On Mon, 6 Nov 2017, Jason Merrill wrote: > On Mon, Nov 6, 2017 at 10:37 AM, Marek Polacek <pola...@redhat.com> wrote: > > 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. > > Sure. > > >> > + 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? > > Hmm, maybe leave it as it is and just document this assumption about > FIELD_DECL with null DECL_NAME, both here and in tree.def.
But are you sure you are not changing the ABI for a language other than C++ then? I don't think DECL_NAME has any special meaning - why not check DECL_ARTIFICIAL or another flag that has appropriate semantic - _what_ semantic are you looking for after all? Thanks, Richard.
