[Qt-interest] SIGSEGV with single-line gdb backtrace

[Bill King]

On 09/28/2009 11:38 AM, ext Josiah Bryan wrote:
> Hey All -
>
> I'm working on a project that uses ffmpeg to decode video that plays in 
> a QGraphicsItem in a QGraphicsView. The scene/items are reused in a 
> custom QAbstractListView to paint thumnail snaphots of the scene as its 
> being edited.
>
> Well, as the program is loading, it goes through the process of building 
> the snapshots - then all of a sudden, throws a SIGSEGV. Being a good 
> little programmer, I run it inside gdb, and when it dies, I ask gdb for 
> a backtrace (bt). Much to my suprise, it gives a single line backtrace. 
> Right before the SIGSEGV, I get a bunch of QThread destroyed errors:
>
> QThread: Destroyed while thread is still running
> QThread: Destroyed while thread is still running
>
> Then the sigsegv:
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0063ca47 in ?? ()
> (gdb) bt
> #0  0x0063ca47 in ?? ()
>
> Any ideas on how to figure this one out? I mean, this could be in any 
> number of areas of the code - how can I isolate the crash with no stack 
> trace?
>
> Thanks!
> -josiah
>
>
>
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>   
Try using valgrind, --tool=memcheck or possibly also --tool=helgrind
I'd have a look at what's destroying your thread, you may have some race
conditions going on.

-- 
Bill King, Software Engineer
Qt Development Frameworks, Nokia Pty Ltd
Brisbane Office

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