https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99117
--- Comment #26 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:8250987299d01ff318b73a02e4ba245afd46b64b commit r12-11012-g8250987299d01ff318b73a02e4ba245afd46b64b Author: Jonathan Wakely <jwak...@redhat.com> Date: Thu Feb 8 13:59:42 2024 +0000 libstdc++: Avoid aliasing violation in std::valarray [PR99117] The call to __valarray_copy constructs an _Array object to refer to this->_M_data but that means that accesses to this->_M_data are through a restrict-qualified pointer. This leads to undefined behaviour when copying from an _Expr object that actually aliases this->_M_data. Replace the call to __valarray_copy with a plain loop. I think this removes the only use of that overload of __valarray_copy, so it could probably be removed. I haven't done that here. libstdc++-v3/ChangeLog: PR libstdc++/99117 * include/std/valarray (valarray::operator=(const _Expr&)): Use loop to copy instead of __valarray_copy with _Array. * testsuite/26_numerics/valarray/99117.cc: New test. (cherry picked from commit b58f0e5216a3053486e7f1aa96c3f2443b14d630)
