Re: [PATCH v14 3/4] Add support for lookup, overload resolution and invocation of C++ debug methods

[Doug Evans <dje at google dot com>]

Siva Chandra writes:
 > Attached is the v14 of this part of the patch series. This version
 > addresses a concern raised by Doug during his v12/v13 review.

Hi.

I've been playing with the patch set a bit.

Another issue I have is this bit of code in, e.g., value_x_binop:

  value_user_defined_op (&arg1, argvec + 1, tstr, &static_memfuncp, 2,
			 &argvec[0], &dm_worker);

  if (argvec[0])
    {
      if (static_memfuncp)
	{
	  argvec[1] = argvec[0];
	  argvec++;
	}
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  struct type *return_type;

	  return_type
	    = TYPE_TARGET_TYPE (check_typedef (value_type (argvec[0])));
	  return value_zero (return_type, VALUE_LVAL (arg1));
	}
      return call_function_by_hand (argvec[0], 2 - static_memfuncp,
				    argvec + 1);
    }
  if (dm_worker != NULL)
    {
      struct cleanup *dm_worker_cleanup = make_cleanup (xfree, dm_worker);
      struct value *ret_val = invoke_debug_method (dm_worker, arg1, &arg2, 1);

      do_cleanups (dm_worker_cleanup);
      return ret_val;
    }

Does this mean we call the debug method (assuming it wins) for the
case of noside == EVAL_AVOID_SIDE_EFFECTS?

Here and elsewhere there's logic that the debug method code is not
being included in, and it makes me want to do things differently.

Fortunately, I think (though I haven't implemented it) it won't be hard.
Just like we have TYPE_CODE_INTERNAL_FUNCTION we could also have
TYPE_CODE_EXTERNAL_FUNCTION, and use that to make debug methods less
special case.
clone_debug_method_worker could return a struct value that is a
TYPE_CODE_EXTERNAL_FUNCTION, and then just before the call to
call_function_by_hand that would happen for normal methods,
we'd have a check for TYPE_CODE_EXTERNAL_FUNCTION and call
call_debug_method instead.

This would be akin to this code in eval.c:

      if (TYPE_CODE (value_type (argvec[0])) == TYPE_CODE_INTERNAL_FUNCTION)
	return call_internal_function (exp->gdbarch, exp->language_defn,
				       argvec[0], nargs, argvec + 1);

      return call_function_by_hand (argvec[0], nargs, argvec + 1);

[I know the function to do this is currently named invoke_debug_method
but Consistency Is Good makes me want to have:
call_function_by_hand, call_internal_function, and call_debug_method
instead of:
call_function_by_hand, call_internal_function, and invoke_debug_method.]

This might(!) then let us remove the dm_worker arg to find_overload_match.
If a debug method is found *valp is a TYPE_CODE_EXTERNAL_FUNCTION
instead of a TYPE_CODE_FUNC.

Thoughts?