Improvements detection of features, part 15, added FASTFLOAT_NO_UNIQUE_ADDRESS and improves more.

include/fast_float/ascii_number.h

@@ -473,19 +473,19 @@ enum class parse_error : uint_fast8_t {
 };
 
 template <typename UC> struct parsed_number_string_t {
-  am_mant_t mantissa;
-  am_pow_t exponent;
-  UC const *lastmatch;
+  FASTFLOAT_NO_UNIQUE_ADDRESS am_mant_t mantissa;
+  FASTFLOAT_NO_UNIQUE_ADDRESS am_pow_t exponent;
+  FASTFLOAT_NO_UNIQUE_ADDRESS UC const *lastmatch;
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-  bool negative;
+  FASTFLOAT_NO_UNIQUE_ADDRESS bool negative;
 #endif
-  bool invalid;
-  bool too_many_digits;
-  parse_error error;
+  FASTFLOAT_NO_UNIQUE_ADDRESS bool invalid;
+  FASTFLOAT_NO_UNIQUE_ADDRESS bool too_many_digits;
+  FASTFLOAT_NO_UNIQUE_ADDRESS parse_error error;
 
   // contains the range of the significant digits
-  span<UC const> integer;  // non-nullable
-  span<UC const> fraction; // nullable
+  FASTFLOAT_NO_UNIQUE_ADDRESS span<UC const> integer; // non-nullable
+  FASTFLOAT_NO_UNIQUE_ADDRESS span<UC const> fraction; // nullable
 };
 
 using byte_span = span<char const>;
@@ -774,9 +774,8 @@ parse_int_string(UC const *p, UC const *pend, T &value,
   FASTFLOAT_ASSUME(p < pend); // so dereference without checks
   from_chars_result_t<UC> answer;
 
-  auto const *const first = p;
-
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
+  auto const *const first = p;
   // Read sign
   auto const negative = (*p == UC('-'));
 #ifdef FASTFLOAT_VISUAL_STUDIO

include/fast_float/constexpr_feature_detect.h

@@ -1,16 +1,42 @@
 #ifndef FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H
 #define FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H
 
-#ifdef __has_include
-#if __has_include(<version>)
-#include <version>
+#ifdef _MSVC_LANG
+#define FASTFLOAT_CPLUSPLUS _MSVC_LANG
+#else
+#define FASTFLOAT_CPLUSPLUS __cplusplus
 #endif
+
+// Detect __has_*.
+#ifdef __has_feature
+#define FASTFLOAT_HAS_FEATURE(x) __has_feature(x)
+#else
+#define FASTFLOAT_HAS_FEATURE(x) 0
+#endif
+#ifdef __has_include
+#define FASTFLOAT_HAS_INCLUDE(x) __has_include(x)
+#else
+#define FASTFLOAT_HAS_INCLUDE(x) 0
+#endif
+#ifdef __has_builtin
+#define FASTFLOAT_HAS_BUILTIN(x) __has_builtin(x)
+#else
+#define FASTFLOAT_HAS_BUILTIN(x) 0
+#endif
+#ifdef __has_cpp_attribute
+#define FASTFLOAT_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
+#else
+#define FASTFLOAT_HAS_CPP_ATTRIBUTE(x) 0
+#endif
+
+#if FASTFLOAT_HAS_INCLUDE(<version>)
+#include <version>
 #endif
 
