Hi! 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.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2022-11-23 Jakub Jelinek <ja...@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. --- libstdc++-v3/src/c++17/floating_from_chars.cc.jj 2022-11-08 09:54:37.533397224 +0100 +++ libstdc++-v3/src/c++17/floating_from_chars.cc 2022-11-22 14:03:10.365474110 +0100 @@ -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{}}; } Jakub