Parsing ala boost type_index

doc/pfr.qbk

@@ -508,6 +508,8 @@ By default Boost.PFR [*auto-detects your compiler abilities] and automatically d
     [[*BOOST_PFR_HAS_GUARANTEED_COPY_ELISION*] [Define to `0` if your compiler does not implement C++17 guaranteed copy elision properly and fails to reflect aggregates with non-movable fields. Define to `1` to override Boost.PFR detection logic. ]]
     [[*BOOST_PFR_ENABLE_IMPLICIT_REFLECTION*] [Define to `0` if you are hit by lots of non-effective choices made by implicitly reflection. Define to `1` to override Boost.PFR detection logic. ]]
     [[*BOOST_PFR_ENABLE_GET_NAME_STATIC*] [On platforms where field's names extracting is not supported, the 'boost/pfr/config.hpp' header defines the BOOST_PFR_ENABLE_GET_NAME_STATIC macro equal to 0. Defining this macro as 0 before including the header disables the ability to get a field's name. ]]
+    [[*BOOST_PFR_FUNCTION_SIGNATURE*] [TODO: desc it ]]
+    [[*BOOST_PFR_CORE_NAME_PARSING*] [TODO: desc it ]]
     [[*BOOST_PFR_ENABLED*] [On platforms where Boost.PFR is not supported, the `boost/pfr/config.hpp` header defines the BOOST_PFR_ENABLED macro equal to 0. Defining this macro as 0 before including the header disables the Boost.PFR library. ]]
 ]
 
@@ -528,6 +530,13 @@ The Boost.PFRs reflection has some limitations that depend on a C++ Standard and
 
 [endsect]
 
+
+[section Limitations of field's names reflection]
+
+TODO: write the article and make a link on it inside "Limitations and Configuration"
+
+[endsect]
+
 [section How it works]
 
 Short description:

include/boost/pfr/config.hpp

@@ -99,18 +99,45 @@
 #endif
 
 #ifndef BOOST_PFR_ENABLE_GET_NAME_STATIC
-#   if (defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911) || (__cplusplus >= 202002L && defined(__clang_major__) && __clang_major__ >= 12)
-// Only these 3 compilers have a macro to extract func name
-#       if defined(__clang__) || defined(__GNUC__) || defined(_MSC_VER)
-#          define BOOST_PFR_ENABLE_GET_NAME_STATIC 1
-#       else
-#          define BOOST_PFR_ENABLE_GET_NAME_STATIC 0
-#       endif
+#   if (defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911) \
+     || (__cplusplus >= 202002L && defined(__clang_major__) && __clang_major__ >= 12)
+#       define BOOST_PFR_ENABLE_GET_NAME_STATIC 1
 #   else
 #       define BOOST_PFR_ENABLE_GET_NAME_STATIC 0
 #   endif
 #endif
 
+#ifndef BOOST_PFR_FUNCTION_SIGNATURE
+#   if defined(__FUNCSIG__)
+#       define BOOST_PFR_FUNCTION_SIGNATURE __FUNCSIG__
+#   elif defined(__PRETTY_FUNCTION__) \
+                   || defined(__GNUC__) \
+                   || defined(__clang__)
+#       define BOOST_PFR_FUNCTION_SIGNATURE __PRETTY_FUNCTION__
+#   else
+// TODO: specify in the doc that this is unsupported value
+#       define BOOST_PFR_FUNCTION_SIGNATURE ""
+#   endif
+#endif
+
+#ifndef BOOST_PFR_CORE_NAME_PARSING
+#   if defined(_MSC_VER)
+        // sizeof("auto __cdecl boost::pfr::detail::name_of_field_impl<") - 1, sizeof(">(void) noexcept") - 1
+#       define BOOST_PFR_CORE_NAME_PARSING (52, 16, "->")
+#   elif defined(__clang__)
+        // sizeof("auto boost::pfr::detail::name_of_field_impl() [MsvcWorkaround = ") - 1, sizeof("}]") - 1
+#       define BOOST_PFR_CORE_NAME_PARSING (64, 2, ".")
+#   elif defined(__GNUC__)
+        // sizeof("consteval auto boost::pfr::detail::name_of_field_impl() [with MsvcWorkaround = ") - 1, sizeof(")]") - 1
+#       define BOOST_PFR_CORE_NAME_PARSING (79, 2, "::")
+#   else
+// TODO: specify in the doc that this is unsupported value
+// TODO: .. and even if value is supported, there still no gurantee that it correct! also make a compile-fail test for such case
+        // Deafult parser for other platforms... Just skip nothing!
+#       define BOOST_PFR_CORE_NAME_PARSING (0, 0, "")
+#   endif
+#endif
+
 #if defined(__has_cpp_attribute)
 #   if __has_cpp_attribute(maybe_unused)
 #       define BOOST_PFR_MAYBE_UNUSED [[maybe_unused]]

