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Re: think-o: dwarf2 CFA != frame->frame (x86-64)
- From: Daniel Berlin <dan at dberlin dot org>
- To: Andrew Cagney <ac131313 at cygnus dot com>
- Cc: gdb at sources dot redhat dot com
- Date: Tue, 9 Apr 2002 15:42:35 -0400 (EDT)
- Subject: Re: think-o: dwarf2 CFA != frame->frame (x86-64)
On Tue, 9 Apr 2002, Andrew Cagney wrote:
> >> Please re-read what I wrote.
> > You said " The problem is that this algorithm assumes that each frame uses
> > the same mechanism for locating register values. With
> > the introduction of dwarf2cfi, this is no longer
> > true. Some frames may use the debug info while others may use the
> > old prologue analysis technique.
> > "
> > You are incorrect.
> We're going to have to agree to disagree.
> > It's an either-or case. Never is their a mixture of methods, unless you do
> > something illegal.
> If GDB decides to do what you state, it will be incapable of unwinding
> through libraries (where there is no debug info).
Libraries have debug info as well.
Even those without debug info, can still have dwarf2 frame info.
Most do these days.
You just don't realize it.
The default libc that came with my ppc linux distribution contains unwind
info for all routines, fer instance. It's glibc 2.2.4 based, for the
curious. I installed this distribution a *while* ago, so it's not a
All the libraries have unwind info as well.
No debug info, just unwind info.
> I think that is a significant feature loss and one I don't consder
Who says you have lost a feature?
> I see no reason why GDB shouldn't act ``illegally'' and use the
> traditional prolog scanner as a fallback to debug info.
Now you've twisted my words.
I said it would be illegal to attempt to use .eh_frame under the
assumption it contains unwind info for all routines. It might, it might
I said nothing about prolog scanning, besides that it is unnecessary when
the dwarf2 unwind info is present.