, begin);
-    return arg_id_ < num_args ? parse_funcs_[arg_id_](context_) : begin;
-  }
+  iterator out;
+  const format_specs<Char>& specs;
+  locale_ref locale;
 
-  FMT_CONSTEXPR void on_error(const char* message) {
-    context_.on_error(message);
+  template <typename T>
+  FMT_CONSTEXPR FMT_INLINE auto operator()(T value) -> iterator {
+    return detail::write(out, value, specs, locale);
   }
+  auto operator()(typename basic_format_arg<context>::handle) -> iterator {
+    // User-defined types are handled separately because they require access
+    // to the parse context.
+    return out;
+  }
+};
 
- private:
-  using parse_context_type = basic_format_parse_context<Char, ErrorHandler>;
-  enum { num_args = sizeof...(Args) };
+struct width_checker {
+  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
+  FMT_CONSTEXPR auto operator()(T value) -> unsigned long long {
+    if (is_negative(value)) throw_format_error("negative width");
+    return static_cast<unsigned long long>(value);
+  }
 
-  FMT_CONSTEXPR void check_arg_id() {
-    if (arg_id_ >= num_args) context_.on_error("argument index out of range");
+  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
+  FMT_CONSTEXPR auto operator()(T) -> unsigned long long {
+    throw_format_error("width is not integer");
+    return 0;
   }
+};
 
-  // Format specifier parsing function.
-  using parse_func = const Char* (*)(parse_context_type&);
+struct precision_checker {
+  template <typename T, FMT_ENABLE_IF(is_integer<T>::value)>
+  FMT_CONSTEXPR auto operator()(T value) -> unsigned long long {
+    if (is_negative(value)) throw_format_error("negative precision");
+    return static_cast<unsigned long long>(value);
+  }
 
-  int arg_id_;
-  parse_context_type context_;
-  parse_func parse_funcs_[num_args > 0 ? num_args : 1];
+  template <typename T, FMT_ENABLE_IF(!is_integer<T>::value)>
+  FMT_CONSTEXPR auto operator()(T) -> unsigned long long {
+    throw_format_error("precision is not integer");
+    return 0;
+  }
 };
 
-template <typename Char, typename ErrorHandler, typename... Args>
-FMT_CONSTEXPR bool do_check_format_string(basic_string_view<Char> s,
-                                          ErrorHandler eh = ErrorHandler()) {
-  format_string_checker<Char, ErrorHandler, Args...> checker(s, eh);
-  parse_format_string<true>(s, checker);
-  return true;
+template <typename Handler, typename FormatArg>
+FMT_CONSTEXPR auto get_dynamic_spec(FormatArg arg) -> int {
+  unsigned long long value = visit_format_arg(Handler(), arg);
+  if (value > to_unsigned(max_value<int>()))
+    throw_format_error("number is too big");
+  return static_cast<int>(value);
 }
 
-template <typename... Args, typename S,
-          enable_if_t<(is_compile_string<S>::value), int>>
-void check_format_string(S format_str) {
-  FMT_CONSTEXPR_DECL bool invalid_format = internal::do_check_format_string<
-      typename S::char_type, internal::error_handler,
-      remove_const_t<remove_reference_t<Args>>...>(to_string_view(format_str));
-  (void)invalid_format;
+template <typename Context, typename ID>
+FMT_CONSTEXPR auto get_arg(Context& ctx, ID id) -> decltype(ctx.arg(id)) {
+  auto arg = ctx.arg(id);
+  if (!arg) ctx.on_error("argument not found");
+  return arg;
 }
 
-template <template <typename> class Handler, typename Context>
-void handle_dynamic_spec(int& value, arg_ref<typename Context::char_type> ref,
-                         Context& ctx) {
+template <typename Handler, typename Context>
+FMT_CONSTEXPR void handle_dynamic_spec(int& value,
+                                       arg_ref<typename Context::char_type> ref,
+                                       Context& ctx) {
   switch (ref.kind) {
   case arg_id_kind::none:
     break;
   case arg_id_kind::index:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(get_arg(ctx, ref.val.index));
     break;
   case arg_id_kind::name:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(get_arg(ctx, ref.val.name));
     break;
   }
 }
 
-using format_func = void (*)(internal::buffer<char>&, int, string_view);
+#if FMT_USE_USER_DEFINED_LITERALS
+#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <typename T, typename Char, size_t N,
+          fmt::detail_exported::fixed_string<Char, N> Str>
+struct statically_named_arg : view {
+  static constexpr auto name = Str.data;
+
+  const T& value;
+  statically_named_arg(const T& v) : value(v) {}
+};
 
-FMT_API void format_error_code(buffer<char>& out, int error_code,
-                               string_view message) FMT_NOEXCEPT;
+template <typename T, typename Char, size_t N,
+          fmt::detail_exported::fixed_string<Char, N> Str>
+struct is_named_arg<statically_named_arg<T, Char, N, Str>> : std::true_type {};
 
-FMT_API void report_error(format_func func, int error_code,
-                          string_view message) FMT_NOEXCEPT;
-}  // namespace internal
+template <typename T, typename Char, size_t N,
+          fmt::detail_exported::fixed_string<Char, N> Str>
+struct is_statically_named_arg<statically_named_arg<T, Char, N, Str>>
+    : std::true_type {};
 
-template <typename Range>
-using basic_writer FMT_DEPRECATED_ALIAS = internal::basic_writer<Range>;
-using writer FMT_DEPRECATED_ALIAS = internal::writer;
-using wwriter FMT_DEPRECATED_ALIAS =
-    internal::basic_writer<buffer_range<wchar_t>>;
+template <typename Char, size_t N,
+          fmt::detail_exported::fixed_string<Char, N> Str>
+struct udl_arg {
+  template <typename T> auto operator=(T&& value) const {
+    return statically_named_arg<T, Char, N, Str>(std::forward<T>(value));
+  }
+};
+#  else
+template <typename Char> struct udl_arg {
+  const Char* str;
 
-/** The default argument formatter. */
-template <typename Range>
-class arg_formatter : public internal::arg_formatter_base<Range> {
- private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_format_context<typename base::iterator, char_type>;
+  template <typename T> auto operator=(T&& value) const -> named_arg<Char, T> {
+    return {str, std::forward<T>(value)};
+  }
+};
+#  endif
+#endif  // FMT_USE_USER_DEFINED_LITERALS
 
-  context_type& ctx_;
-  basic_format_parse_context<char_type>* parse_ctx_;
+template <typename Locale, typename Char>
+auto vformat(const Locale& loc, basic_string_view<Char> fmt,
+             basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
+  auto buf = basic_memory_buffer<Char>();
+  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
+  return {buf.data(), buf.size()};
+}
 
- public:
-  using range = Range;
-  using iterator = typename base::iterator;
-  using format_specs = typename base::format_specs;
+using format_func = void (*)(detail::buffer<char>&, int, const char*);
 
-  /**
-    \rst
-    Constructs an argument formatter object.
-    *ctx* is a reference to the formatting context,
-    *specs* contains format specifier information for standard argument types.
-    \endrst
-   */
-  explicit arg_formatter(
-      context_type& ctx,
-      basic_format_parse_context<char_type>* parse_ctx = nullptr,
-      format_specs* specs = nullptr)
-      : base(Range(ctx.out()), specs, ctx.locale()),
-        ctx_(ctx),
-        parse_ctx_(parse_ctx) {}
+FMT_API void format_error_code(buffer<char>& out, int error_code,
+                               string_view message) noexcept;
 
-  using base::operator();
+FMT_API void report_error(format_func func, int error_code,
+                          const char* message) noexcept;
+}  // namespace detail
 
-  /** Formats an argument of a user-defined type. */
-  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
-    handle.format(*parse_ctx_, ctx_);
-    return ctx_.out();
-  }
-};
+FMT_API auto vsystem_error(int error_code, string_view format_str,
+                           format_args args) -> std::system_error;
 
 /**
- An error returned by an operating system or a language runtime,
- for example a file opening error.
-*/
-FMT_CLASS_API
-class FMT_API system_error : public std::runtime_error {
- private:
-  void init(int err_code, string_view format_str, format_args args);
-
- protected:
-  int error_code_;
+  \rst
+  Constructs :class:`std::system_error` with a message formatted with
+  ``fmt::format(fmt, args...)``.
+  *error_code* is a system error code as given by ``errno``.
 
-  system_error() : std::runtime_error(""), error_code_(0) {}
+  **Example**::
 
- public:
-  /**
-   \rst
-   Constructs a :class:`fmt::system_error` object with a description
-   formatted with `fmt::format_system_error`. *message* and additional
-   arguments passed into the constructor are formatted similarly to
-   `fmt::format`.
-
-   **Example**::
-
-     // This throws a system_error with the description
-     //   cannot open file 'madeup': No such file or directory
-     // or similar (system message may vary).
-     const char *filename = "madeup";
-     std::FILE *file = std::fopen(filename, "r");
-     if (!file)
-       throw fmt::system_error(errno, "cannot open file '{}'", filename);
-   \endrst
-  */
-  template <typename... Args>
-  system_error(int error_code, string_view message, const Args&... args)
-      : std::runtime_error("") {
-    init(error_code, message, make_format_args(args...));
-  }
-  system_error(const system_error&) = default;
-  system_error& operator=(const system_error&) = default;
-  system_error(system_error&&) = default;
-  system_error& operator=(system_error&&) = default;
-  ~system_error() FMT_NOEXCEPT FMT_OVERRIDE;
-
-  int error_code() const { return error_code_; }
-};
+    // This throws std::system_error with the description
+    //   cannot open file 'madeup': No such file or directory
+    // or similar (system message may vary).
+    const char* filename = "madeup";
+    std::FILE* file = std::fopen(filename, "r");
+    if (!file)
+      throw fmt::system_error(errno, "cannot open file '{}'", filename);
+  \endrst
+ */
+template <typename... T>
+auto system_error(int error_code, format_string<T...> fmt, T&&... args)
+    -> std::system_error {
+  return vsystem_error(error_code, fmt, fmt::make_format_args(args...));
+}
 
 /**
   \rst
-  Formats an error returned by an operating system or a language runtime,
-  for example a file opening error, and writes it to *out* in the following
-  form:
+  Formats an error message for an error returned by an operating system or a
+  language runtime, for example a file opening error, and writes it to *out*.
+  The format is the same as the one used by ``std::system_error(ec, message)``
+  where ``ec`` is ``std::error_code(error_code, std::generic_category()})``.
+  It is implementation-defined but normally looks like:
 
   .. parsed-literal::
      *<message>*: *<system-message>*
 
-  where *<message>* is the passed message and *<system-message>* is
-  the system message corresponding to the error code.
+  where *<message>* is the passed message and *<system-message>* is the system
+  message corresponding to the error code.
   *error_code* is a system error code as given by ``errno``.
-  If *error_code* is not a valid error code such as -1, the system message
-  may look like "Unknown error -1" and is platform-dependent.
   \endrst
  */
-FMT_API void format_system_error(internal::buffer<char>& out, int error_code,
-                                 string_view message) FMT_NOEXCEPT;
+FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
+                                 const char* message) noexcept;
 
 // Reports a system error without throwing an exception.
 // Can be used to report errors from destructors.
-FMT_API void report_system_error(int error_code,
-                                 string_view message) FMT_NOEXCEPT;
+FMT_API void report_system_error(int error_code, const char* message) noexcept;
 
 /** Fast integer formatter. */
 class format_int {
@@ -2858,60 +3975,45 @@ class format_int {
   mutable char buffer_[buffer_size];
   char* str_;
 
-  // Formats value in reverse and returns a pointer to the beginning.
-  char* format_decimal(unsigned long long value) {
-    char* ptr = buffer_ + (buffer_size - 1);  // Parens to workaround MSVC bug.
-    while (value >= 100) {
-      // Integer division is slow so do it for a group of two digits instead
-      // of for every digit. The idea comes from the talk by Alexandrescu
-      // "Three Optimization Tips for C++". See speed-test for a comparison.
-      auto index = static_cast<unsigned>((value % 100) * 2);
-      value /= 100;
-      *--ptr = internal::data::digits[index + 1];
-      *--ptr = internal::data::digits[index];
-    }
-    if (value < 10) {
-      *--ptr = static_cast<char>('0' + value);
-      return ptr;
-    }
-    auto index = static_cast<unsigned>(value * 2);
-    *--ptr = internal::data::digits[index + 1];
-    *--ptr = internal::data::digits[index];
-    return ptr;
+  template <typename UInt> auto format_unsigned(UInt value) -> char* {
+    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
+    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
   }
 
-  void format_signed(long long value) {
-    auto abs_value = static_cast<unsigned long long>(value);
+  template <typename Int> auto format_signed(Int value) -> char* {
+    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
     bool negative = value < 0;
     if (negative) abs_value = 0 - abs_value;
-    str_ = format_decimal(abs_value);
-    if (negative) *--str_ = '-';
+    auto begin = format_unsigned(abs_value);
+    if (negative) *--begin = '-';
+    return begin;
   }
 
  public:
-  explicit format_int(int value) { format_signed(value); }
-  explicit format_int(long value) { format_signed(value); }
-  explicit format_int(long long value) { format_signed(value); }
-  explicit format_int(unsigned value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long long value) : str_(format_decimal(value)) {}
+  explicit format_int(int value) : str_(format_signed(value)) {}
+  explicit format_int(long value) : str_(format_signed(value)) {}
+  explicit format_int(long long value) : str_(format_signed(value)) {}
+  explicit format_int(unsigned value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long long value)
+      : str_(format_unsigned(value)) {}
 
   /** Returns the number of characters written to the output buffer. */
-  std::size_t size() const {
-    return internal::to_unsigned(buffer_ - str_ + buffer_size - 1);
+  auto size() const -> size_t {
+    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
   }
 
   /**
     Returns a pointer to the output buffer content. No terminating null
     character is appended.
    */
-  const char* data() const { return str_; }
+  auto data() const -> const char* { return str_; }
 
   /**
     Returns a pointer to the output buffer content with terminating null
     character appended.
    */
-  const char* c_str() const {
+  auto c_str() const -> const char* {
     buffer_[buffer_size - 1] = '\0';
     return str_;
   }
@@ -2921,361 +4023,249 @@ class format_int {
     Returns the content of the output buffer as an ``std::string``.
     \endrst
    */
-  std::string str() const { return std::string(str_, size()); }
+  auto str() const -> std::string { return std::string(str_, size()); }
 };
 
-// A formatter specialization for the core types corresponding to internal::type
-// constants.
 template <typename T, typename Char>
-struct formatter<T, Char,
-                 enable_if_t<internal::type_constant<T, Char>::value !=
-                             internal::type::custom_type>> {
-  FMT_CONSTEXPR formatter() = default;
-
-  // Parses format specifiers stopping either at the end of the range or at the
-  // terminating '}'.
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    using handler_type = internal::dynamic_specs_handler<ParseContext>;
-    auto type = internal::type_constant<T, Char>::value;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                  type);
-    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
-    auto eh = ctx.error_handler();
-    switch (type) {
-    case internal::type::none_type:
-    case internal::type::named_arg_type:
-      FMT_ASSERT(false, "invalid argument type");
-      break;
-    case internal::type::int_type:
-    case internal::type::uint_type:
-    case internal::type::long_long_type:
-    case internal::type::ulong_long_type:
-    case internal::type::int128_type:
-    case internal::type::uint128_type:
-    case internal::type::bool_type:
-      handle_int_type_spec(specs_.type,
-                           internal::int_type_checker<decltype(eh)>(eh));
-      break;
-    case internal::type::char_type:
-      handle_char_specs(
-          &specs_, internal::char_specs_checker<decltype(eh)>(specs_.type, eh));
-      break;
-    case internal::type::float_type:
-      if (internal::const_check(FMT_USE_FLOAT)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
-        FMT_ASSERT(false, "float support disabled");
-      }
-      break;
-    case internal::type::double_type:
-      if (internal::const_check(FMT_USE_DOUBLE)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
-        FMT_ASSERT(false, "double support disabled");
-      }
-      break;
-    case internal::type::long_double_type:
-      if (internal::const_check(FMT_USE_LONG_DOUBLE)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
-        FMT_ASSERT(false, "long double support disabled");
-      }
-      break;
-    case internal::type::cstring_type:
-      internal::handle_cstring_type_spec(
-          specs_.type, internal::cstring_type_checker<decltype(eh)>(eh));
-      break;
-    case internal::type::string_type:
-      internal::check_string_type_spec(specs_.type, eh);
-      break;
-    case internal::type::pointer_type:
-      internal::check_pointer_type_spec(specs_.type, eh);
-      break;
-    case internal::type::custom_type:
-      // Custom format specifiers should be checked in parse functions of
-      // formatter specializations.
-      break;
-    }
-    return it;
-  }
-
+struct formatter<T, Char, enable_if_t<detail::has_format_as<T>::value>>
+    : formatter<detail::format_as_t<T>, Char> {
   template <typename FormatContext>
-  auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
-        specs_.precision, specs_.precision_ref, ctx);
-    using range_type =
-        internal::output_range<typename FormatContext::iterator,
-                               typename FormatContext::char_type>;
-    return visit_format_arg(arg_formatter<range_type>(ctx, nullptr, &specs_),
-                            internal::make_arg<FormatContext>(val));
+  auto format(const T& value, FormatContext& ctx) const -> decltype(ctx.out()) {
+    using base = formatter<detail::format_as_t<T>, Char>;
+    return base::format(format_as(value), ctx);
   }
-
- private:
-  internal::dynamic_format_specs<Char> specs_;
 };
 
-#define FMT_FORMAT_AS(Type, Base)                                             \
-  template <typename Char>                                                    \
-  struct formatter<Type, Char> : formatter<Base, Char> {                      \
-    template <typename FormatContext>                                         \
-    auto format(Type const& val, FormatContext& ctx) -> decltype(ctx.out()) { \
-      return formatter<Base, Char>::format(val, ctx);                         \
-    }                                                                         \
-  }
+#define FMT_FORMAT_AS(Type, Base) \
+  template <typename Char>        \
+  struct formatter<Type, Char> : formatter<Base, Char> {}
 
 FMT_FORMAT_AS(signed char, int);
 FMT_FORMAT_AS(unsigned char, unsigned);
 FMT_FORMAT_AS(short, int);
 FMT_FORMAT_AS(unsigned short, unsigned);
-FMT_FORMAT_AS(long, long long);
-FMT_FORMAT_AS(unsigned long, unsigned long long);
+FMT_FORMAT_AS(long, detail::long_type);
+FMT_FORMAT_AS(unsigned long, detail::ulong_type);
 FMT_FORMAT_AS(Char*, const Char*);
 FMT_FORMAT_AS(std::basic_string<Char>, basic_string_view<Char>);
 FMT_FORMAT_AS(std::nullptr_t, const void*);
-FMT_FORMAT_AS(internal::std_string_view<Char>, basic_string_view<Char>);
-
-template <typename Char>
-struct formatter<void*, Char> : formatter<const void*, Char> {
-  template <typename FormatContext>
-  auto format(void* val, FormatContext& ctx) -> decltype(ctx.out()) {
-    return formatter<const void*, Char>::format(val, ctx);
-  }
-};
+FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
+FMT_FORMAT_AS(void*, const void*);
 
 template <typename Char, size_t N>
-struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {
-  template <typename FormatContext>
-  auto format(const Char* val, FormatContext& ctx) -> decltype(ctx.out()) {
-    return formatter<basic_string_view<Char>, Char>::format(val, ctx);
-  }
+struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {};
+
+/**
+  \rst
+  Converts ``p`` to ``const void*`` for pointer formatting.
+
+  **Example**::
+
+    auto s = fmt::format("{}", fmt::ptr(p));
+  \endrst
+ */
+template <typename T> auto ptr(T p) -> const void* {
+  static_assert(std::is_pointer<T>::value, "");
+  return detail::bit_cast<const void*>(p);
+}
+template <typename T, typename Deleter>
+auto ptr(const std::unique_ptr<T, Deleter>& p) -> const void* {
+  return p.get();
+}
+template <typename T> auto ptr(const std::shared_ptr<T>& p) -> const void* {
+  return p.get();
+}
+
+/**
+  \rst
+  Converts ``e`` to the underlying type.
+
+  **Example**::
+
+    enum class color { red, green, blue };
+    auto s = fmt::format("{}", fmt::underlying(color::red));
+  \endrst
+ */
+template <typename Enum>
+constexpr auto underlying(Enum e) noexcept -> underlying_t<Enum> {
+  return static_cast<underlying_t<Enum>>(e);
+}
+
+namespace enums {
+template <typename Enum, FMT_ENABLE_IF(std::is_enum<Enum>::value)>
+constexpr auto format_as(Enum e) noexcept -> underlying_t<Enum> {
+  return static_cast<underlying_t<Enum>>(e);
+}
+}  // namespace enums
+
+class bytes {
+ private:
+  string_view data_;
+  friend struct formatter<bytes>;
+
+ public:
+  explicit bytes(string_view data) : data_(data) {}
 };
 
-// A formatter for types known only at run time such as variant alternatives.
-//
-// Usage:
-//   using variant = std::variant<int, std::string>;
-//   template <>
-//   struct formatter<variant>: dynamic_formatter<> {
-//     void format(buffer &buf, const variant &v, context &ctx) {
-//       visit([&](const auto &val) { format(buf, val, ctx); }, v);
-//     }
-//   };
-template <typename Char = char> class dynamic_formatter {
+template <> struct formatter<bytes> {
  private:
-  struct null_handler : internal::error_handler {
-    void on_align(align_t) {}
-    void on_plus() {}
-    void on_minus() {}
-    void on_space() {}
-    void on_hash() {}
-  };
+  detail::dynamic_format_specs<> specs_;
 
  public:
   template <typename ParseContext>
-  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    format_str_ = ctx.begin();
-    // Checks are deferred to formatting time when the argument type is known.
-    internal::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
-    return parse_format_specs(ctx.begin(), ctx.end(), handler);
-  }
-
-  template <typename T, typename FormatContext>
-  auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    handle_specs(ctx);
-    internal::specs_checker<null_handler> checker(
-        null_handler(),
-        internal::mapped_type_constant<T, FormatContext>::value);
-    checker.on_align(specs_.align);
-    switch (specs_.sign) {
-    case sign::none:
-      break;
-    case sign::plus:
-      checker.on_plus();
-      break;
-    case sign::minus:
-      checker.on_minus();
-      break;
-    case sign::space:
-      checker.on_space();
-      break;
-    }
-    if (specs_.alt) checker.on_hash();
-    if (specs_.precision >= 0) checker.end_precision();
-    using range = internal::output_range<typename FormatContext::iterator,
-                                         typename FormatContext::char_type>;
-    visit_format_arg(arg_formatter<range>(ctx, nullptr, &specs_),
-                     internal::make_arg<FormatContext>(val));
-    return ctx.out();
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const char* {
+    return parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
+                              detail::type::string_type);
   }
 
- private:
-  template <typename Context> void handle_specs(Context& ctx) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+  template <typename FormatContext>
+  auto format(bytes b, FormatContext& ctx) -> decltype(ctx.out()) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
+    return detail::write_bytes(ctx.out(), b.data_, specs_);
   }
+};
 
-  internal::dynamic_format_specs<Char> specs_;
-  const Char* format_str_;
+// group_digits_view is not derived from view because it copies the argument.
+template <typename T> struct group_digits_view {
+  T value;
 };
 
-template <typename Range, typename Char>
-typename basic_format_context<Range, Char>::format_arg
-basic_format_context<Range, Char>::arg(basic_string_view<char_type> name) {
-  map_.init(args_);
-  format_arg arg = map_.find(name);
-  if (arg.type() == internal::type::none_type)
-    this->on_error("argument not found");
-  return arg;
-}
+/**
+  \rst
+  Returns a view that formats an integer value using ',' as a locale-independent
+  thousands separator.
 
-template <typename Char, typename ErrorHandler>
-FMT_CONSTEXPR void advance_to(
-    basic_format_parse_context<Char, ErrorHandler>& ctx, const Char* p) {
-  ctx.advance_to(ctx.begin() + (p - &*ctx.begin()));
-}
+  **Example**::
 
-template <typename ArgFormatter, typename Char, typename Context>
-struct format_handler : internal::error_handler {
-  using range = typename ArgFormatter::range;
+    fmt::print("{}", fmt::group_digits(12345));
+    // Output: "12,345"
+  \endrst
+ */
+template <typename T> auto group_digits(T value) -> group_digits_view<T> {
+  return {value};
+}
 
-  format_handler(range r, basic_string_view<Char> str,
-                 basic_format_args<Context> format_args,
-                 internal::locale_ref loc)
-      : parse_context(str), context(r.begin(), format_args, loc) {}
+template <typename T> struct formatter<group_digits_view<T>> : formatter<T> {
+ private:
+  detail::dynamic_format_specs<> specs_;
 
-  void on_text(const Char* begin, const Char* end) {
-    auto size = internal::to_unsigned(end - begin);
-    auto out = context.out();
-    auto&& it = internal::reserve(out, size);
-    it = std::copy_n(begin, size, it);
-    context.advance_to(out);
+ public:
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const char* {
+    return parse_format_specs(ctx.begin(), ctx.end(), specs_, ctx,
+                              detail::type::int_type);
   }
 
-  void get_arg(int id) { arg = internal::get_arg(context, id); }
-
-  void on_arg_id() { get_arg(parse_context.next_arg_id()); }
-  void on_arg_id(int id) {
-    parse_context.check_arg_id(id);
-    get_arg(id);
+  template <typename FormatContext>
+  auto format(group_digits_view<T> t, FormatContext& ctx)
+      -> decltype(ctx.out()) {
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
+        specs_.precision, specs_.precision_ref, ctx);
+    return detail::write_int(
+        ctx.out(), static_cast<detail::uint64_or_128_t<T>>(t.value), 0, specs_,
+        detail::digit_grouping<char>("\3", ","));
   }
-  void on_arg_id(basic_string_view<Char> id) { arg = context.arg(id); }
+};
 
-  void on_replacement_field(const Char* p) {
-    advance_to(parse_context, p);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context), arg));
-  }
+template <typename T> struct nested_view {
+  const formatter<T>* fmt;
+  const T* value;
+};
 
-  const Char* on_format_specs(const Char* begin, const Char* end) {
-    advance_to(parse_context, begin);
-    internal::custom_formatter<Context> f(parse_context, context);
-    if (visit_format_arg(f, arg)) return parse_context.begin();
-    basic_format_specs<Char> specs;
-    using internal::specs_handler;
-    using parse_context_t = basic_format_parse_context<Char>;
-    internal::specs_checker<specs_handler<parse_context_t, Context>> handler(
-        specs_handler<parse_context_t, Context>(specs, parse_context, context),
-        arg.type());
-    begin = parse_format_specs(begin, end, handler);
-    if (begin == end || *begin != '}') on_error("missing '}' in format string");
-    advance_to(parse_context, begin);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context, &specs), arg));
-    return begin;
+template <typename T> struct formatter<nested_view<T>> {
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> const char* {
+    return ctx.begin();
+  }
+  auto format(nested_view<T> view, format_context& ctx) const
+      -> decltype(ctx.out()) {
+    return view.fmt->format(*view.value, ctx);
   }
-
-  basic_format_parse_context<Char> parse_context;
-  Context context;
-  basic_format_arg<Context> arg;
 };
 
-/** Formats arguments and writes the output to the range. */
-template <typename ArgFormatter, typename Char, typename Context>
-typename Context::iterator vformat_to(
-    typename ArgFormatter::range out, basic_string_view<Char> format_str,
-    basic_format_args<Context> args,
-    internal::locale_ref loc = internal::locale_ref()) {
-  format_handler<ArgFormatter, Char, Context> h(out, format_str, args, loc);
-  internal::parse_format_string<false>(format_str, h);
-  return h.context.out();
-}
-
-// Casts ``p`` to ``const void*`` for pointer formatting.
-// Example:
-//   auto s = format("{}", ptr(p));
-template <typename T> inline const void* ptr(const T* p) { return p; }
-template <typename T> inline const void* ptr(const std::unique_ptr<T>& p) {
-  return p.get();
-}
-template <typename T> inline const void* ptr(const std::shared_ptr<T>& p) {
-  return p.get();
-}
-
-class bytes {
+template <typename T> struct nested_formatter {
  private:
-  string_view data_;
-  friend struct formatter<bytes>;
+  int width_;
+  detail::fill_t<char> fill_;
+  align_t align_ : 4;
+  formatter<T> formatter_;
 
  public:
-  explicit bytes(string_view data) : data_(data) {}
-};
+  constexpr nested_formatter() : width_(0), align_(align_t::none) {}
 
-template <> struct formatter<bytes> {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    using handler_type = internal::dynamic_specs_handler<ParseContext>;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                  internal::type::string_type);
-    auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
-    internal::check_string_type_spec(specs_.type, ctx.error_handler());
-    return it;
+  FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> const char* {
+    auto specs = detail::dynamic_format_specs<char>();
+    auto it = parse_format_specs(ctx.begin(), ctx.end(), specs, ctx,
+                                 detail::type::none_type);
+    width_ = specs.width;
+    fill_ = specs.fill;
+    align_ = specs.align;
+    ctx.advance_to(it);
+    return formatter_.parse(ctx);
   }
 
-  template <typename FormatContext>
-  auto format(bytes b, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
-        specs_.precision, specs_.precision_ref, ctx);
-    using range_type =
-        internal::output_range<typename FormatContext::iterator, char>;
-    internal::basic_writer<range_type> writer(range_type(ctx.out()));
-    writer.write_bytes(b.data_, specs_);
-    return writer.out();
+  template <typename F>
+  auto write_padded(format_context& ctx, F write) const -> decltype(ctx.out()) {
+    if (width_ == 0) return write(ctx.out());
+    auto buf = memory_buffer();
+    write(std::back_inserter(buf));
+    auto specs = format_specs<>();
+    specs.width = width_;
+    specs.fill = fill_;
+    specs.align = align_;
+    return detail::write(ctx.out(), string_view(buf.data(), buf.size()), specs);
   }
 
- private:
-  internal::dynamic_format_specs<char> specs_;
+  auto nested(const T& value) const -> nested_view<T> {
+    return nested_view<T>{&formatter_, &value};
+  }
 };
 
-template <typename It, typename Char> struct arg_join : internal::view {
+// DEPRECATED! join_view will be moved to ranges.h.
+template <typename It, typename Sentinel, typename Char = char>
+struct join_view : detail::view {
   It begin;
-  It end;
+  Sentinel end;
   basic_string_view<Char> sep;
 
-  arg_join(It b, It e, basic_string_view<Char> s) : begin(b), end(e), sep(s) {}
+  join_view(It b, Sentinel e, basic_string_view<Char> s)
+      : begin(b), end(e), sep(s) {}
 };
 
-template <typename It, typename Char>
-struct formatter<arg_join<It, Char>, Char>
-    : formatter<typename std::iterator_traits<It>::value_type, Char> {
+template <typename It, typename Sentinel, typename Char>
+struct formatter<join_view<It, Sentinel, Char>, Char> {
+ private:
+  using value_type =
+#ifdef __cpp_lib_ranges
+      std::iter_value_t<It>;
+#else
+      typename std::iterator_traits<It>::value_type;
+#endif
+  formatter<remove_cvref_t<value_type>, Char> value_formatter_;
+
+ public:
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> const Char* {
+    return value_formatter_.parse(ctx);
+  }
+
   template <typename FormatContext>
-  auto format(const arg_join<It, Char>& value, FormatContext& ctx)
-      -> decltype(ctx.out()) {
-    using base = formatter<typename std::iterator_traits<It>::value_type, Char>;
+  auto format(const join_view<It, Sentinel, Char>& value,
+              FormatContext& ctx) const -> decltype(ctx.out()) {
     auto it = value.begin;
     auto out = ctx.out();
     if (it != value.end) {
-      out = base::format(*it++, ctx);
+      out = value_formatter_.format(*it, ctx);
+      ++it;
       while (it != value.end) {
-        out = std::copy(value.sep.begin(), value.sep.end(), out);
+        out = detail::copy_str<Char>(value.sep.begin(), value.sep.end(), out);
         ctx.advance_to(out);
-        out = base::format(*it++, ctx);
+        out = value_formatter_.format(*it, ctx);
+        ++it;
       }
     }
     return out;
@@ -3283,22 +4273,17 @@ struct formatter<arg_join<It, Char>, Char>
 };
 
 /**
-  Returns an object that formats the iterator range `[begin, end)` with elements
+  Returns a view that formats the iterator range `[begin, end)` with elements
   separated by `sep`.
  */
-template <typename It>
-arg_join<It, char> join(It begin, It end, string_view sep) {
-  return {begin, end, sep};
-}
-
-template <typename It>
-arg_join<It, wchar_t> join(It begin, It end, wstring_view sep) {
+template <typename It, typename Sentinel>
+auto join(It begin, Sentinel end, string_view sep) -> join_view<It, Sentinel> {
   return {begin, end, sep};
 }
 
 /**
   \rst
-  Returns an object that formats `range` with elements separated by `sep`.
+  Returns a view that formats `range` with elements separated by `sep`.
 
