fbCombineInReverseC (CARD32 *dest, CARD32 *src, CARD32 *mask, int width)
{
    int i;

    for (i = 0; i < width; ++i) {
        CARD32 s = READ(src + i);
        CARD32 m = READ(mask + i);
        CARD32 a;

	fbCombineMaskAlphaC (&s, &m);

	a = m;
        if (a != 0xffffffff)
        {
            CARD32 d = 0;
            if (a)
            {
                d = READ(dest + i);
                FbByteMulC(d, a);
            }
            WRITE(dest + i, d); 
        }
    }
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.