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. Jason
