Re: Does GDB 6.7.1 for PowerPC require the framepointer register for backtracing?

[Stefan Bylund <steby@enea.se>]

Hi Daniel,

Thanks for all your valuable answers! We will use -fomit-frame-pointer 
as a workaround for now. Later on we will add support for handling the 
frame pointer register in our OS kernel. That seems to be the 
future-proof solution.

Regards,
Stefan


Daniel Jacobowitz wrote:

>On Mon, Feb 11, 2008 at 06:28:31PM +0100, Stefan Bylund wrote:
>  
>
>>Hi Daniel,
>>
>>Thanks for your information. We use GCC 3.4.4, and when debugging we use  
>>the compiler options -g -O0. I tried to add the compiler option  
>>-fomit-frame-pointer (which seems to be included by -O1 and higher but  
>>not by -O0) and then it works!!! So, my conclusion is that GDB 6.7.1 for  
>>PowerPC tries to take advantage of frame pointer information in the  
>>DWARF-2 debug information while GDB 6.3 does not. Is that correct? Is it  
>>always safe to use -fomit-frame-pointer on PowerPC, i.e. will it not make 
>>some type of C/C++ code undebuggable?
>>    
>>
>
>GDB 6.7 does use DWARF.  GDB 6.3 did not.
>
>It sounds to me like you have a bug in the debug information generated
>by your compiler.  I've seen some other bugs in the unwind tables
>generated by GCC 3.4.x that were fixed in GCC 4.x.
>
>-fomit-frame-pointer should not cause a problem for GDB as long as you
>have valid DWARF information.
>
>  
>


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Stefan Bylund
Senior Software Engineer
Enea
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Mobile: +46 709 71 43 25
stefan.bylund@enea.com
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