[Bug c/86453] [8/9 Regression] error: type variant differs by TYPE_PACKED in free_lang_data since r255469

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86453

--- Comment #6 from rguenther at suse dot de <rguenther at suse dot de> ---
On July 11, 2018 8:12:17 PM GMT+02:00, "msebor at gcc dot gnu.org"
<gcc-bugzilla@gcc.gnu.org> wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86453
>
>--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
>The attribute exclusion framework only excludes conflicting attributes
>if they
>aren't applied by their handler.  It doesn't know how to undo changes
>that the
>handler makes, like modifying tree nodes in place.  It would need to be
>extended to also let each handler detect the conflicts before making
>these
>kinds of changes.

Note that no_add_attr doesn't mean the attribute isn't applied. Instead some
attributes are optimized and translated to tree flags. There isn't really a way
the handler can signal the attribute wasn't applied.