   **Example**::
 
@@ -3313,14 +4298,8 @@ arg_join<It, wchar_t> join(It begin, It end, wstring_view sep) {
   \endrst
  */
 template <typename Range>
-arg_join<internal::iterator_t<const Range>, char> join(const Range& range,
-                                                       string_view sep) {
-  return join(std::begin(range), std::end(range), sep);
-}
-
-template <typename Range>
-arg_join<internal::iterator_t<const Range>, wchar_t> join(const Range& range,
-                                                          wstring_view sep) {
+auto join(Range&& range, string_view sep)
+    -> join_view<detail::iterator_t<Range>, detail::sentinel_t<Range>> {
   return join(std::begin(range), std::end(range), sep);
 }
 
@@ -3335,258 +4314,127 @@ arg_join<internal::iterator_t<const Range>, wchar_t> join(const Range& range,
     std::string answer = fmt::to_string(42);
   \endrst
  */
-template <typename T> inline std::string to_string(const T& value) {
-  return format("{}", value);
-}
-
-/**
-  Converts *value* to ``std::wstring`` using the default format for type *T*.
- */
-template <typename T> inline std::wstring to_wstring(const T& value) {
-  return format(L"{}", value);
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
+                                    !detail::has_format_as<T>::value)>
+inline auto to_string(const T& value) -> std::string {
+  auto buffer = memory_buffer();
+  detail::write<char>(appender(buffer), value);
+  return {buffer.data(), buffer.size()};
 }
 
-template <typename Char, std::size_t SIZE>
-std::basic_string<Char> to_string(const basic_memory_buffer<Char, SIZE>& buf) {
-  return std::basic_string<Char>(buf.data(), buf.size());
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+FMT_NODISCARD inline auto to_string(T value) -> std::string {
+  // The buffer should be large enough to store the number including the sign
+  // or "false" for bool.
+  constexpr int max_size = detail::digits10<T>() + 2;
+  char buffer[max_size > 5 ? static_cast<unsigned>(max_size) : 5];
+  char* begin = buffer;
+  return std::string(begin, detail::write<char>(begin, value));
 }
 
-template <typename Char>
-typename buffer_context<Char>::iterator internal::vformat_to(
-    internal::buffer<Char>& buf, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str),
-                                          args);
-}
-
-template <typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
-inline typename buffer_context<Char>::iterator vformat_to(
-    internal::buffer<Char>& buf, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat_to(buf, to_string_view(format_str), args);
-}
-
-template <typename S, typename... Args, std::size_t SIZE = inline_buffer_size,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
-inline typename buffer_context<Char>::iterator format_to(
-    basic_memory_buffer<Char, SIZE>& buf, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = buffer_context<Char>;
-  return internal::vformat_to(buf, to_string_view(format_str),
-                              make_format_args<context>(args...));
-}
-
-template <typename OutputIt, typename Char = char>
-using format_context_t = basic_format_context<OutputIt, Char>;
-
-template <typename OutputIt, typename Char = char>
-using format_args_t = basic_format_args<format_context_t<OutputIt, Char>>;
-
-template <typename S, typename OutputIt, typename... Args,
-          FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
-inline OutputIt vformat_to(
-    OutputIt out, const S& format_str,
-    format_args_t<type_identity_t<OutputIt>, char_t<S>> args) {
-  using range = internal::output_range<OutputIt, char_t<S>>;
-  return vformat_to<arg_formatter<range>>(range(out),
-                                          to_string_view(format_str), args);
+template <typename Char, size_t SIZE>
+FMT_NODISCARD auto to_string(const basic_memory_buffer<Char, SIZE>& buf)
+    -> std::basic_string<Char> {
+  auto size = buf.size();
+  detail::assume(size < std::basic_string<Char>().max_size());
+  return std::basic_string<Char>(buf.data(), size);
 }
 
-/**
- \rst
- Formats arguments, writes the result to the output iterator ``out`` and returns
- the iterator past the end of the output range.
-
- **Example**::
-
-   std::vector<char> out;
-   fmt::format_to(std::back_inserter(out), "{}", 42);
- \endrst
- */
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value &&
-              internal::is_string<S>::value)>
-inline OutputIt format_to(OutputIt out, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_context_t<OutputIt, char_t<S>>;
-  return vformat_to(out, to_string_view(format_str),
-                    make_format_args<context>(args...));
-}
-
-template <typename OutputIt> struct format_to_n_result {
-  /** Iterator past the end of the output range. */
-  OutputIt out;
-  /** Total (not truncated) output size. */
-  std::size_t size;
-};
-
-template <typename OutputIt, typename Char = typename OutputIt::value_type>
-using format_to_n_context =
-    format_context_t<internal::truncating_iterator<OutputIt>, Char>;
-
-template <typename OutputIt, typename Char = typename OutputIt::value_type>
-using format_to_n_args = basic_format_args<format_to_n_context<OutputIt, Char>>;
-
-template <typename OutputIt, typename Char, typename... Args>
-inline format_arg_store<format_to_n_context<OutputIt, Char>, Args...>
-make_format_to_n_args(const Args&... args) {
-  return format_arg_store<format_to_n_context<OutputIt, Char>, Args...>(
-      args...);
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
+                                    detail::has_format_as<T>::value)>
+inline auto to_string(const T& value) -> std::string {
+  return to_string(format_as(value));
 }
 
-template <typename OutputIt, typename Char, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
-inline format_to_n_result<OutputIt> vformat_to_n(
-    OutputIt out, std::size_t n, basic_string_view<Char> format_str,
-    format_to_n_args<type_identity_t<OutputIt>, type_identity_t<Char>> args) {
-  auto it = vformat_to(internal::truncating_iterator<OutputIt>(out, n),
-                       format_str, args);
-  return {it.base(), it.count()};
-}
+FMT_END_EXPORT
 
-/**
- \rst
- Formats arguments, writes up to ``n`` characters of the result to the output
- iterator ``out`` and returns the total output size and the iterator past the
- end of the output range.
- \endrst
- */
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value&&
-                            internal::is_output_iterator<OutputIt>::value)>
-inline format_to_n_result<OutputIt> format_to_n(OutputIt out, std::size_t n,
-                                                const S& format_str,
-                                                const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_to_n_context<OutputIt, char_t<S>>;
-  return vformat_to_n(out, n, to_string_view(format_str),
-                      make_format_args<context>(args...));
-}
+namespace detail {
 
 template <typename Char>
-inline std::basic_string<Char> internal::vformat(
-    basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
-  return to_string(buffer);
-}
+void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
+                typename vformat_args<Char>::type args, locale_ref loc) {
+  auto out = buffer_appender<Char>(buf);
+  if (fmt.size() == 2 && equal2(fmt.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) throw_format_error("argument not found");
+    visit_format_arg(default_arg_formatter<Char>{out, args, loc}, arg);
+    return;
+  }
+
+  struct format_handler : error_handler {
+    basic_format_parse_context<Char> parse_context;
+    buffer_context<Char> context;
+
+    format_handler(buffer_appender<Char> p_out, basic_string_view<Char> str,
+                   basic_format_args<buffer_context<Char>> p_args,
+                   locale_ref p_loc)
+        : parse_context(str), context(p_out, p_args, p_loc) {}
+
+    void on_text(const Char* begin, const Char* end) {
+      auto text = basic_string_view<Char>(begin, to_unsigned(end - begin));
+      context.advance_to(write<Char>(context.out(), text));
+    }
 
-/**
-  Returns the number of characters in the output of
-  ``format(format_str, args...)``.
- */
-template <typename... Args>
-inline std::size_t formatted_size(string_view format_str, const Args&... args) {
-  return format_to(internal::counting_iterator(), format_str, args...).count();
-}
+    FMT_CONSTEXPR auto on_arg_id() -> int {
+      return parse_context.next_arg_id();
+    }
+    FMT_CONSTEXPR auto on_arg_id(int id) -> int {
+      return parse_context.check_arg_id(id), id;
+    }
+    FMT_CONSTEXPR auto on_arg_id(basic_string_view<Char> id) -> int {
+      int arg_id = context.arg_id(id);
+      if (arg_id < 0) throw_format_error("argument not found");
+      return arg_id;
+    }
 
-template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
-void vprint(std::FILE* f, basic_string_view<Char> format_str,
-            wformat_args args) {
-  wmemory_buffer buffer;
-  internal::vformat_to(buffer, format_str, args);
-  buffer.push_back(L'\0');
-  if (std::fputws(buffer.data(), f) == -1)
-    FMT_THROW(system_error(errno, "cannot write to file"));
-}
+    FMT_INLINE void on_replacement_field(int id, const Char*) {
+      auto arg = get_arg(context, id);
+      context.advance_to(visit_format_arg(
+          default_arg_formatter<Char>{context.out(), context.args(),
+                                      context.locale()},
+          arg));
+    }
 
-template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
-void vprint(basic_string_view<Char> format_str, wformat_args args) {
-  vprint(stdout, format_str, args);
+    auto on_format_specs(int id, const Char* begin, const Char* end)
+        -> const Char* {
+      auto arg = get_arg(context, id);
+      // Not using a visitor for custom types gives better codegen.
+      if (arg.format_custom(begin, parse_context, context))
+        return parse_context.begin();
+      auto specs = detail::dynamic_format_specs<Char>();
+      begin = parse_format_specs(begin, end, specs, parse_context, arg.type());
+      detail::handle_dynamic_spec<detail::width_checker>(
+          specs.width, specs.width_ref, context);
+      detail::handle_dynamic_spec<detail::precision_checker>(
+          specs.precision, specs.precision_ref, context);
+      if (begin == end || *begin != '}')
+        throw_format_error("missing '}' in format string");
+      auto f = arg_formatter<Char>{context.out(), specs, context.locale()};
+      context.advance_to(visit_format_arg(f, arg));
+      return begin;
+    }
+  };
+  detail::parse_format_string<false>(fmt, format_handler(out, fmt, args, loc));
 }
 
-#if FMT_USE_USER_DEFINED_LITERALS
-namespace internal {
-
-#  if FMT_USE_UDL_TEMPLATE
-template <typename Char, Char... CHARS> class udl_formatter {
- public:
-  template <typename... Args>
-  std::basic_string<Char> operator()(Args&&... args) const {
-    FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
-    FMT_CONSTEXPR_DECL bool invalid_format =
-        do_check_format_string<Char, error_handler, remove_cvref_t<Args>...>(
-            basic_string_view<Char>(s, sizeof...(CHARS)));
-    (void)invalid_format;
-    return format(s, std::forward<Args>(args)...);
-  }
-};
-#  else
-template <typename Char> struct udl_formatter {
-  basic_string_view<Char> str;
-
-  template <typename... Args>
-  std::basic_string<Char> operator()(Args&&... args) const {
-    return format(str, std::forward<Args>(args)...);
-  }
-};
-#  endif  // FMT_USE_UDL_TEMPLATE
-
-template <typename Char> struct udl_arg {
-  basic_string_view<Char> str;
-
-  template <typename T> named_arg<T, Char> operator=(T&& value) const {
-    return {str, std::forward<T>(value)};
-  }
-};
+FMT_BEGIN_EXPORT
 
-// Converts string literals to basic_string_view.
-template <typename Char, size_t N>
-FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
-    const Char (&s)[N]) {
-  // Remove trailing null character if needed. Won't be present if this is used
-  // with raw character array (i.e. not defined as a string).
-  return {s,
-          N - ((std::char_traits<Char>::to_int_type(s[N - 1]) == 0) ? 1 : 0)};
-}
+#ifndef FMT_HEADER_ONLY
+extern template FMT_API void vformat_to(buffer<char>&, string_view,
+                                        typename vformat_args<>::type,
+                                        locale_ref);
+extern template FMT_API auto thousands_sep_impl<char>(locale_ref)
+    -> thousands_sep_result<char>;
+extern template FMT_API auto thousands_sep_impl<wchar_t>(locale_ref)
+    -> thousands_sep_result<wchar_t>;
+extern template FMT_API auto decimal_point_impl(locale_ref) -> char;
+extern template FMT_API auto decimal_point_impl(locale_ref) -> wchar_t;
+#endif  // FMT_HEADER_ONLY
 
-// Converts string_view to basic_string_view.
-template <typename Char>
-FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
-    const std_string_view<Char>& s) {
-  return {s.data(), s.size()};
-}
-}  // namespace internal
+}  // namespace detail
 
+#if FMT_USE_USER_DEFINED_LITERALS
 inline namespace literals {
-#  if FMT_USE_UDL_TEMPLATE
-#    pragma GCC diagnostic push
-#    if FMT_CLANG_VERSION
-#      pragma GCC diagnostic ignored "-Wgnu-string-literal-operator-template"
-#    endif
-template <typename Char, Char... CHARS>
-FMT_CONSTEXPR internal::udl_formatter<Char, CHARS...> operator""_format() {
-  return {};
-}
-#    pragma GCC diagnostic pop
-#  else
-/**
-  \rst
-  User-defined literal equivalent of :func:`fmt::format`.
-
-  **Example**::
-
-    using namespace fmt::literals;
-    std::string message = "The answer is {}"_format(42);
-  \endrst
- */
-FMT_CONSTEXPR internal::udl_formatter<char> operator"" _format(const char* s,
-                                                               std::size_t n) {
-  return {{s, n}};
-}
-FMT_CONSTEXPR internal::udl_formatter<wchar_t> operator"" _format(
-    const wchar_t* s, std::size_t n) {
-  return {{s, n}};
-}
-#  endif  // FMT_USE_UDL_TEMPLATE
-
 /**
   \rst
   User-defined literal equivalent of :func:`fmt::arg`.
@@ -3597,46 +4445,85 @@ FMT_CONSTEXPR internal::udl_formatter<wchar_t> operator"" _format(
     fmt::print("Elapsed time: {s:.2f} seconds", "s"_a=1.23);
   \endrst
  */
-FMT_CONSTEXPR internal::udl_arg<char> operator"" _a(const char* s,
-                                                    std::size_t n) {
-  return {{s, n}};
+#  if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <detail_exported::fixed_string Str> constexpr auto operator""_a() {
+  using char_t = remove_cvref_t<decltype(Str.data[0])>;
+  return detail::udl_arg<char_t, sizeof(Str.data) / sizeof(char_t), Str>();
 }
-FMT_CONSTEXPR internal::udl_arg<wchar_t> operator"" _a(const wchar_t* s,
-                                                       std::size_t n) {
-  return {{s, n}};
+#  else
+constexpr auto operator""_a(const char* s, size_t) -> detail::udl_arg<char> {
+  return {s};
 }
+#  endif
 }  // namespace literals
 #endif  // FMT_USE_USER_DEFINED_LITERALS
-FMT_END_NAMESPACE
 
-#define FMT_STRING_IMPL(s, ...)                                     \
-  [] {                                                              \
-    /* Use a macro-like name to avoid shadowing warnings. */        \
-    struct FMT_COMPILE_STRING : fmt::compile_string {               \
-      using char_type = fmt::remove_cvref_t<decltype(s[0])>;        \
-      FMT_MAYBE_UNUSED __VA_ARGS__ FMT_CONSTEXPR                    \
-      operator fmt::basic_string_view<char_type>() const {          \
-        return fmt::internal::compile_string_to_view<char_type>(s); \
-      }                                                             \
-    };                                                              \
-    return FMT_COMPILE_STRING();                                    \
-  }()
+template <typename Locale, FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
+inline auto vformat(const Locale& loc, string_view fmt, format_args args)
+    -> std::string {
+  return detail::vformat(loc, fmt, args);
+}
 
-/**
-  \rst
-  Constructs a compile-time format string from a string literal *s*.
+template <typename Locale, typename... T,
+          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
+inline auto format(const Locale& loc, format_string<T...> fmt, T&&... args)
+    -> std::string {
+  return fmt::vformat(loc, string_view(fmt), fmt::make_format_args(args...));
+}
 
-  **Example**::
+template <typename OutputIt, typename Locale,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
+                            detail::is_locale<Locale>::value)>
+auto vformat_to(OutputIt out, const Locale& loc, string_view fmt,
+                format_args args) -> OutputIt {
+  using detail::get_buffer;
+  auto&& buf = get_buffer<char>(out);
+  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
+  return detail::get_iterator(buf, out);
+}
 
-    // A compile-time error because 'd' is an invalid specifier for strings.
-    std::string s = format(FMT_STRING("{:d}"), "foo");
-  \endrst
- */
-#define FMT_STRING(s) FMT_STRING_IMPL(s, )
+template <typename OutputIt, typename Locale, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
+                            detail::is_locale<Locale>::value)>
+FMT_INLINE auto format_to(OutputIt out, const Locale& loc,
+                          format_string<T...> fmt, T&&... args) -> OutputIt {
+  return vformat_to(out, loc, fmt, fmt::make_format_args(args...));
+}
 
-#if defined(FMT_STRING_ALIAS) && FMT_STRING_ALIAS
-#  define fmt(s) FMT_STRING_IMPL(s, [[deprecated]])
-#endif
+template <typename Locale, typename... T,
+          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
+FMT_NODISCARD FMT_INLINE auto formatted_size(const Locale& loc,
+                                             format_string<T...> fmt,
+                                             T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<>();
+  detail::vformat_to<char>(buf, fmt, fmt::make_format_args(args...),
+                           detail::locale_ref(loc));
+  return buf.count();
+}
+
+FMT_END_EXPORT
+
+template <typename T, typename Char>
+template <typename FormatContext>
+FMT_CONSTEXPR FMT_INLINE auto
+formatter<T, Char,
+          enable_if_t<detail::type_constant<T, Char>::value !=
+                      detail::type::custom_type>>::format(const T& val,
+                                                          FormatContext& ctx)
+    const -> decltype(ctx.out()) {
+  if (specs_.width_ref.kind == detail::arg_id_kind::none &&
+      specs_.precision_ref.kind == detail::arg_id_kind::none) {
+    return detail::write<Char>(ctx.out(), val, specs_, ctx.locale());
+  }
+  auto specs = specs_;
+  detail::handle_dynamic_spec<detail::width_checker>(specs.width,
+                                                     specs.width_ref, ctx);
+  detail::handle_dynamic_spec<detail::precision_checker>(
+      specs.precision, specs.precision_ref, ctx);
+  return detail::write<Char>(ctx.out(), val, specs, ctx.locale());
+}
+
+FMT_END_NAMESPACE
 
 #ifdef FMT_HEADER_ONLY
 #  define FMT_FUNC inline
diff --git a/contrib/fmt/include/fmt/locale.h b/contrib/fmt/include/fmt/locale.h
deleted file mode 100644
index 70bc1935efa..00000000000
--- a/contrib/fmt/include/fmt/locale.h
+++ /dev/null
@@ -1,78 +0,0 @@
-// Formatting library for C++ - std::locale support
-//
-// Copyright (c) 2012 - present, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#ifndef FMT_LOCALE_H_
-#define FMT_LOCALE_H_
-
-#include <locale>
-
-#include "format.h"
-
-FMT_BEGIN_NAMESPACE
-
-namespace internal {
-template <typename Char>
-typename buffer_context<Char>::iterator vformat_to(
-    const std::locale& loc, buffer<Char>& buf,
-    basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str), args,
-                                          internal::locale_ref(loc));
-}
-
-template <typename Char>
-std::basic_string<Char> vformat(
-    const std::locale& loc, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  internal::vformat_to(loc, buffer, format_str, args);
-  return fmt::to_string(buffer);
-}
-}  // namespace internal
-
-template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
-    const std::locale& loc, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat(loc, to_string_view(format_str), args);
-}
-
-template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const std::locale& loc,
-                                      const S& format_str, Args&&... args) {
-  return internal::vformat(
-      loc, to_string_view(format_str),
-      internal::make_args_checked<Args...>(format_str, args...));
-}
-
-template <typename S, typename OutputIt, typename... Args,
-          typename Char = enable_if_t<
-              internal::is_output_iterator<OutputIt>::value, char_t<S>>>
-inline OutputIt vformat_to(
-    OutputIt out, const std::locale& loc, const S& format_str,
-    format_args_t<type_identity_t<OutputIt>, Char> args) {
-  using range = internal::output_range<OutputIt, Char>;
-  return vformat_to<arg_formatter<range>>(
-      range(out), to_string_view(format_str), args, internal::locale_ref(loc));
-}
-
-template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value&&
-                            internal::is_string<S>::value)>
-inline OutputIt format_to(OutputIt out, const std::locale& loc,
-                          const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
-  using context = format_context_t<OutputIt, char_t<S>>;
-  format_arg_store<context, Args...> as{args...};
-  return vformat_to(out, loc, to_string_view(format_str),
-                    basic_format_args<context>(as));
-}
-
-FMT_END_NAMESPACE
-
-#endif  // FMT_LOCALE_H_
diff --git a/contrib/fmt/include/fmt/os.h b/contrib/fmt/include/fmt/os.h
index a1a0d03b635..3c7b3ccb481 100644
--- a/contrib/fmt/include/fmt/os.h
+++ b/contrib/fmt/include/fmt/os.h
@@ -8,33 +8,33 @@
 #ifndef FMT_OS_H_
 #define FMT_OS_H_
 
-#if defined(__MINGW32__) || defined(__CYGWIN__)
-// Workaround MinGW bug https://sourceforge.net/p/mingw/bugs/2024/.
-#  undef __STRICT_ANSI__
-#endif
-
 #include <cerrno>
-#include <clocale>  // for locale_t
 #include <cstddef>
 #include <cstdio>
-#include <cstdlib>  // for strtod_l
+#include <system_error>  // std::system_error
+
+#include "format.h"
 
 #if defined __APPLE__ || defined(__FreeBSD__)
-#  include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
+#  if FMT_HAS_INCLUDE(<xlocale.h>)
+#    include <xlocale.h>  // for LC_NUMERIC_MASK on OS X
+#  endif
 #endif
 
-#include "format.h"
-
+#ifndef FMT_USE_FCNTL
 // UWP doesn't provide _pipe.
-#if FMT_HAS_INCLUDE("winapifamily.h")
-#  include <winapifamily.h>
-#endif
-#if FMT_HAS_INCLUDE("fcntl.h") && \
-    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
-#  include <fcntl.h>  // for O_RDONLY
-#  define FMT_USE_FCNTL 1
-#else
-#  define FMT_USE_FCNTL 0
+#  if FMT_HAS_INCLUDE("winapifamily.h")
+#    include <winapifamily.h>
+#  endif
+#  if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
+       defined(__linux__)) &&                              \
+      (!defined(WINAPI_FAMILY) ||                          \
+       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#    include <fcntl.h>  // for O_RDONLY
+#    define FMT_USE_FCNTL 1
+#  else
+#    define FMT_USE_FCNTL 0
+#  endif
 #endif
 
 #ifndef FMT_POSIX
@@ -48,9 +48,10 @@
 
 // Calls to system functions are wrapped in FMT_SYSTEM for testability.
 #ifdef FMT_SYSTEM
+#  define FMT_HAS_SYSTEM
 #  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
 #else
-#  define FMT_SYSTEM(call) call
+#  define FMT_SYSTEM(call) ::call
 #  ifdef _WIN32
 // Fix warnings about deprecated symbols.
 #    define FMT_POSIX_CALL(call) ::_##call
@@ -73,6 +74,7 @@
 #define FMT_RETRY(result, expression) FMT_RETRY_VAL(result, expression, -1)
 
 FMT_BEGIN_NAMESPACE
+FMT_BEGIN_EXPORT
 
 /**
   \rst
@@ -115,95 +117,74 @@ template <typename Char> class basic_cstring_view {
   basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}
 
   /** Returns the pointer to a C string. */
-  const Char* c_str() const { return data_; }
+  auto c_str() const -> const Char* { return data_; }
 };
 
 using cstring_view = basic_cstring_view<char>;
 using wcstring_view = basic_cstring_view<wchar_t>;
 
-// An error code.
-class error_code {
- private:
-  int value_;
-
- public:
-  explicit error_code(int value = 0) FMT_NOEXCEPT : value_(value) {}
-
-  int get() const FMT_NOEXCEPT { return value_; }
-};
-
 #ifdef _WIN32
-namespace internal {
-// A converter from UTF-16 to UTF-8.
-// It is only provided for Windows since other systems support UTF-8 natively.
-class utf16_to_utf8 {
- private:
-  memory_buffer buffer_;
-
- public:
-  utf16_to_utf8() {}
-  FMT_API explicit utf16_to_utf8(wstring_view s);
-  operator string_view() const { return string_view(&buffer_[0], size()); }
-  size_t size() const { return buffer_.size() - 1; }
-  const char* c_str() const { return &buffer_[0]; }
-  std::string str() const { return std::string(&buffer_[0], size()); }
-
-  // Performs conversion returning a system error code instead of
-  // throwing exception on conversion error. This method may still throw
-  // in case of memory allocation error.
-  FMT_API int convert(wstring_view s);
-};
+FMT_API const std::error_category& system_category() noexcept;
 
+namespace detail {
 FMT_API void format_windows_error(buffer<char>& out, int error_code,
-                                  string_view message) FMT_NOEXCEPT;
-}  // namespace internal
+                                  const char* message) noexcept;
+}
 
-/** A Windows error. */
-class windows_error : public system_error {
- private:
-  FMT_API void init(int error_code, string_view format_str, format_args args);
+FMT_API std::system_error vwindows_error(int error_code, string_view format_str,
+                                         format_args args);
 
- public:
-  /**
-   \rst
-   Constructs a :class:`fmt::windows_error` object with the description
-   of the form
-
-   .. parsed-literal::
-     *<message>*: *<system-message>*
-
-   where *<message>* is the formatted message and *<system-message>* is the
-   system message corresponding to the error code.
-   *error_code* is a Windows error code as given by ``GetLastError``.
-   If *error_code* is not a valid error code such as -1, the system message
-   will look like "error -1".
-
-   **Example**::
-
-     // This throws a windows_error with the description
-     //   cannot open file 'madeup': The system cannot find the file specified.
-     // or similar (system message may vary).
-     const char *filename = "madeup";
-     LPOFSTRUCT of = LPOFSTRUCT();
-     HFILE file = OpenFile(filename, &of, OF_READ);
-     if (file == HFILE_ERROR) {
-       throw fmt::windows_error(GetLastError(),
-                                "cannot open file '{}'", filename);
-     }
-   \endrst
-  */
-  template <typename... Args>
-  windows_error(int error_code, string_view message, const Args&... args) {
-    init(error_code, message, make_format_args(args...));
-  }
-};
+/**
+ \rst
+ Constructs a :class:`std::system_error` object with the description
+ of the form
+
+ .. parsed-literal::
+   *<message>*: *<system-message>*
+
+ where *<message>* is the formatted message and *<system-message>* is the
+ system message corresponding to the error code.
+ *error_code* is a Windows error code as given by ``GetLastError``.
+ If *error_code* is not a valid error code such as -1, the system message
+ will look like "error -1".
+
+ **Example**::
+
+   // This throws a system_error with the description
+   //   cannot open file 'madeup': The system cannot find the file specified.
+   // or similar (system message may vary).
+   const char *filename = "madeup";
+   LPOFSTRUCT of = LPOFSTRUCT();
+   HFILE file = OpenFile(filename, &of, OF_READ);
+   if (file == HFILE_ERROR) {
+     throw fmt::windows_error(GetLastError(),
+                              "cannot open file '{}'", filename);
+   }
+ \endrst
+*/
+template <typename... Args>
+std::system_error windows_error(int error_code, string_view message,
+                                const Args&... args) {
+  return vwindows_error(error_code, message, fmt::make_format_args(args...));
+}
 
 // Reports a Windows error without throwing an exception.
 // Can be used to report errors from destructors.
-FMT_API void report_windows_error(int error_code,
-                                  string_view message) FMT_NOEXCEPT;
+FMT_API void report_windows_error(int error_code, const char* message) noexcept;
+#else
+inline auto system_category() noexcept -> const std::error_category& {
+  return std::system_category();
+}
 #endif  // _WIN32
 
+// std::system is not available on some platforms such as iOS (#2248).
+#ifdef __OSX__
+template <typename S, typename... Args, typename Char = char_t<S>>
+void say(const S& format_str, Args&&... args) {
+  std::system(format("say \"{}\"", format(format_str, args...)).c_str());
+}
+#endif
+
 // A buffered file.
 class buffered_file {
  private:
@@ -218,17 +199,17 @@ class buffered_file {
   void operator=(const buffered_file&) = delete;
 
   // Constructs a buffered_file object which doesn't represent any file.
-  buffered_file() FMT_NOEXCEPT : file_(nullptr) {}
+  buffered_file() noexcept : file_(nullptr) {}
 
   // Destroys the object closing the file it represents if any.
-  FMT_API ~buffered_file() FMT_NOEXCEPT;
+  FMT_API ~buffered_file() noexcept;
 
  public:
-  buffered_file(buffered_file&& other) FMT_NOEXCEPT : file_(other.file_) {
+  buffered_file(buffered_file&& other) noexcept : file_(other.file_) {
     other.file_ = nullptr;
   }
 
-  buffered_file& operator=(buffered_file&& other) {
+  auto operator=(buffered_file&& other) -> buffered_file& {
     close();
     file_ = other.file_;
     other.file_ = nullptr;
@@ -242,11 +223,9 @@ class buffered_file {
   FMT_API void close();
 
   // Returns the pointer to a FILE object representing this file.
-  FILE* get() const FMT_NOEXCEPT { return file_; }
+  auto get() const noexcept -> FILE* { return file_; }
 
-  // We place parentheses around fileno to workaround a bug in some versions
-  // of MinGW that define fileno as a macro.
-  FMT_API int(fileno)() const;
+  FMT_API auto descriptor() const -> int;
 
   void vprint(string_view format_str, format_args args) {
     fmt::vprint(file_, format_str, args);
@@ -254,18 +233,18 @@ class buffered_file {
 
   template <typename... Args>
   inline void print(string_view format_str, const Args&... args) {
-    vprint(format_str, make_format_args(args...));
+    vprint(format_str, fmt::make_format_args(args...));
   }
 };
 
 #if FMT_USE_FCNTL
 // A file. Closed file is represented by a file object with descriptor -1.
-// Methods that are not declared with FMT_NOEXCEPT may throw
+// Methods that are not declared with noexcept may throw
 // fmt::system_error in case of failure. Note that some errors such as
 // closing the file multiple times will cause a crash on Windows rather
 // than an exception. You can get standard behavior by overriding the
 // invalid parameter handler with _set_invalid_parameter_handler.
-class file {
+class FMT_API file {
  private:
   int fd_;  // File descriptor.
 
