On Fri, Nov 03, 2017 at 12:19:05PM -0400, Jason Merrill wrote:
> On Fri, Nov 3, 2017 at 9:55 AM, Marek Polacek <pola...@redhat.com> wrote:
> > + TYPE_EMPTY_P (t) = targetm.calls.empty_record_p (t);
>
> I think we want to set this in finalize_type_size; since the point of
> all this is becoming compliant with the psABI (and compatible with the
> C front end), I wouldn't think it should be specific to the C++ front
> end.
Sure, that works. I'd wanted to do the TYPE_EMPTY_P setting in layout_type,
but that wasn't called for the classes in my testcases. I've moved the
setting of TYPE_EMPTY_P to finalize_type_size now.
> > + TYPE_WARN_EMPTY_P (t) = warn_abi && abi_version_crosses (12);
>
> Can this flag go on the TRANSLATION_UNIT_DECL rather than the type?
Yeah, that works, too. To avoid needing a lang hook, I'm setting the
flag in cxx_init_decl_processing, hope that's ok.
> > + if (TREE_CODE (field) == FIELD_DECL
> > + && (DECL_NAME (field)
> > + || RECORD_OR_UNION_TYPE_P (TREE_TYPE (field)))
> > + && !default_is_empty_type (TREE_TYPE (field)))
> > + return false;
> > + return true;
>
> Hmm, this assumes that any unnamed field can be ignored; I'm concerned
> that some front end might clear DECL_NAME for a reason that doesn't
> imply that the field is just padding.
In that case I guess we need a new lang hook, right? Because in
default_is_empty_type we can't check FE-specific flags such as
DECL_C_BIT_FIELD. For C++, should that lang hook be just
is_really_empty_class? Or is there anything else I can do?
Marek
