From e2ab9ab22b4e138bb5004dcbcacc3a200218db08 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@meta.com>
Date: Tue, 2 Jan 2024 16:00:05 -0800
Subject: [PATCH] Add FMT_GLIBCXX_RELEASE

---
 include/fmt/core.h   | 27 ++++++++++++++-------------
 test/compile-test.cc |  2 +-
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 338e534b..fa82fb99 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -58,6 +58,12 @@
 #  define FMT_MSC_WARNING(...)
 #endif
 
+#ifdef _GLIBCXX_RELEASE
+#  define FMT_GLIBCXX_RELEASE _GLIBCXX_RELEASE
+#else
+#  define FMT_GLIBCXX_RELEASE 0
+#endif
+
 #ifdef _MSVC_LANG
 #  define FMT_CPLUSPLUS _MSVC_LANG
 #else
@@ -121,7 +127,7 @@
 
 #if (FMT_CPLUSPLUS >= 202002L ||                                \
      (FMT_CPLUSPLUS >= 201709L && FMT_GCC_VERSION >= 1002)) &&  \
-    ((!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 10) &&  \
+    ((!FMT_GLIBCXX_RELEASE || FMT_GLIBCXX_RELEASE >= 10) &&     \
      (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 10000) && \
      (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1928)) &&          \
     defined(__cpp_lib_is_constant_evaluated)
@@ -131,15 +137,11 @@
 #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
+#if FMT_CPLUSPLUS < 201703L
+// Not supported.
+#elif FMT_GLIBCXX_RELEASE >= 7 ||                            \
+    (defined(_LIBCPP_VERSION) && _LIBCPP_VERSION >= 4000) || \
+    FMT_MSC_VERSION >= 1914
 #  define FMT_CONSTEXPR_CHAR_TRAITS constexpr
 #endif
 #ifndef FMT_CONSTEXPR_CHAR_TRAITS
@@ -262,7 +264,7 @@
 #  endif
 #endif
 
-// GCC < 5 requires this-> in decltype
+// GCC < 5 requires this-> in decltype.
 #ifndef FMT_DECLTYPE_THIS
 #  if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
 #    define FMT_DECLTYPE_THIS this->
@@ -337,8 +339,7 @@ constexpr FMT_INLINE auto is_constant_evaluated(
 // 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 &&                                \
+#if FMT_CPLUSPLUS >= 202002L && FMT_GLIBCXX_RELEASE >= 12 && \
     (FMT_CLANG_VERSION >= 1400 && FMT_CLANG_VERSION < 1500)
   ignore_unused(default_value);
   return __builtin_is_constant_evaluated();
diff --git a/test/compile-test.cc b/test/compile-test.cc
index 1b6d2157..171516c5 100644
--- a/test/compile-test.cc
+++ b/test/compile-test.cc
@@ -288,7 +288,7 @@ TEST(compile_test, compile_format_string_literal) {
 //  line 8635)
 #if (FMT_CPLUSPLUS >= 202002L ||                                \
      (FMT_CPLUSPLUS >= 201709L && FMT_GCC_VERSION >= 1002)) &&  \
-    ((!defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE >= 10) &&  \
+    ((!FMT_GLIBCXX_RELEASE || FMT_GLIBCXX_RELEASE >= 10) &&  \
      (!defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 10000) && \
      (!FMT_MSC_VERSION ||                                       \
       (FMT_MSC_VERSION >= 1928 && FMT_MSC_VERSION < 1930))) &&  \