https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115399

--- Comment #4 from GCC 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:bd3a312728fbf8c35a09239b9180269f938f872e

commit r15-1213-gbd3a312728fbf8c35a09239b9180269f938f872e
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Mon Jun 10 14:08:16 2024 +0100

    libstdc++: Fix std::tr2::dynamic_bitset shift operations [PR115399]

    The shift operations for dynamic_bitset fail to zero out words where the
    non-zero bits were shifted to a completely different word.

    For a right shift we don't need to sanitize the unused bits in the high
    word, because we know they were already clear and a right shift doesn't
    change that.

    libstdc++-v3/ChangeLog:

            PR libstdc++/115399
            * include/tr2/dynamic_bitset (operator>>=): Remove redundant
            call to _M_do_sanitize.
            * include/tr2/dynamic_bitset.tcc (_M_do_left_shift): Zero out
            low bits in words that should no longer be populated.
            (_M_do_right_shift): Likewise for high bits.
            * testsuite/tr2/dynamic_bitset/pr115399.cc: New test.

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