[Bug c++/115223] [15 regression] ICE when building KDE kontrast with LTO (error: ‘TYPE_CANONICAL’ has different ‘TYPE_CANONICAL’) since r15-779-g3c98d06a9016a0

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115223

--- Comment #4 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:58b8c87b7fb281e35a6817cc91a292096fdc02dc

commit r15-892-g58b8c87b7fb281e35a6817cc91a292096fdc02dc
Author: Patrick Palka <ppalka@redhat.com>
Date:   Wed May 29 04:49:37 2024 -0400

    c++: canonicity of fn types w/ instantiated eh specs [PR115223]

    When propagating structural equality in build_cp_fntype_variant, we
    should consider structural equality of the exception-less variant, not
    of the given type which might use structural equality only because it
    has a (complex) noexcept-spec that we're intending to replace, as in
    maybe_instantiate_noexcept which calls build_exception_variant using
    the deferred-noexcept function type.  Otherwise we might pessimistically
    use structural equality for a function type with a simple instantiated
    noexcept-spec, leading to a LTO-triggered type verification failure if we
    later use that (structural-equality) type as the canonical version of
    some other variant.

            PR c++/115223

    gcc/cp/ChangeLog:

            * tree.cc (build_cp_fntype_variant): Propagate structural
            equality of the exception-less variant.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp0x/noexcept87.C: New test.

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