[Bug libstdc++/94354] std::reverse_iterator comparison operators defined incorrectly

cvs-commit at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Wed May 27 20:59:24 GMT 2020


--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:


commit r11-672-g979e89a9a94f66241fa8355e2b2e8f4a680c83e1
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed May 27 21:58:56 2020 +0100

    libstdc++: Fix std::reverse_iterator comparisons (PR 94354)

    The std::reverse_iterator comparisons have always been implemented only
    in terms of equality and less than. In C++98 that made no difference for
    reasonable code, because when the underlying operators are the same type
    they are required to support all comparisons anyway.

    But since LWG 280 it's possible to compare reverse_iterator<X> and
    reverse_iterator<Y>, and comparisons between X and Y might not support
    the full set of equality and relational operators. This means that it
    matters whether we implement operator!= as x.base() != y.base() or
    !(x.base() == y.base()), and the current implementation is

    This was already fixed in GCC 10.1 for C++20, this change also fixes it
    for all other -std modes.

            PR libstdc++/94354
            * include/bits/stl_iterator.h (reverse_iterator): Fix comparison
            operators to use the correct operations on the underlying
            * testsuite/24_iterators/reverse_iterator/rel_ops.cc: New test.

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