https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109758
--- Comment #12 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:af595613acbd9863198ae69c7b1c9e856bca9e4f commit r14-700-gaf595613acbd9863198ae69c7b1c9e856bca9e4f Author: Jonathan Wakely <jwak...@redhat.com> Date: Wed May 10 12:20:58 2023 +0100 libstdc++: Fix std::abs(__float128) for -NaN and -0.0 [PR109758] The current implementation of this non-standard overload of std::abs incorrectly returns a negative value for negative NaNs and negative zero, because x < 0 is false in both cases. Use fabsl(long double) or fabsf128(_Float128) if those do the right thing. Otherwise, use __builtin_signbit(x) instead of x < 0 to detect negative inputs. This assumes that __builtin_signbit handles __float128 correctly, but that seems to be true for all of GCC, clang and icc. libstdc++-v3/ChangeLog: PR libstdc++/109758 * include/bits/std_abs.h (abs(__float128)): Handle negative NaN and negative zero correctly. * testsuite/26_numerics/headers/cmath/109758.cc: New test.
