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Improvements in detection of C++14 constexpr and C++20 consteval. I really want to drop support for C++11 entirely, and may be for C++14 too because it's been 12 years ago and 15 since C++11!

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This commit is contained in:
HedgehogInTheCPP 2026-08-21 18:20:32 +03:00
parent 25e448109d
commit 6714db59ae
1 changed files with 31 additions and 19 deletions
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50
include/fast_float/constexpr_feature_detect.h
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@ -8,12 +8,16 @@
#endif
// C++14 constexpr
#if defined(__cpp_constexpr) && __cpp_constexpr >= 201304L
#if defined(_MSC_VER)
#if _MSVC_LANG >= 201402L
#define FASTFLOAT_CONSTEXPR14 constexpr
#else
#define FASTFLOAT_CONSTEXPR14
#endif
#elif defined(__cpp_constexpr) && __cpp_constexpr >= 201304L
#define FASTFLOAT_CONSTEXPR14 constexpr
#elif __cplusplus >= 201402L
#define FASTFLOAT_CONSTEXPR14 constexpr
#elif defined(_MSC_VER) && _MSC_VER >= 1910 && _MSVC_LANG >= 201402L
#define FASTFLOAT_CONSTEXPR14 constexpr
#else
#define FASTFLOAT_CONSTEXPR14
#endif
@ -37,13 +41,32 @@
#define FASTFLOAT_HAS_BIT_CAST 0
#endif
#if defined(__cpp_lib_is_constant_evaluated) && \
// Detect consteval, C++20 constexpr extensions and std::is_constant_evaluated.
#if !defined(__cpp_lib_is_constant_evaluated)
#define FASTFLOAT__USE_CONSTEVAL 0
#elif __cplusplus < 201709L
#define FASTFLOAT_USE_CONSTEVAL 0
#elif defined(__apple_build_version__) && __apple_build_version__ < 14000029L
#define FASTFLOAT_USE_CONSTEVAL 0 // consteval is broken in Apple clang < 14.
#elif _MSC_VER && _MSC_VER < 1940
#define FASTFLOAT_USE_CONSTEVAL \
0 // consteval is broken in some MSVC2022 versions.
#elif defined(__cpp_consteval)
#define FASTFLOAT_USE_CONSTEVAL 1
#elif defined(__cpp_lib_is_constant_evaluated) && \
__cpp_lib_is_constant_evaluated >= 201811L
#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 1
#define FASTFLOAT_CONSTEVAL consteval
#define FASTFLOAT_USE_CONSTEVAL 1
#elif FMT_GCC_VERSION >= 1002 || FMT_CLANG_VERSION >= 1101
#define FASTFLOAT_USE_CONSTEVAL 1
#else
#define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 0
#define FASTFLOAT_CONSTEVAL FASTFLOAT_CONSTEXPR14
#define FASTFLOAT_USE_CONSTEVAL 0
#endif
#if FASTFLOAT_USE_CONSTEVAL
#define FASTFLOAT_CONSTEVAL consteval
#define FASTFLOAT_CONSTEXPR20 constexpr
#else
#define FASTFLOAT_CONSTEVAL
#define FASTFLOAT_CONSTEXPR20
#endif
#if defined(__cpp_lib_byteswap)
@ -76,17 +99,6 @@
#define FASTFLOAT_INLINE_VARIABLE static constexpr
#endif
// Testing for relevant C++20 constexpr library features
#if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED && FASTFLOAT_HAS_BIT_CAST && \
defined(__cpp_lib_constexpr_algorithms) && \
__cpp_lib_constexpr_algorithms >= 201806L /*For std::copy and std::fill*/
#define FASTFLOAT_CONSTEXPR20 constexpr
#define FASTFLOAT_IS_CONSTEXPR 1
#else
#define FASTFLOAT_CONSTEXPR20
#define FASTFLOAT_IS_CONSTEXPR 0
#endif
#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
#define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 0
#else