https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110860
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:bb3ceeb6520c13fc5ca08af7d43fbd3f975e72b0 commit r14-3069-gbb3ceeb6520c13fc5ca08af7d43fbd3f975e72b0 Author: Jonathan Wakely <jwak...@redhat.com> Date: Mon Aug 7 15:30:03 2023 +0100 libstdc++: Fix incorrect use of abs and log10 in std::format [PR110860] The std::formatter implementation for floating-point types uses __builtin_abs and __builtin_log10 to avoid including all of <cmath>, but those functions are not generic. The result of abs(2e304) is -INT_MIN which is undefined, and then log10(INT_MIN) is NaN. As well as being undefined, we fail to grow the buffer correctly, and then loop more times than needed to allocate a buffer and try formatting the value into it again. We can use if-constexpr to choose the correct form of log10 to use for the type, and avoid using abs entirely. This avoids the undefined behaviour and should mean we only reallocate and retry std::to_chars once. libstdc++-v3/ChangeLog: PR libstdc++/110860 * include/std/format (__formatter_fp::format): Do not use __builtin_abs and __builtin_log10 with arbitrary floating-point types.
