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Removed inline constexpr as it doesn't work in C++11, instead relying on the compiler cannonizing char litteral arrays in order to avoid duplicating the array definition per translation unit

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Cazadorro 2026-03-28 23:16:40 -05:00
parent 432f5899e3
commit dedbeeebb0
1 changed files with 21 additions and 7 deletions
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28
include/fmt/format.h
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@ -3149,12 +3149,6 @@ FMT_CONSTEXPR20 void format_hexfloat(Float value, format_specs specs,
format_hexfloat(static_cast<double>(value), specs, buf);
}
// pre C++23 does not allow static constexpr inside of constexpr functions
// so we must declare this outside of fractional_part_rounding_thresholds
inline constexpr uint32_t rounding_thresholds[8] = {
0x9999999au, 0x828f5c29u, 0x80418938u, 0x80068db9,
0x8000a7c6u, 0x800010c7u, 0x800001aeu, 0x8000002bu};
constexpr auto fractional_part_rounding_thresholds(int index) -> uint32_t {
// For checking rounding thresholds.
// The kth entry is chosen to be the smallest integer such that the
@ -3163,7 +3157,27 @@ constexpr auto fractional_part_rounding_thresholds(int index) -> uint32_t {
// These are stored in a string literal because we cannot have static arrays
// in constexpr functions and non-static ones are poorly optimized.
return rounding_thresholds[index];
// while in C++23 we can use static constexpr, and in c++17 we can use out of
// function defintion of inline constexpr, in C++11 we have to rely on string
// literals in order to avoid duplicating constant definitions across
// translation units. We take the following uint32 array definition:
// {0x9999999au, 0x828f5c29u, 0x80418938u, 0x80068db9,
// 0x8000a7c6u, 0x800010c7u, 0x800001aeu, 0x8000002bu};
// and convert that into a series of char hexidecimal literals in a char array:
// "\x99\x99\x99\x9a \x82\x8f\x5c\x29 \x80\x41\x89\x38 \x80\x06\x8d\xb9
// \x80\x00\xa7\xc6 \x80\x00\x10\xc7 \x80\x00\x01\xae \x80\x00\x00\x2b"
// Then we split this up into four seperate arrays of bytes, so the bytes can
// be properly recombined into endian-correct uint32_t.
uint32_t byte_3 = static_cast<uint8_t>("\x99\x82\x80\x80\x80\x80\x80\x80"[index]);
uint32_t byte_2 = static_cast<uint8_t>("\x99\x8f\x41\x06\x00\x00\x00\x00"[index]);
uint32_t byte_1 = static_cast<uint8_t>("\x99\x5c\x89\x8d\xa7\x10\x01\x00"[index]);
uint32_t byte_0 = static_cast<uint8_t>("\x9a\x29\x38\xb9\xc6\xc7\xae\x2b"[index]);
//recombine as uint32, this should eliminate endian issues, as now we are shifting
//btyes as uint32 which should match platform endian.
return byte_3 << 24u | byte_2 << 16u | byte_1 << 8u | byte_0;
}
template <typename Float>