[PATCH] i386: Don't use frame pointer without stack access

[Michael Matz]

Hi,

On Mon, 7 Aug 2017, H.J. Lu wrote:

> >> [hjl@gnu-tools-1 pr81736]$
> >>
> >> Does it mean clang is broken?
> >
> > In my book, yes.
> 
> Does GCC do this for all targets or just x86?

No idea.  If so I'd say those other targets are broken as well (as long as 
the concept of frame pointer makes sense on them, their ABI defines one 
but leaves it optional and something like an unwinder could make use of 
it).

> I am looking for a run-time test which breaks unwinder.

I don't have one handy.  Idea: make two threads, one endlessly looping in 
the "frame-less" function, the other causing a signal to the first thread, 
and the signal handler checking that unwinding up to caller of 
frame_less() is possible via %[er]bp chaining.


Ciao,
Michael.