Hi Yonghong. > On 12/15/22 10:43 AM, Jose E. Marchesi wrote: >> Of the two problems discussed: >> 1. DW_TAG_LLVM_annotation not being able to denote annotations to >> non-pointed based types. clang currently ignores these instances. >> We discussed two possible options to deal with this: >> 1.1 To continue ignoring these cases in the front-end, keep the dwarf >> expressiveness limitation, and document it. >> 1.2 To change DW_TAG_LLVM_annotation so it behaves like a qualifier >> DIE (like const, volatile, etc.) so it can apply to any type. > > Thanks for the detailed update. Yes, we do want to __tag behaving like > a qualifier. > > Today clang only support 'base_type <type_tag> *' style of code. > But we are open to support non-pointer style of tagging like > 'base_type <type_tag> global_var'. Because of this, the following > dwarf output should be adopted: > C: int __tag1 * __tag2 * p; > dwarf: ptr -> __tag2 --> ptr -> __tag1 -> int > or > C: int __tag1 g; > dwarf: var_g -> __tag1 --> int > > The above format *might* require particular dwarf tools to add support > for __tag attribute. But I think it is a good thing in the long run > esp. if we might add support to non-pointer types. In current > implementation, dwarf tools can simply ignore the children of ptr > which they may already do it. I wonder, since these annotations are atomic, is there a reason for not using an attribute instead of a DIE tag? Something like DW_AT_annotation. The attribute could then be used by any DIE (declaration, type, ...) and existing DWARF consumers that don't support the new attribute would happily just ignore it.
