[Bug tree-optimization/100366] [11/12/13 Regression] spurious warning - std::vector::clear followed by std::vector::insert(vec.end(), ...) with -O2

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100366

--- Comment #16 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:cca06f0d6d76b08ed4ddb7667eda93e2e9f2589e

commit r13-4393-gcca06f0d6d76b08ed4ddb7667eda93e2e9f2589e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Nov 29 15:50:06 2022 +0000

    libstdc++: Avoid bogus warning in std::vector::insert [PR107852]

    GCC assumes that any global variable might be modified by operator new,
    and so in the testcase for this PR all data members get reloaded after
    allocating new storage. By making local copies of the _M_start and
    _M_finish members we avoid that, and then the compiler has enough info
    to remove the dead branches that trigger bogus -Warray-bounds warnings.

    libstdc++-v3/ChangeLog:

            PR libstdc++/107852
            PR libstdc++/106199
            PR libstdc++/100366
            * include/bits/vector.tcc (vector::_M_fill_insert): Copy
            _M_start and _M_finish members before allocating.
            (vector::_M_default_append): Likewise.
            (vector::_M_range_insert): Likewise.