[PATCH] RTEMS: Use strict DWARF-2 on ARM, PowerPC, SPARC

Chris Johns chrisj at rtems.org
Tue Jun 18 23:54:56 UTC 2013

Sebastian Huber wrote:
> Some debuggers do not cope with the new DWARF3/4 debug format introduced
> with GCC 4.8.  Default to strict DWARF-2 on ARM, PowerPC and SPARC for
> now.
> This patch should be committed to GCC 4.8 and 4.9.

I am not convinced about this change on technical grounds. When I say I 
am not convinced, I am not sure what we gain and what we give up and I 
would like to understand that a little better before agreeing to it.

I should also point out I am using ARM with gcc-4.8.1 and gdb-7.6 and it 
is working well (my OpenOCD changes need more work) and any change to 
DWARF2 that alters this would be a regression.

I have taken a look at the differences between DWARF2, DWARF3 and 
DWARF4. There is better language support in the later versions and debug 
data compression. These improvements are nice. What I am not sure about 
is the way limiting gcc to DWARF2 effects the debugging experience. If 
the flag is just a format change and the experience is the same that is 
ok, if however the C++ or C debugging experience is reduced that would 
be a regression.

My major concern is locking us into this and it being forgotten and we 
sit on DWARF2 for ages and we do not see or notice regressions related 
to DWARF3/4 when it breaks on these archs. Can ARM/PowerPC/SPARC tools 
be built with a target option that limits the target libraries to DWARF2 ?

Did a gdb bug get raised about the DWARF read error reported on the 
mailing list ?


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