From 62ceff43c89d755085e1900c34fc71f0ce1dc4b4 Mon Sep 17 00:00:00 2001
From: Marcus Holland-Moritz <github@mhxnet.de>
Date: Thu, 10 Oct 2024 12:17:58 +0200
Subject: [PATCH] build: make dependency on fast_float optional in CMake build

The fast_float library isn't widely available, especially for older
distributions. Furthermore, `FOLLY_CONV_ATOD_MODE` isn't even set by
the CMake build, so conversion doesn't actually use fast_float.
---
 CMake/folly-config.h.cmake | 2 ++
 CMake/folly-deps.cmake     | 7 +++++--
 folly/Conv.cpp             | 6 +++++-
 folly/Conv.h               | 2 ++
 folly/test/ConvTest.cpp    | 2 ++
 5 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/CMake/folly-config.h.cmake b/CMake/folly-config.h.cmake
index 84954764499..73c23788ce8 100644
--- a/CMake/folly-config.h.cmake
+++ b/CMake/folly-config.h.cmake
@@ -33,6 +33,8 @@
 #cmakedefine FOLLY_HAVE_PTHREAD 1
 #cmakedefine FOLLY_HAVE_PTHREAD_ATFORK 1
 
+#cmakedefine FOLLY_HAVE_FASTFLOAT 1
+
 #cmakedefine FOLLY_HAVE_LIBGFLAGS 1
 #cmakedefine FOLLY_UNUSUAL_GFLAGS_NAMESPACE 1
 #cmakedefine FOLLY_GFLAGS_NAMESPACE @FOLLY_GFLAGS_NAMESPACE@
diff --git a/CMake/folly-deps.cmake b/CMake/folly-deps.cmake
index 6ce4c679a42..362c67c2f74 100644
--- a/CMake/folly-deps.cmake
+++ b/CMake/folly-deps.cmake
@@ -52,8 +52,11 @@ find_package(DoubleConversion MODULE REQUIRED)
 list(APPEND FOLLY_LINK_LIBRARIES ${DOUBLE_CONVERSION_LIBRARY})
 list(APPEND FOLLY_INCLUDE_DIRECTORIES ${DOUBLE_CONVERSION_INCLUDE_DIR})
 
-find_package(FastFloat MODULE REQUIRED)
-list(APPEND FOLLY_INCLUDE_DIRECTORIES ${FASTFLOAT_INCLUDE_DIR})
+find_package(FastFloat MODULE)
+set(FOLLY_HAVE_FASTFLOAT ${FASTFLOAT_FOUND})
+if(FASTFLOAT_FOUND)
+  list(APPEND FOLLY_INCLUDE_DIRECTORIES ${FASTFLOAT_INCLUDE_DIR})
+endif()
 
 find_package(Gflags MODULE)
 set(FOLLY_HAVE_LIBGFLAGS ${LIBGFLAGS_FOUND})
diff --git a/folly/Conv.cpp b/folly/Conv.cpp
index 4e392685613..d7b8ed4f274 100644
--- a/folly/Conv.cpp
+++ b/folly/Conv.cpp
@@ -21,7 +21,9 @@
 
 #include <folly/lang/SafeAssert.h>
 
+#if FOLLY_HAVE_FASTFLOAT
 #include <fast_float/fast_float.h> // @manual=fbsource//third-party/fast_float:fast_float
+#endif
 
 namespace folly {
 namespace detail {
@@ -462,6 +464,7 @@ Expected<Tgt, ConversionCode> str_to_floating_double_conversion(
   return Tgt(result);
 }
 
+#if FOLLY_HAVE_FASTFLOAT
 /// Uses `fast_float::from_chars` to convert from string to an integer.
 template <class Tgt>
 Expected<Tgt, ConversionCode> str_to_floating_fast_float_from_chars(
@@ -505,6 +508,7 @@ template Expected<float, ConversionCode>
 str_to_floating_fast_float_from_chars<float>(StringPiece* src) noexcept;
 template Expected<double, ConversionCode>
 str_to_floating_fast_float_from_chars<double>(StringPiece* src) noexcept;
+#endif
 
 /**
  * StringPiece to double, with progress information. Alters the
@@ -512,7 +516,7 @@ str_to_floating_fast_float_from_chars<double>(StringPiece* src) noexcept;
  */
 template <class Tgt>
 Expected<Tgt, ConversionCode> str_to_floating(StringPiece* src) noexcept {
-#if defined(FOLLY_CONV_ATOD_MODE) && FOLLY_CONV_ATOD_MODE == 1
+#if FOLLY_HAVE_FASTFLOAT && defined(FOLLY_CONV_ATOD_MODE) && FOLLY_CONV_ATOD_MODE == 1
   return detail::str_to_floating_fast_float_from_chars<Tgt>(src);
 #else
   return detail::str_to_floating_double_conversion<Tgt>(src);
diff --git a/folly/Conv.h b/folly/Conv.h
index c7b61cacfc8..839ae90ff1e 100644
--- a/folly/Conv.h
+++ b/folly/Conv.h
@@ -1461,6 +1461,7 @@ extern template Expected<float, ConversionCode> str_to_floating<float>(
 extern template Expected<double, ConversionCode> str_to_floating<double>(
     StringPiece* src) noexcept;
 
+#if FOLLY_HAVE_FASTFLOAT
 template <typename T>
 Expected<T, ConversionCode> str_to_floating_fast_float_from_chars(
     StringPiece* src) noexcept;
@@ -1469,6 +1470,7 @@ extern template Expected<float, ConversionCode>
 str_to_floating_fast_float_from_chars<float>(StringPiece* src) noexcept;
 extern template Expected<double, ConversionCode>
 str_to_floating_fast_float_from_chars<double>(StringPiece* src) noexcept;
+#endif
 
 template <class Tgt>
 Expected<Tgt, ConversionCode> digits_to(const char* b, const char* e) noexcept;
diff --git a/folly/test/ConvTest.cpp b/folly/test/ConvTest.cpp
index 0680ff692b7..98188a7ad75 100644
--- a/folly/test/ConvTest.cpp
+++ b/folly/test/ConvTest.cpp
@@ -1772,6 +1772,7 @@ TEST(Conv, TryStringToFloat) {
   tryStringToFloat<folly::StringPiece>(StrToFloatTryTo<folly::StringPiece>());
 }
 
+#if FOLLY_HAVE_FASTFLOAT
 /// Uses `folly::detail::str_to_floating_fast_float_from_chars` to convert a
 /// string to a float.
 template <class String>
@@ -1792,6 +1793,7 @@ TEST(Conv, TryStringToFloat_FastFloatFromChars) {
   tryStringToFloat<folly::StringPiece>(
       StrToFloatFastFloatFromChars<folly::StringPiece>());
 }
+#endif
 
 template <class String>
 void tryToDouble() {