Identifying bottom-of-stack

[Andrew Cagney]

> [Andrew says:]
> 
>>>> >    > - GLIBC marking those outermost frames with CFI indicating that both the 
>>>> >    > CFA and the RA are "unknown"?
>>
>>> 
>>> s/unknown/undefined/
> 
> 
> Perhaps this addresses Mark's request for precision in terminology, but it
> doesn't clarify anything for me.  Does this "undefined" mean the
> "undefined" used in the DWARF spec?  Does DW_CFA_def_cfa with some register +
> DW_CFA_undefined on that register in fact yield this?  Is that the only way
> to produce it?

Yes.  CFA's "undefined", that would yield what we need.

 > Is it the optimal way?

I don't know.

> These are the questions I meant to imply when I asked,
> "What would such CFI look like exactly?" 
> 
> If you want me to do it, step one is always to specify it completely.

I gather that no one's found a hole in the theory, I guess it is time to 
prototype it in, I guess, GDB's testsuite.

Andrew