fbBlt - memcpy on overlapping ranges

[Michal Srb]

Hi,

In fb/fbblt.c in fbBlt function, memcpy is used to blit inside lines:

if (!upsidedown)
     for (i = 0; i < height; i++)
         MEMCPY_WRAPPED(dst + i * dstStride, src + i * srcStride, width);
else
     for (i = height - 1; i >= 0; i--)
         MEMCPY_WRAPPED(dst + i * dstStride, src + i * srcStride, width);


Where MEMCPY_WRAPPED is normaly expanded to standard memcpy function.

In case of blitting in horizontal direction of less than width overlapping 
will occur. According to memcpy documentation, result is undefined in such 
case. Shouldn't memmove be used instead?

(This does happen, found using clang's AddressSanitizer - steps I used: run X 
without any client in vmware, then kate and then kwin.)

Michal