[Bug c++/95976] [[no_unique_address]] on union members has the opposite-of-intended effect

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95976

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:3bb330022ce47a3e8966a9930f392e497c608f59

commit r10-8456-g3bb330022ce47a3e8966a9930f392e497c608f59
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jul 9 15:11:12 2020 -0400

    c++: [[no_unique_address]] fixes. [PR96105]

    We were wrongly checking is_empty_class on the result of strip_array_types
    rather than the actual field type.  We weren't considering the alignment of
    the data member.  We needed to handle unions the same way as
    layout_nonempty_base_or_field.

    gcc/cp/ChangeLog:

            PR c++/96105
            PR c++/96052
            PR c++/95976
            * class.c (check_field_decls): An array of empty classes is not an
            empty data member.
            (layout_empty_base_or_field): Handle explicit alignment.
            Fix union handling.

    gcc/testsuite/ChangeLog:

            PR c++/96105
            PR c++/96052
            PR c++/95976
            * g++.dg/cpp2a/no_unique_address4.C: New test.
            * g++.dg/cpp2a/no_unique_address5.C: New test.
            * g++.dg/cpp2a/no_unique_address6.C: New test.