[Bug c++/98770] [modules] including certain stdlib headers in the global module fragment of different modules causes conflicting global module declarations

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98770

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathan Sidwell <nathan@gcc.gnu.org>:

https://gcc.gnu.org/g:af66f4f1b06f5e0c099dfced2fcf7b1b23fa53e7

commit r11-6954-gaf66f4f1b06f5e0c099dfced2fcf7b1b23fa53e7
Author: Nathan Sidwell <nathan@acm.org>
Date:   Thu Jan 28 04:48:33 2021 -0800

    c++: header unit template alias merging [PR 98770]

    Typedefs are streamed by streaming the underlying type, and then
    recreating the typedef.  But this breaks checking a duplicate is the
    same as the original when it is a template alias -- we end up checking
    a template alias (eg __void_t) against the underlying type (void).
    And those are not the same template alias.  This stops pretendig that
    the underlying type is the typedef for that checking and tells
    is_matching_decl 'you have a typedef', so it knows what to do.  (We do
    not want to recreate the typedef of the duplicate, because that whole
    set of nodes is going to go away.)

            PR c++/98770
            gcc/cp/
            * module.cc (trees_out::decl_value): Swap is_typedef & TYPE_NAME
            check order.
            (trees_in::decl_value): Do typedef frobbing only when installing
            a new typedef, adjust is_matching_decl call.  Swap is_typedef
            & TYPE_NAME check.
            (trees_in::is_matching_decl): Add is_typedef parm. Adjust variable
            names and deal with typedef checking.
            gcc/testsuite/
            * g++.dg/modules/pr98770_a.C: New.
            * g++.dg/modules/pr98770_b.C: New.