[Bug c++/86491] bogus and unsuppressible warning: 'YYY' has a base 'ZZZ' whose type uses the anonymous namespace

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86491

--- Comment #14 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:8ef5fa4c56c82dfbd6e8fc5e4e08c4be843abc3e

commit r13-2627-g8ef5fa4c56c82dfbd6e8fc5e4e08c4be843abc3e
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jun 30 17:53:26 2022 +0100

    c++: Refer to internal linkage for -Wsubobject-linkage [PR86491]

    Since C++11 relaxed the requirement for template arguments to have
    external linkage, it's possible to get -Wsubobject-linkage warnings
    without using any anonymous namespaces. This confuses users when they
    get diagnostics that refer to an anonymous namespace that doesn't exist
    in their code.

    This changes the diagnostic to say "has internal linkage" for C++11 and
    later, if the type isn't actually a member of the anonymous namespace.
    Making that distinction involved renaming the current decl_anon_ns_mem_p to
    something that better expresses its semantics.

    For C++98 template arguments declared with 'static' are ill-formed
    anyway, so the only way this warning can arise is via anonymous
    namespaces. That means the existing wording is accurate for C++98 and so
    we can keep it.

            PR c++/86491

    gcc/cp/ChangeLog:

            * decl2.cc (constrain_class_visibility): Adjust wording of
            -Wsubobject-linkage for cases where anonymous
            namespaces aren't used.
            * tree.cc (decl_anon_ns_mem_p): Now only true for actual anonymous
            namespace members, rename old semantics to...
            (decl_internal_context_p): ...this.
            * cp-tree.h, name-lookup.cc, pt.cc: Adjust.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/anonymous-namespace-3.C: Use separate dg-warning
            directives for C++98 and everything else.
            * g++.dg/warn/Wsubobject-linkage-5.C: New test.