[Bug c++/53932] [10 Regression] C++ reference variable to member of anonymous union in global is error

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53932

--- Comment #17 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:04cf6b57c7c467f615a16b7bbda574671e3fb2df

commit r10-11356-g04cf6b57c7c467f615a16b7bbda574671e3fb2df
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Jan 19 23:27:34 2023 +0100

    c++: Fix up handling of references to anon union members in initializers
[PR53932]

    For anonymous union members we create artificial VAR_DECLs which
    have DECL_VALUE_EXPR for the actual COMPONENT_REF.  That works
    just fine inside of functions (including global dynamic constructors),
    because during gimplification such VAR_DECLs are gimplified as
    their DECL_VALUE_EXPR.  This is also done during regimplification.

    But references to these artificial vars in DECL_INITIAL expressions
    aren't ever replaced by the DECL_VALUE_EXPRs, so we end up either
    with link failures like on the testcase below, or worse ICEs with
    LTO.

    The following patch fixes those during cp_fully_fold_init where we
    already walk all the trees (!data->genericize means that
    function rather than cp_fold_function).

    2023-01-19  Jakub Jelinek  <jakub@redhat.com>

            PR c++/53932
            * cp-gimplify.c (cp_fold_r): During cp_fully_fold_init replace
            DECL_ANON_UNION_VAR_P VAR_DECLs with their corresponding
            DECL_VALUE_EXPR.

            * g++.dg/init/pr53932.C: New test.

    (cherry picked from commit 9b9a989adc042b304572fd6d4ade46b47be6ccb8)