Re: [RFC] fixing extract_struct_value_address

[Daniel Jacobowitz <drow at mvista dot com>]

On Wed, Aug 21, 2002 at 03:48:37PM -0700, Michael Snyder wrote:
> Problem: Find a function's return value when it is a struct 
> returned by reference (thru a pointer).
> 
> Solution level one: Take the value of the register that was
> used by the caller to pass the struct return address.
> 
> Shortcoming: that register isn't preserved, so may be clobbered.
> 
> Solution level two: Save the struct_return address when it
> is passed to store_struct_return (or push_arguments), and
> recover it when it is needed by extract_struct_value_address.
> 
> Shortcoming: Not reentrant.  Nested function calls will clobber it.
> 
> Proposed solution: create a stack structure, and "push" the
> struct_return address in store_struct_return, popping it in
> extract_return_address.  If you can't find it on the stack, 
> then use the value of the appropriate arg0 register.
> 
> I think this should work for most targets, so the code for
> managing the stack can be shared.
> 
> What do you think?

Sharing the solution to this across targets would be a good step
forward - I just had to use the same hack for another port.  You want
to be careful of functions which don't return (either GDB is activated
inside the called function and the expression is never finished, or we
longjmp out, or something...) but I believe there's somewhere that
already tries to figure these things out...

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer