https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62196
--- Comment #3 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:abb958ada1e4d195f31740659cd8af8bebce7bfd commit r13-6656-gabb958ada1e4d195f31740659cd8af8bebce7bfd Author: Jonathan Wakely <jwak...@redhat.com> Date: Mon Mar 6 14:41:59 2023 +0000 libstdc++: Add assertions to std::mask_array operations [PR62196] Add assertions to diagnose incorrect uses of valarray masks. The assignment operators of std::mask_array do not have any explicit preconditions in the standard, but the assignment operator valarray<T>::operator=(const mask_array<T>&) requires the lengths to match, so it seems consistent to also require that when the operands are reversed. In support of that interpretation, libstdc++ has undefined behaviour if the right-hand operand has more elements than are selected by the mask, and libc++ has undefined behaviour if it has fewer elements. Our std::mask_array stores the number of selected elements as _M_sz so it's easy to add an assertion that checks it. For the valarray::operator[] that takes a valarray<bool> mask, [valarray.sub] in the standard says: "In each case the selected element(s) shall exist." This makes it undefined to have a mask that refers to out-of-range elements. We can easily check this too. libstdc++-v3/ChangeLog: PR libstdc++/62196 * include/bits/mask_array.h (mask_array): Add assertions to assignment operators. * include/std/valarray (valarray::operator[](valarray<bool>)): Add assertions. * testsuite/26_numerics/valarray/mask-1_neg.cc: New test. * testsuite/26_numerics/valarray/mask-2_neg.cc: New test. * testsuite/26_numerics/valarray/mask-3_neg.cc: New test. * testsuite/26_numerics/valarray/mask-4_neg.cc: New test. * testsuite/26_numerics/valarray/mask-5_neg.cc: New test. * testsuite/26_numerics/valarray/mask-6_neg.cc: New test. * testsuite/26_numerics/valarray/mask-7_neg.cc: New test. * testsuite/26_numerics/valarray/mask-8_neg.cc: New test. * testsuite/26_numerics/valarray/mask.cc: New test.