include/boost/pfr/detail/core_name14_disabled.hpp

@@ -21,7 +21,7 @@ template <class T, std::size_t I>
 constexpr auto get_name() noexcept {
     static_assert(
         sizeof(T) && false,
-        "====================> Boost.PFR: Field's names extracting functionality requires C++20 and compiler that supports __PRETTY_FUNCTION__ or __FUNCSIG__ macro (GCC, Clang or MSVC)."
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
     );
 
     return nullptr;
@@ -31,7 +31,7 @@ template <class T>
 constexpr auto tie_as_names_tuple() noexcept {
     static_assert(
         sizeof(T) && false,
-        "====================> Boost.PFR: Field's names extracting functionality requires C++20 and compiler that supports __PRETTY_FUNCTION__ or __FUNCSIG__ macro (GCC, Clang or MSVC)."
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
     );
 
     return detail::sequence_tuple::make_sequence_tuple();

include/boost/pfr/detail/core_name20_static.hpp

@@ -17,40 +17,80 @@
 #include <boost/pfr/detail/sequence_tuple.hpp>
 #include <boost/pfr/detail/make_integer_sequence.hpp>
 #include <boost/pfr/detail/fields_count.hpp>
+#include <boost/pfr/detail/stdarray.hpp>
 #include <type_traits>
 #include <string_view>
 #include <array>
 #include <algorithm> // for std::ranges::copy
 
 namespace boost { namespace pfr { namespace detail {
 
-consteval std::string_view name_of_field_parse(std::string_view sv,
-                                               std::size_t size_at_begin,
-                                               std::size_t size_at_end,
-                                               std::string_view until_runtime_last) noexcept {
-    sv.remove_prefix(size_at_begin);
-    sv.remove_suffix(size_at_end);
-    return sv.substr(sv.rfind(until_runtime_last) + until_runtime_last.size());
+struct core_name_skip {
+    std::size_t size_at_begin;
+    std::size_t size_at_end;
+    bool more_at_runtime;
+    std::string_view until_runtime_last;
+};
+
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             bool more_at_runtime,
+                                             std::string_view until_runtime_last) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, more_at_runtime, until_runtime_last};
+}
+
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             std::string_view until_runtime_last) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, true, until_runtime_last};
+}
+
+consteval std::string_view apply_core_name_skip(std::string_view sv,
+                                                core_name_skip s) noexcept {
+    sv.remove_prefix((std::min)(s.size_at_begin, sv.size()));
+    sv.remove_suffix((std::min)(s.size_at_end, sv.size()));
+    return s.more_at_runtime ? sv.substr((std::min)(sv.rfind(s.until_runtime_last) + s.until_runtime_last.size(), sv.size()))
+                             : sv;
+                             ;
+}
+
+template <bool Condition>
+consteval void assert_compile_time_legths() noexcept {
+    static_assert(
+        Condition,
+        "PFRs extraction of field name is misconfigured for your compiler. "
+        "Please define BOOST_PFR_CORE_NAME_PARSING to correct values. See section "
+        "Limitations of field's names reflection' of the documentation for more information."
+    );
+}
+
+template <class T>
+consteval void failed_to_get_function_name() noexcept {
+    static_assert(
+        sizeof(T) && false,
+        "PFRs extraction of field name could not detect your compiler. "
+        "Please make the BOOST_PFR_FUNCTION_SIGNATURE macro use "
+        "correct compiler macro for getting the whole function name. "
+        "Define BOOST_PFR_CORE_NAME_PARSING to correct value after that."
+    );
 }
 
 template <typename MsvcWorkaround, auto ptr>
 consteval auto name_of_field_impl() noexcept {
-#ifdef _MSC_VER
-    constexpr auto sv = __FUNCSIG__;
-    // sizeof("auto __cdecl boost::pfr::detail::name_of_field_impl<") - 1, sizeof(">(void) noexcept") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 52, 16, "->");
-#elif __clang__
-    constexpr auto sv = __PRETTY_FUNCTION__;
-    // sizeof("auto boost::pfr::detail::name_of_field_impl() [MsvcWorkaround = ") - 1, sizeof("}]") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 64, 2, ".");
-#else // GCC
-    constexpr auto sv = __PRETTY_FUNCTION__;
-    // sizeof("consteval auto boost::pfr::detail::name_of_field_impl() [with MsvcWorkaround = ") - 1, sizeof(")]") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 79, 2, "::");
-#endif
-    auto res = std::array<char, fn.size()+1>{};
-    std::ranges::copy(fn, res.begin());
-    return res;
+    constexpr std::string_view sv = BOOST_PFR_FUNCTION_SIGNATURE;
+    if constexpr (sv.empty()) {
+        detail::failed_to_get_function_name<MsvcWorkaround>();
+        return detail::make_stdarray<char>(0);
+    } else {
+        constexpr auto skip = detail::make_core_name_skip BOOST_PFR_CORE_NAME_PARSING;
+        constexpr auto fn = detail::apply_core_name_skip(sv, skip);
+        auto res = std::array<char, fn.size()+1>{};
+        detail::assert_compile_time_legths<!fn.empty()>();
+        std::ranges::copy(fn, res.begin());
+        return res;
+    }
 }
 
 template <typename T>

test/config/print_config.cpp

@@ -4,6 +4,7 @@
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 #include <boost/pfr/config.hpp> // inclusion of an another PFR header may fail when BOOST_PFR_ENABLED=0
+#include <boost/preprocessor/stringize.hpp>
 
