[Bug c++/114104] nodiscard not diagnosed on synthesized operator!=

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114104

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:144b6099cdaa9ac1b298687c0cfdb06a970e338b

commit r15-2118-g144b6099cdaa9ac1b298687c0cfdb06a970e338b
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed Jul 17 20:57:54 2024 -0400

    c++: missing -Wunused-value for !<expr> [PR114104]

    Here we're neglecting to issue a -Wunused-value warning for suitable !
    operator expressions, and in turn for != operator expressions that are
    rewritten as !(x == y), only because we don't call warn_if_unused_value
    on TRUTH_NOT_EXPR since its class is tcc_expression.  This patch makes
    us also consider warning for TRUTH_NOT_EXPR and also for ADDR_EXPR.

            PR c++/114104

    gcc/cp/ChangeLog:

            * cvt.cc (convert_to_void): Call warn_if_unused_value for
            TRUTH_NOT_EXPR and ADDR_EXPR as well.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Wunused-20.C: New test.

    Reviewed-by: Jason Merrill <jason@redhat.com>