[Bug c++/112899] odr-using constexpr static data member of class exported from module results in linker error

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112899

--- Comment #2 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:a71c3977d24722ac8ee28d8844c4f96a151f75ab

commit r14-6979-ga71c3977d24722ac8ee28d8844c4f96a151f75ab
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Wed Jan 3 09:28:43 2024 +1100

    c++: Fix ICE when writing nontrivial variable initializers

    The attached testcase Patrick found in PR c++/112899 ICEs because it is
    attempting to write a variable initializer that is no longer in the
    static_aggregates map.

    The issue is that, for non-header modules, the loop in
    c_parse_final_cleanups prunes the static_aggregates list, which means
    that by the time we get to emitting module information those
    initialisers have been lost.

    However, we don't actually need to write non-trivial initialisers for
    non-header modules, because they've already been emitted as part of the
    module TU itself.  Instead let's just only write the initializers from
    header modules (which skipped writing them in c_parse_final_cleanups).

    gcc/cp/ChangeLog:

            * module.cc (trees_out::write_var_def): Only write initializers
            in header modules.

    gcc/testsuite/ChangeLog:

            * g++.dg/modules/init-5_a.C: New test.
            * g++.dg/modules/init-5_b.C: New test.

    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>