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Re: Unwinding CFI gcc practice of assumed `same value' regs


>  Ian Lance Taylor writes:
>   > Andrew Haley <aph@redhat.com> writes:
>   >
>   > > In practice, %ebp either points to a call frame -- not necessarily
>  the
>   > > most recent one -- or is null.  I don't think that having an optional
>   > > frame pointer mees you can use %ebp for anything random at all, but
>  we
>   > > need to make a clarification request of the ABI.
>   >
>   > I don't see that as feasible.  If %ebp/%rbp may be used as a general
>   > callee-saved register, then it can hold any value.
>
>  Sure, we already know that, as has been clear.  The question is *if*
>  %rbp may be used as a general callee-saved register that can hold any
>  value.

The amd64 ABI is specifically *designed* to allow this.

Mark


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