On Mon, 15 Nov 2021, Patrick Palka wrote: > This makes fast_float handle the situation where std::from_chars is > specified to return result_out_of_range, i.e. when the parsed value > is outside the representable range of the floating-point type. > > libstdc++-v3/ChangeLog: > > * src/c++17/fast_float/LOCAL_PATCHES: Update. > * src/c++17/fast_float/parse_number.h (from_chars_advanced): In > case of over/underflow, return errc::result_out_of_range and don't > modify 'value'.
v2: Now in terms of the amalgamated version of the library. -- >8 -- Subject: [PATCH 3/5] libstdc++: Adjust fast_float's over/underflow behavior for conformance This adjusts fast_float's behavior in case of over/underflow: rather than setting value to +-0 or +-infinity, return result_out_of_range and don't modify value, as per [charconv.from.chars]/1. libstdc++-v3/ChangeLog: * src/c++17/fast_float/LOCAL_PATCHES: Update. * src/c++17/fast_float/fast_float.h (from_chars_advanced): In case of over/underflow, return errc::result_out_of_range and don't modify 'value'. --- libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES | 1 + libstdc++-v3/src/c++17/fast_float/fast_float.h | 9 +++++++++ 2 files changed, 10 insertions(+) diff --git a/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES b/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES index e9d7bba6195..1f90f9d1d85 100644 --- a/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES +++ b/libstdc++-v3/src/c++17/fast_float/LOCAL_PATCHES @@ -1 +1,2 @@ r12-???? +r12-???? diff --git a/libstdc++-v3/src/c++17/fast_float/fast_float.h b/libstdc++-v3/src/c++17/fast_float/fast_float.h index c908719ec3a..97d28940944 100644 --- a/libstdc++-v3/src/c++17/fast_float/fast_float.h +++ b/libstdc++-v3/src/c++17/fast_float/fast_float.h @@ -2884,6 +2884,15 @@ from_chars_result from_chars_advanced(const char *first, const char *last, // If we called compute_float<binary_format<T>>(pns.exponent, pns.mantissa) and we have an invalid power (am.power2 < 0), // then we need to go the long way around again. This is very uncommon. if(am.power2 < 0) { am = digit_comp<T>(pns, am); } + + if((pns.mantissa != 0 && am.mantissa == 0 && am.power2 == 0) || am.power2 == binary_format<T>::infinite_power()) { + // In case of over/underflow, return result_out_of_range and don't modify value, + // as per [charconv.from.chars]/1. Note that LWG 3081 wants to modify value in + // this case too. + answer.ec = std::errc::result_out_of_range; + return answer; + } + to_float(pns.negative, am, value); return answer; } -- 2.34.0