@@ -277,22 +256,26 @@ class file {
   enum {
     RDONLY = FMT_POSIX(O_RDONLY),  // Open for reading only.
     WRONLY = FMT_POSIX(O_WRONLY),  // Open for writing only.
-    RDWR = FMT_POSIX(O_RDWR)       // Open for reading and writing.
+    RDWR = FMT_POSIX(O_RDWR),      // Open for reading and writing.
+    CREATE = FMT_POSIX(O_CREAT),   // Create if the file doesn't exist.
+    APPEND = FMT_POSIX(O_APPEND),  // Open in append mode.
+    TRUNC = FMT_POSIX(O_TRUNC)     // Truncate the content of the file.
   };
 
   // Constructs a file object which doesn't represent any file.
-  file() FMT_NOEXCEPT : fd_(-1) {}
+  file() noexcept : fd_(-1) {}
 
   // Opens a file and constructs a file object representing this file.
-  FMT_API file(cstring_view path, int oflag);
+  file(cstring_view path, int oflag);
 
  public:
   file(const file&) = delete;
   void operator=(const file&) = delete;
 
-  file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
+  file(file&& other) noexcept : fd_(other.fd_) { other.fd_ = -1; }
 
-  file& operator=(file&& other) FMT_NOEXCEPT {
+  // Move assignment is not noexcept because close may throw.
+  auto operator=(file&& other) -> file& {
     close();
     fd_ = other.fd_;
     other.fd_ = -1;
@@ -300,93 +283,173 @@ class file {
   }
 
   // Destroys the object closing the file it represents if any.
-  FMT_API ~file() FMT_NOEXCEPT;
+  ~file() noexcept;
 
   // Returns the file descriptor.
-  int descriptor() const FMT_NOEXCEPT { return fd_; }
+  auto descriptor() const noexcept -> int { return fd_; }
 
   // Closes the file.
-  FMT_API void close();
+  void close();
 
   // Returns the file size. The size has signed type for consistency with
   // stat::st_size.
-  FMT_API long long size() const;
+  auto size() const -> long long;
 
   // Attempts to read count bytes from the file into the specified buffer.
-  FMT_API std::size_t read(void* buffer, std::size_t count);
+  auto read(void* buffer, size_t count) -> size_t;
 
   // Attempts to write count bytes from the specified buffer to the file.
-  FMT_API std::size_t write(const void* buffer, std::size_t count);
+  auto write(const void* buffer, size_t count) -> size_t;
 
   // Duplicates a file descriptor with the dup function and returns
   // the duplicate as a file object.
-  FMT_API static file dup(int fd);
+  static auto dup(int fd) -> file;
 
   // Makes fd be the copy of this file descriptor, closing fd first if
   // necessary.
-  FMT_API void dup2(int fd);
+  void dup2(int fd);
 
   // Makes fd be the copy of this file descriptor, closing fd first if
   // necessary.
-  FMT_API void dup2(int fd, error_code& ec) FMT_NOEXCEPT;
+  void dup2(int fd, std::error_code& ec) noexcept;
 
   // Creates a pipe setting up read_end and write_end file objects for reading
   // and writing respectively.
-  FMT_API static void pipe(file& read_end, file& write_end);
+  // DEPRECATED! Taking files as out parameters is deprecated.
+  static void pipe(file& read_end, file& write_end);
 
   // Creates a buffered_file object associated with this file and detaches
   // this file object from the file.
-  FMT_API buffered_file fdopen(const char* mode);
+  auto fdopen(const char* mode) -> buffered_file;
+
+#  if defined(_WIN32) && !defined(__MINGW32__)
+  // Opens a file and constructs a file object representing this file by
+  // wcstring_view filename. Windows only.
+  static file open_windows_file(wcstring_view path, int oflag);
+#  endif
 };
 
 // Returns the memory page size.
-long getpagesize();
-#endif  // FMT_USE_FCNTL
+auto getpagesize() -> long;
 
-#ifdef FMT_LOCALE
-// A "C" numeric locale.
-class locale {
- private:
-#  ifdef _WIN32
-  using locale_t = _locale_t;
+namespace detail {
+
+struct buffer_size {
+  buffer_size() = default;
+  size_t value = 0;
+  auto operator=(size_t val) const -> buffer_size {
+    auto bs = buffer_size();
+    bs.value = val;
+    return bs;
+  }
+};
 
-  static void freelocale(locale_t loc) { _free_locale(loc); }
+struct ostream_params {
+  int oflag = file::WRONLY | file::CREATE | file::TRUNC;
+  size_t buffer_size = BUFSIZ > 32768 ? BUFSIZ : 32768;
 
-  static double strtod_l(const char* nptr, char** endptr, _locale_t loc) {
-    return _strtod_l(nptr, endptr, loc);
+  ostream_params() {}
+
+  template <typename... T>
+  ostream_params(T... params, int new_oflag) : ostream_params(params...) {
+    oflag = new_oflag;
+  }
+
+  template <typename... T>
+  ostream_params(T... params, detail::buffer_size bs)
+      : ostream_params(params...) {
+    this->buffer_size = bs.value;
   }
+
+// Intel has a bug that results in failure to deduce a constructor
+// for empty parameter packs.
+#  if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 2000
+  ostream_params(int new_oflag) : oflag(new_oflag) {}
+  ostream_params(detail::buffer_size bs) : buffer_size(bs.value) {}
 #  endif
+};
 
-  locale_t locale_;
+class file_buffer final : public buffer<char> {
+  file file_;
+
+  FMT_API void grow(size_t) override;
 
  public:
-  using type = locale_t;
-  locale(const locale&) = delete;
-  void operator=(const locale&) = delete;
+  FMT_API file_buffer(cstring_view path, const ostream_params& params);
+  FMT_API file_buffer(file_buffer&& other);
+  FMT_API ~file_buffer();
+
+  void flush() {
+    if (size() == 0) return;
+    file_.write(data(), size() * sizeof(data()[0]));
+    clear();
+  }
 
-  locale() {
-#  ifndef _WIN32
-    locale_ = FMT_SYSTEM(newlocale(LC_NUMERIC_MASK, "C", nullptr));
-#  else
-    locale_ = _create_locale(LC_NUMERIC, "C");
-#  endif
-    if (!locale_) FMT_THROW(system_error(errno, "cannot create locale"));
+  void close() {
+    flush();
+    file_.close();
   }
-  ~locale() { freelocale(locale_); }
+};
+
+}  // namespace detail
+
+// Added {} below to work around default constructor error known to
+// occur in Xcode versions 7.2.1 and 8.2.1.
+constexpr detail::buffer_size buffer_size{};
+
+/** A fast output stream which is not thread-safe. */
+class FMT_API ostream {
+ private:
+  FMT_MSC_WARNING(suppress : 4251)
+  detail::file_buffer buffer_;
 
-  type get() const { return locale_; }
+  ostream(cstring_view path, const detail::ostream_params& params)
+      : buffer_(path, params) {}
 
-  // Converts string to floating-point number and advances str past the end
-  // of the parsed input.
-  double strtod(const char*& str) const {
-    char* end = nullptr;
-    double result = strtod_l(str, &end, locale_);
-    str = end;
-    return result;
+ public:
+  ostream(ostream&& other) : buffer_(std::move(other.buffer_)) {}
+
+  ~ostream();
+
+  void flush() { buffer_.flush(); }
+
+  template <typename... T>
+  friend auto output_file(cstring_view path, T... params) -> ostream;
+
+  void close() { buffer_.close(); }
+
+  /**
+    Formats ``args`` according to specifications in ``fmt`` and writes the
+    output to the file.
+   */
+  template <typename... T> void print(format_string<T...> fmt, T&&... args) {
+    vformat_to(std::back_inserter(buffer_), fmt,
+               fmt::make_format_args(args...));
   }
 };
-using Locale FMT_DEPRECATED_ALIAS = locale;
-#endif  // FMT_LOCALE
+
+/**
+  \rst
+  Opens a file for writing. Supported parameters passed in *params*:
+
+  * ``<integer>``: Flags passed to `open
+    <https://pubs.opengroup.org/onlinepubs/007904875/functions/open.html>`_
+    (``file::WRONLY | file::CREATE | file::TRUNC`` by default)
+  * ``buffer_size=<integer>``: Output buffer size
+
+  **Example**::
+
+    auto out = fmt::output_file("guide.txt");
+    out.print("Don't {}", "Panic");
+  \endrst
+ */
+template <typename... T>
+inline auto output_file(cstring_view path, T... params) -> ostream {
+  return {path, detail::ostream_params(params...)};
+}
+#endif  // FMT_USE_FCNTL
+
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_OS_H_
diff --git a/contrib/fmt/include/fmt/ostream.h b/contrib/fmt/include/fmt/ostream.h
index 4526f523838..26fb3b5ac07 100644
--- a/contrib/fmt/include/fmt/ostream.h
+++ b/contrib/fmt/include/fmt/ostream.h
@@ -8,79 +8,107 @@
 #ifndef FMT_OSTREAM_H_
 #define FMT_OSTREAM_H_
 
-#include <ostream>
+#include <fstream>  // std::filebuf
+
+#ifdef _WIN32
+#  ifdef __GLIBCXX__
+#    include <ext/stdio_filebuf.h>
+#    include <ext/stdio_sync_filebuf.h>
+#  endif
+#  include <io.h>
+#endif
 
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
+namespace detail {
 
-template <typename CHar> class basic_printf_parse_context;
-template <typename OutputIt, typename Char> class basic_printf_context;
-
-namespace internal {
-
-template <class Char> class formatbuf : public std::basic_streambuf<Char> {
+template <typename Streambuf> class formatbuf : public Streambuf {
  private:
-  using int_type = typename std::basic_streambuf<Char>::int_type;
-  using traits_type = typename std::basic_streambuf<Char>::traits_type;
+  using char_type = typename Streambuf::char_type;
+  using streamsize = decltype(std::declval<Streambuf>().sputn(nullptr, 0));
+  using int_type = typename Streambuf::int_type;
+  using traits_type = typename Streambuf::traits_type;
 
-  buffer<Char>& buffer_;
+  buffer<char_type>& buffer_;
 
  public:
-  formatbuf(buffer<Char>& buf) : buffer_(buf) {}
+  explicit formatbuf(buffer<char_type>& buf) : buffer_(buf) {}
 
  protected:
-  // The put-area is actually always empty. This makes the implementation
-  // simpler and has the advantage that the streambuf and the buffer are always
-  // in sync and sputc never writes into uninitialized memory. The obvious
-  // disadvantage is that each call to sputc always results in a (virtual) call
-  // to overflow. There is no disadvantage here for sputn since this always
-  // results in a call to xsputn.
-
-  int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
+  // The put area is always empty. This makes the implementation simpler and has
+  // the advantage that the streambuf and the buffer are always in sync and
+  // sputc never writes into uninitialized memory. A disadvantage is that each
+  // call to sputc always results in a (virtual) call to overflow. There is no
+  // disadvantage here for sputn since this always results in a call to xsputn.
+
+  auto overflow(int_type ch) -> int_type override {
     if (!traits_type::eq_int_type(ch, traits_type::eof()))
-      buffer_.push_back(static_cast<Char>(ch));
+      buffer_.push_back(static_cast<char_type>(ch));
     return ch;
   }
 
-  std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
+  auto xsputn(const char_type* s, streamsize count) -> streamsize override {
     buffer_.append(s, s + count);
     return count;
   }
 };
 
-template <typename Char> struct test_stream : std::basic_ostream<Char> {
- private:
-  // Hide all operator<< from std::basic_ostream<Char>.
-  void_t<> operator<<(null<>);
-  void_t<> operator<<(const Char*);
-
-  template <typename T, FMT_ENABLE_IF(std::is_convertible<T, int>::value &&
-                                      !std::is_enum<T>::value)>
-  void_t<> operator<<(T);
+// Generate a unique explicit instantion in every translation unit using a tag
+// type in an anonymous namespace.
+namespace {
+struct file_access_tag {};
+}  // namespace
+template <typename Tag, typename BufType, FILE* BufType::*FileMemberPtr>
+class file_access {
+  friend auto get_file(BufType& obj) -> FILE* { return obj.*FileMemberPtr; }
 };
 
-// Checks if T has a user-defined operator<< (e.g. not a member of
-// std::ostream).
-template <typename T, typename Char> class is_streamable {
- private:
-  template <typename U>
-  static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
-                                              << std::declval<U>()),
-                                     void_t<>>::value>
-  test(int);
-
-  template <typename> static std::false_type test(...);
-
-  using result = decltype(test<T>(0));
+#if FMT_MSC_VERSION
+template class file_access<file_access_tag, std::filebuf,
+                           &std::filebuf::_Myfile>;
+auto get_file(std::filebuf&) -> FILE*;
+#endif
 
- public:
-  static const bool value = result::value;
-};
+inline auto write_ostream_unicode(std::ostream& os, fmt::string_view data)
+    -> bool {
+  FILE* f = nullptr;
+#if FMT_MSC_VERSION
+  if (auto* buf = dynamic_cast<std::filebuf*>(os.rdbuf()))
+    f = get_file(*buf);
+  else
+    return false;
+#elif defined(_WIN32) && defined(__GLIBCXX__)
+  auto* rdbuf = os.rdbuf();
+  if (auto* sfbuf = dynamic_cast<__gnu_cxx::stdio_sync_filebuf<char>*>(rdbuf))
+    f = sfbuf->file();
+  else if (auto* fbuf = dynamic_cast<__gnu_cxx::stdio_filebuf<char>*>(rdbuf))
+    f = fbuf->file();
+  else
+    return false;
+#else
+  ignore_unused(os, data, f);
+#endif
+#ifdef _WIN32
+  if (f) {
+    int fd = _fileno(f);
+    if (_isatty(fd)) {
+      os.flush();
+      return write_console(fd, data);
+    }
+  }
+#endif
+  return false;
+}
+inline auto write_ostream_unicode(std::wostream&,
+                                  fmt::basic_string_view<wchar_t>) -> bool {
+  return false;
+}
 
 // Write the content of buf to os.
+// It is a separate function rather than a part of vprint to simplify testing.
 template <typename Char>
-void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
+void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   const Char* buf_data = buf.data();
   using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
   unsigned_streamsize size = buf.size();
@@ -94,56 +122,83 @@ void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
 }
 
 template <typename Char, typename T>
-void format_value(buffer<Char>& buf, const T& value,
-                  locale_ref loc = locale_ref()) {
-  formatbuf<Char> format_buf(buf);
-  std::basic_ostream<Char> output(&format_buf);
+void format_value(buffer<Char>& buf, const T& value) {
+  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
+  auto&& output = std::basic_ostream<Char>(&format_buf);
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-  if (loc) output.imbue(loc.get<std::locale>());
+  output.imbue(std::locale::classic());  // The default is always unlocalized.
 #endif
-  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
   output << value;
-  buf.resize(buf.size());
+  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
 }
 
+template <typename T> struct streamed_view {
+  const T& value;
+};
+
+}  // namespace detail
+
 // Formats an object of type T that has an overloaded ostream operator<<.
-template <typename T, typename Char>
-struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
-    : private formatter<basic_string_view<Char>, Char> {
-  auto parse(basic_format_parse_context<Char>& ctx) -> decltype(ctx.begin()) {
-    return formatter<basic_string_view<Char>, Char>::parse(ctx);
-  }
-  template <typename ParseCtx,
-            FMT_ENABLE_IF(std::is_same<
-                          ParseCtx, basic_printf_parse_context<Char>>::value)>
-  auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
+template <typename Char>
+struct basic_ostream_formatter : formatter<basic_string_view<Char>, Char> {
+  void set_debug_format() = delete;
 
-  template <typename OutputIt>
-  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
+  template <typename T, typename OutputIt>
+  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx) const
       -> OutputIt {
-    basic_memory_buffer<Char> buffer;
-    format_value(buffer, value, ctx.locale());
-    basic_string_view<Char> str(buffer.data(), buffer.size());
-    return formatter<basic_string_view<Char>, Char>::format(str, ctx);
+    auto buffer = basic_memory_buffer<Char>();
+    detail::format_value(buffer, value);
+    return formatter<basic_string_view<Char>, Char>::format(
+        {buffer.data(), buffer.size()}, ctx);
   }
+};
+
+using ostream_formatter = basic_ostream_formatter<char>;
+
+template <typename T, typename Char>
+struct formatter<detail::streamed_view<T>, Char>
+    : basic_ostream_formatter<Char> {
   template <typename OutputIt>
-  auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
-      -> OutputIt {
-    basic_memory_buffer<Char> buffer;
-    format_value(buffer, value, ctx.locale());
-    return std::copy(buffer.begin(), buffer.end(), ctx.out());
+  auto format(detail::streamed_view<T> view,
+              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+    return basic_ostream_formatter<Char>::format(view.value, ctx);
   }
 };
-}  // namespace internal
 
-template <typename Char>
-void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
+/**
+  \rst
+  Returns a view that formats `value` via an ostream ``operator<<``.
+
+  **Example**::
+
+    fmt::print("Current thread id: {}\n",
+               fmt::streamed(std::this_thread::get_id()));
+  \endrst
+ */
+template <typename T>
+constexpr auto streamed(const T& value) -> detail::streamed_view<T> {
+  return {value};
+}
+
+namespace detail {
+
+inline void vprint_directly(std::ostream& os, string_view format_str,
+                            format_args args) {
+  auto buffer = memory_buffer();
+  detail::vformat_to(buffer, format_str, args);
+  detail::write_buffer(os, buffer);
+}
+
+}  // namespace detail
+
+FMT_EXPORT template <typename Char>
+void vprint(std::basic_ostream<Char>& os,
+            basic_string_view<type_identity_t<Char>> format_str,
             basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
-  internal::write(os, buffer);
+  auto buffer = basic_memory_buffer<Char>();
+  detail::vformat_to(buffer, format_str, args);
+  if (detail::write_ostream_unicode(os, {buffer.data(), buffer.size()})) return;
+  detail::write_buffer(os, buffer);
 }
 
 /**
@@ -155,12 +210,36 @@ void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
     fmt::print(cerr, "Don't {}!", "panic");
   \endrst
  */
-template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
-void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
-  vprint(os, to_string_view(format_str),
-         internal::make_args_checked<Args...>(format_str, args...));
+FMT_EXPORT template <typename... T>
+void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
+  const auto& vargs = fmt::make_format_args(args...);
+  if (detail::is_utf8())
+    vprint(os, fmt, vargs);
+  else
+    detail::vprint_directly(os, fmt, vargs);
 }
+
+FMT_EXPORT
+template <typename... Args>
+void print(std::wostream& os,
+           basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
+           Args&&... args) {
+  vprint(os, fmt, fmt::make_format_args<buffer_context<wchar_t>>(args...));
+}
+
+FMT_EXPORT template <typename... T>
+void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
+  fmt::print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+FMT_EXPORT
+template <typename... Args>
+void println(std::wostream& os,
+             basic_format_string<wchar_t, type_identity_t<Args>...> fmt,
+             Args&&... args) {
+  print(os, L"{}\n", fmt::format(fmt, std::forward<Args>(args)...));
+}
+
 FMT_END_NAMESPACE
 
 #endif  // FMT_OSTREAM_H_
diff --git a/contrib/fmt/include/fmt/posix.h b/contrib/fmt/include/fmt/posix.h
deleted file mode 100644
index 0e7bc646e07..00000000000
--- a/contrib/fmt/include/fmt/posix.h
+++ /dev/null
@@ -1,2 +0,0 @@
-#include "os.h"
-#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
\ No newline at end of file
diff --git a/contrib/fmt/include/fmt/printf.h b/contrib/fmt/include/fmt/printf.h
index 5e0c4810ab9..07e81577cf3 100644
--- a/contrib/fmt/include/fmt/printf.h
+++ b/contrib/fmt/include/fmt/printf.h
@@ -11,62 +11,106 @@
 #include <algorithm>  // std::max
 #include <limits>     // std::numeric_limits
 
-#include "ostream.h"
+#include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+FMT_BEGIN_EXPORT
+
+template <typename T> struct printf_formatter {
+  printf_formatter() = delete;
+};
+
+template <typename Char> class basic_printf_context {
+ private:
+  detail::buffer_appender<Char> out_;
+  basic_format_args<basic_printf_context> args_;
+
+  static_assert(std::is_same<Char, char>::value ||
+                    std::is_same<Char, wchar_t>::value,
+                "Unsupported code unit type.");
+
+ public:
+  using char_type = Char;
+  using parse_context_type = basic_format_parse_context<Char>;
+  template <typename T> using formatter_type = printf_formatter<T>;
+
+  /**
+    \rst
+    Constructs a ``printf_context`` object. References to the arguments are
+    stored in the context object so make sure they have appropriate lifetimes.
+    \endrst
+   */
+  basic_printf_context(detail::buffer_appender<Char> out,
+                       basic_format_args<basic_printf_context> args)
+      : out_(out), args_(args) {}
+
+  auto out() -> detail::buffer_appender<Char> { return out_; }
+  void advance_to(detail::buffer_appender<Char>) {}
+
+  auto locale() -> detail::locale_ref { return {}; }
+
+  auto arg(int id) const -> basic_format_arg<basic_printf_context> {
+    return args_.get(id);
+  }
+
+  FMT_CONSTEXPR void on_error(const char* message) {
+    detail::error_handler().on_error(message);
+  }
+};
+
+namespace detail {
 
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
 template <bool IsSigned> struct int_checker {
-  template <typename T> static bool fits_in_int(T value) {
+  template <typename T> static auto fits_in_int(T value) -> bool {
     unsigned max = max_value<int>();
     return value <= max;
   }
-  static bool fits_in_int(bool) { return true; }
+  static auto fits_in_int(bool) -> bool { return true; }
 };
 
 template <> struct int_checker<true> {
-  template <typename T> static bool fits_in_int(T value) {
+  template <typename T> static auto fits_in_int(T value) -> bool {
     return value >= (std::numeric_limits<int>::min)() &&
            value <= max_value<int>();
   }
-  static bool fits_in_int(int) { return true; }
+  static auto fits_in_int(int) -> bool { return true; }
 };
 
-class printf_precision_handler {
- public:
+struct printf_precision_handler {
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  int operator()(T value) {
+  auto operator()(T value) -> int {
     if (!int_checker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
-      FMT_THROW(format_error("number is too big"));
+      throw_format_error("number is too big");
     return (std::max)(static_cast<int>(value), 0);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  int operator()(T) {
-    FMT_THROW(format_error("precision is not integer"));
+  auto operator()(T) -> int {
+    throw_format_error("precision is not integer");
     return 0;
   }
 };
 
 // An argument visitor that returns true iff arg is a zero integer.
-class is_zero_int {
- public:
+struct is_zero_int {
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  bool operator()(T value) {
+  auto operator()(T value) -> bool {
     return value == 0;
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  bool operator()(T) {
+  auto operator()(T) -> bool {
     return false;
   }
 };
 
 template <typename T> struct make_unsigned_or_bool : std::make_unsigned<T> {};
 
-template <> struct make_unsigned_or_bool<bool> { using type = bool; };
+template <> struct make_unsigned_or_bool<bool> {
+  using type = bool;
+};
 
 template <typename T, typename Context> class arg_converter {
  private:
@@ -90,22 +134,23 @@ template <typename T, typename Context> class arg_converter {
     if (const_check(sizeof(target_type) <= sizeof(int))) {
       // Extra casts are used to silence warnings.
       if (is_signed) {
-        arg_ = internal::make_arg<Context>(
-            static_cast<int>(static_cast<target_type>(value)));
+        auto n = static_cast<int>(static_cast<target_type>(value));
+        arg_ = detail::make_arg<Context>(n);
       } else {
         using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
-        arg_ = internal::make_arg<Context>(
-            static_cast<unsigned>(static_cast<unsigned_type>(value)));
+        auto n = static_cast<unsigned>(static_cast<unsigned_type>(value));
+        arg_ = detail::make_arg<Context>(n);
       }
     } else {
       if (is_signed) {
         // glibc's printf doesn't sign extend arguments of smaller types:
         //   std::printf("%lld", -42);  // prints "4294967254"
         // but we don't have to do the same because it's a UB.
-        arg_ = internal::make_arg<Context>(static_cast<long long>(value));
+        auto n = static_cast<long long>(value);
+        arg_ = detail::make_arg<Context>(n);
       } else {
-        arg_ = internal::make_arg<Context>(
-            static_cast<typename make_unsigned_or_bool<U>::type>(value));
+        auto n = static_cast<typename make_unsigned_or_bool<U>::type>(value);
+        arg_ = detail::make_arg<Context>(n);
       }
     }
   }
@@ -133,255 +178,142 @@ template <typename Context> class char_converter {
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   void operator()(T value) {
-    arg_ = internal::make_arg<Context>(
-        static_cast<typename Context::char_type>(value));
+    auto c = static_cast<typename Context::char_type>(value);
+    arg_ = detail::make_arg<Context>(c);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
   void operator()(T) {}  // No conversion needed for non-integral types.
 };
 
+// An argument visitor that return a pointer to a C string if argument is a
+// string or null otherwise.
+template <typename Char> struct get_cstring {
+  template <typename T> auto operator()(T) -> const Char* { return nullptr; }
+  auto operator()(const Char* s) -> const Char* { return s; }
+};
+
 // Checks if an argument is a valid printf width specifier and sets
 // left alignment if it is negative.
 template <typename Char> class printf_width_handler {
  private:
-  using format_specs = basic_format_specs<Char>;
-
-  format_specs& specs_;
+  format_specs<Char>& specs_;
 
  public:
-  explicit printf_width_handler(format_specs& specs) : specs_(specs) {}
+  explicit printf_width_handler(format_specs<Char>& specs) : specs_(specs) {}
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-  unsigned operator()(T value) {
+  auto operator()(T value) -> unsigned {
     auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
-    if (internal::is_negative(value)) {
+    if (detail::is_negative(value)) {
       specs_.align = align::left;
       width = 0 - width;
     }
     unsigned int_max = max_value<int>();
-    if (width > int_max) FMT_THROW(format_error("number is too big"));
+    if (width > int_max) throw_format_error("number is too big");
     return static_cast<unsigned>(width);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-  unsigned operator()(T) {
-    FMT_THROW(format_error("width is not integer"));
+  auto operator()(T) -> unsigned {
+    throw_format_error("width is not integer");
     return 0;
   }
 };
 
