[mythtv] segfault problem with current CVS.

Isaac Richards ijr at po.cwru.edu
Sun Feb 23 13:28:20 EST 2003


On Sunday 23 February 2003 11:46 am, Chris Pinkham wrote:
> I'm receiving a segfault running current CVS code and was wondering if
> anyone else was noticing or receiving this.
>
> Occasionally when exiting playback or the playback list screen (in MythTV),
> I will get a segfault.  I tried running using under gdb with
> MALLOC_CHECK_=2 one time and with electric fence the other time.  Both
> pointed back to a line in libavcodec trying to free memory.  I'm assuming
> this is a pointer that has already been freed or was somehow changed to
> point to different memory and can't be freed now.
>
> In MC/libs/libavcodec/mpegvideo.c around line 363 you'll find a line like
> this:
>
>     av_freep(&pic->mbskip_table);
>
> That's the line it's segfaulting on.  If I comment out that line (just to
> test), then it just segfaults later so obviously something is seriously
> hosed.
>
> Isaac (or anyone else), can you point me in the right direction to see
> where the problem might be occuring.  I'm seeing it even when I don't use
> the commercial skip feature so I'm wondering if it's an unrelated problem.
>
> I'm still working on trying to figure out how the libavcoded code
> allocates/deallocates/uses memory during the whole decoding process but
> haven't seen enough yet to know where to look to see if somehow this is
> being re-freed or what.
>
> Any pointers would be greatly appreciated.  I want to make sure this isn't
> in the current commercial skip stuff before I modify it further with my new
> patch.

Can you try running things in valgrind ( http://developer.kde.org/~sewardj/ ), 
maybe?

Isaac


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