 // C++14 constexpr
 #if defined(__cpp_constexpr) && __cpp_constexpr >= 201304L
 #define FASTFLOAT_CONSTEXPR14 constexpr
-#elif __cplusplus >= 201402L
+#elif FASTFLOAT_CPLUSPLUS >= 201402L
 #define FASTFLOAT_CONSTEXPR14 constexpr
 #elif defined(_MSC_VER) && _MSC_VER >= 1910 && _MSVC_LANG >= 201402L
 #define FASTFLOAT_CONSTEXPR14 constexpr
@@ -21,10 +47,7 @@
 // C++14 variable templates
 #if defined(__cpp_variable_templates) && __cpp_variable_templates >= 201304L
 #define FASTFLOAT_HAS_VARIABLE_TEMPLATES 1
-#elif __cplusplus >= 201402L
-#define FASTFLOAT_HAS_VARIABLE_TEMPLATES 1
-#elif defined(_MSC_FULL_VER) && _MSC_FULL_VER >= 190023918L &&                 \
-    defined(_MSC_VER) && _MSVC_LANG >= 201402L
+#elif FASTFLOAT_CPLUSPLUS >= 201402L
 #define FASTFLOAT_HAS_VARIABLE_TEMPLATES 1
 #else
 #define FASTFLOAT_HAS_VARIABLE_TEMPLATES 0
@@ -35,9 +58,7 @@
 #define FASTFLOAT_CONSTEXPR17 constexpr
 #elif defined(__cpp_constexpr) && __cpp_constexpr >= 201603L
 #define FASTFLOAT_CONSTEXPR17 constexpr
-#elif __cplusplus >= 201703L
-#define FASTFLOAT_CONSTEXPR17 constexpr
-#elif defined(_MSC_VER) && _MSC_VER >= 1911 && _MSVC_LANG >= 201703L
+#elif FASTFLOAT_CPLUSPLUS >= 201703L
 #define FASTFLOAT_CONSTEXPR17 constexpr
 #else
 #define FASTFLOAT_CONSTEXPR17
@@ -55,7 +76,7 @@
 #endif
 
 // Before C++17 constexpr variables may need an out-of-class definition.
-#if __cplusplus >= 201703L || (defined(_MSC_VER) && _MSVC_LANG >= 201703L)
+#if FASTFLOAT_CPLUSPLUS >= 201703L
 #define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 0
 #else
 #define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 1
@@ -92,17 +113,23 @@
 #define FASTFLOAT_HAS_BYTESWAP 0
 #endif
 
-#if defined(__has_builtin)
-#define FASTFLOAT_HAS_BUILTIN(x) __has_builtin(x)
-#else
-#define FASTFLOAT_HAS_BUILTIN(x) false
-#endif
-
-#if defined(__cpp_attrubute_assume)
-//  For support attribute [[assume]] is declared in P1774
+#ifdef FASTFLOAT_ASSUME
+// Use the provided definition.
+#elif FASTFLOAT_HAS_CPP_ATTRIBUTE(assume)
 #define FASTFLOAT_ASSUME(expr) [[assume(expr)]]
 #else
 #define FASTFLOAT_ASSUME(expr)
 #endif
 
+#ifdef FASTFLOAT_NO_UNIQUE_ADDRESS
+// Use the provided definition.
+#elif FASTFLOAT_CPLUSPLUS < 202002L
+// Not supported.
+#elif FASTFLOAT_HAS_CPP_ATTRIBUTE(no_unique_address)
+#define FASTFLOAT_NO_UNIQUE_ADDRESS [[no_unique_address]]
+// VS2019 v16.10 and later except clang-cl (https://reviews.llvm.org/D110485).
+#elif defined(_MSC_VER) && _MSC_VER >= 1929 && !defined(__clang__)
+#define FASTFLOAT_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#endif
+
 #endif // FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H

include/fast_float/float_common.h

@@ -687,8 +687,8 @@ full_multiplication(uint64_t a, uint64_t b) noexcept {
 
 /* alignas(16) - better data cache usage without align */
 struct adjusted_mantissa {
-  am_mant_t mantissa;
-  am_pow_t power2;
+  FASTFLOAT_NO_UNIQUE_ADDRESS am_mant_t mantissa;
+  FASTFLOAT_NO_UNIQUE_ADDRESS am_pow_t power2;
 
   constexpr adjusted_mantissa() noexcept : mantissa(0), power2(0) {}