-template <typename Char, typename Context>
-void printf(buffer<Char>& buf, basic_string_view<Char> format,
-            basic_format_args<Context> args) {
-  Context(std::back_inserter(buf), format, args).format();
-}
-
-template <typename OutputIt, typename Char, typename Context>
-internal::truncating_iterator<OutputIt> printf(
-    internal::truncating_iterator<OutputIt> it, basic_string_view<Char> format,
-    basic_format_args<Context> args) {
-  return Context(it, format, args).format();
+// Workaround for a bug with the XL compiler when initializing
+// printf_arg_formatter's base class.
+template <typename Char>
+auto make_arg_formatter(buffer_appender<Char> iter, format_specs<Char>& s)
+    -> arg_formatter<Char> {
+  return {iter, s, locale_ref()};
 }
-}  // namespace internal
-
-using internal::printf;  // For printing into memory_buffer.
-
-template <typename Range> class printf_arg_formatter;
 
+// The ``printf`` argument formatter.
 template <typename Char>
-class basic_printf_parse_context : public basic_format_parse_context<Char> {
-  using basic_format_parse_context<Char>::basic_format_parse_context;
-};
-template <typename OutputIt, typename Char> class basic_printf_context;
-
-/**
-  \rst
-  The ``printf`` argument formatter.
-  \endrst
- */
-template <typename Range>
-class printf_arg_formatter : public internal::arg_formatter_base<Range> {
- public:
-  using iterator = typename Range::iterator;
-
+class printf_arg_formatter : public arg_formatter<Char> {
  private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_printf_context<iterator, char_type>;
+  using base = arg_formatter<Char>;
+  using context_type = basic_printf_context<Char>;
 
   context_type& context_;
 
-  void write_null_pointer(char) {
-    this->specs()->type = 0;
-    this->write("(nil)");
-  }
-
-  void write_null_pointer(wchar_t) {
-    this->specs()->type = 0;
-    this->write(L"(nil)");
+  void write_null_pointer(bool is_string = false) {
+    auto s = this->specs;
+    s.type = presentation_type::none;
+    write_bytes(this->out, is_string ? "(null)" : "(nil)", s);
   }
 
  public:
-  using format_specs = typename base::format_specs;
+  printf_arg_formatter(buffer_appender<Char> iter, format_specs<Char>& s,
+                       context_type& ctx)
+      : base(make_arg_formatter(iter, s)), context_(ctx) {}
 
-  /**
-    \rst
-    Constructs an argument formatter object.
-    *buffer* is a reference to the output buffer and *specs* contains format
-    specifier information for standard argument types.
-    \endrst
-   */
-  printf_arg_formatter(iterator iter, format_specs& specs, context_type& ctx)
-      : base(Range(iter), &specs, internal::locale_ref()), context_(ctx) {}
-
-  template <typename T, FMT_ENABLE_IF(fmt::internal::is_integral<T>::value)>
-  iterator operator()(T value) {
-    // MSVC2013 fails to compile separate overloads for bool and char_type so
-    // use std::is_same instead.
-    if (std::is_same<T, bool>::value) {
-      format_specs& fmt_specs = *this->specs();
-      if (fmt_specs.type != 's') return base::operator()(value ? 1 : 0);
-      fmt_specs.type = 0;
-      this->write(value != 0);
-    } else if (std::is_same<T, char_type>::value) {
-      format_specs& fmt_specs = *this->specs();
-      if (fmt_specs.type && fmt_specs.type != 'c')
-        return (*this)(static_cast<int>(value));
-      fmt_specs.sign = sign::none;
-      fmt_specs.alt = false;
-      fmt_specs.align = align::right;
-      return base::operator()(value);
-    } else {
-      return base::operator()(value);
+  void operator()(monostate value) { base::operator()(value); }
+
+  template <typename T, FMT_ENABLE_IF(detail::is_integral<T>::value)>
+  void operator()(T value) {
+    // MSVC2013 fails to compile separate overloads for bool and Char so use
+    // std::is_same instead.
+    if (!std::is_same<T, Char>::value) {
+      base::operator()(value);
+      return;
+    }
+    format_specs<Char> fmt_specs = this->specs;
+    if (fmt_specs.type != presentation_type::none &&
+        fmt_specs.type != presentation_type::chr) {
+      return (*this)(static_cast<int>(value));
     }
-    return this->out();
+    fmt_specs.sign = sign::none;
+    fmt_specs.alt = false;
+    fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
+    // align::numeric needs to be overwritten here since the '0' flag is
+    // ignored for non-numeric types
+    if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
+      fmt_specs.align = align::right;
+    write<Char>(this->out, static_cast<Char>(value), fmt_specs);
   }
 
   template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value) {
-    return base::operator()(value);
+  void operator()(T value) {
+    base::operator()(value);
   }
 
   /** Formats a null-terminated C string. */
-  iterator operator()(const char* value) {
+  void operator()(const char* value) {
     if (value)
       base::operator()(value);
-    else if (this->specs()->type == 'p')
-      write_null_pointer(char_type());
     else
-      this->write("(null)");
-    return this->out();
+      write_null_pointer(this->specs.type != presentation_type::pointer);
   }
 
   /** Formats a null-terminated wide C string. */
-  iterator operator()(const wchar_t* value) {
+  void operator()(const wchar_t* value) {
     if (value)
       base::operator()(value);
-    else if (this->specs()->type == 'p')
-      write_null_pointer(char_type());
     else
-      this->write(L"(null)");
-    return this->out();
+      write_null_pointer(this->specs.type != presentation_type::pointer);
   }
 
-  iterator operator()(basic_string_view<char_type> value) {
-    return base::operator()(value);
-  }
-
-  iterator operator()(monostate value) { return base::operator()(value); }
+  void operator()(basic_string_view<Char> value) { base::operator()(value); }
 
   /** Formats a pointer. */
-  iterator operator()(const void* value) {
-    if (value) return base::operator()(value);
-    this->specs()->type = 0;
-    write_null_pointer(char_type());
-    return this->out();
+  void operator()(const void* value) {
+    if (value)
+      base::operator()(value);
+    else
+      write_null_pointer();
   }
 
   /** Formats an argument of a custom (user-defined) type. */
-  iterator operator()(typename basic_format_arg<context_type>::handle handle) {
-    handle.format(context_.parse_context(), context_);
-    return this->out();
+  void operator()(typename basic_format_arg<context_type>::handle handle) {
+    auto parse_ctx = basic_format_parse_context<Char>({});
+    handle.format(parse_ctx, context_);
   }
 };
 
-template <typename T> struct printf_formatter {
-  printf_formatter() = delete;
-
-  template <typename ParseContext>
-  auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-
-  template <typename FormatContext>
-  auto format(const T& value, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::format_value(internal::get_container(ctx.out()), value);
-    return ctx.out();
-  }
-};
-
-/** This template formats data and writes the output to a writer. */
-template <typename OutputIt, typename Char> class basic_printf_context {
- public:
-  /** The character type for the output. */
-  using char_type = Char;
-  using iterator = OutputIt;
-  using format_arg = basic_format_arg<basic_printf_context>;
-  using parse_context_type = basic_printf_parse_context<Char>;
-  template <typename T> using formatter_type = printf_formatter<T>;
-
- private:
-  using format_specs = basic_format_specs<char_type>;
-
-  OutputIt out_;
-  basic_format_args<basic_printf_context> args_;
-  parse_context_type parse_ctx_;
-
-  static void parse_flags(format_specs& specs, const Char*& it,
-                          const Char* end);
-
-  // Returns the argument with specified index or, if arg_index is -1, the next
-  // argument.
-  format_arg get_arg(int arg_index = -1);
-
-  // Parses argument index, flags and width and returns the argument index.
-  int parse_header(const Char*& it, const Char* end, format_specs& specs);
-
- public:
-  /**
-   \rst
-   Constructs a ``printf_context`` object. References to the arguments and
-   the writer are stored in the context object so make sure they have
-   appropriate lifetimes.
-   \endrst
-   */
-  basic_printf_context(OutputIt out, basic_string_view<char_type> format_str,
-                       basic_format_args<basic_printf_context> args)
-      : out_(out), args_(args), parse_ctx_(format_str) {}
-
-  OutputIt out() { return out_; }
-  void advance_to(OutputIt it) { out_ = it; }
-
-  internal::locale_ref locale() { return {}; }
-
-  format_arg arg(int id) const { return args_.get(id); }
-
-  parse_context_type& parse_context() { return parse_ctx_; }
-
-  FMT_CONSTEXPR void on_error(const char* message) {
-    parse_ctx_.on_error(message);
-  }
-
-  /** Formats stored arguments and writes the output to the range. */
-  template <typename ArgFormatter = printf_arg_formatter<buffer_range<Char>>>
-  OutputIt format();
-};
-
-template <typename OutputIt, typename Char>
-void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
-                                                       const Char*& it,
-                                                       const Char* end) {
+template <typename Char>
+void parse_flags(format_specs<Char>& specs, const Char*& it, const Char* end) {
   for (; it != end; ++it) {
     switch (*it) {
     case '-':
@@ -394,7 +326,7 @@ void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
       specs.fill[0] = '0';
       break;
     case ' ':
-      specs.sign = sign::space;
+      if (specs.sign != sign::plus) specs.sign = sign::space;
       break;
     case '#':
       specs.alt = true;
@@ -405,35 +337,24 @@ void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
   }
 }
 
-template <typename OutputIt, typename Char>
-typename basic_printf_context<OutputIt, Char>::format_arg
-basic_printf_context<OutputIt, Char>::get_arg(int arg_index) {
-  if (arg_index < 0)
-    arg_index = parse_ctx_.next_arg_id();
-  else
-    parse_ctx_.check_arg_id(--arg_index);
-  return internal::get_arg(*this, arg_index);
-}
-
-template <typename OutputIt, typename Char>
-int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
-                                                       const Char* end,
-                                                       format_specs& specs) {
+template <typename Char, typename GetArg>
+auto parse_header(const Char*& it, const Char* end, format_specs<Char>& specs,
+                  GetArg get_arg) -> int {
   int arg_index = -1;
-  char_type c = *it;
+  Char c = *it;
   if (c >= '0' && c <= '9') {
     // Parse an argument index (if followed by '$') or a width possibly
     // preceded with '0' flag(s).
-    internal::error_handler eh;
-    int value = parse_nonnegative_int(it, end, eh);
+    int value = parse_nonnegative_int(it, end, -1);
     if (it != end && *it == '$') {  // value is an argument index
       ++it;
-      arg_index = value;
+      arg_index = value != -1 ? value : max_value<int>();
     } else {
       if (c == '0') specs.fill[0] = '0';
       if (value != 0) {
         // Nonzero value means that we parsed width and don't need to
         // parse it or flags again, so return now.
+        if (value == -1) throw_format_error("number is too big");
         specs.width = value;
         return arg_index;
       }
@@ -443,71 +364,140 @@ int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
   // Parse width.
   if (it != end) {
     if (*it >= '0' && *it <= '9') {
-      internal::error_handler eh;
-      specs.width = parse_nonnegative_int(it, end, eh);
+      specs.width = parse_nonnegative_int(it, end, -1);
+      if (specs.width == -1) throw_format_error("number is too big");
     } else if (*it == '*') {
       ++it;
       specs.width = static_cast<int>(visit_format_arg(
-          internal::printf_width_handler<char_type>(specs), get_arg()));
+          detail::printf_width_handler<Char>(specs), get_arg(-1)));
     }
   }
   return arg_index;
 }
 
-template <typename OutputIt, typename Char>
-template <typename ArgFormatter>
-OutputIt basic_printf_context<OutputIt, Char>::format() {
-  auto out = this->out();
-  const Char* start = parse_ctx_.begin();
-  const Char* end = parse_ctx_.end();
+inline auto parse_printf_presentation_type(char c, type t)
+    -> presentation_type {
+  using pt = presentation_type;
+  constexpr auto integral_set = sint_set | uint_set | bool_set | char_set;
+  switch (c) {
+  case 'd':
+    return in(t, integral_set) ? pt::dec : pt::none;
+  case 'o':
+    return in(t, integral_set) ? pt::oct : pt::none;
+  case 'x':
+    return in(t, integral_set) ? pt::hex_lower : pt::none;
+  case 'X':
+    return in(t, integral_set) ? pt::hex_upper : pt::none;
+  case 'a':
+    return in(t, float_set) ? pt::hexfloat_lower : pt::none;
+  case 'A':
+    return in(t, float_set) ? pt::hexfloat_upper : pt::none;
+  case 'e':
+    return in(t, float_set) ? pt::exp_lower : pt::none;
+  case 'E':
+    return in(t, float_set) ? pt::exp_upper : pt::none;
+  case 'f':
+    return in(t, float_set) ? pt::fixed_lower : pt::none;
+  case 'F':
+    return in(t, float_set) ? pt::fixed_upper : pt::none;
+  case 'g':
+    return in(t, float_set) ? pt::general_lower : pt::none;
+  case 'G':
+    return in(t, float_set) ? pt::general_upper : pt::none;
+  case 'c':
+    return in(t, integral_set) ? pt::chr : pt::none;
+  case 's':
+    return in(t, string_set | cstring_set) ? pt::string : pt::none;
+  case 'p':
+    return in(t, pointer_set | cstring_set) ? pt::pointer : pt::none;
+  default:
+    return pt::none;
+  }
+}
+
+template <typename Char, typename Context>
+void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
+             basic_format_args<Context> args) {
+  using iterator = buffer_appender<Char>;
+  auto out = iterator(buf);
+  auto context = basic_printf_context<Char>(out, args);
+  auto parse_ctx = basic_format_parse_context<Char>(format);
+
+  // Returns the argument with specified index or, if arg_index is -1, the next
+  // argument.
+  auto get_arg = [&](int arg_index) {
+    if (arg_index < 0)
+      arg_index = parse_ctx.next_arg_id();
+    else
+      parse_ctx.check_arg_id(--arg_index);
+    return detail::get_arg(context, arg_index);
+  };
+
+  const Char* start = parse_ctx.begin();
+  const Char* end = parse_ctx.end();
   auto it = start;
   while (it != end) {
-    char_type c = *it++;
-    if (c != '%') continue;
+    if (!find<false, Char>(it, end, '%', it)) {
+      it = end;  // find leaves it == nullptr if it doesn't find '%'.
+      break;
+    }
+    Char c = *it++;
     if (it != end && *it == c) {
-      out = std::copy(start, it, out);
+      write(out, basic_string_view<Char>(start, to_unsigned(it - start)));
       start = ++it;
       continue;
     }
-    out = std::copy(start, it - 1, out);
+    write(out, basic_string_view<Char>(start, to_unsigned(it - 1 - start)));
 
-    format_specs specs;
+    auto specs = format_specs<Char>();
     specs.align = align::right;
 
     // Parse argument index, flags and width.
-    int arg_index = parse_header(it, end, specs);
-    if (arg_index == 0) on_error("argument index out of range");
+    int arg_index = parse_header(it, end, specs, get_arg);
+    if (arg_index == 0) throw_format_error("argument not found");
 
     // Parse precision.
     if (it != end && *it == '.') {
       ++it;
       c = it != end ? *it : 0;
       if ('0' <= c && c <= '9') {
-        internal::error_handler eh;
-        specs.precision = parse_nonnegative_int(it, end, eh);
+        specs.precision = parse_nonnegative_int(it, end, 0);
       } else if (c == '*') {
         ++it;
         specs.precision = static_cast<int>(
-            visit_format_arg(internal::printf_precision_handler(), get_arg()));
+            visit_format_arg(printf_precision_handler(), get_arg(-1)));
       } else {
         specs.precision = 0;
       }
     }
 
-    format_arg arg = get_arg(arg_index);
-    if (specs.alt && visit_format_arg(internal::is_zero_int(), arg))
-      specs.alt = false;
+    auto arg = get_arg(arg_index);
+    // For d, i, o, u, x, and X conversion specifiers, if a precision is
+    // specified, the '0' flag is ignored
+    if (specs.precision >= 0 && arg.is_integral()) {
+      // Ignore '0' for non-numeric types or if '-' present.
+      specs.fill[0] = ' ';
+    }
+    if (specs.precision >= 0 && arg.type() == type::cstring_type) {
+      auto str = visit_format_arg(get_cstring<Char>(), arg);
+      auto str_end = str + specs.precision;
+      auto nul = std::find(str, str_end, Char());
+      auto sv = basic_string_view<Char>(
+          str, to_unsigned(nul != str_end ? nul - str : specs.precision));
+      arg = make_arg<basic_printf_context<Char>>(sv);
+    }
+    if (specs.alt && visit_format_arg(is_zero_int(), arg)) specs.alt = false;
     if (specs.fill[0] == '0') {
-      if (arg.is_arithmetic())
+      if (arg.is_arithmetic() && specs.align != align::left)
         specs.align = align::numeric;
       else
-        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types.
+        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types or if '-'
+                              // flag is also present.
     }
 
     // Parse length and convert the argument to the required type.
     c = it != end ? *it++ : 0;
-    char_type t = it != end ? *it : 0;
-    using internal::convert_arg;
+    Char t = it != end ? *it : 0;
     switch (c) {
     case 'h':
       if (t == 'h') {
@@ -531,7 +521,7 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
       convert_arg<intmax_t>(arg, t);
       break;
     case 'z':
-      convert_arg<std::size_t>(arg, t);
+      convert_arg<size_t>(arg, t);
       break;
     case 't':
       convert_arg<std::ptrdiff_t>(arg, t);
@@ -546,37 +536,35 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
     }
 
     // Parse type.
-    if (it == end) FMT_THROW(format_error("invalid format string"));
-    specs.type = static_cast<char>(*it++);
+    if (it == end) throw_format_error("invalid format string");
+    char type = static_cast<char>(*it++);
     if (arg.is_integral()) {
       // Normalize type.
-      switch (specs.type) {
+      switch (type) {
       case 'i':
       case 'u':
-        specs.type = 'd';
+        type = 'd';
         break;
       case 'c':
-        visit_format_arg(internal::char_converter<basic_printf_context>(arg),
-                         arg);
+        visit_format_arg(char_converter<basic_printf_context<Char>>(arg), arg);
         break;
       }
     }
+    specs.type = parse_printf_presentation_type(type, arg.type());
+    if (specs.type == presentation_type::none)
+      throw_format_error("invalid format specifier");
 
     start = it;
 
     // Format argument.
-    visit_format_arg(ArgFormatter(out, specs, *this), arg);
+    visit_format_arg(printf_arg_formatter<Char>(out, specs, context), arg);
   }
-  return std::copy(start, it, out);
+  write(out, basic_string_view<Char>(start, to_unsigned(it - start)));
 }
+}  // namespace detail
 
-template <typename Char>
-using basic_printf_context_t =
-    basic_printf_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
-
-using printf_context = basic_printf_context_t<char>;
-using wprintf_context = basic_printf_context_t<wchar_t>;
+using printf_context = basic_printf_context<char>;
+using wprintf_context = basic_printf_context<wchar_t>;
 
 using printf_args = basic_format_args<printf_context>;
 using wprintf_args = basic_format_args<wprintf_context>;
@@ -587,31 +575,27 @@ using wprintf_args = basic_format_args<wprintf_context>;
   arguments and can be implicitly converted to `~fmt::printf_args`.
   \endrst
  */
-template <typename... Args>
-inline format_arg_store<printf_context, Args...> make_printf_args(
-    const Args&... args) {
+template <typename... T>
+inline auto make_printf_args(const T&... args)
+    -> format_arg_store<printf_context, T...> {
   return {args...};
 }
 
-/**
-  \rst
-  Constructs an `~fmt::format_arg_store` object that contains references to
-  arguments and can be implicitly converted to `~fmt::wprintf_args`.
-  \endrst
- */
-template <typename... Args>
-inline format_arg_store<wprintf_context, Args...> make_wprintf_args(
-    const Args&... args) {
+// DEPRECATED!
+template <typename... T>
+inline auto make_wprintf_args(const T&... args)
+    -> format_arg_store<wprintf_context, T...> {
   return {args...};
 }
 
-template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vsprintf(
-    const S& format,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  return to_string(buffer);
+template <typename Char>
+inline auto vsprintf(
+    basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
+  auto buf = basic_memory_buffer<Char>();
+  detail::vprintf(buf, fmt, args);
+  return to_string(buf);
 }
 
 /**
@@ -623,21 +607,22 @@ inline std::basic_string<Char> vsprintf(
     std::string message = fmt::sprintf("The answer is %d", 42);
   \endrst
 */
-template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
-inline std::basic_string<Char> sprintf(const S& format, const Args&... args) {
-  using context = basic_printf_context_t<Char>;
-  return vsprintf(to_string_view(format), make_format_args<context>(args...));
+template <typename S, typename... T,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
+inline auto sprintf(const S& fmt, const T&... args) -> std::basic_string<Char> {
+  return vsprintf(detail::to_string_view(fmt),
+                  fmt::make_format_args<basic_printf_context<Char>>(args...));
 }
 
-template <typename S, typename Char = char_t<S>>
-inline int vfprintf(
-    std::FILE* f, const S& format,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  std::size_t size = buffer.size();
-  return std::fwrite(buffer.data(), sizeof(Char), size, f) < size
+template <typename Char>
+inline auto vfprintf(
+    std::FILE* f, basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
+    -> int {
+  auto buf = basic_memory_buffer<Char>();
+  detail::vprintf(buf, fmt, args);
+  size_t size = buf.size();
+  return std::fwrite(buf.data(), sizeof(Char), size, f) < size
              ? -1
              : static_cast<int>(size);
 }
@@ -651,19 +636,18 @@ inline int vfprintf(
     fmt::fprintf(stderr, "Don't %s!", "panic");
   \endrst
  */
-template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
-inline int fprintf(std::FILE* f, const S& format, const Args&... args) {
-  using context = basic_printf_context_t<Char>;
-  return vfprintf(f, to_string_view(format),
-                  make_format_args<context>(args...));
+template <typename S, typename... T, typename Char = char_t<S>>
+inline auto fprintf(std::FILE* f, const S& fmt, const T&... args) -> int {
+  return vfprintf(f, detail::to_string_view(fmt),
+                  fmt::make_format_args<basic_printf_context<Char>>(args...));
 }
 
-template <typename S, typename Char = char_t<S>>
-inline int vprintf(
-    const S& format,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
-  return vfprintf(stdout, to_string_view(format), args);
+template <typename Char>
+FMT_DEPRECATED inline auto vprintf(
+    basic_string_view<Char> fmt,
+    basic_format_args<basic_printf_context<type_identity_t<Char>>> args)
+    -> int {
+  return vfprintf(stdout, fmt, args);
 }
 
 /**
@@ -675,52 +659,17 @@ inline int vprintf(
     fmt::printf("Elapsed time: %.2f seconds", 1.23);
   \endrst
  */
-template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
-inline int printf(const S& format_str, const Args&... args) {
-  using context = basic_printf_context_t<char_t<S>>;
-  return vprintf(to_string_view(format_str),
-                 make_format_args<context>(args...));
-}
-
-template <typename S, typename Char = char_t<S>>
-inline int vfprintf(
-    std::basic_ostream<Char>& os, const S& format,
-    basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  internal::write(os, buffer);
-  return static_cast<int>(buffer.size());
+template <typename... T>
+inline auto printf(string_view fmt, const T&... args) -> int {
+  return vfprintf(stdout, fmt, make_printf_args(args...));
 }
-
-/** Formats arguments and writes the output to the range. */
-template <typename ArgFormatter, typename Char,
-          typename Context =
-              basic_printf_context<typename ArgFormatter::iterator, Char>>
-typename ArgFormatter::iterator vprintf(
-    internal::buffer<Char>& out, basic_string_view<Char> format_str,
-    basic_format_args<type_identity_t<Context>> args) {
-  typename ArgFormatter::iterator iter(out);
-  Context(iter, format_str, args).template format<ArgFormatter>();
-  return iter;
+template <typename... T>
+FMT_DEPRECATED inline auto printf(basic_string_view<wchar_t> fmt,
+                                  const T&... args) -> int {
+  return vfprintf(stdout, fmt, make_wprintf_args(args...));
 }
 
-/**
-  \rst
-  Prints formatted data to the stream *os*.
-
-  **Example**::
-
-    fmt::fprintf(cerr, "Don't %s!", "panic");
-  \endrst
- */
-template <typename S, typename... Args, typename Char = char_t<S>>
-inline int fprintf(std::basic_ostream<Char>& os, const S& format_str,
-                   const Args&... args) {
-  using context = basic_printf_context_t<Char>;
-  return vfprintf(os, to_string_view(format_str),
-                  make_format_args<context>(args...));
-}
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_PRINTF_H_
diff --git a/contrib/fmt/include/fmt/ranges.h b/contrib/fmt/include/fmt/ranges.h
index f8f9adb715c..3638fffb83b 100644
--- a/contrib/fmt/include/fmt/ranges.h
+++ b/contrib/fmt/include/fmt/ranges.h
@@ -1,341 +1,696 @@
-// Formatting library for C++ - experimental range support
+// Formatting library for C++ - range and tuple support
 //
-// Copyright (c) 2012 - present, Victor Zverovich
+// Copyright (c) 2012 - present, Victor Zverovich and {fmt} contributors
 // All rights reserved.
 //
 // For the license information refer to format.h.
-//
-// Copyright (c) 2018 - present, Remotion (Igor Schulz)
-// All Rights Reserved
-// {fmt} support for ranges, containers and types tuple interface.
 
