[Bug c++/105320] Use of shared_ptr within a type exported from a module results in spurious compiler error

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105320

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathaniel Shead <nshead@gcc.gnu.org>:

https://gcc.gnu.org/g:b5f6a56940e70838a07e885de03a92e2bd64674a

commit r15-59-gb5f6a56940e70838a07e885de03a92e2bd64674a
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Mon Apr 29 17:00:13 2024 +1000

    c++: Fix instantiation of imported temploid friends [PR114275]

    This patch fixes a number of issues with the handling of temploid friend
    declarations.

    The primary issue is that instantiations of friend declarations should
    attach the declaration to the same module as the befriending class, by
    [module.unit] p7.1 and [temp.friend] p2; this could be a different
    module from the current TU, and so needs special handling.

    The other main issue here is that we can't assume that just because name
    lookup didn't find a definition for a hidden class template, that it
    doesn't exist at all: it could be a non-exported entity that we've
    nevertheless streamed in from an imported module.  We need to ensure
    that when instantiating template friend classes that we return the same
    TEMPLATE_DECL that we got from our imports, otherwise we will get later
    issues with 'duplicate_decls' (rightfully) complaining that they're
    different when trying to merge.

    This doesn't appear necessary for function templates due to the existing
    name lookup handling already finding these hidden declarations.

            PR c++/105320
            PR c++/114275

    gcc/cp/ChangeLog:

            * cp-tree.h (propagate_defining_module): Declare.
            (lookup_imported_hidden_friend): Declare.
            * decl.cc (duplicate_decls): Also check if hidden decls can be
            redeclared in this module.
            * module.cc (imported_temploid_friends): New.
            (init_modules): Initialize it.
            (trees_out::decl_value): Write it; don't consider imported
            temploid friends as attached to a module.
            (trees_in::decl_value): Read it.
            (get_originating_module_decl): Follow the owning decl for an
            imported temploid friend.
            (propagate_defining_module): New.
            * name-lookup.cc (get_mergeable_namespace_binding): New.
            (lookup_imported_hidden_friend): New.
            * pt.cc (tsubst_friend_function): Propagate defining module for
            new friend functions.
            (tsubst_friend_class): Lookup imported hidden friends.  Check
            for valid module attachment of existing names.  Propagate
            defining module for new classes.

    gcc/testsuite/ChangeLog:

            * g++.dg/modules/tpl-friend-10_a.C: New test.
            * g++.dg/modules/tpl-friend-10_b.C: New test.
            * g++.dg/modules/tpl-friend-10_c.C: New test.
            * g++.dg/modules/tpl-friend-10_d.C: New test.
            * g++.dg/modules/tpl-friend-11_a.C: New test.
            * g++.dg/modules/tpl-friend-11_b.C: New test.
            * g++.dg/modules/tpl-friend-12_a.C: New test.
            * g++.dg/modules/tpl-friend-12_b.C: New test.
            * g++.dg/modules/tpl-friend-12_c.C: New test.
            * g++.dg/modules/tpl-friend-12_d.C: New test.
            * g++.dg/modules/tpl-friend-12_e.C: New test.
            * g++.dg/modules/tpl-friend-12_f.C: New test.
            * g++.dg/modules/tpl-friend-13_a.C: New test.
            * g++.dg/modules/tpl-friend-13_b.C: New test.
            * g++.dg/modules/tpl-friend-13_c.C: New test.
            * g++.dg/modules/tpl-friend-13_d.C: New test.
            * g++.dg/modules/tpl-friend-13_e.C: New test.
            * g++.dg/modules/tpl-friend-13_f.C: New test.
            * g++.dg/modules/tpl-friend-13_g.C: New test.
            * g++.dg/modules/tpl-friend-14_a.C: New test.
            * g++.dg/modules/tpl-friend-14_b.C: New test.
            * g++.dg/modules/tpl-friend-14_c.C: New test.
            * g++.dg/modules/tpl-friend-14_d.C: New test.
            * g++.dg/modules/tpl-friend-9.C: New test.

    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
    Reviewed-by: Jason Merrill <jason@redhat.com>