Re: [RFC] fixing extract_struct_value_address

[Andrew Cagney <ac131313@ges.redhat.com>]

> I get the feeling that all that is needed is for the above to be enabled
>> for all targets.
>> 
>> enjoy,
>> Andrew
> 
> 
> Wouldn't that only work for targets that return the value on the stack?
> Those targets already work properly (I think the 386 is one).
> I'm concerned here with targets where the struct is returned
> by reference (thru a pointer provided by the caller.)

See:

/* elz: I defined this new macro for the hppa architecture only.
    this gives us a way to get the value returned by the function from 
the stack,
    at the same address we told the function to put it.
    We cannot assume on the pa that r28 still contains the address of 
the returned
    structure. Usually this will be overwritten by the callee.
    I don't know about other architectures, so I defined this macro
  */

The comment appears to describe a situtation identical to yours.

As for the more generic problem, per:

> Discussed before in:
> 
> http://sources.redhat.com/ml/gdb-patches/2001-11/msg00571.html
> and
> http://sources.redhat.com/ml/gdb-patches/2001-12/msg00325.html
> 
> never resolved.
> 
> Elena

My understanding is that, for some ABIs, it just isn't possible to find 
the address of the returned value (unless debug info (cfi?) somehow 
helps).  For such cases, I think EXTRACT_STRUCT_VALUE_ADDRESS() should 
return zero.

enjoy,
Andrew