Re: RFA: tolerate unavailable struct return values

[Elena Zannoni <ezannoni at cygnus dot com>]

Jim Blandy writes:
 > > Have you looked at the macro VALUE_RETURNED_FROM_STACK ? I defined that
 > > long time ago for hppa. It looks like the rs6000-tdep.c tries to deal
 > > with the same problem as well.
 > > 
 > > Maybe we should clean up that code, which came in as part of the HP
 > > merge :-(.
 > 
 > Looking at the following code in infcmd.c:
 > 
 >       /* We cannot determine the contents of the structure because
 > 	 it is on the stack, and we don't know where, since we did not
 > 	 initiate the call, as opposed to the call_function_by_hand case */
 > #ifdef VALUE_RETURNED_FROM_STACK
 >       value = 0;
 > #ifdef UI_OUT
 >       ui_out_text (uiout, "Value returned has type: ");
 >       ui_out_field_string (uiout, "return-type", TYPE_NAME (value_type));
 >       ui_out_text (uiout, ".");
 >       ui_out_text (uiout, " Cannot determine contents\n");
 > #else /* UI_OUT */
 >       printf_filtered ("Value returned has type: %s.", TYPE_NAME (value_type));
 >       printf_filtered (" Cannot determine contents\n");
 > #endif /* UI_OUT */
 > #else
 >       value = value_being_returned (value_type, stop_registers, structure_return);
 > 
 > and then at the following code in valops.c:
 > 
 > #ifdef VALUE_RETURNED_FROM_STACK
 >     if (struct_return)
 >       return (value_ptr) VALUE_RETURNED_FROM_STACK (value_type, struct_addr);
 > #endif
 > 
 > the stuff in infcmd.c looks backwards to me.  Wasn't the intention to
 > fall back to printing the type when VALUE_RETURNED_FROM_STACK is *not*
 > defined?

Not all the times, no, it was meant to be only used by hpux. I didn't
have any way to test other targets when I wrote that, so I didn't want
to touch anything else (whether or not such other targets could
display the structre correctly). It should definitely be cleaned up.

 > 
 > TYPE_NAME is just the structure tag; don't we want to print the
 > `struct' or `union' there?  The `type_print' function takes care of
 > that.
 > 

Probably.

 > Frankly, I don't even think it's that useful to print the type.  The
 > user knows what function was called, and can use `ptype' or `whatis'
 > if they want to know the type.

I wanted it to be more informative, and remind the user of what the
result would have been, w/o them having to do an extra step.

Elena