[flang-commits] [flang] [flang][debug] Support ClassType. (PR #114809)

[Abid Qadeer via flang-commits]

abidh wrote:

> DW_TAG_dynamic_type



> he `fir.class` type is used for polymorphic entities (including unlimited polymorphic entities, `CLASS(*)`).
> 
> Does DWARF provide support for querying the dynamic type at runtime?
> 
> I saw dwarf has a DW_TAG_dynamic_type tag, but that seems related to POINTER/ALLOCATABLE length parametrized derived types rather than polymorphism.

Sorry I missed this comment earlier. I agree that `DW_TAG_dynamic_type` does not seem to be intended for polymorphism. I have noticed that gfortran uses an artificial type in such cases which have a data, vptr and len field. I was thinking that we can also use a type that exposes `elem_len` and `type` field from the descriptor.

```
(gdb) ptype p_t2
type = Type __class__STAR_p
    PTR TO -> ( void :: _data )
    PTR TO -> ( Type __vtype__STAR :: _vptr )
    integer(kind=8) :: _len
End Type __class__STAR_p
```

https://github.com/llvm/llvm-project/pull/114809