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libstdc++: Fix libstdc++ build on some targets [PR107811]

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fast_float library relies on size_t being 32-bit or larger and float/double
being IEEE single/double.  Otherwise we only use strtod/strtof.
In 3 spots I've used fast_float namespace stuff unconditionally in one
function, which breaks the build if fast_float is disabled.

2022-11-23  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/107811
	* src/c++17/floating_from_chars.cc (__floating_from_chars_hex): Guard
	fast_float uses with #if USE_LIB_FAST_FLOAT and for mantissa_bits and
	exponent_bits provide a fallback.
This commit is contained in:
Jakub Jelinek 2022-11-23 11:53:54 +01:00
parent 1cac00d013
commit e6a32c12b4
1 changed files with 11 additions and 1 deletions
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12
libstdc++-v3/src/c++17/floating_from_chars.cc
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@ -783,11 +783,16 @@ namespace
using uint_t = conditional_t<is_same_v<T, float>, uint32_t,
conditional_t<is_same_v<T, double>, uint64_t,
uint16_t>>;
#if USE_LIB_FAST_FLOAT
constexpr int mantissa_bits
= fast_float::binary_format<T>::mantissa_explicit_bits();
constexpr int exponent_bits
= is_same_v<T, double> ? 11
: is_same_v<T, fast_float::floating_type_float16_t> ? 5 : 8;
#else
constexpr int mantissa_bits = is_same_v<T, float> ? 23 : 52;
constexpr int exponent_bits = is_same_v<T, float> ? 8 : 11;
#endif
constexpr int exponent_bias = (1 << (exponent_bits - 1)) - 1;
__glibcxx_requires_valid_range(first, last);
@ -945,8 +950,11 @@ namespace
else if (mantissa_idx >= -4)
{
if constexpr (is_same_v<T, float>
#if USE_LIB_FAST_FLOAT
|| is_same_v<T,
fast_float::floating_type_bfloat16_t>)
fast_float::floating_type_bfloat16_t>
#endif
)
{
__glibcxx_assert(mantissa_idx == -1);
mantissa |= hexit >> 1;
@ -1130,6 +1138,7 @@ namespace
}
if constexpr (is_same_v<T, float> || is_same_v<T, double>)
memcpy(&value, &result, sizeof(result));
#if USE_LIB_FAST_FLOAT
else if constexpr (is_same_v<T, fast_float::floating_type_bfloat16_t>)
{
uint32_t res = uint32_t{result} << 16;
@ -1156,6 +1165,7 @@ namespace
| ((uint32_t{result} & 0x8000) << 16));
memcpy(value.x, &res, sizeof(res));
}
#endif
return {first, errc{}};
}