Re: [Libunwind-devel] Crash when unwinding using ARM exidx info

[Fischer, Matt]

Any more thoughts on this?  I put together a patch containing the change I mentioned below, so if everybody does agree that it’s the right fix, you should be able to easily merge it in.  The patch is located at https://github.com/mattfischer/libunwind, branch “unwind-info-free”.  Let me know what you think.

 

--Matt

 

From: Fischer, Matt
Sent: Thursday, May 09, 2013 5:09 PM
To: 'Arun Sharma'
Cc: address@hidden; Tommi Rantala; Ken Werner
Subject: RE: [Libunwind-devel] Crash when unwinding using ARM exidx info

 

I just ran it in a loop on a simple backtrace done using DWARF info, and one done using EXIDX info, and neither of them seems to leak in my test.  But I’m not sure whether there are other edge cases that would need to be examined.

 

From: address@hidden [mailto:address@hidden] On Behalf Of Arun Sharma
Sent: Thursday, May 09, 2013 9:52 AM
To: Fischer, Matt
Cc: address@hidden; Tommi Rantala; Ken Werner
Subject: Re: [Libunwind-devel] Crash when unwinding using ARM exidx info

 

+Ken, Tommi

On Tue, May 7, 2013 at 3:58 PM, Fischer, Matt <address@hidden> wrote:

I think the right fix is to change the condition to:

  else if (pi->unwind_info && pi->format == UNW_INFO_FORMAT_TABLE)

This works, because the DWARF code sets pi->format to that value when allocating an unwind_info, but the exidx code sets it instead to UNW_INFO_FORMAT_ARM_EXIDX.  But I'm not very familiar with this code, so I'm not positive this is the correct fix.  Could somebody let me know whether I'm on the right track?  If so, I'll happily put a patch together.

 

I think your analysis is right, but I'm not convinced that we're properly freeing memory here. Do you see leaks if you unwind in a loop?

 

 -Arun 

 

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