 #ifndef FMT_RANGES_H_
 #define FMT_RANGES_H_
 
 #include <initializer_list>
+#include <tuple>
 #include <type_traits>
 
 #include "format.h"
 
-// output only up to N items from the range.
-#ifndef FMT_RANGE_OUTPUT_LENGTH_LIMIT
-#  define FMT_RANGE_OUTPUT_LENGTH_LIMIT 256
-#endif
-
 FMT_BEGIN_NAMESPACE
 
-template <typename Char> struct formatting_base {
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-};
+namespace detail {
 
-template <typename Char, typename Enable = void>
-struct formatting_range : formatting_base<Char> {
-  static FMT_CONSTEXPR_DECL const std::size_t range_length_limit =
-      FMT_RANGE_OUTPUT_LENGTH_LIMIT;  // output only up to N items from the
-                                      // range.
-  Char prefix;
-  Char delimiter;
-  Char postfix;
-  formatting_range() : prefix('{'), delimiter(','), postfix('}') {}
-  static FMT_CONSTEXPR_DECL const bool add_delimiter_spaces = true;
-  static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
-};
-
-template <typename Char, typename Enable = void>
-struct formatting_tuple : formatting_base<Char> {
-  Char prefix;
-  Char delimiter;
-  Char postfix;
-  formatting_tuple() : prefix('('), delimiter(','), postfix(')') {}
-  static FMT_CONSTEXPR_DECL const bool add_delimiter_spaces = true;
-  static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
-};
-
-namespace internal {
-
-template <typename RangeT, typename OutputIterator>
-OutputIterator copy(const RangeT& range, OutputIterator out) {
+template <typename Range, typename OutputIt>
+auto copy(const Range& range, OutputIt out) -> OutputIt {
   for (auto it = range.begin(), end = range.end(); it != end; ++it)
     *out++ = *it;
   return out;
 }
 
-template <typename OutputIterator>
-OutputIterator copy(const char* str, OutputIterator out) {
+template <typename OutputIt>
+auto copy(const char* str, OutputIt out) -> OutputIt {
   while (*str) *out++ = *str++;
   return out;
 }
 
-template <typename OutputIterator>
-OutputIterator copy(char ch, OutputIterator out) {
+template <typename OutputIt> auto copy(char ch, OutputIt out) -> OutputIt {
+  *out++ = ch;
+  return out;
+}
+
+template <typename OutputIt> auto copy(wchar_t ch, OutputIt out) -> OutputIt {
   *out++ = ch;
   return out;
 }
 
-/// Return true value if T has std::string interface, like std::string_view.
-template <typename T> class is_like_std_string {
+// Returns true if T has a std::string-like interface, like std::string_view.
+template <typename T> class is_std_string_like {
   template <typename U>
   static auto check(U* p)
       -> decltype((void)p->find('a'), p->length(), (void)p->data(), int());
   template <typename> static void check(...);
 
  public:
-  static FMT_CONSTEXPR_DECL const bool value =
-      is_string<T>::value || !std::is_void<decltype(check<T>(nullptr))>::value;
+  static constexpr const bool value =
+      is_string<T>::value ||
+      std::is_convertible<T, std_string_view<char>>::value ||
+      !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
 template <typename Char>
-struct is_like_std_string<fmt::basic_string_view<Char>> : std::true_type {};
+struct is_std_string_like<fmt::basic_string_view<Char>> : std::true_type {};
+
+template <typename T> class is_map {
+  template <typename U> static auto check(U*) -> typename U::mapped_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_MAP_AS_LIST  // DEPRECATED!
+  static constexpr const bool value = false;
+#else
+  static constexpr const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+#endif
+};
+
+template <typename T> class is_set {
+  template <typename U> static auto check(U*) -> typename U::key_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_SET_AS_LIST  // DEPRECATED!
+  static constexpr const bool value = false;
+#else
+  static constexpr const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
+#endif
+};
 
 template <typename... Ts> struct conditional_helper {};
 
 template <typename T, typename _ = void> struct is_range_ : std::false_type {};
 
-#if !FMT_MSC_VER || FMT_MSC_VER > 1800
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION > 1800
+
+#  define FMT_DECLTYPE_RETURN(val)  \
+    ->decltype(val) { return val; } \
+    static_assert(                  \
+        true, "")  // This makes it so that a semicolon is required after the
+                   // macro, which helps clang-format handle the formatting.
+
+// C array overload
+template <typename T, std::size_t N>
+auto range_begin(const T (&arr)[N]) -> const T* {
+  return arr;
+}
+template <typename T, std::size_t N>
+auto range_end(const T (&arr)[N]) -> const T* {
+  return arr + N;
+}
+
+template <typename T, typename Enable = void>
+struct has_member_fn_begin_end_t : std::false_type {};
+
+template <typename T>
+struct has_member_fn_begin_end_t<T, void_t<decltype(std::declval<T>().begin()),
+                                           decltype(std::declval<T>().end())>>
+    : std::true_type {};
+
+// Member function overload
+template <typename T>
+auto range_begin(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).begin());
+template <typename T>
+auto range_end(T&& rng) FMT_DECLTYPE_RETURN(static_cast<T&&>(rng).end());
+
+// ADL overload. Only participates in overload resolution if member functions
+// are not found.
+template <typename T>
+auto range_begin(T&& rng)
+    -> enable_if_t<!has_member_fn_begin_end_t<T&&>::value,
+                   decltype(begin(static_cast<T&&>(rng)))> {
+  return begin(static_cast<T&&>(rng));
+}
 template <typename T>
-struct is_range_<
-    T, conditional_t<false,
-                     conditional_helper<decltype(std::declval<T>().begin()),
-                                        decltype(std::declval<T>().end())>,
-                     void>> : std::true_type {};
+auto range_end(T&& rng) -> enable_if_t<!has_member_fn_begin_end_t<T&&>::value,
+                                       decltype(end(static_cast<T&&>(rng)))> {
+  return end(static_cast<T&&>(rng));
+}
+
+template <typename T, typename Enable = void>
+struct has_const_begin_end : std::false_type {};
+template <typename T, typename Enable = void>
+struct has_mutable_begin_end : std::false_type {};
+
+template <typename T>
+struct has_const_begin_end<
+    T,
+    void_t<
+        decltype(detail::range_begin(std::declval<const remove_cvref_t<T>&>())),
+        decltype(detail::range_end(std::declval<const remove_cvref_t<T>&>()))>>
+    : std::true_type {};
+
+template <typename T>
+struct has_mutable_begin_end<
+    T, void_t<decltype(detail::range_begin(std::declval<T>())),
+              decltype(detail::range_end(std::declval<T>())),
+              // the extra int here is because older versions of MSVC don't
+              // SFINAE properly unless there are distinct types
+              int>> : std::true_type {};
+
+template <typename T>
+struct is_range_<T, void>
+    : std::integral_constant<bool, (has_const_begin_end<T>::value ||
+                                    has_mutable_begin_end<T>::value)> {};
+#  undef FMT_DECLTYPE_RETURN
 #endif
 
-/// tuple_size and tuple_element check.
+// tuple_size and tuple_element check.
 template <typename T> class is_tuple_like_ {
   template <typename U>
   static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
   template <typename> static void check(...);
 
  public:
-  static FMT_CONSTEXPR_DECL const bool value =
+  static constexpr const bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
 // Check for integer_sequence
-#if defined(__cpp_lib_integer_sequence) || FMT_MSC_VER >= 1900
+#if defined(__cpp_lib_integer_sequence) || FMT_MSC_VERSION >= 1900
 template <typename T, T... N>
 using integer_sequence = std::integer_sequence<T, N...>;
-template <std::size_t... N> using index_sequence = std::index_sequence<N...>;
-template <std::size_t N>
-using make_index_sequence = std::make_index_sequence<N>;
+template <size_t... N> using index_sequence = std::index_sequence<N...>;
+template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 #else
 template <typename T, T... N> struct integer_sequence {
   using value_type = T;
 
-  static FMT_CONSTEXPR std::size_t size() { return sizeof...(N); }
+  static FMT_CONSTEXPR auto size() -> size_t { return sizeof...(N); }
 };
 
-template <std::size_t... N>
-using index_sequence = integer_sequence<std::size_t, N...>;
+template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
 
-template <typename T, std::size_t N, T... Ns>
+template <typename T, size_t N, T... Ns>
 struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Ns...> {};
 template <typename T, T... Ns>
 struct make_integer_sequence<T, 0, Ns...> : integer_sequence<T, Ns...> {};
 
-template <std::size_t N>
-using make_index_sequence = make_integer_sequence<std::size_t, N>;
+template <size_t N>
+using make_index_sequence = make_integer_sequence<size_t, N>;
 #endif
 
-template <class Tuple, class F, size_t... Is>
-void for_each(index_sequence<Is...>, Tuple&& tup, F&& f) FMT_NOEXCEPT {
+template <typename T>
+using tuple_index_sequence = make_index_sequence<std::tuple_size<T>::value>;
+
+template <typename T, typename C, bool = is_tuple_like_<T>::value>
+class is_tuple_formattable_ {
+ public:
+  static constexpr const bool value = false;
+};
+template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
+  template <std::size_t... Is>
+  static auto check2(index_sequence<Is...>,
+                     integer_sequence<bool, (Is == Is)...>) -> std::true_type;
+  static auto check2(...) -> std::false_type;
+  template <std::size_t... Is>
+  static auto check(index_sequence<Is...>) -> decltype(check2(
+      index_sequence<Is...>{},
+      integer_sequence<bool,
+                       (is_formattable<typename std::tuple_element<Is, T>::type,
+                                       C>::value)...>{}));
+
+ public:
+  static constexpr const bool value =
+      decltype(check(tuple_index_sequence<T>{}))::value;
+};
+
+template <typename Tuple, typename F, size_t... Is>
+FMT_CONSTEXPR void for_each(index_sequence<Is...>, Tuple&& t, F&& f) {
   using std::get;
-  // using free function get<I>(T) now.
-  const int _[] = {0, ((void)f(get<Is>(tup)), 0)...};
-  (void)_;  // blocks warnings
+  // Using a free function get<Is>(Tuple) now.
+  const int unused[] = {0, ((void)f(get<Is>(t)), 0)...};
+  ignore_unused(unused);
 }
 
-template <class T>
-FMT_CONSTEXPR make_index_sequence<std::tuple_size<T>::value> get_indexes(
-    T const&) {
-  return {};
+template <typename Tuple, typename F>
+FMT_CONSTEXPR void for_each(Tuple&& t, F&& f) {
+  for_each(tuple_index_sequence<remove_cvref_t<Tuple>>(),
+           std::forward<Tuple>(t), std::forward<F>(f));
 }
 
-template <class Tuple, class F> void for_each(Tuple&& tup, F&& f) {
-  const auto indexes = get_indexes(tup);
-  for_each(indexes, std::forward<Tuple>(tup), std::forward<F>(f));
+template <typename Tuple1, typename Tuple2, typename F, size_t... Is>
+void for_each2(index_sequence<Is...>, Tuple1&& t1, Tuple2&& t2, F&& f) {
+  using std::get;
+  const int unused[] = {0, ((void)f(get<Is>(t1), get<Is>(t2)), 0)...};
+  ignore_unused(unused);
 }
 
-template <typename Arg, FMT_ENABLE_IF(!is_like_std_string<
-                                      typename std::decay<Arg>::type>::value)>
-FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&) {
-  return add_space ? " {}" : "{}";
+template <typename Tuple1, typename Tuple2, typename F>
+void for_each2(Tuple1&& t1, Tuple2&& t2, F&& f) {
+  for_each2(tuple_index_sequence<remove_cvref_t<Tuple1>>(),
+            std::forward<Tuple1>(t1), std::forward<Tuple2>(t2),
+            std::forward<F>(f));
 }
 
-template <typename Arg, FMT_ENABLE_IF(is_like_std_string<
-                                      typename std::decay<Arg>::type>::value)>
-FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const Arg&) {
-  return add_space ? " \"{}\"" : "\"{}\"";
-}
+namespace tuple {
+// Workaround a bug in MSVC 2019 (v140).
+template <typename Char, typename... T>
+using result_t = std::tuple<formatter<remove_cvref_t<T>, Char>...>;
+
+using std::get;
+template <typename Tuple, typename Char, std::size_t... Is>
+auto get_formatters(index_sequence<Is...>)
+    -> result_t<Char, decltype(get<Is>(std::declval<Tuple>()))...>;
+}  // namespace tuple
+
+#if FMT_MSC_VERSION && FMT_MSC_VERSION < 1920
+// Older MSVC doesn't get the reference type correctly for arrays.
+template <typename R> struct range_reference_type_impl {
+  using type = decltype(*detail::range_begin(std::declval<R&>()));
+};
 
-FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char*) {
-  return add_space ? " \"{}\"" : "\"{}\"";
-}
-FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t*) {
-  return add_space ? L" \"{}\"" : L"\"{}\"";
-}
+template <typename T, std::size_t N> struct range_reference_type_impl<T[N]> {
+  using type = T&;
+};
 
-FMT_CONSTEXPR const char* format_str_quoted(bool add_space, const char) {
-  return add_space ? " '{}'" : "'{}'";
-}
-FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t) {
-  return add_space ? L" '{}'" : L"'{}'";
+template <typename T>
+using range_reference_type = typename range_reference_type_impl<T>::type;
+#else
+template <typename Range>
+using range_reference_type =
+    decltype(*detail::range_begin(std::declval<Range&>()));
+#endif
+
+// We don't use the Range's value_type for anything, but we do need the Range's
+// reference type, with cv-ref stripped.
+template <typename Range>
+using uncvref_type = remove_cvref_t<range_reference_type<Range>>;
+
+template <typename Formatter>
+FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
+    -> decltype(f.set_debug_format(set)) {
+  f.set_debug_format(set);
 }
+template <typename Formatter>
+FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}
+
+// These are not generic lambdas for compatibility with C++11.
+template <typename ParseContext> struct parse_empty_specs {
+  template <typename Formatter> FMT_CONSTEXPR void operator()(Formatter& f) {
+    f.parse(ctx);
+    detail::maybe_set_debug_format(f, true);
+  }
+  ParseContext& ctx;
+};
+template <typename FormatContext> struct format_tuple_element {
+  using char_type = typename FormatContext::char_type;
+
+  template <typename T>
+  void operator()(const formatter<T, char_type>& f, const T& v) {
+    if (i > 0)
+      ctx.advance_to(detail::copy_str<char_type>(separator, ctx.out()));
+    ctx.advance_to(f.format(v, ctx));
+    ++i;
+  }
+
+  int i;
+  FormatContext& ctx;
+  basic_string_view<char_type> separator;
+};
 
-}  // namespace internal
+}  // namespace detail
 
 template <typename T> struct is_tuple_like {
-  static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_tuple_like_<T>::value && !internal::is_range_<T>::value;
+  static constexpr const bool value =
+      detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
+};
+
+template <typename T, typename C> struct is_tuple_formattable {
+  static constexpr const bool value =
+      detail::is_tuple_formattable_<T, C>::value;
 };
 
-template <typename TupleT, typename Char>
-struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
+template <typename Tuple, typename Char>
+struct formatter<Tuple, Char,
+                 enable_if_t<fmt::is_tuple_like<Tuple>::value &&
+                             fmt::is_tuple_formattable<Tuple, Char>::value>> {
  private:
-  // C++11 generic lambda for format()
-  template <typename FormatContext> struct format_each {
-    template <typename T> void operator()(const T& v) {
-      if (i > 0) {
-        if (formatting.add_prepostfix_space) {
-          *out++ = ' ';
-        }
-        out = internal::copy(formatting.delimiter, out);
-      }
-      out = format_to(out,
-                      internal::format_str_quoted(
-                          (formatting.add_delimiter_spaces && i > 0), v),
-                      v);
-      ++i;
-    }
+  decltype(detail::tuple::get_formatters<Tuple, Char>(
+      detail::tuple_index_sequence<Tuple>())) formatters_;
 
-    formatting_tuple<Char>& formatting;
-    std::size_t& i;
-    typename std::add_lvalue_reference<decltype(
-        std::declval<FormatContext>().out())>::type out;
-  };
+  basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
+  basic_string_view<Char> opening_bracket_ =
+      detail::string_literal<Char, '('>{};
+  basic_string_view<Char> closing_bracket_ =
+      detail::string_literal<Char, ')'>{};
 
  public:
-  formatting_tuple<Char> formatting;
+  FMT_CONSTEXPR formatter() {}
 
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return formatting.parse(ctx);
+  FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
+    separator_ = sep;
   }
 
-  template <typename FormatContext = format_context>
-  auto format(const TupleT& values, FormatContext& ctx) -> decltype(ctx.out()) {
-    auto out = ctx.out();
-    std::size_t i = 0;
-    internal::copy(formatting.prefix, out);
+  FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
+                                  basic_string_view<Char> close) {
+    opening_bracket_ = open;
+    closing_bracket_ = close;
+  }
 
-    internal::for_each(values, format_each<FormatContext>{formatting, i, out});
-    if (formatting.add_prepostfix_space) {
-      *out++ = ' ';
-    }
-    internal::copy(formatting.postfix, out);
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    auto it = ctx.begin();
+    if (it != ctx.end() && *it != '}')
+      FMT_THROW(format_error("invalid format specifier"));
+    detail::for_each(formatters_, detail::parse_empty_specs<ParseContext>{ctx});
+    return it;
+  }
 
-    return ctx.out();
+  template <typename FormatContext>
+  auto format(const Tuple& value, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    ctx.advance_to(detail::copy_str<Char>(opening_bracket_, ctx.out()));
+    detail::for_each2(
+        formatters_, value,
+        detail::format_tuple_element<FormatContext>{0, ctx, separator_});
+    return detail::copy_str<Char>(closing_bracket_, ctx.out());
   }
 };
 
 template <typename T, typename Char> struct is_range {
-  static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_range_<T>::value &&
-      !internal::is_like_std_string<T>::value &&
+  static constexpr const bool value =
+      detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
       !std::is_convertible<T, std::basic_string<Char>>::value &&
-      !std::is_constructible<internal::std_string_view<Char>, T>::value;
+      !std::is_convertible<T, detail::std_string_view<Char>>::value;
 };
 
-template <typename RangeT, typename Char>
-struct formatter<RangeT, Char,
-                 enable_if_t<fmt::is_range<RangeT, Char>::value>> {
-  formatting_range<Char> formatting;
+namespace detail {
+template <typename Context> struct range_mapper {
+  using mapper = arg_mapper<Context>;
+
+  template <typename T,
+            FMT_ENABLE_IF(has_formatter<remove_cvref_t<T>, Context>::value)>
+  static auto map(T&& value) -> T&& {
+    return static_cast<T&&>(value);
+  }
+  template <typename T,
+            FMT_ENABLE_IF(!has_formatter<remove_cvref_t<T>, Context>::value)>
+  static auto map(T&& value)
+      -> decltype(mapper().map(static_cast<T&&>(value))) {
+    return mapper().map(static_cast<T&&>(value));
+  }
+};
+
+template <typename Char, typename Element>
+using range_formatter_type =
+    formatter<remove_cvref_t<decltype(range_mapper<buffer_context<Char>>{}.map(
+                  std::declval<Element>()))>,
+              Char>;
+
+template <typename R>
+using maybe_const_range =
+    conditional_t<has_const_begin_end<R>::value, const R, R>;
+
+// Workaround a bug in MSVC 2015 and earlier.
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
+template <typename R, typename Char>
+struct is_formattable_delayed
+    : is_formattable<uncvref_type<maybe_const_range<R>>, Char> {};
+#endif
+}  // namespace detail
+
+template <typename...> struct conjunction : std::true_type {};
+template <typename P> struct conjunction<P> : P {};
+template <typename P1, typename... Pn>
+struct conjunction<P1, Pn...>
+    : conditional_t<bool(P1::value), conjunction<Pn...>, P1> {};
+
+template <typename T, typename Char, typename Enable = void>
+struct range_formatter;
+
+template <typename T, typename Char>
+struct range_formatter<
+    T, Char,
+    enable_if_t<conjunction<std::is_same<T, remove_cvref_t<T>>,
+                            is_formattable<T, Char>>::value>> {
+ private:
+  detail::range_formatter_type<Char, T> underlying_;
+  basic_string_view<Char> separator_ = detail::string_literal<Char, ',', ' '>{};
+  basic_string_view<Char> opening_bracket_ =
+      detail::string_literal<Char, '['>{};
+  basic_string_view<Char> closing_bracket_ =
+      detail::string_literal<Char, ']'>{};
+
+ public:
+  FMT_CONSTEXPR range_formatter() {}
+
+  FMT_CONSTEXPR auto underlying() -> detail::range_formatter_type<Char, T>& {
+    return underlying_;
+  }
+
+  FMT_CONSTEXPR void set_separator(basic_string_view<Char> sep) {
+    separator_ = sep;
+  }
+
+  FMT_CONSTEXPR void set_brackets(basic_string_view<Char> open,
+                                  basic_string_view<Char> close) {
+    opening_bracket_ = open;
+    closing_bracket_ = close;
+  }
 
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return formatting.parse(ctx);
+    auto it = ctx.begin();
+    auto end = ctx.end();
+
+    if (it != end && *it == 'n') {
+      set_brackets({}, {});
+      ++it;
+    }
+
+    if (it != end && *it != '}') {
+      if (*it != ':') FMT_THROW(format_error("invalid format specifier"));
+      ++it;
+    } else {
+      detail::maybe_set_debug_format(underlying_, true);
+    }
+
+    ctx.advance_to(it);
+    return underlying_.parse(ctx);
   }
 
-  template <typename FormatContext>
-  typename FormatContext::iterator format(const RangeT& values,
-                                          FormatContext& ctx) {
-    auto out = internal::copy(formatting.prefix, ctx.out());
-    std::size_t i = 0;
-    for (auto it = values.begin(), end = values.end(); it != end; ++it) {
-      if (i > 0) {
-        if (formatting.add_prepostfix_space) *out++ = ' ';
-        out = internal::copy(formatting.delimiter, out);
-      }
-      out = format_to(out,
-                      internal::format_str_quoted(
-                          (formatting.add_delimiter_spaces && i > 0), *it),
-                      *it);
-      if (++i > formatting.range_length_limit) {
-        out = format_to(out, " ... <other elements>");
-        break;
-      }
+  template <typename R, typename FormatContext>
+  auto format(R&& range, FormatContext& ctx) const -> decltype(ctx.out()) {
+    detail::range_mapper<buffer_context<Char>> mapper;
+    auto out = ctx.out();
+    out = detail::copy_str<Char>(opening_bracket_, out);
+    int i = 0;
+    auto it = detail::range_begin(range);
+    auto end = detail::range_end(range);
+    for (; it != end; ++it) {
+      if (i > 0) out = detail::copy_str<Char>(separator_, out);
+      ctx.advance_to(out);
+      auto&& item = *it;
+      out = underlying_.format(mapper.map(item), ctx);
+      ++i;
     }
-    if (formatting.add_prepostfix_space) *out++ = ' ';
-    return internal::copy(formatting.postfix, out);
+    out = detail::copy_str<Char>(closing_bracket_, out);
+    return out;
   }
 };
 
-template <typename Char, typename... T> struct tuple_arg_join : internal::view {
+enum class range_format { disabled, map, set, sequence, string, debug_string };
+
+namespace detail {
+template <typename T>
+struct range_format_kind_
+    : std::integral_constant<range_format,
+                             std::is_same<uncvref_type<T>, T>::value
+                                 ? range_format::disabled
+                             : is_map<T>::value ? range_format::map
+                             : is_set<T>::value ? range_format::set
+                                                : range_format::sequence> {};
+
+template <range_format K, typename R, typename Char, typename Enable = void>
+struct range_default_formatter;
+
+template <range_format K>
+using range_format_constant = std::integral_constant<range_format, K>;
+
+template <range_format K, typename R, typename Char>
+struct range_default_formatter<
+    K, R, Char,
+    enable_if_t<(K == range_format::sequence || K == range_format::map ||
+                 K == range_format::set)>> {
+  using range_type = detail::maybe_const_range<R>;
+  range_formatter<detail::uncvref_type<range_type>, Char> underlying_;
+
+  FMT_CONSTEXPR range_default_formatter() { init(range_format_constant<K>()); }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::set>) {
+    underlying_.set_brackets(detail::string_literal<Char, '{'>{},
+                             detail::string_literal<Char, '}'>{});
+  }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::map>) {
+    underlying_.set_brackets(detail::string_literal<Char, '{'>{},
+                             detail::string_literal<Char, '}'>{});
+    underlying_.underlying().set_brackets({}, {});
+    underlying_.underlying().set_separator(
+        detail::string_literal<Char, ':', ' '>{});
+  }
+
+  FMT_CONSTEXPR void init(range_format_constant<range_format::sequence>) {}
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return underlying_.parse(ctx);
+  }
+
+  template <typename FormatContext>
+  auto format(range_type& range, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return underlying_.format(range, ctx);
+  }
+};
+}  // namespace detail
+
+template <typename T, typename Char, typename Enable = void>
+struct range_format_kind
+    : conditional_t<
+          is_range<T, Char>::value, detail::range_format_kind_<T>,
+          std::integral_constant<range_format, range_format::disabled>> {};
+
+template <typename R, typename Char>
+struct formatter<
+    R, Char,
+    enable_if_t<conjunction<bool_constant<range_format_kind<R, Char>::value !=
+                                          range_format::disabled>
+// Workaround a bug in MSVC 2015 and earlier.
+#if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1910
+                            ,
+                            detail::is_formattable_delayed<R, Char>
+#endif
+                            >::value>>
+    : detail::range_default_formatter<range_format_kind<R, Char>::value, R,
+                                      Char> {
+};
+
+template <typename Char, typename... T> struct tuple_join_view : detail::view {
   const std::tuple<T...>& tuple;
   basic_string_view<Char> sep;
 
-  tuple_arg_join(const std::tuple<T...>& t, basic_string_view<Char> s)
-      : tuple{t}, sep{s} {}
+  tuple_join_view(const std::tuple<T...>& t, basic_string_view<Char> s)
+      : tuple(t), sep{s} {}
 };
 
+// Define FMT_TUPLE_JOIN_SPECIFIERS to enable experimental format specifiers
+// support in tuple_join. It is disabled by default because of issues with
+// the dynamic width and precision.
+#ifndef FMT_TUPLE_JOIN_SPECIFIERS
+#  define FMT_TUPLE_JOIN_SPECIFIERS 0
+#endif
+
 template <typename Char, typename... T>
-struct formatter<tuple_arg_join<Char, T...>, Char> {
+struct formatter<tuple_join_view<Char, T...>, Char> {
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
+    return do_parse(ctx, std::integral_constant<size_t, sizeof...(T)>());
   }
 
   template <typename FormatContext>
-  typename FormatContext::iterator format(
-      const tuple_arg_join<Char, T...>& value, FormatContext& ctx) {
-    return format(value, ctx, internal::make_index_sequence<sizeof...(T)>{});
+  auto format(const tuple_join_view<Char, T...>& value,
+              FormatContext& ctx) const -> typename FormatContext::iterator {
+    return do_format(value, ctx,
+                     std::integral_constant<size_t, sizeof...(T)>());
   }
 
  private:
-  template <typename FormatContext, size_t... N>
-  typename FormatContext::iterator format(
-      const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
-      internal::index_sequence<N...>) {
-    return format_args(value, ctx, std::get<N>(value.tuple)...);
+  std::tuple<formatter<typename std::decay<T>::type, Char>...> formatters_;
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+                              std::integral_constant<size_t, 0>)
+      -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename ParseContext, size_t N>
+  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+                              std::integral_constant<size_t, N>)
+      -> decltype(ctx.begin()) {
+    auto end = ctx.begin();
+#if FMT_TUPLE_JOIN_SPECIFIERS
+    end = std::get<sizeof...(T) - N>(formatters_).parse(ctx);
+    if (N > 1) {
+      auto end1 = do_parse(ctx, std::integral_constant<size_t, N - 1>());
+      if (end != end1)
+        FMT_THROW(format_error("incompatible format specs for tuple elements"));
+    }
+#endif
+    return end;
   }
 
   template <typename FormatContext>
-  typename FormatContext::iterator format_args(
-      const tuple_arg_join<Char, T...>&, FormatContext& ctx) {
-    // NOTE: for compilers that support C++17, this empty function instantiation
-    // can be replaced with a constexpr branch in the variadic overload.
+  auto do_format(const tuple_join_view<Char, T...>&, FormatContext& ctx,
+                 std::integral_constant<size_t, 0>) const ->
+      typename FormatContext::iterator {
     return ctx.out();
   }
 
-  template <typename FormatContext, typename Arg, typename... Args>
-  typename FormatContext::iterator format_args(
-      const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
-      const Arg& arg, const Args&... args) {
-    using base = formatter<typename std::decay<Arg>::type, Char>;
-    auto out = ctx.out();
-    out = base{}.format(arg, ctx);
-    if (sizeof...(Args) > 0) {
+  template <typename FormatContext, size_t N>
+  auto do_format(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
+                 std::integral_constant<size_t, N>) const ->
+      typename FormatContext::iterator {
+    auto out = std::get<sizeof...(T) - N>(formatters_)
+                   .format(std::get<sizeof...(T) - N>(value.tuple), ctx);
+    if (N > 1) {
       out = std::copy(value.sep.begin(), value.sep.end(), out);
       ctx.advance_to(out);
-      return format_args(value, ctx, args...);
+      return do_format(value, ctx, std::integral_constant<size_t, N - 1>());
     }
     return out;
   }
 };
 
+namespace detail {
+// Check if T has an interface like a container adaptor (e.g. std::stack,
+// std::queue, std::priority_queue).
+template <typename T> class is_container_adaptor_like {
+  template <typename U> static auto check(U* p) -> typename U::container_type;
+  template <typename> static void check(...);
+
+ public:
+  static constexpr const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+};
+
+template <typename Container> struct all {
+  const Container& c;
+  auto begin() const -> typename Container::const_iterator { return c.begin(); }
+  auto end() const -> typename Container::const_iterator { return c.end(); }
+};
+}  // namespace detail
+
+template <typename T, typename Char>
+struct formatter<
+    T, Char,
+    enable_if_t<conjunction<detail::is_container_adaptor_like<T>,
+                            bool_constant<range_format_kind<T, Char>::value ==
+                                          range_format::disabled>>::value>>
+    : formatter<detail::all<typename T::container_type>, Char> {
+  using all = detail::all<typename T::container_type>;
+  template <typename FormatContext>
+  auto format(const T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
+    struct getter : T {
+      static auto get(const T& t) -> all {
+        return {t.*(&getter::c)};  // Access c through the derived class.
+      }
+    };
+    return formatter<all>::format(getter::get(t), ctx);
+  }
+};
+
+FMT_BEGIN_EXPORT
+
 /**
   \rst
   Returns an object that formats `tuple` with elements separated by `sep`.
@@ -348,14 +703,15 @@ struct formatter<tuple_arg_join<Char, T...>, Char> {
   \endrst
  */
 template <typename... T>
-FMT_CONSTEXPR tuple_arg_join<char, T...> join(const std::tuple<T...>& tuple,
-                                              string_view sep) {
+FMT_CONSTEXPR auto join(const std::tuple<T...>& tuple, string_view sep)
+    -> tuple_join_view<char, T...> {
   return {tuple, sep};
 }
 
 template <typename... T>
-FMT_CONSTEXPR tuple_arg_join<wchar_t, T...> join(const std::tuple<T...>& tuple,
-                                                 wstring_view sep) {
+FMT_CONSTEXPR auto join(const std::tuple<T...>& tuple,
+                        basic_string_view<wchar_t> sep)
+    -> tuple_join_view<wchar_t, T...> {
   return {tuple, sep};
 }
 
@@ -371,17 +727,12 @@ FMT_CONSTEXPR tuple_arg_join<wchar_t, T...> join(const std::tuple<T...>& tuple,
   \endrst
  */
 template <typename T>
-arg_join<internal::iterator_t<const std::initializer_list<T>>, char> join(
-    std::initializer_list<T> list, string_view sep) {
-  return join(std::begin(list), std::end(list), sep);
-}
-
-template <typename T>
-arg_join<internal::iterator_t<const std::initializer_list<T>>, wchar_t> join(
-    std::initializer_list<T> list, wstring_view sep) {
+auto join(std::initializer_list<T> list, string_view sep)
+    -> join_view<const T*, const T*> {
   return join(std::begin(list), std::end(list), sep);
 }
 
