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Re: [RFC] Supporting alternative ABIs

Corinna Vinschen <> writes:

  gdbarch_push_dummy_code gdbarch methods would be changed to expect
  the type of the function, not the type of its return value.  They
  can use TYPE_TARGET_TYPE to get the return value type, but this will
  also give them access to the `calling_convention' for the function type.

- gdbarch_push_dummy_call and EXTRACT_STRUCT_VALUE_ADDRESS would
  receive the function's type as an additional argument, to give them
  access to the function's calling convention information.

- USE_STRUCT_CONVENTION and gdbarch_push_dummy_code would not require
  the `gcc_p' and `using_gcc' flags anymore since this information
  is now given in the function type node.  Due to the way,
  gdbarch_parse_dwarf2_calling_convention evaluates the `calling_convention'
  value, all inferior call-related gdbarch methods could simply trust its

I was working on the (32-bit) SPARC target today, and wished I had the
function type available, so I'm positive this would be a good move.

... so seconded.

Going through them:

I'd rename the existing USE_STRUCT_CONVENTION to DEPRECATED_USE_STRUCT_CONVENTION and then introduce new arch method gdbarch_use_struct_convention (gdbarch, struct type *func) that defaults to the old.

Similar. The struct_return parameter is now very redundant (the assertions "struct_return == new USE_STRUCT_CONVENTION (new function parameter)", and "(struct_return != 0) == (STRUCT_ADDR != 0)" should hold).

Is this one needed? Instead always use EXTRACT_RETURN_VALUE to obtain the return value. Renaming this to DEPRECATED_STRUCT_VALUE_ADDRESS_V2.

Rename the existing to deprecated_store_return_value_v2? Anyway, looking at set_return_value(), I think the replacement's default implementation should incorporate both of:
  if (code == TYPE_CODE_STRUCT
      || code == TYPE_CODE_UNION)       /* FIXME, implement struct return.  */
    error ("GDB does not support specifying a struct or union return value.");

STORE_RETURN_VALUE (type, current_regcache, VALUE_CONTENTS (val));
some ABI's allow struct return, some don't. Generic code shouldn't be making the decision.

Rename the existing to deprecated_extract_return_value_v2? Looking at value_being_returned, and given the comment above on EXTRACT_STRUCT_VALUE_ADDRESS, I think the default method should contain much of the existing value_being_returned function.


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