 #include <iostream>
 
@@ -15,6 +16,8 @@ int main() {
         << "BOOST_PFR_HAS_GUARANTEED_COPY_ELISION == " << BOOST_PFR_HAS_GUARANTEED_COPY_ELISION << '\n'
         << "BOOST_PFR_ENABLE_IMPLICIT_REFLECTION == " << BOOST_PFR_ENABLE_IMPLICIT_REFLECTION << '\n'
         << "BOOST_PFR_ENABLE_GET_NAME_STATIC == " << BOOST_PFR_ENABLE_GET_NAME_STATIC << '\n'
+        << "BOOST_PFR_FUNCTION_SIGNATURE == " << BOOST_PP_STRINGIZE(BOOST_PFR_FUNCTION_SIGNATURE) << '\n'
+        << "BOOST_PFR_CORE_NAME_PARSING == " << BOOST_PP_STRINGIZE(BOOST_PFR_CORE_NAME_PARSING) << '\n'
         << "BOOST_PFR_ENABLED == " << BOOST_PFR_ENABLED << '\n'
         << "__cplusplus == " << __cplusplus << '\n'
 #ifdef __cpp_structured_bindings

test/core_name/Jamfile.v2

@@ -43,6 +43,8 @@ project
         [ check-target-builds ../core_name//compiler_supports_cxx20_nontype_template_args : : [ check-target-builds ../core_name//compiler_supports_cxx20_clang_workaround : : <build>no ] ]
     ;
 
+local ENABLED_ENGINE = <define>BOOST_PFR_ENABLE_GET_NAME_STATIC=1 ;
+local DISABLED_ENGINE = <define>BOOST_PFR_ENABLE_GET_NAME_STATIC=0 ;
 
 
 
@@ -54,12 +56,20 @@ actions invoke_python_generator
 make fields_names_nonascii.cpp : generate_fields_names_nonascii.cpp.py : @invoke_python_generator ;
 make fields_names_big.cpp : generate_fields_names_big.cpp.py : @invoke_python_generator ;
 
-test-suite pfr_tests
+test-suite pfr_name_tests
   :
     [ run fields_names.cpp : : : : ]
     [ run fields_names_constexpr.cpp : : : : ]
     [ run fields_names_nonascii.cpp : : : <toolset>msvc:<cxxflags>"/utf-8" : ]
     [ run fields_names_big.cpp : : : <toolset>msvc:<cxxflags>"/bigobj" : ]
+    [ run print_name.cpp : : : <test-info>always_show_run_output ]
   ;
 
+for local source_file in [ glob ./compile-fail/*.cpp ]
+{
+    local target_name = $(source_file[1]:B) ;
+    pfr_name_tests += [ compile-fail $(source_file) : $(ENABLED_ENGINE) : $(target_name)_on ] ;
+    pfr_name_tests += [ compile-fail $(source_file) : $(DISABLED_ENGINE) : $(target_name)_off ] ;
+}
+
 

test/core_name/compile-fail/fields_names_could_not_detect_compiler.cpp

@@ -0,0 +1,20 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#define BOOST_PFR_FUNCTION_SIGNATURE ""
+#include <boost/pfr/core_name.hpp>
+
+struct A { int field; };
+
+int main() {
+    (void)boost::pfr::get_name<0, A>(); // Must be a compile time error
+}
+
+

test/core_name/compile-fail/fields_names_misconfigured_compiler.cpp

@@ -0,0 +1,21 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#define BOOST_PFR_FUNCTION_SIGNATURE "dummy"
+#define BOOST_PFR_CORE_NAME_PARSING (0,0,"")
+#include <boost/pfr/core_name.hpp>
+
+struct A { int field; };
+
+int main() {
+    (void)boost::pfr::get_name<0, A>(); // Must be a compile time error
+}
+
+

test/core_name/print_name.cpp

@@ -0,0 +1,33 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+#include <iostream>
+
+// This cpp file:
+// * tests BOOST_PFR_CORE_NAME_PARSING macro
+// * outputs full name of the function so that PFRs extraction of field name could be adjust to new compiler without requesting regression tester's help
+#define BOOST_PFR_CORE_NAME_PARSING (0,0,false,"")
+#include <boost/pfr/core_name.hpp>
+
+namespace user_defined_namespace {
+    struct user_defined_class { int user_defined_field; };
+}
+
+int main()
+{
+    using namespace boost::pfr;
+
+    std::cout << "user_defined_namespace::user_defined_class::user_defined_field: "
+        << get_name<0, user_defined_namespace::user_defined_class>() << '\n';
+
+
+    return 0;
+}
+