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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/100366] [11/12 Regression] spurious warning -
 std::vector::clear followed by std::vector::insert(vec.end(), ...) with -O2
Date: Thu, 20 Apr 2023 13:57:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100366

--- Comment #17 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:2e4210698c644e44f9e0645dc7bc49710fd60ce8

commit r12-9457-g2e4210698c644e44f9e0645dc7bc49710fd60ce8
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.

    (cherry picked from commit cca06f0d6d76b08ed4ddb7667eda93e2e9f2589e)=