From 677cfe842547d41051f05677968191256ec3b1e9 Mon Sep 17 00:00:00 2001
From: HedgehogInTheCPP <a.rainman@gmail.com>
Date: Fri, 21 Aug 2026 23:10:50 +0300
Subject: [PATCH] Improvements detection of features, part 12.

---
 include/fast_float/ascii_number.h             | 2 +-
 include/fast_float/bigint.h                   | 4 +---
 include/fast_float/constexpr_feature_detect.h | 2 +-
 include/fast_float/digit_comparison.h         | 2 +-
 include/fast_float/float_common.h             | 8 ++++----
 5 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/include/fast_float/ascii_number.h b/include/fast_float/ascii_number.h
index f72ffa1..a3de75d 100644
--- a/include/fast_float/ascii_number.h
+++ b/include/fast_float/ascii_number.h
@@ -19,7 +19,7 @@
 namespace fast_float {
 
 template <typename UC>
-fastfloat_really_inline constexpr bool has_simd_opt() noexcept {
+fastfloat_really_inline FASTFLOAT_CONSTEVAL bool has_simd_opt() noexcept {
 #ifdef FASTFLOAT_USE_SIMD
   return std::is_same<UC, char16_t>::value;
 #else
diff --git a/include/fast_float/bigint.h b/include/fast_float/bigint.h
index 297bad4..69c2db6 100644
--- a/include/fast_float/bigint.h
+++ b/include/fast_float/bigint.h
@@ -212,13 +212,11 @@ fastfloat_really_inline FASTFLOAT_CONSTEXPR20 limb
 scalar_add(limb x, limb y, bool &overflow) noexcept {
   limb z;
 // gcc and clang
-#if defined(__has_builtin)
-#if __has_builtin(__builtin_add_overflow)
+#if FASTFLOAT_HAS_BUILTIN(__builtin_add_overflow)
   if (!is_constant_evaluated()) {
     overflow = __builtin_add_overflow(x, y, &z);
     return z;
   }
-#endif
 #endif
 
   // generic, this still optimizes correctly on MSVC.
diff --git a/include/fast_float/constexpr_feature_detect.h b/include/fast_float/constexpr_feature_detect.h
index 269f1af..20a998e 100644
--- a/include/fast_float/constexpr_feature_detect.h
+++ b/include/fast_float/constexpr_feature_detect.h
@@ -79,7 +79,7 @@
 #define FASTFLOAT_IS_CONSTEXPR 1
 #define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 1
 #else
-#define FASTFLOAT_CONSTEVAL
+#define FASTFLOAT_CONSTEVAL FASTFLOAT_CONSTEXPR14
 #define FASTFLOAT_CONSTEXPR20
 #define FASTFLOAT_IS_CONSTEXPR 0
 #define FASTFLOAT_HAS_IS_CONSTANT_EVALUATED 0
diff --git a/include/fast_float/digit_comparison.h b/include/fast_float/digit_comparison.h
index bac10e3..f9019b8 100644
--- a/include/fast_float/digit_comparison.h
+++ b/include/fast_float/digit_comparison.h
@@ -241,7 +241,7 @@ parse_eight_digits(UC const *&p, limb &value, am_digits &counter,
 }
 
 template <typename UC>
-fastfloat_really_inline FASTFLOAT_CONSTEXPR20 void
+fastfloat_really_inline FASTFLOAT_CONSTEXPR14 void
 parse_four_digits(UC const *&p, limb &value, am_digits &counter,
                   am_digits &count) noexcept {
   value = value * 10000 + parse_4_digits(read_chars_to_unsigned<uint32_t>(p));
diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index 8ee495f..a4b944b 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -294,7 +294,7 @@ namespace fast_float {
 using std::bit_cast;
 #else
 template <typename To, typename From>
-fastfloat_really_inline FASTFLOAT_CONSTEXPR20 To bit_cast(const From &from) {
+fastfloat_really_inline FASTFLOAT_CONSTEXPR14 To bit_cast(const From &from) {
   // Implementation of std::bit_cast for pre-C++20.
   auto to = To();
   // The cast suppresses a bogus -Wclass-memaccess on GCC.
@@ -355,7 +355,7 @@ struct is_supported_char_type
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
 
 template <typename UC>
-inline FASTFLOAT_CONSTEXPR14 bool
+inline FASTFLOAT_CONSTEXPR20 bool
 fastfloat_strncasecmp3(UC const *actual_mixedcase,
                        UC const *expected_lowercase) {
   if (is_constant_evaluated()) {
@@ -396,7 +396,7 @@ fastfloat_strncasecmp3(UC const *actual_mixedcase,
 }
 
 template <typename UC>
-inline FASTFLOAT_CONSTEXPR14 bool
+inline FASTFLOAT_CONSTEXPR20 bool
 fastfloat_strncasecmp5(UC const *actual_mixedcase,
                        UC const *expected_lowercase) noexcept {
   if (is_constant_evaluated()) {
@@ -447,7 +447,7 @@ fastfloat_strncasecmp5(UC const *actual_mixedcase,
 
 // Compares two ASCII strings in a case insensitive manner.
 template <typename UC>
-inline FASTFLOAT_CONSTEXPR14 bool
+inline FASTFLOAT_CONSTEXPR20 bool
 fastfloat_strncasecmp(UC const *actual_mixedcase, UC const *expected_lowercase,
                       uint_fast8_t const length) noexcept {
   if (is_constant_evaluated()) {