Re: [RFA] Repost ARM frame patches

[Daniel Jacobowitz <drow@mvista.com>]

On Tue, Sep 02, 2003 at 11:52:26PM +0100, Richard Earnshaw wrote:
> Daniel,
> 
> My appologies for not reviewing this before.  Just way too much day job...
> 
> It looks fine to me (at least, it seems better than what's there at 
> present).
> 
> My only question is, once we start using the dwarf2 unwinder, can it cope 
> with the fact that gcc currently does not emit frame unwind information 
> for Thumb code? (ie can it handle a mix of code that uses dwarf2 and 
> traditional unwinding?)

I was going to say yes, but...

drow@nevyn:/big/fsf/projects/arm/obj/gdb/testsuite/interwork% readelf -wf test1.o
The section .debug_frame contains:

00000000 0000000c ffffffff CIE
  Version:               1
  Augmentation:          ""
  Code alignment factor: 1
  Data alignment factor: -4
  Return address column: 14

  DW_CFA_def_cfa: r13 ofs 0

00000010 0000000c 00000000 FDE cie=00000000 pc=00000000..0000001c

00000020 0000000c 00000000 FDE cie=00000000 pc=0000001c..00000046


i.e. GCC emits _empty_ dwarf unwind information for thumb functions,
rather than none at all.  That's unlikely to work.  We'd need to modify
the dwarf2 unwinder to ignore empty FDEs.

I'll check in the non-dwarf parts now, and then we can figure out what
to do about that.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer