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sna: Avoid accessing past the end of the clip boxes for incremental clipping 

During incremental clipping of the trapezoids, we can assign the end
BoxPtr to begin, and so we should be careful not to dereference that
pointer (as it points passed the end of the clip boxes).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2015-02-08 22:13:35 +00:00
parent 357a798156
commit 5b033d638b
1 changed files with 11 additions and 5 deletions
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16
src/sna/sna.h
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@ -1194,12 +1194,18 @@ __find_clip_box_for_y(const BoxRec *begin, const BoxRec *end, int16_t y);
inline static const BoxRec *
find_clip_box_for_y(const BoxRec *begin, const BoxRec *end, int16_t y)
{
if (begin->y2 > y)
return begin;
if (y > end[-1].y2)
return end;
/* Special case for incremental trapezoid clipping */
if (begin == end)
return end;
return __find_clip_box_for_y(begin, end, y);
/* Quick test if scanline is within range of clip boxes */
if (begin->y2 > y)
return begin;
if (y > end[-1].y2)
return end;
/* Otherwise bisect to find the first box crossing y */
return __find_clip_box_for_y(begin, end, y);
}
unsigned sna_cpu_detect(void);