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #endif  // FMT_RANGES_H_
diff --git a/contrib/fmt/include/fmt/std.h b/contrib/fmt/include/fmt/std.h
new file mode 100644
index 00000000000..7cff1159201
--- /dev/null
+++ b/contrib/fmt/include/fmt/std.h
@@ -0,0 +1,537 @@
+// Formatting library for C++ - formatters for standard library types
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_STD_H_
+#define FMT_STD_H_
+
+#include <atomic>
+#include <bitset>
+#include <cstdlib>
+#include <exception>
+#include <memory>
+#include <thread>
+#include <type_traits>
+#include <typeinfo>
+#include <utility>
+#include <vector>
+
+#include "format.h"
+#include "ostream.h"
+
+#if FMT_HAS_INCLUDE(<version>)
+#  include <version>
+#endif
+// Checking FMT_CPLUSPLUS for warning suppression in MSVC.
+#if FMT_CPLUSPLUS >= 201703L
+#  if FMT_HAS_INCLUDE(<filesystem>)
+#    include <filesystem>
+#  endif
+#  if FMT_HAS_INCLUDE(<variant>)
+#    include <variant>
+#  endif
+#  if FMT_HAS_INCLUDE(<optional>)
+#    include <optional>
+#  endif
+#endif
+
+#if FMT_CPLUSPLUS > 201703L && FMT_HAS_INCLUDE(<source_location>)
+#  include <source_location>
+#endif
+
+// GCC 4 does not support FMT_HAS_INCLUDE.
+#if FMT_HAS_INCLUDE(<cxxabi.h>) || defined(__GLIBCXX__)
+#  include <cxxabi.h>
+// Android NDK with gabi++ library on some architectures does not implement
+// abi::__cxa_demangle().
+#  ifndef __GABIXX_CXXABI_H__
+#    define FMT_HAS_ABI_CXA_DEMANGLE
+#  endif
+#endif
+
+// Check if typeid is available.
+#ifndef FMT_USE_TYPEID
+// __RTTI is for EDG compilers. In MSVC typeid is available without RTTI.
+#  if defined(__GXX_RTTI) || FMT_HAS_FEATURE(cxx_rtti) || FMT_MSC_VERSION || \
+      defined(__INTEL_RTTI__) || defined(__RTTI)
+#    define FMT_USE_TYPEID 1
+#  else
+#    define FMT_USE_TYPEID 0
+#  endif
+#endif
+
+// For older Xcode versions, __cpp_lib_xxx flags are inaccurately defined.
+#ifndef FMT_CPP_LIB_FILESYSTEM
+#  ifdef __cpp_lib_filesystem
+#    define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
+#  else
+#    define FMT_CPP_LIB_FILESYSTEM 0
+#  endif
+#endif
+
+#ifndef FMT_CPP_LIB_VARIANT
+#  ifdef __cpp_lib_variant
+#    define FMT_CPP_LIB_VARIANT __cpp_lib_variant
+#  else
+#    define FMT_CPP_LIB_VARIANT 0
+#  endif
+#endif
+
+#if FMT_CPP_LIB_FILESYSTEM
+FMT_BEGIN_NAMESPACE
+
+namespace detail {
+
+template <typename Char, typename PathChar>
+auto get_path_string(const std::filesystem::path& p,
+                     const std::basic_string<PathChar>& native) {
+  if constexpr (std::is_same_v<Char, char> && std::is_same_v<PathChar, wchar_t>)
+    return to_utf8<wchar_t>(native, to_utf8_error_policy::replace);
+  else
+    return p.string<Char>();
+}
+
+template <typename Char, typename PathChar>
+void write_escaped_path(basic_memory_buffer<Char>& quoted,
+                        const std::filesystem::path& p,
+                        const std::basic_string<PathChar>& native) {
+  if constexpr (std::is_same_v<Char, char> &&
+                std::is_same_v<PathChar, wchar_t>) {
+    auto buf = basic_memory_buffer<wchar_t>();
+    write_escaped_string<wchar_t>(std::back_inserter(buf), native);
+    bool valid = to_utf8<wchar_t>::convert(quoted, {buf.data(), buf.size()});
+    FMT_ASSERT(valid, "invalid utf16");
+  } else if constexpr (std::is_same_v<Char, PathChar>) {
+    write_escaped_string<std::filesystem::path::value_type>(
+        std::back_inserter(quoted), native);
+  } else {
+    write_escaped_string<Char>(std::back_inserter(quoted), p.string<Char>());
+  }
+}
+
+}  // namespace detail
+
+FMT_EXPORT
+template <typename Char> struct formatter<std::filesystem::path, Char> {
+ private:
+  format_specs<Char> specs_;
+  detail::arg_ref<Char> width_ref_;
+  bool debug_ = false;
+  char path_type_ = 0;
+
+ public:
+  FMT_CONSTEXPR void set_debug_format(bool set = true) { debug_ = set; }
+
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+    auto it = ctx.begin(), end = ctx.end();
+    if (it == end) return it;
+
+    it = detail::parse_align(it, end, specs_);
+    if (it == end) return it;
+
+    it = detail::parse_dynamic_spec(it, end, specs_.width, width_ref_, ctx);
+    if (it != end && *it == '?') {
+      debug_ = true;
+      ++it;
+    }
+    if (it != end && (*it == 'g')) path_type_ = *it++;
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(const std::filesystem::path& p, FormatContext& ctx) const {
+    auto specs = specs_;
+#  ifdef _WIN32
+    auto path_string = !path_type_ ? p.native() : p.generic_wstring();
+#  else
+    auto path_string = !path_type_ ? p.native() : p.generic_string();
+#  endif
+
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref_,
+                                                       ctx);
+    if (!debug_) {
+      auto s = detail::get_path_string<Char>(p, path_string);
+      return detail::write(ctx.out(), basic_string_view<Char>(s), specs);
+    }
+    auto quoted = basic_memory_buffer<Char>();
+    detail::write_escaped_path(quoted, p, path_string);
+    return detail::write(ctx.out(),
+                         basic_string_view<Char>(quoted.data(), quoted.size()),
+                         specs);
+  }
+};
+FMT_END_NAMESPACE
+#endif  // FMT_CPP_LIB_FILESYSTEM
+
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <std::size_t N, typename Char>
+struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
+ private:
+  // Functor because C++11 doesn't support generic lambdas.
+  struct writer {
+    const std::bitset<N>& bs;
+
+    template <typename OutputIt>
+    FMT_CONSTEXPR auto operator()(OutputIt out) -> OutputIt {
+      for (auto pos = N; pos > 0; --pos) {
+        out = detail::write<Char>(out, bs[pos - 1] ? Char('1') : Char('0'));
+      }
+
+      return out;
+    }
+  };
+
+ public:
+  template <typename FormatContext>
+  auto format(const std::bitset<N>& bs, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return write_padded(ctx, writer{bs});
+  }
+};
+
+FMT_EXPORT
+template <typename Char>
+struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
+FMT_END_NAMESPACE
+
+#ifdef __cpp_lib_optional
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<std::optional<T>, Char,
+                 std::enable_if_t<is_formattable<T, Char>::value>> {
+ private:
+  formatter<T, Char> underlying_;
+  static constexpr basic_string_view<Char> optional =
+      detail::string_literal<Char, 'o', 'p', 't', 'i', 'o', 'n', 'a', 'l',
+                             '('>{};
+  static constexpr basic_string_view<Char> none =
+      detail::string_literal<Char, 'n', 'o', 'n', 'e'>{};
+
+  template <class U>
+  FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, bool set)
+      -> decltype(u.set_debug_format(set)) {
+    u.set_debug_format(set);
+  }
+
+  template <class U>
+  FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
+
+ public:
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+    maybe_set_debug_format(underlying_, true);
+    return underlying_.parse(ctx);
+  }
+
+  template <typename FormatContext>
+  auto format(const std::optional<T>& opt, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    if (!opt) return detail::write<Char>(ctx.out(), none);
+
+    auto out = ctx.out();
+    out = detail::write<Char>(out, optional);
+    ctx.advance_to(out);
+    out = underlying_.format(*opt, ctx);
+    return detail::write(out, ')');
+  }
+};
+FMT_END_NAMESPACE
+#endif  // __cpp_lib_optional
+
+#ifdef __cpp_lib_source_location
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <> struct formatter<std::source_location> {
+  template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const std::source_location& loc, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    out = detail::write(out, loc.file_name());
+    out = detail::write(out, ':');
+    out = detail::write<char>(out, loc.line());
+    out = detail::write(out, ':');
+    out = detail::write<char>(out, loc.column());
+    out = detail::write(out, ": ");
+    out = detail::write(out, loc.function_name());
+    return out;
+  }
+};
+FMT_END_NAMESPACE
+#endif
+
+#if FMT_CPP_LIB_VARIANT
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+template <typename T>
+using variant_index_sequence =
+    std::make_index_sequence<std::variant_size<T>::value>;
+
+template <typename> struct is_variant_like_ : std::false_type {};
+template <typename... Types>
+struct is_variant_like_<std::variant<Types...>> : std::true_type {};
+
+// formattable element check.
+template <typename T, typename C> class is_variant_formattable_ {
+  template <std::size_t... Is>
+  static std::conjunction<
+      is_formattable<std::variant_alternative_t<Is, T>, C>...>
+      check(std::index_sequence<Is...>);
+
+ public:
+  static constexpr const bool value =
+      decltype(check(variant_index_sequence<T>{}))::value;
+};
+
+template <typename Char, typename OutputIt, typename T>
+auto write_variant_alternative(OutputIt out, const T& v) -> OutputIt {
+  if constexpr (is_string<T>::value)
+    return write_escaped_string<Char>(out, detail::to_string_view(v));
+  else if constexpr (std::is_same_v<T, Char>)
+    return write_escaped_char(out, v);
+  else
+    return write<Char>(out, v);
+}
+
+}  // namespace detail
+
+template <typename T> struct is_variant_like {
+  static constexpr const bool value = detail::is_variant_like_<T>::value;
+};
+
+template <typename T, typename C> struct is_variant_formattable {
+  static constexpr const bool value =
+      detail::is_variant_formattable_<T, C>::value;
+};
+
+FMT_EXPORT
+template <typename Char> struct formatter<std::monostate, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const std::monostate&, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return detail::write<Char>(ctx.out(), "monostate");
+  }
+};
+
+FMT_EXPORT
+template <typename Variant, typename Char>
+struct formatter<
+    Variant, Char,
+    std::enable_if_t<std::conjunction_v<
+        is_variant_like<Variant>, is_variant_formattable<Variant, Char>>>> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  auto format(const Variant& value, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+
+    out = detail::write<Char>(out, "variant(");
+    FMT_TRY {
+      std::visit(
+          [&](const auto& v) {
+            out = detail::write_variant_alternative<Char>(out, v);
+          },
+          value);
+    }
+    FMT_CATCH(const std::bad_variant_access&) {
+      detail::write<Char>(out, "valueless by exception");
+    }
+    *out++ = ')';
+    return out;
+  }
+};
+FMT_END_NAMESPACE
+#endif  // FMT_CPP_LIB_VARIANT
+
+FMT_BEGIN_NAMESPACE
+FMT_EXPORT
+template <typename Char> struct formatter<std::error_code, Char> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const std::error_code& ec, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    out = detail::write_bytes(out, ec.category().name(), format_specs<Char>());
+    out = detail::write<Char>(out, Char(':'));
+    out = detail::write<Char>(out, ec.value());
+    return out;
+  }
+};
+
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<
+    T, Char,  // DEPRECATED! Mixing code unit types.
+    typename std::enable_if<std::is_base_of<std::exception, T>::value>::type> {
+ private:
+  bool with_typename_ = false;
+
+ public:
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    auto it = ctx.begin();
+    auto end = ctx.end();
+    if (it == end || *it == '}') return it;
+    if (*it == 't') {
+      ++it;
+      with_typename_ = FMT_USE_TYPEID != 0;
+    }
+    return it;
+  }
+
+  template <typename OutputIt>
+  auto format(const std::exception& ex,
+              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+    format_specs<Char> spec;
+    auto out = ctx.out();
+    if (!with_typename_)
+      return detail::write_bytes(out, string_view(ex.what()), spec);
+
+#if FMT_USE_TYPEID
+    const std::type_info& ti = typeid(ex);
+#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
+    int status = 0;
+    std::size_t size = 0;
+    std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
+        abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &std::free);
+
+    string_view demangled_name_view;
+    if (demangled_name_ptr) {
+      demangled_name_view = demangled_name_ptr.get();
+
+      // Normalization of stdlib inline namespace names.
+      // libc++ inline namespaces.
+      //  std::__1::*       -> std::*
+      //  std::__1::__fs::* -> std::*
+      // libstdc++ inline namespaces.
+      //  std::__cxx11::*             -> std::*
+      //  std::filesystem::__cxx11::* -> std::filesystem::*
+      if (demangled_name_view.starts_with("std::")) {
+        char* begin = demangled_name_ptr.get();
+        char* to = begin + 5;  // std::
+        for (char *from = to, *end = begin + demangled_name_view.size();
+             from < end;) {
+          // This is safe, because demangled_name is NUL-terminated.
+          if (from[0] == '_' && from[1] == '_') {
+            char* next = from + 1;
+            while (next < end && *next != ':') next++;
+            if (next[0] == ':' && next[1] == ':') {
+              from = next + 2;
+              continue;
+            }
+          }
+          *to++ = *from++;
+        }
+        demangled_name_view = {begin, detail::to_unsigned(to - begin)};
+      }
+    } else {
+      demangled_name_view = string_view(ti.name());
+    }
+    out = detail::write_bytes(out, demangled_name_view, spec);
+#  elif FMT_MSC_VERSION
+    string_view demangled_name_view(ti.name());
+    if (demangled_name_view.starts_with("class "))
+      demangled_name_view.remove_prefix(6);
+    else if (demangled_name_view.starts_with("struct "))
+      demangled_name_view.remove_prefix(7);
+    out = detail::write_bytes(out, demangled_name_view, spec);
+#  else
+    out = detail::write_bytes(out, string_view(ti.name()), spec);
+#  endif
+    *out++ = ':';
+    *out++ = ' ';
+    return detail::write_bytes(out, string_view(ex.what()), spec);
+#endif
+  }
+};
+
+namespace detail {
+
+template <typename T, typename Enable = void>
+struct has_flip : std::false_type {};
+
+template <typename T>
+struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
+    : std::true_type {};
+
+template <typename T> struct is_bit_reference_like {
+  static constexpr const bool value =
+      std::is_convertible<T, bool>::value &&
+      std::is_nothrow_assignable<T, bool>::value && has_flip<T>::value;
+};
+
+#ifdef _LIBCPP_VERSION
+
+// Workaround for libc++ incompatibility with C++ standard.
+// According to the Standard, `bitset::operator[] const` returns bool.
+template <typename C>
+struct is_bit_reference_like<std::__bit_const_reference<C>> {
+  static constexpr const bool value = true;
+};
+
+#endif
+
+}  // namespace detail
+
+// We can't use std::vector<bool, Allocator>::reference and
+// std::bitset<N>::reference because the compiler can't deduce Allocator and N
+// in partial specialization.
+FMT_EXPORT
+template <typename BitRef, typename Char>
+struct formatter<BitRef, Char,
+                 enable_if_t<detail::is_bit_reference_like<BitRef>::value>>
+    : formatter<bool, Char> {
+  template <typename FormatContext>
+  FMT_CONSTEXPR auto format(const BitRef& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<bool, Char>::format(v, ctx);
+  }
+};
+
+FMT_EXPORT
+template <typename T, typename Char>
+struct formatter<std::atomic<T>, Char,
+                 enable_if_t<is_formattable<T, Char>::value>>
+    : formatter<T, Char> {
+  template <typename FormatContext>
+  auto format(const std::atomic<T>& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<T, Char>::format(v.load(), ctx);
+  }
+};
+
+#ifdef __cpp_lib_atomic_flag_test
+FMT_EXPORT
+template <typename Char>
+struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
+  template <typename FormatContext>
+  auto format(const std::atomic_flag& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<bool, Char>::format(v.test(), ctx);
+  }
+};
+#endif  // __cpp_lib_atomic_flag_test
+
+FMT_END_NAMESPACE
+#endif  // FMT_STD_H_
diff --git a/contrib/fmt/include/fmt/xchar.h b/contrib/fmt/include/fmt/xchar.h
new file mode 100644
index 00000000000..f609c5c41a2
--- /dev/null
+++ b/contrib/fmt/include/fmt/xchar.h
@@ -0,0 +1,259 @@
+// Formatting library for C++ - optional wchar_t and exotic character support
+//
+// Copyright (c) 2012 - present, Victor Zverovich
+// All rights reserved.
+//
+// For the license information refer to format.h.
+
+#ifndef FMT_XCHAR_H_
+#define FMT_XCHAR_H_
+
+#include <cwchar>
+
+#include "format.h"
+
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+#  include <locale>
+#endif
+
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
+template <typename T>
+using is_exotic_char = bool_constant<!std::is_same<T, char>::value>;
+
+inline auto write_loc(std::back_insert_iterator<detail::buffer<wchar_t>> out,
+                      loc_value value, const format_specs<wchar_t>& specs,
+                      locale_ref loc) -> bool {
+#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
+  auto& numpunct =
+      std::use_facet<std::numpunct<wchar_t>>(loc.get<std::locale>());
+  auto separator = std::wstring();
+  auto grouping = numpunct.grouping();
+  if (!grouping.empty()) separator = std::wstring(1, numpunct.thousands_sep());
+  return value.visit(loc_writer<wchar_t>{out, specs, separator, grouping, {}});
+#endif
+  return false;
+}
+}  // namespace detail
+
+FMT_BEGIN_EXPORT
+
+using wstring_view = basic_string_view<wchar_t>;
+using wformat_parse_context = basic_format_parse_context<wchar_t>;
+using wformat_context = buffer_context<wchar_t>;
+using wformat_args = basic_format_args<wformat_context>;
+using wmemory_buffer = basic_memory_buffer<wchar_t>;
+
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+// Workaround broken conversion on older gcc.
+template <typename... Args> using wformat_string = wstring_view;
+inline auto runtime(wstring_view s) -> wstring_view { return s; }
+#else
+template <typename... Args>
+using wformat_string = basic_format_string<wchar_t, type_identity_t<Args>...>;
+inline auto runtime(wstring_view s) -> runtime_format_string<wchar_t> {
+  return {{s}};
+}
+#endif
+
+template <> struct is_char<wchar_t> : std::true_type {};
+template <> struct is_char<detail::char8_type> : std::true_type {};
+template <> struct is_char<char16_t> : std::true_type {};
+template <> struct is_char<char32_t> : std::true_type {};
+
+template <typename... T>
+constexpr auto make_wformat_args(const T&... args)
+    -> format_arg_store<wformat_context, T...> {
+  return {args...};
+}
+
+inline namespace literals {
+#if FMT_USE_USER_DEFINED_LITERALS && !FMT_USE_NONTYPE_TEMPLATE_ARGS
+constexpr auto operator""_a(const wchar_t* s, size_t)
+    -> detail::udl_arg<wchar_t> {
+  return {s};
+}
+#endif
+}  // namespace literals
+
+template <typename It, typename Sentinel>
+auto join(It begin, Sentinel end, wstring_view sep)
+    -> join_view<It, Sentinel, wchar_t> {
+  return {begin, end, sep};
+}
+
+template <typename Range>
+auto join(Range&& range, wstring_view sep)
+    -> join_view<detail::iterator_t<Range>, detail::sentinel_t<Range>,
+                 wchar_t> {
+  return join(std::begin(range), std::end(range), sep);
+}
+
+template <typename T>
+auto join(std::initializer_list<T> list, wstring_view sep)
+    -> join_view<const T*, const T*, wchar_t> {
+  return join(std::begin(list), std::end(list), sep);
+}
+
+template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+auto vformat(basic_string_view<Char> format_str,
+             basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
+  auto buf = basic_memory_buffer<Char>();
+  detail::vformat_to(buf, format_str, args);
+  return to_string(buf);
+}
+
+template <typename... T>
+auto format(wformat_string<T...> fmt, T&&... args) -> std::wstring {
+  return vformat(fmt::wstring_view(fmt), fmt::make_wformat_args(args...));
+}
+
+// Pass char_t as a default template parameter instead of using
+// std::basic_string<char_t<S>> to reduce the symbol size.
+template <typename S, typename... T, typename Char = char_t<S>,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value &&
+                        !std::is_same<Char, wchar_t>::value)>
+auto format(const S& format_str, T&&... args) -> std::basic_string<Char> {
+  return vformat(detail::to_string_view(format_str),
+                 fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+template <typename Locale, typename S, typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
+                            detail::is_exotic_char<Char>::value)>
+inline auto vformat(
+    const Locale& loc, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> std::basic_string<Char> {
+  return detail::vformat(loc, detail::to_string_view(format_str), args);
+}
+
+template <typename Locale, typename S, typename... T, typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
+                            detail::is_exotic_char<Char>::value)>
+inline auto format(const Locale& loc, const S& format_str, T&&... args)
+    -> std::basic_string<Char> {
+  return detail::vformat(loc, detail::to_string_view(format_str),
+                         fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+template <typename OutputIt, typename S, typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
+                            detail::is_exotic_char<Char>::value)>
+auto vformat_to(OutputIt out, const S& format_str,
+                basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> OutputIt {
+  auto&& buf = detail::get_buffer<Char>(out);
+  detail::vformat_to(buf, detail::to_string_view(format_str), args);
+  return detail::get_iterator(buf, out);
+}
+
+template <typename OutputIt, typename S, typename... T,
+          typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
+                            detail::is_exotic_char<Char>::value)>
+inline auto format_to(OutputIt out, const S& fmt, T&&... args) -> OutputIt {
+  return vformat_to(out, detail::to_string_view(fmt),
+                    fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+template <typename Locale, typename S, typename OutputIt, typename... Args,
+          typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
+                            detail::is_locale<Locale>::value&&
+                                detail::is_exotic_char<Char>::value)>
+inline auto vformat_to(
+    OutputIt out, const Locale& loc, const S& format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args) -> OutputIt {
+  auto&& buf = detail::get_buffer<Char>(out);
+  vformat_to(buf, detail::to_string_view(format_str), args,
+             detail::locale_ref(loc));
+  return detail::get_iterator(buf, out);
+}
+
+template <typename OutputIt, typename Locale, typename S, typename... T,
+          typename Char = char_t<S>,
+          bool enable = detail::is_output_iterator<OutputIt, Char>::value &&
+                        detail::is_locale<Locale>::value &&
+                        detail::is_exotic_char<Char>::value>
+inline auto format_to(OutputIt out, const Locale& loc, const S& format_str,
+                      T&&... args) ->
+    typename std::enable_if<enable, OutputIt>::type {
+  return vformat_to(out, loc, detail::to_string_view(format_str),
+                    fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+template <typename OutputIt, typename Char, typename... Args,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
+                            detail::is_exotic_char<Char>::value)>
+inline auto vformat_to_n(
+    OutputIt out, size_t n, basic_string_view<Char> format_str,
+    basic_format_args<buffer_context<type_identity_t<Char>>> args)
+    -> format_to_n_result<OutputIt> {
+  using traits = detail::fixed_buffer_traits;
+  auto buf = detail::iterator_buffer<OutputIt, Char, traits>(out, n);
+  detail::vformat_to(buf, format_str, args);
+  return {buf.out(), buf.count()};
+}
+
+template <typename OutputIt, typename S, typename... T,
+          typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
+                            detail::is_exotic_char<Char>::value)>
+inline auto format_to_n(OutputIt out, size_t n, const S& fmt, T&&... args)
+    -> format_to_n_result<OutputIt> {
+  return vformat_to_n(out, n, detail::to_string_view(fmt),
+                      fmt::make_format_args<buffer_context<Char>>(args...));
+}
+
+template <typename S, typename... T, typename Char = char_t<S>,
+          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
+inline auto formatted_size(const S& fmt, T&&... args) -> size_t {
+  auto buf = detail::counting_buffer<Char>();
+  detail::vformat_to(buf, detail::to_string_view(fmt),
+                     fmt::make_format_args<buffer_context<Char>>(args...));
+  return buf.count();
+}
+
+inline void vprint(std::FILE* f, wstring_view fmt, wformat_args args) {
+  auto buf = wmemory_buffer();
+  detail::vformat_to(buf, fmt, args);
+  buf.push_back(L'\0');
+  if (std::fputws(buf.data(), f) == -1)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
+}
+
+inline void vprint(wstring_view fmt, wformat_args args) {
+  vprint(stdout, fmt, args);
+}
+
+template <typename... T>
+void print(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
+  return vprint(f, wstring_view(fmt), fmt::make_wformat_args(args...));
+}
+
+template <typename... T> void print(wformat_string<T...> fmt, T&&... args) {
+  return vprint(wstring_view(fmt), fmt::make_wformat_args(args...));
+}
+
+template <typename... T>
+void println(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
+  return print(f, L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+template <typename... T> void println(wformat_string<T...> fmt, T&&... args) {
+  return print(L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
+}
+
+/**
+  Converts *value* to ``std::wstring`` using the default format for type *T*.
+ */
+template <typename T> inline auto to_wstring(const T& value) -> std::wstring {
+  return format(FMT_STRING(L"{}"), value);
+}
+FMT_END_EXPORT
+FMT_END_NAMESPACE
+
+#endif  // FMT_XCHAR_H_
diff --git a/contrib/fmt/src/fmt.cc b/contrib/fmt/src/fmt.cc
new file mode 100644
index 00000000000..5330463a932
--- /dev/null
+++ b/contrib/fmt/src/fmt.cc
@@ -0,0 +1,108 @@
+module;
+
+// Put all implementation-provided headers into the global module fragment
+// to prevent attachment to this module.
+#include <algorithm>
+#include <cerrno>
+#include <chrono>
+#include <climits>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <exception>
+#include <filesystem>
+#include <fstream>
+#include <functional>
+#include <iterator>
+#include <limits>
+#include <locale>
+#include <memory>
+#include <optional>
+#include <ostream>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <system_error>
+#include <thread>
+#include <type_traits>
+#include <typeinfo>
+#include <utility>
+#include <variant>
+#include <vector>
+#include <version>
+
+#if __has_include(<cxxabi.h>)
+#  include <cxxabi.h>
+#endif
+#if defined(_MSC_VER) || defined(__MINGW32__)
+#  include <intrin.h>
+#endif
+#if defined __APPLE__ || defined(__FreeBSD__)
+#  include <xlocale.h>
+#endif
+#if __has_include(<winapifamily.h>)
+#  include <winapifamily.h>
+#endif
+#if (__has_include(<fcntl.h>) || defined(__APPLE__) || \
+     defined(__linux__)) &&                            \
+    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#  include <fcntl.h>
+#  include <sys/stat.h>
+#  include <sys/types.h>
+#  ifndef _WIN32
+#    include <unistd.h>
+#  else
+#    include <io.h>
+#  endif
+#endif
+#ifdef _WIN32
+#  if defined(__GLIBCXX__)
+#    include <ext/stdio_filebuf.h>
+#    include <ext/stdio_sync_filebuf.h>
+#  endif
+#  define WIN32_LEAN_AND_MEAN
+#  include <windows.h>
+#endif
+
+export module fmt;
+
+#define FMT_EXPORT export
+#define FMT_BEGIN_EXPORT export {
+#define FMT_END_EXPORT }
+
+// If you define FMT_ATTACH_TO_GLOBAL_MODULE
+//  - all declarations are detached from module 'fmt'
+//  - the module behaves like a traditional static library, too
+//  - all library symbols are mangled traditionally
+//  - you can mix TUs with either importing or #including the {fmt} API
+#ifdef FMT_ATTACH_TO_GLOBAL_MODULE
+extern "C++" {
+#endif
+
+// All library-provided declarations and definitions must be in the module
+// purview to be exported.
+#include "fmt/args.h"
+#include "fmt/chrono.h"
+#include "fmt/color.h"
+#include "fmt/compile.h"
+#include "fmt/format.h"
+#include "fmt/os.h"
+#include "fmt/printf.h"
+#include "fmt/std.h"
+#include "fmt/xchar.h"
+
+#ifdef FMT_ATTACH_TO_GLOBAL_MODULE
+}
+#endif
+
+// gcc doesn't yet implement private module fragments
+#if !FMT_GCC_VERSION
+module :private;
+#endif
+
+#include "format.cc"
+#include "os.cc"
diff --git a/contrib/fmt/src/format.cc b/contrib/fmt/src/format.cc
index 9a9abf8d0a7..391d3a248c2 100644
--- a/contrib/fmt/src/format.cc
+++ b/contrib/fmt/src/format.cc
@@ -8,169 +8,36 @@
 #include "fmt/format-inl.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
-template <typename T>
-int format_float(char* buf, std::size_t size, const char* format, int precision,
-                 T value) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-  if (precision > 100000)
-    throw std::runtime_error(
-        "fuzz mode - avoid large allocation inside snprintf");
-#endif
-  // Suppress the warning about nonliteral format string.
-  int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
-  return precision < 0 ? snprintf_ptr(buf, size, format, value)
-                       : snprintf_ptr(buf, size, format, precision, value);
-}
-struct sprintf_specs {
-  int precision;
-  char type;
-  bool alt : 1;
-
-  template <typename Char>
-  constexpr sprintf_specs(basic_format_specs<Char> specs)
-      : precision(specs.precision), type(specs.type), alt(specs.alt) {}
-
-  constexpr bool has_precision() const { return precision >= 0; }
-};
-
-// This is deprecated and is kept only to preserve ABI compatibility.
-template <typename Double>
-char* sprintf_format(Double value, internal::buffer<char>& buf,
-                     sprintf_specs specs) {
-  // Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
-  FMT_ASSERT(buf.capacity() != 0, "empty buffer");
-
-  // Build format string.
-  enum { max_format_size = 10 };  // longest format: %#-*.*Lg
-  char format[max_format_size];
-  char* format_ptr = format;
-  *format_ptr++ = '%';
-  if (specs.alt || !specs.type) *format_ptr++ = '#';
-  if (specs.precision >= 0) {
-    *format_ptr++ = '.';
-    *format_ptr++ = '*';
-  }
-  if (std::is_same<Double, long double>::value) *format_ptr++ = 'L';
-
-  char type = specs.type;
-
-  if (type == '%')
-    type = 'f';
-  else if (type == 0 || type == 'n')
-    type = 'g';
-#if FMT_MSC_VER
-  if (type == 'F') {
-    // MSVC's printf doesn't support 'F'.
-    type = 'f';
-  }
-#endif
-  *format_ptr++ = type;
-  *format_ptr = '\0';
-
-  // Format using snprintf.
-  char* start = nullptr;
-  char* decimal_point_pos = nullptr;
-  for (;;) {
-    std::size_t buffer_size = buf.capacity();
-    start = &buf[0];
-    int result =
-        format_float(start, buffer_size, format, specs.precision, value);
-    if (result >= 0) {
-      unsigned n = internal::to_unsigned(result);
-      if (n < buf.capacity()) {
-        // Find the decimal point.
-        auto p = buf.data(), end = p + n;
-        if (*p == '+' || *p == '-') ++p;
-        if (specs.type != 'a' && specs.type != 'A') {
-          while (p < end && *p >= '0' && *p <= '9') ++p;
-          if (p < end && *p != 'e' && *p != 'E') {
-            decimal_point_pos = p;
-            if (!specs.type) {
-              // Keep only one trailing zero after the decimal point.
-              ++p;
-              if (*p == '0') ++p;
-              while (p != end && *p >= '1' && *p <= '9') ++p;
-              char* where = p;
-              while (p != end && *p == '0') ++p;
-              if (p == end || *p < '0' || *p > '9') {
-                if (p != end) std::memmove(where, p, to_unsigned(end - p));
-                n -= static_cast<unsigned>(p - where);
-              }
-            }
-          }
-        }
-        buf.resize(n);
-        break;  // The buffer is large enough - continue with formatting.
-      }
-      buf.reserve(n + 1);
-    } else {
-      // If result is negative we ask to increase the capacity by at least 1,
-      // but as std::vector, the buffer grows exponentially.
-      buf.reserve(buf.capacity() + 1);
-    }
-  }
-  return decimal_point_pos;
-}
-}  // namespace internal
-
-template FMT_API char* internal::sprintf_format(double, internal::buffer<char>&,
-                                                sprintf_specs);
-template FMT_API char* internal::sprintf_format(long double,
-                                                internal::buffer<char>&,
-                                                sprintf_specs);
-
-template struct FMT_INSTANTIATION_DEF_API internal::basic_data<void>;
-
-// Workaround a bug in MSVC2013 that prevents instantiation of format_float.
-int (*instantiate_format_float)(double, int, internal::float_specs,
-                                internal::buffer<char>&) =
-    internal::format_float;
+template FMT_API auto dragonbox::to_decimal(float x) noexcept
+    -> dragonbox::decimal_fp<float>;
+template FMT_API auto dragonbox::to_decimal(double x) noexcept
+    -> dragonbox::decimal_fp<double>;
 
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-template FMT_API internal::locale_ref::locale_ref(const std::locale& loc);
-template FMT_API std::locale internal::locale_ref::get<std::locale>() const;
+template FMT_API locale_ref::locale_ref(const std::locale& loc);
+template FMT_API auto locale_ref::get<std::locale>() const -> std::locale;
 #endif
 
 // Explicit instantiations for char.
 
