Re: [Mesa3d-dev] crucial VBO bug

[Brian P. <bri...@tu...>]

David Reveman wrote:
> I've found a pretty serious vertex buffer object bug in mesa. 
> 
> When a VBO is delete with glDeleteBuffers, VBO array pointers for vertex
> arrays and similar arrays that matches the deleted VBO are reverted to
> "Null Buffer Object" without incrementing the "Null Buffer Object"'s
> reference count. Next time the array pointer is updated the "Null Buffer
> Object"'s reference count is decremented wrongfully. The reference count
> for "Null Buffer Objects" are initialized to 1000 so nothing will really
> go wrong until this has been repeated a 1000 times, as the reference
> count has then reached 0 and the "Null Buffer Object" is deleted. Once
> that happens, you're of course in trouble.
> 
> I guess it's a pretty big chance that nothing will happen and the
> reference count variable located in deallocated memory will just
> continue decrementing to negative infinity. This is probably why the bug
> is a bit hard to detect.
> 
> I've attached a simple test program that should expose the bug. If you
> apply the attached assertion patch to mesa you'll get an assertion
> failure at the 1000th redraw loop in the attached test program if mesa
> is compiled with debugging code.  
> 
> I've put, what I think is the appropriate fix in the attached mesa-VBO-
> fix.diff patch. With that one applied to mesa the test program should
> run fine.

I've checked in your patches.  Thanks, David!

-Brian