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From: Mark Kettenis <mark.kettenis@xs4all.nl>
To: aristovski@qnx.com
CC: gdb@sources.redhat.com
In-reply-to: <g264bk$5bo$1@ger.gmane.org> (message from Aleksandar Ristovski 	on Wed, 04 Jun 2008 09:12:20 -0400)
Subject: Re: Frame lost after 'leave' and before 'ret' instruction on i386?
References: <482DA814.7030703@qnx.com> 	 <20080516155828.GA31038@caradoc.them.org> <48358355.7050500@qnx.com> 	 <20080522143936.GA32221@caradoc.them.org>  <48358860.5010703@qnx.com> <1211479573.3601.84.camel@localhost.localdomain> <4836E0A7.8050800@qnx.com> <g264bk$5bo$1@ger.gmane.org>
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> From: Aleksandar Ristovski <aristovski@qnx.com>
> Date:  Wed, 04 Jun 2008 09:12:20 -0400
> 
> Any comments on this? 

Isn't it possible to do this by adding a "normal" unwinder?  It should
be properly stacked such that it is checked before the dwarf unwinder
of course.  You can check the frame level to short-circuit things the
same way as your diff does.

Adding a hook in the sentinel frame stuff feels wrong...

> Aleksandar Ristovski wrote:
> > Hello,
> > The patch is an attempt to solve the issue from the subject. It 
> > introduces a check for in_function_epilogue_p and introduces 
> > architecture level prev_register_from_epilogue.
> > 
> > The patch is a draft (works but is not complete).
> > Rationale: Dealing with epilogue in frame unwinders needs to be done 
> > only in sentinel frame (older frames will never be in epilogue).
> > Comments appreciated.
> > 
> > 
> > Thanks,
> > 
> > Aleksandar Ristovski
> > QNX Software Systems
> > 
> > 
> > ChangeLog (for reference only):
> > 
> >     * gdbarch.c, gdbarch.h: Regenerated.
> >     * gdbarch.sh: Introduce gdbarch_prev_frame_from_epilogue and provide
> >     default_prev_frame_from_epilogue.
> >     * i386-tdep.c (i386_in_function_epilogue_p, 
> >     i386_prev_register_from_epilogue): New functions.
> >     (struct frame_unwind_cache): Struct definition.
> >     (i386_gdbarch_init): Register i386_prev_register_from_epilogue and
> >     i386_in_function_epilogue_p.
> >     * sentinel-frame.c (sentinel_frame_prev_register): Check if we are
> >     in epilogue and if so, call gdbarch provided prev_frame_from_epilogue.
> >     If this returns NULL do as before.
> > 
> 
> 
>