https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94017
--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:712b182a8bc2d7510d7a2fbede43bf134c539f25 commit r10-7006-g712b182a8bc2d7510d7a2fbede43bf134c539f25 Author: Patrick Palka <ppa...@redhat.com> Date: Tue Mar 3 16:16:05 2020 -0500 libstdc++: Fix incorrect use of memset in ranges::fill_n (PR 94017) When deciding whether to perform the memset optimization in ranges::fill_n, we were crucially neglecting to check that the output pointer's value type is a byte type. This patch adds such a check to the problematic condition in ranges::fill_n. At the same time, this patch relaxes the overly conservative __is_byte<_Tp>::__value check that requires the fill type be a byte type. It's overly conservative because it means we won't enable the memset optimization in the following example char c[100]; ranges::fill(c, 37); because the fill type is deduced to be int here. Rather than requiring that the fill type be a byte type, it seems safe to just require the fill type be an integral type, which is what this patch does. libstdc++-v3/ChangeLog: PR libstdc++/94017 * include/bits/ranges_algobase.h (__fill_n_fn::operator()): Refine condition for when to use memset, making sure to additionally check that the output pointer's value type is a non-volatile byte type. Instead of requiring that the fill type is a byte type, just require that it's an integral type. * testsuite/20_util/specialized_algorithms/uninitialized_fill/94017.cc: New test. * testsuite/20_util/specialized_algorithms/uninitialized_fill_n/94017.cc: New test. * testsuite/25_algorithms/fill/94013.cc: Uncomment part that was blocked by PR 94017. * testsuite/25_algorithms/fill/94017.cc: New test. * testsuite/25_algorithms/fill_n/94017.cc: New test.
