dest_write_back_narrow (pixman_iter_t *iter)
{
    bits_image_t *  image  = &iter->image->bits;
    int             x      = iter->x;
    int             y      = iter->y;
    int             width  = iter->width;
    const uint32_t *buffer = iter->buffer;

    image->store_scanline_32 (image, x, y, width, buffer);

    if (image->common.alpha_map)
    {
	x -= image->common.alpha_origin_x;
	y -= image->common.alpha_origin_y;

	image->common.alpha_map->store_scanline_32 (
	    image->common.alpha_map, x, y, width, buffer);
    }

    iter->y++;
}

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