Created attachment 126795 [details] [review]
patch of pixman-fast-path.c

it is wrong to compute offsets like so:

   int rowstride = something;
   char *buffer = base_ptr + y*rowstride + x*4;

That idiom fails in 64-bit architectures where integers are 32 bit.  Consider a not-so-uncommon A0 poster at 600 dpi.  It results in a 19860x28080 image.  While width and heights are 16 bit numbers, their product multiplied by a bpp of 4 results in a negative integer.

A better choice than int would be ptrdiff_t (POSIX ssize_t wouldn't work on x86-16, according to
http://stackoverflow.com/questions/8649018/what-is-the-difference-between-ssize-t-and-ptrdiff-t)

The patch attached wildly uses (long).  I'd suggest to define a one-liner inline function using a well thought cast, which can always be tweaked for specific architectures, should problems arise.

Ale