-template FMT_API std::string internal::grouping_impl<char>(locale_ref);
-template FMT_API char internal::thousands_sep_impl(locale_ref);
-template FMT_API char internal::decimal_point_impl(locale_ref);
-
-template FMT_API void internal::buffer<char>::append(const char*, const char*);
-
-template FMT_API void internal::arg_map<format_context>::init(
-    const basic_format_args<format_context>& args);
-
-template FMT_API std::string internal::vformat<char>(
-    string_view, basic_format_args<format_context>);
+template FMT_API auto thousands_sep_impl(locale_ref)
+    -> thousands_sep_result<char>;
+template FMT_API auto decimal_point_impl(locale_ref) -> char;
 
-template FMT_API format_context::iterator internal::vformat_to(
-    internal::buffer<char>&, string_view, basic_format_args<format_context>);
+template FMT_API void buffer<char>::append(const char*, const char*);
 
-template FMT_API int internal::snprintf_float(double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::snprintf_float(long double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::format_float(double, int, internal::float_specs,
-                                            internal::buffer<char>&);
-template FMT_API int internal::format_float(long double, int,
-                                            internal::float_specs,
-                                            internal::buffer<char>&);
+template FMT_API void vformat_to(buffer<char>&, string_view,
+                                 typename vformat_args<>::type, locale_ref);
 
 // Explicit instantiations for wchar_t.
 
-template FMT_API std::string internal::grouping_impl<wchar_t>(locale_ref);
-template FMT_API wchar_t internal::thousands_sep_impl(locale_ref);
-template FMT_API wchar_t internal::decimal_point_impl(locale_ref);
+template FMT_API auto thousands_sep_impl(locale_ref)
+    -> thousands_sep_result<wchar_t>;
+template FMT_API auto decimal_point_impl(locale_ref) -> wchar_t;
 
-template FMT_API void internal::buffer<wchar_t>::append(const wchar_t*,
-                                                        const wchar_t*);
+template FMT_API void buffer<wchar_t>::append(const wchar_t*, const wchar_t*);
 
-template FMT_API std::wstring internal::vformat<wchar_t>(
-    wstring_view, basic_format_args<wformat_context>);
+}  // namespace detail
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/src/os.cc b/contrib/fmt/src/os.cc
index 10a372a4603..a639e78c602 100644
--- a/contrib/fmt/src/os.cc
+++ b/contrib/fmt/src/os.cc
@@ -18,6 +18,10 @@
 #  include <sys/stat.h>
 #  include <sys/types.h>
 
+#  ifdef _WRS_KERNEL    // VxWorks7 kernel
+#    include <ioLib.h>  // getpagesize
+#  endif
+
 #  ifndef _WIN32
 #    include <unistd.h>
 #  else
@@ -25,21 +29,24 @@
 #      define WIN32_LEAN_AND_MEAN
 #    endif
 #    include <io.h>
-#    include <windows.h>
-
-#    define O_CREAT _O_CREAT
-#    define O_TRUNC _O_TRUNC
 
 #    ifndef S_IRUSR
 #      define S_IRUSR _S_IREAD
 #    endif
-
 #    ifndef S_IWUSR
 #      define S_IWUSR _S_IWRITE
 #    endif
-
-#    ifdef __MINGW32__
-#      define _SH_DENYNO 0x40
+#    ifndef S_IRGRP
+#      define S_IRGRP 0
+#    endif
+#    ifndef S_IWGRP
+#      define S_IWGRP 0
+#    endif
+#    ifndef S_IROTH
+#      define S_IROTH 0
+#    endif
+#    ifndef S_IWOTH
+#      define S_IWOTH 0
 #    endif
 #  endif  // _WIN32
 #endif    // FMT_USE_FCNTL
@@ -48,23 +55,19 @@
 #  include <windows.h>
 #endif
 
-#ifdef fileno
-#  undef fileno
-#endif
-
 namespace {
 #ifdef _WIN32
 // Return type of read and write functions.
-using RWResult = int;
+using rwresult = int;
 
 // On Windows the count argument to read and write is unsigned, so convert
 // it from size_t preventing integer overflow.
 inline unsigned convert_rwcount(std::size_t count) {
   return count <= UINT_MAX ? static_cast<unsigned>(count) : UINT_MAX;
 }
-#else
+#elif FMT_USE_FCNTL
 // Return type of read and write functions.
-using RWResult = ssize_t;
+using rwresult = ssize_t;
 
 inline std::size_t convert_rwcount(std::size_t count) { return count; }
 #endif
@@ -73,81 +76,91 @@ inline std::size_t convert_rwcount(std::size_t count) { return count; }
 FMT_BEGIN_NAMESPACE
 
 #ifdef _WIN32
-internal::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
-  if (int error_code = convert(s)) {
-    FMT_THROW(windows_error(error_code,
-                            "cannot convert string from UTF-16 to UTF-8"));
+namespace detail {
+
+class system_message {
+  system_message(const system_message&) = delete;
+  void operator=(const system_message&) = delete;
+
+  unsigned long result_;
+  wchar_t* message_;
+
+  static bool is_whitespace(wchar_t c) noexcept {
+    return c == L' ' || c == L'\n' || c == L'\r' || c == L'\t' || c == L'\0';
   }
-}
 
-int internal::utf16_to_utf8::convert(wstring_view s) {
-  if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
-  int s_size = static_cast<int>(s.size());
-  if (s_size == 0) {
-    // WideCharToMultiByte does not support zero length, handle separately.
-    buffer_.resize(1);
-    buffer_[0] = 0;
-    return 0;
+ public:
+  explicit system_message(unsigned long error_code)
+      : result_(0), message_(nullptr) {
+    result_ = FormatMessageW(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
+            FORMAT_MESSAGE_IGNORE_INSERTS,
+        nullptr, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+        reinterpret_cast<wchar_t*>(&message_), 0, nullptr);
+    if (result_ != 0) {
+      while (result_ != 0 && is_whitespace(message_[result_ - 1])) {
+        --result_;
+      }
+    }
+  }
+  ~system_message() { LocalFree(message_); }
+  explicit operator bool() const noexcept { return result_ != 0; }
+  operator basic_string_view<wchar_t>() const noexcept {
+    return basic_string_view<wchar_t>(message_, result_);
+  }
+};
+
+class utf8_system_category final : public std::error_category {
+ public:
+  const char* name() const noexcept override { return "system"; }
+  std::string message(int error_code) const override {
+    auto&& msg = system_message(error_code);
+    if (msg) {
+      auto utf8_message = to_utf8<wchar_t>();
+      if (utf8_message.convert(msg)) {
+        return utf8_message.str();
+      }
+    }
+    return "unknown error";
   }
+};
 
-  int length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, nullptr, 0,
-                                   nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_.resize(length + 1);
-  length = WideCharToMultiByte(CP_UTF8, 0, s.data(), s_size, &buffer_[0],
-                               length, nullptr, nullptr);
-  if (length == 0) return GetLastError();
-  buffer_[length] = 0;
-  return 0;
+}  // namespace detail
+
+FMT_API const std::error_category& system_category() noexcept {
+  static const detail::utf8_system_category category;
+  return category;
 }
 
-void windows_error::init(int err_code, string_view format_str,
-                         format_args args) {
-  error_code_ = err_code;
-  memory_buffer buffer;
-  internal::format_windows_error(buffer, err_code, vformat(format_str, args));
-  std::runtime_error& base = *this;
-  base = std::runtime_error(to_string(buffer));
+std::system_error vwindows_error(int err_code, string_view format_str,
+                                 format_args args) {
+  auto ec = std::error_code(err_code, system_category());
+  return std::system_error(ec, vformat(format_str, args));
 }
 
-void internal::format_windows_error(internal::buffer<char>& out, int error_code,
-                                    string_view message) FMT_NOEXCEPT {
+void detail::format_windows_error(detail::buffer<char>& out, int error_code,
+                                  const char* message) noexcept {
   FMT_TRY {
-    wmemory_buffer buf;
-    buf.resize(inline_buffer_size);
-    for (;;) {
-      wchar_t* system_message = &buf[0];
-      int result = FormatMessageW(
-          FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr,
-          error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), system_message,
-          static_cast<uint32_t>(buf.size()), nullptr);
-      if (result != 0) {
-        utf16_to_utf8 utf8_message;
-        if (utf8_message.convert(system_message) == ERROR_SUCCESS) {
-          internal::writer w(out);
-          w.write(message);
-          w.write(": ");
-          w.write(utf8_message);
-          return;
-        }
-        break;
+    auto&& msg = system_message(error_code);
+    if (msg) {
+      auto utf8_message = to_utf8<wchar_t>();
+      if (utf8_message.convert(msg)) {
+        fmt::format_to(appender(out), FMT_STRING("{}: {}"), message,
+                       string_view(utf8_message));
+        return;
       }
-      if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
-        break;  // Can't get error message, report error code instead.
-      buf.resize(buf.size() * 2);
     }
   }
   FMT_CATCH(...) {}
   format_error_code(out, error_code, message);
 }
 
-void report_windows_error(int error_code,
-                          fmt::string_view message) FMT_NOEXCEPT {
-  report_error(internal::format_windows_error, error_code, message);
+void report_windows_error(int error_code, const char* message) noexcept {
+  report_error(detail::format_windows_error, error_code, message);
 }
 #endif  // _WIN32
 
-buffered_file::~buffered_file() FMT_NOEXCEPT {
+buffered_file::~buffered_file() noexcept {
   if (file_ && FMT_SYSTEM(fclose(file_)) != 0)
     report_system_error(errno, "cannot close file");
 }
@@ -156,39 +169,54 @@ buffered_file::buffered_file(cstring_view filename, cstring_view mode) {
   FMT_RETRY_VAL(file_, FMT_SYSTEM(fopen(filename.c_str(), mode.c_str())),
                 nullptr);
   if (!file_)
-    FMT_THROW(system_error(errno, "cannot open file {}", filename.c_str()));
+    FMT_THROW(system_error(errno, FMT_STRING("cannot open file {}"),
+                           filename.c_str()));
 }
 
 void buffered_file::close() {
   if (!file_) return;
   int result = FMT_SYSTEM(fclose(file_));
   file_ = nullptr;
-  if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }
 
-// A macro used to prevent expansion of fileno on broken versions of MinGW.
-#define FMT_ARGS
-
-int buffered_file::fileno() const {
-  int fd = FMT_POSIX_CALL(fileno FMT_ARGS(file_));
-  if (fd == -1) FMT_THROW(system_error(errno, "cannot get file descriptor"));
+int buffered_file::descriptor() const {
+#if !defined(fileno)
+  int fd = FMT_POSIX_CALL(fileno(file_));
+#elif defined(FMT_HAS_SYSTEM)
+  // fileno is a macro on OpenBSD so we cannot use FMT_POSIX_CALL.
+#  define FMT_DISABLE_MACRO
+  int fd = FMT_SYSTEM(fileno FMT_DISABLE_MACRO(file_));
+#else
+  int fd = fileno(file_);
+#endif
+  if (fd == -1)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get file descriptor")));
   return fd;
 }
 
 #if FMT_USE_FCNTL
+#  ifdef _WIN32
+using mode_t = int;
+#  endif
+constexpr mode_t default_open_mode =
+    S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
+
 file::file(cstring_view path, int oflag) {
-  int mode = S_IRUSR | S_IWUSR;
 #  if defined(_WIN32) && !defined(__MINGW32__)
   fd_ = -1;
-  FMT_POSIX_CALL(sopen_s(&fd_, path.c_str(), oflag, _SH_DENYNO, mode));
+  auto converted = detail::utf8_to_utf16(string_view(path.c_str()));
+  *this = file::open_windows_file(converted.c_str(), oflag);
 #  else
-  FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, mode)));
-#  endif
+  FMT_RETRY(fd_, FMT_POSIX_CALL(open(path.c_str(), oflag, default_open_mode)));
   if (fd_ == -1)
-    FMT_THROW(system_error(errno, "cannot open file {}", path.c_str()));
+    FMT_THROW(
+        system_error(errno, FMT_STRING("cannot open file {}"), path.c_str()));
+#  endif
 }
 
-file::~file() FMT_NOEXCEPT {
+file::~file() noexcept {
   // Don't retry close in case of EINTR!
   // See http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
   if (fd_ != -1 && FMT_POSIX_CALL(close(fd_)) != 0)
@@ -201,7 +229,8 @@ void file::close() {
   // See http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
   int result = FMT_POSIX_CALL(close(fd_));
   fd_ = -1;
-  if (result != 0) FMT_THROW(system_error(errno, "cannot close file"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }
 
 long long file::size() const {
@@ -223,7 +252,7 @@ long long file::size() const {
   using Stat = struct stat;
   Stat file_stat = Stat();
   if (FMT_POSIX_CALL(fstat(fd_, &file_stat)) == -1)
-    FMT_THROW(system_error(errno, "cannot get file attributes"));
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get file attributes")));
   static_assert(sizeof(long long) >= sizeof(file_stat.st_size),
                 "return type of file::size is not large enough");
   return file_stat.st_size;
@@ -231,17 +260,19 @@ long long file::size() const {
 }
 
 std::size_t file::read(void* buffer, std::size_t count) {
-  RWResult result = 0;
+  rwresult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
-  if (result < 0) FMT_THROW(system_error(errno, "cannot read from file"));
-  return internal::to_unsigned(result);
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot read from file")));
+  return detail::to_unsigned(result);
 }
 
 std::size_t file::write(const void* buffer, std::size_t count) {
-  RWResult result = 0;
+  rwresult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
-  if (result < 0) FMT_THROW(system_error(errno, "cannot write to file"));
-  return internal::to_unsigned(result);
+  if (result < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot write to file")));
+  return detail::to_unsigned(result);
 }
 
 file file::dup(int fd) {
@@ -249,7 +280,8 @@ file file::dup(int fd) {
   // http://pubs.opengroup.org/onlinepubs/009695399/functions/dup.html
   int new_fd = FMT_POSIX_CALL(dup(fd));
   if (new_fd == -1)
-    FMT_THROW(system_error(errno, "cannot duplicate file descriptor {}", fd));
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot duplicate file descriptor {}"), fd));
   return file(new_fd);
 }
 
@@ -257,15 +289,16 @@ void file::dup2(int fd) {
   int result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(dup2(fd_, fd)));
   if (result == -1) {
-    FMT_THROW(system_error(errno, "cannot duplicate file descriptor {} to {}",
-                           fd_, fd));
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot duplicate file descriptor {} to {}"), fd_,
+        fd));
   }
 }
 
-void file::dup2(int fd, error_code& ec) FMT_NOEXCEPT {
+void file::dup2(int fd, std::error_code& ec) noexcept {
   int result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(dup2(fd_, fd)));
-  if (result == -1) ec = error_code(errno);
+  if (result == -1) ec = std::error_code(errno, std::generic_category());
 }
 
 void file::pipe(file& read_end, file& write_end) {
@@ -283,7 +316,8 @@ void file::pipe(file& read_end, file& write_end) {
   // http://pubs.opengroup.org/onlinepubs/009696799/functions/pipe.html
   int result = FMT_POSIX_CALL(pipe(fds));
 #  endif
-  if (result != 0) FMT_THROW(system_error(errno, "cannot create pipe"));
+  if (result != 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot create pipe")));
   // The following assignments don't throw because read_fd and write_fd
   // are closed.
   read_end = file(fds[0]);
@@ -291,26 +325,78 @@ void file::pipe(file& read_end, file& write_end) {
 }
 
 buffered_file file::fdopen(const char* mode) {
-  // Don't retry as fdopen doesn't return EINTR.
+// Don't retry as fdopen doesn't return EINTR.
+#  if defined(__MINGW32__) && defined(_POSIX_)
+  FILE* f = ::fdopen(fd_, mode);
+#  else
   FILE* f = FMT_POSIX_CALL(fdopen(fd_, mode));
-  if (!f)
-    FMT_THROW(
-        system_error(errno, "cannot associate stream with file descriptor"));
+#  endif
+  if (!f) {
+    FMT_THROW(system_error(
+        errno, FMT_STRING("cannot associate stream with file descriptor")));
+  }
   buffered_file bf(f);
   fd_ = -1;
   return bf;
 }
 
+#  if defined(_WIN32) && !defined(__MINGW32__)
+file file::open_windows_file(wcstring_view path, int oflag) {
+  int fd = -1;
+  auto err = _wsopen_s(&fd, path.c_str(), oflag, _SH_DENYNO, default_open_mode);
+  if (fd == -1) {
+    FMT_THROW(system_error(err, FMT_STRING("cannot open file {}"),
+                           detail::to_utf8<wchar_t>(path.c_str()).c_str()));
+  }
+  return file(fd);
+}
+#  endif
+
+#  if !defined(__MSDOS__)
 long getpagesize() {
-#  ifdef _WIN32
+#    ifdef _WIN32
   SYSTEM_INFO si;
   GetSystemInfo(&si);
   return si.dwPageSize;
-#  else
+#    else
+#      ifdef _WRS_KERNEL
+  long size = FMT_POSIX_CALL(getpagesize());
+#      else
   long size = FMT_POSIX_CALL(sysconf(_SC_PAGESIZE));
-  if (size < 0) FMT_THROW(system_error(errno, "cannot get memory page size"));
+#      endif
+
+  if (size < 0)
+    FMT_THROW(system_error(errno, FMT_STRING("cannot get memory page size")));
   return size;
+#    endif
+}
 #  endif
+
+namespace detail {
+
+void file_buffer::grow(size_t) {
+  if (this->size() == this->capacity()) flush();
 }
+
+file_buffer::file_buffer(cstring_view path,
+                         const detail::ostream_params& params)
+    : file_(path, params.oflag) {
+  set(new char[params.buffer_size], params.buffer_size);
+}
+
+file_buffer::file_buffer(file_buffer&& other)
+    : detail::buffer<char>(other.data(), other.size(), other.capacity()),
+      file_(std::move(other.file_)) {
+  other.clear();
+  other.set(nullptr, 0);
+}
+
+file_buffer::~file_buffer() {
+  flush();
+  delete[] data();
+}
+}  // namespace detail
+
+ostream::~ostream() = default;
 #endif  // FMT_USE_FCNTL
 FMT_END_NAMESPACE
diff --git a/contrib/fmt/support/cmake/JoinPaths.cmake b/contrib/fmt/support/cmake/JoinPaths.cmake
new file mode 100644
index 00000000000..32d6d6685c0
--- /dev/null
+++ b/contrib/fmt/support/cmake/JoinPaths.cmake
@@ -0,0 +1,26 @@
+# This module provides function for joining paths
+# known from from most languages
+#
+# Original license:
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Explicit permission given to distribute this module under
+# the terms of the project as described in /LICENSE.rst.
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()
diff --git a/contrib/fmt/support/cmake/cxx14.cmake b/contrib/fmt/support/cmake/cxx14.cmake
deleted file mode 100644
index 16ff57541b1..00000000000
--- a/contrib/fmt/support/cmake/cxx14.cmake
+++ /dev/null
@@ -1,70 +0,0 @@
-# C++14 feature support detection
-
-include(CheckCXXSourceCompiles)
-include(CheckCXXCompilerFlag)
-
-if (NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 11)
-endif()
-message(STATUS "CXX_STANDARD: ${CMAKE_CXX_STANDARD}")
-
-if (CMAKE_CXX_STANDARD EQUAL 20)
-  check_cxx_compiler_flag(-std=c++20 has_std_20_flag)
-  check_cxx_compiler_flag(-std=c++2a has_std_2a_flag)
-
-  if (has_std_20_flag)
-    set(CXX_STANDARD_FLAG -std=c++20)
-  elseif (has_std_2a_flag)
-    set(CXX_STANDARD_FLAG -std=c++2a)
-  endif ()
-elseif (CMAKE_CXX_STANDARD EQUAL 17)
-  check_cxx_compiler_flag(-std=c++17 has_std_17_flag)
-  check_cxx_compiler_flag(-std=c++1z has_std_1z_flag)
-
-  if (has_std_17_flag)
-    set(CXX_STANDARD_FLAG -std=c++17)
-  elseif (has_std_1z_flag)
-    set(CXX_STANDARD_FLAG -std=c++1z)
-  endif ()
-elseif (CMAKE_CXX_STANDARD EQUAL 14)
-  check_cxx_compiler_flag(-std=c++14 has_std_14_flag)
-  check_cxx_compiler_flag(-std=c++1y has_std_1y_flag)
-
-  if (has_std_14_flag)
-    set(CXX_STANDARD_FLAG -std=c++14)
-  elseif (has_std_1y_flag)
-    set(CXX_STANDARD_FLAG -std=c++1y)
-  endif ()
-elseif (CMAKE_CXX_STANDARD EQUAL 11)
-  check_cxx_compiler_flag(-std=c++11 has_std_11_flag)
-  check_cxx_compiler_flag(-std=c++0x has_std_0x_flag)
-
-  if (has_std_11_flag)
-    set(CXX_STANDARD_FLAG -std=c++11)
-  elseif (has_std_0x_flag)
-    set(CXX_STANDARD_FLAG -std=c++0x)
-  endif ()
-endif ()
-
-set(CMAKE_REQUIRED_FLAGS ${CXX_STANDARD_FLAG})
-
-# Check if user-defined literals are available
-check_cxx_source_compiles("
-  void operator\"\" _udl(long double);
-  int main() {}"
-  SUPPORTS_USER_DEFINED_LITERALS)
-if (NOT SUPPORTS_USER_DEFINED_LITERALS)
-  set (SUPPORTS_USER_DEFINED_LITERALS OFF)
-endif ()
-
-# Check if <variant> is available
-set(CMAKE_REQUIRED_FLAGS -std=c++1z)
-check_cxx_source_compiles("
-  #include <variant>
-  int main() {}"
-  FMT_HAS_VARIANT)
-if (NOT FMT_HAS_VARIANT)
-  set (FMT_HAS_VARIANT OFF)
-endif ()
-
-set(CMAKE_REQUIRED_FLAGS )
diff --git a/contrib/fmt/support/cmake/fmt-config.cmake.in b/contrib/fmt/support/cmake/fmt-config.cmake.in
index 71e302860bc..bc1684f245c 100644
--- a/contrib/fmt/support/cmake/fmt-config.cmake.in
+++ b/contrib/fmt/support/cmake/fmt-config.cmake.in
@@ -1,4 +1,7 @@
 @PACKAGE_INIT@
 
-include(${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake)
+if (NOT TARGET fmt::fmt)
+  include(${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake)
+endif ()
+
 check_required_components(fmt)
diff --git a/contrib/fmt/support/cmake/fmt.pc.in b/contrib/fmt/support/cmake/fmt.pc.in
index 4e030afdf52..29976a8af0b 100644
--- a/contrib/fmt/support/cmake/fmt.pc.in
+++ b/contrib/fmt/support/cmake/fmt.pc.in
@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=@CMAKE_INSTALL_PREFIX@
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
 
 Name: fmt
 Description: A modern formatting library
diff --git a/contrib/vcacheopt/vcacheopt.h b/contrib/vcacheopt/vcacheopt.h
index cbcd52a048b..5260091e845 100644
--- a/contrib/vcacheopt/vcacheopt.h
+++ b/contrib/vcacheopt/vcacheopt.h
@@ -1,17 +1,17 @@
 /*
  * vcacheopt.h - Vertex Cache Optimizer
  * Copyright 2009 Michael Georgoulpoulos <mgeorgoulopoulos at gmail>
- * 
+ *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
- * 
+ *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
- * 
+ *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
@@ -38,13 +38,13 @@ class TVertexCacheData
 	int total_valence; // toatl number of triangles using this vertex
 	int remaining_valence; // number of triangles using it but not yet rendered
 	std::vector<T> tri_indices; // indices to the indices that use this vertex
-	bool calculated; // was the score calculated during this iteration?
+	bool calculated = false; // was the score calculated during this iteration?
 
