[Bug libstdc++/111327] std::bind_front (and std::not_fn) doesn't always perfectly forward according to value category of the call wrapper object

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111327

--- Comment #3 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:4289f6ceefe74ea46e792692448c06197ac20c86

commit r14-3902-g4289f6ceefe74ea46e792692448c06197ac20c86
Author: Patrick Palka <ppa...@redhat.com>
Date:   Tue Sep 12 11:23:12 2023 -0400

    libstdc++: Fix std::bind_front perfect forwarding [PR111327]

    In order to properly implement a perfect forwarding call wrapper (without
    C++23 deducing 'this') we need a total of 8 operator() overloads, 4
    enabled ones and 4 deleted ones, i.e. two for each const/ref qual pair,
    as described in section 5.5 of P0847R6.  Otherwise the wrapper may not
    do the right thing if the underlying function object has a deleted
    const/ref-qualified operator() overload.  This patch fixes this issue in
    std::bind_front.

            PR libstdc++/111327

    libstdc++-v3/ChangeLog:

            * include/std/functional (_Bind_front::operator()): Add deleted
            fallback overloads for each const/ref qualifier pair.  Give the
            enabled overloads dummy constraints to make each one more
            specialized than the corresponding deleted overload.
            * testsuite/20_util/function_objects/bind_front/111327.cc: New
test.