Hello Patrick,
On 11/01/2011 02:28 PM, Patrick Hartling wrote:
> I have been tracking down some memory corruption crashes related to
> loading animated GIFs with OpenSG 2, and I think I have narrowed down at
> least one cause. The GIF I have been using to cause a crash in the GIF
> loader itself has two frames of different dimensions where the first is
> smaller than the second. Valgrind tells me that there is an invalid
> write to the memory returned by OSG::Image::editData(), and that leads
> me to believe that the buffer used by OSG::Image is the wrong size.
it's quite possible, I didn't know it's valid to have animated GIFs with
different frame sizes and it's likely that case was never tested before.
> My current fix for this is to modify the GIF loader so that the width
> and height passed to OSG::Image::set() come from the GIFStream object
> rather than from the GIFData object for the first frame. This seems to
> work because the image reports its width and height as being that of the
> largest frame. The width and height for the current GIFData still need
> to be used for reading the bytes for that frame, and I think I am doing
> that correctly.
I'm not up to speed on the GIF spec or the loader, but your description
sounds absolutely reasonable to me.
> Does this sound like a valid approach? I don't know if a patch would be
> helpful since we're using a version of OpenSG that is about 6 months out
> of date. I can submit one if it would help clarify what I have
> described. If nothing else, I have attached a GIF that demonstrates the
> crash in the GIF loader.
I just ran a git blame on the GIF loader and with the exception of some
cosmetic changes the code was last touched in 2006 or before, so if you
have a patch it is likely to apply with no problems and I'd be very
happy to apply it. Thanks!
Cheers,
Carsten
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