 
-	T FindTriangle(const T tri) const 
+	T FindTriangle(const T tri) const
 	{
 		for (size_t i=0; i<tri_indices.size(); ++i)	{
-			if (tri_indices[i] == tri) 
+			if (tri_indices[i] == tri)
 				return i;
 		}
 		return ERR_VAL;
@@ -208,7 +208,7 @@ class TVertexCacheOptimizer
 			// No tri needs this vertex!
 			return -1.0f;
 		}
-	 
+
 		float ret = 0.0f;
 		if (v->position_in_cache < 0) {
 			// Vertex is not in FIFO cache - no score.
@@ -227,12 +227,12 @@ class TVertexCacheOptimizer
 				ret = powf(ret, CacheDecayPower);
 			}
 		}
-	 
+
 		// Bonus points for having a low number of tris still to
 		// use the vert, so we get rid of lone verts quickly.
 		float valence_boost = powf((float)v->remaining_valence, -ValenceBoostPower);
 		ret += ValenceBoostScale * valence_boost;
-	 
+
 		return ret;
 	}
 
@@ -255,9 +255,9 @@ class TVertexCacheOptimizer
 			float sc = verts[tris[i].verts[0]].current_score +
 				verts[tris[i].verts[1]].current_score +
 				verts[tris[i].verts[2]].current_score;
-			
+
 			tris[i].current_score = sc;
-	
+
 			if (first_time || sc > max_score) {
 				first_time = false;
 				max_score = sc;
@@ -277,7 +277,7 @@ class TVertexCacheOptimizer
 
 			verts[index].total_valence++;
 			verts[index].remaining_valence++;
-			
+
 			verts[index].tri_indices.push_back(i/3);
 		}
 
@@ -294,7 +294,7 @@ class TVertexCacheOptimizer
 		// allocate and initialize vertices and triangles
 		verts.clear();
 		for (int i=0; i<vertex_count; ++i) verts.push_back( TVertexCacheData<T, ERR_VAL >() );
-		
+
 		tris.clear();
 		for (int i=0; i<tri_count; ++i) {
 			TTriangleCacheData<T, ERR_VAL > dat;
@@ -325,7 +325,7 @@ class TVertexCacheOptimizer
 
 		TTriangleCacheData<T, ERR_VAL > *t = &tris[tri];
 		if (t->rendered) return; // triangle is already in the draw list
-	
+
 		for (int i=0; i<3; ++i)	{
 			// add all triangle vertices to the cache
 			vertex_cache.AddVertex(t->verts[i]);
@@ -430,7 +430,7 @@ class TVertexCacheOptimizer
 					// calculate triangle score
 					TriangleScoreRecalculation(tri);
 				}
-				
+
 				float sc = t->current_score;
 
 				// we actually found a triangle to process
@@ -476,7 +476,7 @@ class TVertexCacheOptimizer
 
 		best_tri = 0;
 	}
-	
+
 	// stores new indices in place
 	Result Optimize(T *inds, int tri_count)
 	{
diff --git a/src/Background.cpp b/src/Background.cpp
index 861c0537cf0..cbbe73cdf88 100644
--- a/src/Background.cpp
+++ b/src/Background.cpp
@@ -250,7 +250,7 @@ namespace Background {
 
 	struct StarQueryInfo {
 		const SystemPath *systemPath;
-		int32_t numStars;
+		uint32_t numStars;
 		int32_t sectorMin;
 		int32_t sectorMax;
 		int32_t visibleRadiusSqr;
diff --git a/src/CityOnPlanet.cpp b/src/CityOnPlanet.cpp
index 415799f5d59..d512280585e 100644
--- a/src/CityOnPlanet.cpp
+++ b/src/CityOnPlanet.cpp
@@ -151,7 +151,7 @@ void CityOnPlanet::LoadBuildingType(std::string_view key, const Json &buildingDe
 	}
 
 	Log::Verbose("\tLoaded city building {} ({}x{}c, atm: {}, arl: {}, kind: {}, idleAnim: {})",
-		key, out.cellSize[0], out.cellSize[1], out.rarityAtmo, out.rarityAirless, out.buildingKind, out.idleAnimation != nullptr);
+		key, out.cellSize[0], out.cellSize[1], out.rarityAtmo, out.rarityAirless, int(out.buildingKind), out.idleAnimation != nullptr);
 }
 
 void CityOnPlanet::LoadCityFlavour(const FileSystem::FileInfo &file)
diff --git a/src/Input.cpp b/src/Input.cpp
index 6ae04683854..17fac45acc1 100644
--- a/src/Input.cpp
+++ b/src/Input.cpp
@@ -135,8 +135,8 @@ static JoystickInfo loadJoystick(SDL_Joystick *joystick, const IniConfig *config
 
 	std::array<char, 33> joystickGUIDName;
 	SDL_JoystickGetGUIDString(state.guid, joystickGUIDName.data(), joystickGUIDName.size());
-	Output("Found joystick '%s' (GUID: %s)\n", SDL_JoystickName(state.joystick), joystickGUIDName.data());
-	Output("  - %ld axes, %ld buttons, %ld hats\n", state.axes.size(), state.buttons.size(), state.hats.size());
+	Log::Info("Found joystick '{}' (GUID: {})\n", SDL_JoystickName(state.joystick), joystickGUIDName.data());
+	Log::Info("  - {} axes, {} buttons, {} hats\n", state.axes.size(), state.buttons.size(), state.hats.size());
 
 	std::string joystickName = "Joystick." + std::string(joystickGUIDName.data());
 
@@ -148,7 +148,7 @@ static JoystickInfo loadJoystick(SDL_Joystick *joystick, const IniConfig *config
 		}
 
 		loadAxisConfig(config->String(joystickName, axisName, ""), state.axes[i]);
-		Output("  - axis %ld: deadzone %.2f, curve: %.2f, half-axis mode: %b\n",
+		Log::Info("  - axis {}: deadzone {:.2f}, curve: {:.2f}, half-axis mode: {}\n",
 			i, state.axes[i].deadzone, state.axes[i].curve, state.axes[i].zeroToOne);
 	}
 	return state;
@@ -349,6 +349,11 @@ void ClearInputFrameState(InputFrame *frame)
 	}
 }
 
+bool Manager::HasInputFrame(InputFrame *frame)
+{
+	return std::count(m_inputFrames.begin(), m_inputFrames.end(), frame) > 0;
+}
+
 void Manager::RemoveInputFrame(InputFrame *frame)
 {
 	auto it = std::find(m_inputFrames.begin(), m_inputFrames.end(), frame);
diff --git a/src/Input.h b/src/Input.h
index f5c67fc3914..8a1d7d91010 100644
--- a/src/Input.h
+++ b/src/Input.h
@@ -148,10 +148,7 @@ class Input::Manager {
 	const std::vector<InputFrame *> &GetInputFrames() { return m_inputFrames; }
 
 	// Check if a specific input frame is currently on the stack.
-	bool HasInputFrame(InputFrame *frame)
-	{
-		return std::count(m_inputFrames.begin(), m_inputFrames.end(), frame) > 0;
-	}
+	bool HasInputFrame(InputFrame *frame);
 
 	// Remove an arbitrary input frame from the input stack.
 	void RemoveInputFrame(InputFrame *frame);
diff --git a/src/InputBindings.cpp b/src/InputBindings.cpp
index da7f70264c4..66f4eee2db2 100644
--- a/src/InputBindings.cpp
+++ b/src/InputBindings.cpp
@@ -7,6 +7,7 @@
 #include "SDL_joystick.h"
 #include "utils.h"
 
+#include <ostream>
 #include <regex>
 
 using namespace InputBindings;
diff --git a/src/core/Application.cpp b/src/core/Application.cpp
index 762045a680a..2dc74a78501 100644
--- a/src/core/Application.cpp
+++ b/src/core/Application.cpp
@@ -199,7 +199,9 @@ void Application::Run()
 
 		EndFrame();
 
+#ifdef PIONEER_PROFILER
 		const bool profileReset = (m_activeLifecycle && !m_activeLifecycle->m_profilerAccumulate);
+#endif
 
 		if (m_activeLifecycle->m_endLifecycle || !m_applicationRunning) {
 			EndLifecycle();
diff --git a/src/core/Log.cpp b/src/core/Log.cpp
index ef5fef861ec..d2af3147bb3 100644
--- a/src/core/Log.cpp
+++ b/src/core/Log.cpp
@@ -166,7 +166,7 @@ void Log::LogFatalInternal(const char *message, fmt::format_args args)
 
 void Log::LogOld(Severity sv, const char *message, fmt::printf_args args)
 {
-	std::string out_message = fmt::vsprintf(message, args);
+	std::string out_message = fmt::vsprintf(fmt::string_view(message), args);
 	GetLog()->LogLevel(sv, out_message);
 	if (sv == Severity::Warning) {
 		SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_WARNING, "Pioneer warning", out_message.c_str(), 0);
@@ -175,7 +175,7 @@ void Log::LogOld(Severity sv, const char *message, fmt::printf_args args)
 
 [[noreturn]] void Log::LogFatalOld(const char *message, fmt::printf_args args)
 {
-	std::string out_message = fmt::vsprintf(message, args);
+	std::string out_message = fmt::vsprintf(fmt::string_view(message), args);
 	GetLog()->LogLevel(Severity::Fatal, out_message);
 	SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Pioneer error", out_message.c_str(), 0);
 
diff --git a/src/core/Log.h b/src/core/Log.h
index a3b13ee9fd8..8c336fdaf81 100644
--- a/src/core/Log.h
+++ b/src/core/Log.h
@@ -4,7 +4,7 @@
 #pragma once
 
 #include "DateTime.h"
-#include <fmt/format.h>
+#include <fmt/core.h>
 #include <fmt/printf.h>
 #include <sigc++/signal.h>
 #include <string_view>
diff --git a/src/editor/UndoStepType.h b/src/editor/UndoStepType.h
index 652a1269368..bf29fdff224 100644
--- a/src/editor/UndoStepType.h
+++ b/src/editor/UndoStepType.h
@@ -19,8 +19,8 @@ namespace Editor {
 	public:
 		template<typename ...Args>
 		UndoClosure(ClosureType &&closure, Args ...args) :
-			m_onUpdate(closure),
-			T(args...)
+			T(args...),
+			m_onUpdate(closure)
 		{}
 
 		void Swap() override {
@@ -60,7 +60,6 @@ namespace Editor {
 			m_dataRef(data),
 			m_state(newValue)
 		{
-			std::swap(m_state, *m_dataRef);
 		}
 
 		void Swap() override { std::swap(*m_dataRef, m_state); }
@@ -84,7 +83,7 @@ namespace Editor {
 	template<typename T>
 	inline void AddUndoSingleValue(UndoSystem *s, T *dataRef, const T &newValue)
 	{
-		s->AddUndoStep<UndoSingleValueStep<T>>(dataRef, newValue);
+		s->AddUndoStep<UndoSingleValueStep<T>>(dataRef, newValue)->Swap();
 	}
 
 	template<typename T, typename UpdateClosure>
@@ -96,7 +95,7 @@ namespace Editor {
 	template<typename T, typename UpdateClosure>
 	inline void AddUndoSingleValueClosure(UndoSystem *s, T *dataRef, const T &newValue, UpdateClosure closure)
 	{
-		s->AddUndoStep<UndoClosure<UpdateClosure, UndoSingleValueStep<T>>>(std::move(closure), dataRef, newValue);
+		s->AddUndoStep<UndoClosure<UpdateClosure, UndoSingleValueStep<T>>>(std::move(closure), dataRef, newValue)->Swap();
 	}
 
 	// ========================================================================
@@ -120,11 +119,11 @@ namespace Editor {
 		{
 		}
 
+		// Convenience constructor to allow updating the value in a single call
 		UndoGetSetValueStep(Obj *data, const ValueType &newValue) :
 			m_dataRef(data),
 			m_state(newValue)
 		{
-			Swap();
 		}
 
 		// two-way swap with opaque setter/getter functions
@@ -154,7 +153,7 @@ namespace Editor {
 	inline void AddUndoGetSetValue(UndoSystem *s, Obj *dataRef, const T &newValue)
 	{
 		using ValueType = decltype((dataRef->*GetterFn)());
-		s->AddUndoStep<UndoGetSetValueStep<GetterFn, SetterFn, ValueType, Obj>>(dataRef, newValue);
+		s->AddUndoStep<UndoGetSetValueStep<GetterFn, SetterFn, ValueType, Obj>>(dataRef, newValue)->Swap();
 	}
 
 	template<auto GetterFn, auto SetterFn, typename Obj, typename UpdateClosure>
@@ -168,7 +167,7 @@ namespace Editor {
 	inline void AddUndoGetSetValueClosure(UndoSystem *s, Obj *dataRef, const T &newValue, UpdateClosure &&closure)
 	{
 		using ValueType = decltype((dataRef->*GetterFn)());
-		s->AddUndoStep<UndoClosure<UpdateClosure, UndoGetSetValueStep<GetterFn, SetterFn, ValueType, Obj>>>(std::move(closure), dataRef, newValue);
+		s->AddUndoStep<UndoClosure<UpdateClosure, UndoGetSetValueStep<GetterFn, SetterFn, ValueType, Obj>>>(std::move(closure), dataRef, newValue)->Swap();
 	}
 
 	// ========================================================================
@@ -195,7 +194,7 @@ namespace Editor {
 			m_idx(insertIdx),
 			m_insert(true)
 		{
-			Swap();
+			// NOTE: the transaction is not yet committed until Swap() is called (for compatibility with UndoClosure)
 		}
 
 		UndoVectorStep(Container *container, size_t removeIdx) :
@@ -204,7 +203,7 @@ namespace Editor {
 			m_idx(removeIdx),
 			m_insert(false)
 		{
-			Swap();
+			// NOTE: the transaction is not yet committed until Swap() is called (for compatibility with UndoClosure)
 		}
 
 		void Swap() override
@@ -272,7 +271,7 @@ namespace Editor {
 		if (idx == size_t(-1))
 			idx = containerRef->size();
 
-		s->AddUndoStep<UndoVectorStep<T>>(containerRef, value, idx);
+		s->AddUndoStep<UndoVectorStep<T>>(containerRef, value, idx)->Swap();
 	}
 
 	template<typename T>
@@ -281,7 +280,7 @@ namespace Editor {
 		if (idx == size_t(-1))
 			idx = containerRef->size() - 1;
 
-		s->AddUndoStep<UndoVectorStep<T>>(containerRef, idx);
+		s->AddUndoStep<UndoVectorStep<T>>(containerRef, idx)->Swap();
 	}
 
 	template<typename T>
@@ -296,13 +295,13 @@ namespace Editor {
 	template<typename T, typename UpdateClosure, typename Value = typename T::value_type>
 	inline void AddUndoVectorInsertClosure(UndoSystem *s, T *containerRef, const Value &value, size_t idx, UpdateClosure closure)
 	{
-		s->AddUndoStep<UndoClosure<UpdateClosure, UndoVectorStep<T>>>(std::move(closure), containerRef, value, idx);
+		s->AddUndoStep<UndoClosure<UpdateClosure, UndoVectorStep<T>>>(std::move(closure), containerRef, value, idx)->Swap();
 	}
 
 	template<typename T, typename UpdateClosure>
 	inline void AddUndoVectorEraseClosure(UndoSystem *s, T *containerRef, size_t idx, UpdateClosure closure)
 	{
-		s->AddUndoStep<UndoClosure<UpdateClosure, UndoVectorStep<T>>>(std::move(closure), containerRef, idx);
+		s->AddUndoStep<UndoClosure<UpdateClosure, UndoVectorStep<T>>>(std::move(closure), containerRef, idx)->Swap();
 	}
 
 	template<typename T, typename UpdateClosure>
diff --git a/src/editor/UndoSystem.h b/src/editor/UndoSystem.h
index f017ab6ae2b..ef97d35e8b5 100644
--- a/src/editor/UndoSystem.h
+++ b/src/editor/UndoSystem.h
@@ -150,9 +150,11 @@ class UndoSystem {
 
 	// Add an undo step to the active undo entry
 	template<typename T, typename ...Args>
-	void AddUndoStep(Args&& ...args)
+	T *AddUndoStep(Args&& ...args)
 	{
-		AddUndoStep(new T(std::forward<Args>(args)...));
+		T *step = new T(std::forward<Args>(args)...);
+		AddUndoStep(step);
+		return step;
 	}
 
 	// End the current undo entry
diff --git a/src/editor/system/GalaxyEditAPI.cpp b/src/editor/system/GalaxyEditAPI.cpp
index cb927eb1850..a89571b286a 100644
--- a/src/editor/system/GalaxyEditAPI.cpp
+++ b/src/editor/system/GalaxyEditAPI.cpp
@@ -155,7 +155,6 @@ void StarSystem::EditorAPI::ReorderBodyIndex(StarSystem *system)
 
 void StarSystem::EditorAPI::ReorderBodyHierarchy(StarSystem *system)
 {
-	size_t index = 0;
 	std::vector<std::pair<SystemBody *, size_t>> orderStack {
 		{ system->GetRootBody().Get(), 0 }
 	};
diff --git a/src/editor/system/SystemEditor.cpp b/src/editor/system/SystemEditor.cpp
index 421ede27559..92c3d90373a 100644
--- a/src/editor/system/SystemEditor.cpp
+++ b/src/editor/system/SystemEditor.cpp
@@ -93,9 +93,9 @@ class SystemEditor::UndoSetSelection : public UndoStep {
 
 SystemEditor::SystemEditor(EditorApp *app) :
 	m_app(app),
-	m_undo(new UndoSystem()),
 	m_system(nullptr),
 	m_systemInfo(),
+	m_undo(new UndoSystem()),
 	m_selectedBody(nullptr),
 	m_contextBody(nullptr),
 	m_pendingOp(),
diff --git a/src/editor/system/SystemEditorHelpers.cpp b/src/editor/system/SystemEditorHelpers.cpp
index 36cdad6d7e1..240ca95d7cd 100644
--- a/src/editor/system/SystemEditorHelpers.cpp
+++ b/src/editor/system/SystemEditorHelpers.cpp
@@ -141,8 +141,6 @@ bool Draw::InputFixedDegrees(const char *str, fixed *val, double val_min, double
 
 bool Draw::InputFixedDistance(const char *str, fixed *val, ImGuiInputTextFlags flags)
 {
-	ImGuiStyle &style = ImGui::GetStyle();
-
 	ImGui::BeginGroup();
 	ImGui::PushID(str);
 
@@ -187,8 +185,6 @@ bool Draw::InputFixedDistance(const char *str, fixed *val, ImGuiInputTextFlags f
 
 bool Draw::InputFixedMass(const char *str, fixed *val, bool is_solar, ImGuiInputTextFlags flags)
 {
-	ImGuiStyle &style = ImGui::GetStyle();
-
 	ImGui::BeginGroup();
 	ImGui::PushID(str);
 
@@ -243,8 +239,6 @@ bool Draw::InputFixedMass(const char *str, fixed *val, bool is_solar, ImGuiInput
 
 bool Draw::InputFixedRadius(const char *str, fixed *val, bool is_solar, ImGuiInputTextFlags flags)
 {
-	ImGuiStyle &style = ImGui::GetStyle();
-
 	ImGui::BeginGroup();
 	ImGui::PushID(str);
 
diff --git a/src/editor/system/SystemEditorViewport.cpp b/src/editor/system/SystemEditorViewport.cpp
index 43d4c809c84..6f2002fe3cc 100644
--- a/src/editor/system/SystemEditorViewport.cpp
+++ b/src/editor/system/SystemEditorViewport.cpp
@@ -111,7 +111,6 @@ void SystemEditorViewport::OnDraw()
 	// Then draw "under" the GUI elements so we can use ImGui::IsItemHovered et al.
 	for (auto &group : groups) {
 		ImVec2 itempos = { group.screenpos.x, group.screenpos.y };
-		ImVec2 iconSize = { ImGui::GetFontSize(), ImGui::GetFontSize() };
 
 		// Simple screen clipping rejection test
 		if (!screen_rect.Contains(itempos))
diff --git a/src/galaxy/CustomSystem.cpp b/src/galaxy/CustomSystem.cpp
index bb999d1dcbf..14168244fab 100644
--- a/src/galaxy/CustomSystem.cpp
+++ b/src/galaxy/CustomSystem.cpp
@@ -56,7 +56,7 @@ static int l_csb_new(lua_State *L)
 	const char *name = luaL_checkstring(L, 2);
 	int type = LuaConstants::GetConstantFromArg(L, "BodyType", 3);
 
-	if (type < SystemBody::TYPE_GRAVPOINT || type > SystemBody::TYPE_MAX) {
+	if (type < int(SystemBody::TYPE_GRAVPOINT) || type > int(SystemBody::TYPE_MAX)) {
 		return luaL_error(L, "body '%s' does not have a valid type", name);
 	}
 
@@ -354,7 +354,7 @@ static unsigned interpret_star_types(int *starTypes, lua_State *L, int idx)
 		lua_rawgeti(L, -1, i + 1);
 		if (lua_type(L, -1) == LUA_TSTRING) {
 			ty = LuaConstants::GetConstantFromArg(L, "BodyType", -1);
-			if ((ty < SystemBody::TYPE_STAR_MIN || ty > SystemBody::TYPE_STAR_MAX) && ty != SystemBody::TYPE_GRAVPOINT) {
+			if ((ty < int(SystemBody::TYPE_STAR_MIN) || ty > int(SystemBody::TYPE_STAR_MAX)) && ty != SystemBody::TYPE_GRAVPOINT) {
 				luaL_error(L, "system star %d does not have a valid star type", i + 1);
 				// unreachable (longjmp in luaL_error)
 			}
@@ -548,9 +548,9 @@ static int l_csys_bodies(lua_State *L)
 	int primary_type = (*primary_ptr)->bodyData.m_type;
 	luaL_checktype(L, 3, LUA_TTABLE);
 
-	if ((primary_type < SystemBody::TYPE_STAR_MIN || primary_type > SystemBody::TYPE_STAR_MAX) && primary_type != SystemBody::TYPE_GRAVPOINT)
+	if ((primary_type < int(SystemBody::TYPE_STAR_MIN) || primary_type > int(SystemBody::TYPE_STAR_MAX)) && primary_type != SystemBody::TYPE_GRAVPOINT)
 		return luaL_error(L, "first body does not have a valid star type");
-	if (primary_type != cs->primaryType[0] && primary_type != SystemBody::TYPE_GRAVPOINT)
+	if (primary_type != int(cs->primaryType[0]) && primary_type != SystemBody::TYPE_GRAVPOINT)
 		return luaL_error(L, "first body type does not match the system's primary star type");
 
 	cs->bodies.push_back(*primary_ptr);
@@ -648,9 +648,9 @@ void CustomSystem::LoadFromJson(const Json &systemdef)
 	sectorY = sector[2].get<int32_t>();
 
 	const Json &position = systemdef["pos"];
-	pos.x = sector[0].get<float>();
-	pos.y = sector[1].get<float>();
-	pos.z = sector[2].get<float>();
+	pos.x = position[0].get<float>();
+	pos.y = position[1].get<float>();
+	pos.z = position[2].get<float>();
 
 	seed = systemdef.value<uint32_t>("seed", 0);
 	explored = systemdef.value<bool>("explored", true);
@@ -1051,10 +1051,10 @@ void CustomSystemsDatabase::RunLuaSystemSanityChecks(CustomSystem *csys)
 }
 
 CustomSystem::CustomSystem() :
+	nameHash(0),
 	sBody(nullptr),
 	numStars(0),
 	seed(0),
-	nameHash(0),
 	want_rand_seed(true),
 	want_rand_explored(true),
 	faction(nullptr),
diff --git a/src/galaxy/StarSystem.cpp b/src/galaxy/StarSystem.cpp
index 7e5eff8c9b4..5f186dba5ef 100644
--- a/src/galaxy/StarSystem.cpp
+++ b/src/galaxy/StarSystem.cpp
@@ -386,7 +386,7 @@ std::string StarSystem::ExportBodyToLua(FILE *f, SystemBody *body)
 	// find the body type index so we can lookup the name
 	const char *pBodyTypeName = nullptr;
 	for (int bodyTypeIdx = 0; ENUM_BodyType[bodyTypeIdx].name != 0; bodyTypeIdx++) {
-		if (ENUM_BodyType[bodyTypeIdx].value == body->GetType()) {
+		if (ENUM_BodyType[bodyTypeIdx].value == int(body->GetType())) {
 			pBodyTypeName = ENUM_BodyType[bodyTypeIdx].name;
 			break;
 		}
@@ -471,7 +471,7 @@ std::string StarSystem::GetStarTypes(SystemBody *body)
 
 	if (body->GetSuperType() == SystemBody::SUPERTYPE_STAR) {
 		for (bodyTypeIdx = 0; ENUM_BodyType[bodyTypeIdx].name != 0; bodyTypeIdx++) {
-			if (ENUM_BodyType[bodyTypeIdx].value == body->GetType())
+			if (ENUM_BodyType[bodyTypeIdx].value == int(body->GetType()))
 				break;
 		}
 
diff --git a/src/galaxy/StarSystemGenerator.cpp b/src/galaxy/StarSystemGenerator.cpp
index aa7a9093534..2a1f7fb302d 100644
--- a/src/galaxy/StarSystemGenerator.cpp
+++ b/src/galaxy/StarSystemGenerator.cpp
@@ -1692,8 +1692,6 @@ void PopulateStarSystemGenerator::PopulateAddStations(SystemBody *sbody, StarSys
 			}
 
 			Uint32 orbitIdx = 0;
-			double orbitSlt = 0.0;
-			const double orbitSeparation = (NumToMake > 1) ? ((M_PI * 2.0) / double(NumToMake - 1)) : M_PI;
 
 			for (Uint32 i = 0; i < NumToMake; i++) {
 				// Pick the orbit we've currently placing a station into.
@@ -1703,7 +1701,6 @@ void PopulateStarSystemGenerator::PopulateAddStations(SystemBody *sbody, StarSys
 				if (orbitIdx >= MAX_ORBIT_SHELLS) // wrap it
 				{
 					orbitIdx = 0;
-					orbitSlt += 1.0;
 				}
 
 				// Begin creation of the new station
diff --git a/src/graphics/opengl/OpenGLLibs.h b/src/graphics/opengl/OpenGLLibs.h
index c694555b3a2..661710bf0c5 100644
--- a/src/graphics/opengl/OpenGLLibs.h
+++ b/src/graphics/opengl/OpenGLLibs.h
@@ -8,4 +8,6 @@
 
 #include <GL/glew.h>
 
+inline const char *glstr_to_str(const GLubyte *str) { return reinterpret_cast<const char *>(str); }
+
 #endif
diff --git a/src/graphics/opengl/Program.cpp b/src/graphics/opengl/Program.cpp
index df334cf49e0..ce30c46e1d1 100644
--- a/src/graphics/opengl/Program.cpp
+++ b/src/graphics/opengl/Program.cpp
@@ -45,7 +45,7 @@ namespace Graphics {
 
 			if (status == GL_FALSE) {
 				Log::Error("Error compiling shader: {}:\n {}\n OpenGL vendor: {}\nOpenGL renderer string: {}",
-					filename, infoLog, glGetString(GL_VENDOR), glGetString(GL_RENDERER));
+					filename, infoLog, glstr_to_str(glGetString(GL_VENDOR)), glstr_to_str(glGetString(GL_RENDERER)));
 				return false;
 			}
 
diff --git a/src/graphics/opengl/RendererGL.cpp b/src/graphics/opengl/RendererGL.cpp
index 0ac6047598a..4f7a365fe6e 100644
--- a/src/graphics/opengl/RendererGL.cpp
+++ b/src/graphics/opengl/RendererGL.cpp
@@ -172,7 +172,7 @@ namespace Graphics {
 		glewExperimental = true;
 		GLenum glew_err;
 		if ((glew_err = glewInit()) != GLEW_OK)
-			Error("GLEW initialisation failed: %s", glewGetErrorString(glew_err));
+			Error("GLEW initialisation failed: %s", glstr_to_str(glewGetErrorString(glew_err)));
 
 		// pump this once as glewExperimental is necessary but spews a single error
 		glGetError();
diff --git a/src/lua/LuaPiGui.cpp b/src/lua/LuaPiGui.cpp
index 21ff2fde6b2..99b5b716cb1 100644
--- a/src/lua/LuaPiGui.cpp
+++ b/src/lua/LuaPiGui.cpp
@@ -2126,7 +2126,7 @@ bool PiGui::first_body_is_more_important_than(Body *body, Body *other)
 	else if (b == ObjectType::PROJECTILE)
 		result = false;
 	else
-		Error("don't know how to compare %i and %i\n", a, b);
+		Error("don't know how to compare %i and %i\n", int(a), int(b));
 
 	return result;
 }
diff --git a/src/lua/LuaPlayer.cpp b/src/lua/LuaPlayer.cpp
index 839f1c0ce42..22a68f9e240 100644
--- a/src/lua/LuaPlayer.cpp
+++ b/src/lua/LuaPlayer.cpp
@@ -580,7 +580,7 @@ static int l_get_alert_state(lua_State *l)
 		LuaPush(l, "ship-firing");
 		break;
 	default:
-		Error("Unknown alert state %i", state);
+		Error("Unknown alert state %i", int(state));
 	}
 	return 1;
 }
diff --git a/src/test/TestLuaPushPull.cpp b/src/test/TestLuaPushPull.cpp
new file mode 100644
index 00000000000..95f20b12158
--- /dev/null
+++ b/src/test/TestLuaPushPull.cpp
@@ -0,0 +1,91 @@
+// Copyright © 2008-2024 Pioneer Developers. See AUTHORS.txt for details
+// Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
+
+#include "lua/Lua.h"
+#include "lua/LuaPushPull.h"
+
+#include <fmt/core.h>
+
+#include "doctest.h"
+
+#include <string>
+#include <tuple>
+
+std::string str(int i)
+{
+	return fmt::format("{}", i);
+}
+
+template <typename T>
+using tuple_t = std::tuple<T, T, T>;
+
+TEST_CASE("Sequence Points")
+{
+	SUBCASE("As-Constructor Test")
+	{
+		int i = 0;
+
+		// Simple test canary to ensure initializer clauses in braced-init-lists
+		// are sequenced-before following clauses in accordance with the C++
+		// specification
+		tuple_t<int> test_tuple = tuple_t<int>{ i++, i++, i++ };
+
+		CHECK(std::get<0>(test_tuple) == 0);
+		CHECK(std::get<1>(test_tuple) == 1);
+		CHECK(std::get<2>(test_tuple) == 2);
+		CHECK(i == 3);
+	}
+
+	SUBCASE("Inside Arguments Test")
+	{
+		int i = 0;
+
+		// Simple test canary to ensure initializer clauses in braced-init-lists
+		// are sequenced-before following clauses in accordance with the C++
+		// specification
+		tuple_t<std::string> test_tuple = tuple_t<std::string>{ str(i++), str(i++), str(i++) };
+
+		CHECK(std::get<0>(test_tuple) == "0");
+		CHECK(std::get<1>(test_tuple) == "1");
+		CHECK(std::get<2>(test_tuple) == "2");
+		CHECK(i == 3);
+	}
+}
+
+TEST_CASE("Lua Push / Pull Basic Values")
+{
+	lua_State *l = luaL_newstate();
+
+	SUBCASE("Sanity Check")
+	{
+		LuaPush<bool>(l, true);
+		LuaPush<int>(l, 1);
+		LuaPush<std::string>(l, "test");
+
+		CHECK(LuaPull<bool>(l, 1) == true);
+		CHECK(LuaPull<int>(l, 2) == 1);
+		CHECK(LuaPull<std::string>(l, 3) == "test");
+	}
+
+	SUBCASE("Multiple-Push")
+	{
+		pi_lua_multiple_push<bool, int, std::string>(l, true, 1, "test");
+
+		CHECK(LuaPull<bool>(l, 1) == true);
+		CHECK(LuaPull<int>(l, 2) == 1);
+		CHECK(LuaPull<std::string>(l, 3) == "test");
+	}
+
+	SUBCASE("Multiple-Pull")
+	{
+		pi_lua_multiple_push<bool, int, std::string>(l, true, 1, "test");
+
+		auto tuple = pi_lua_multiple_pull<bool, int, std::string>(l, 1);
+
+		CHECK(std::get<0>(tuple) == true);
+		CHECK(std::get<1>(tuple) == 1);
+		CHECK(std::get<2>(tuple) == "test");
+	}
+
+	lua_close(l);
+}
diff --git a/src/versioningInfo.cpp b/src/versioningInfo.cpp
index bd5dc20808a..143d172be47 100644
--- a/src/versioningInfo.cpp
+++ b/src/versioningInfo.cpp
@@ -39,7 +39,8 @@ void OutputVersioningInfo()
 	Output("LibCurl Version: %s", LIBCURL_VERSION);
 #endif
 
-	Output("GLEW dynamic version: %s\n", glewGetString(GLEW_VERSION));
+	// glewGetString returns unsigned, fmt uses signed
+	Output("GLEW dynamic version: %s\n", reinterpret_cast<const char *>(glewGetString(GLEW_VERSION)));
 	Output("--------------------\n");
 	Output("\n");
 }