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Re: [RFC] fixing extract_struct_value_address
- From: Jim Blandy <jimb at redhat dot com>
- To: Michael Snyder <msnyder at redhat dot com>
- Cc: gdb-patches at sources dot redhat dot com, kevinb at redhat dot com, cagney at redhat dot com
- Date: 22 Aug 2002 00:32:27 -0500
- Subject: Re: [RFC] fixing extract_struct_value_address
- References: <3D6418C5.FBF117D@redhat.com>
Michael Snyder <msnyder@redhat.com> writes:
> 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.
Doesn't this stack push and pop exactly as the generic dummy frame
stack does? Couldn't we just add a `struct_return_addr' field to
`struct dummy_frame'?