Question

How do I go about avoiding the compiler warning (warning: cast increases required alignment of target type) in the following code?

static int fill_color24 (VisVideo *video, VisColor *color)
{
    int x, y;
    uint32_t *buf;
    uint8_t *rbuf = visual_video_get_pixels (video);
    uint8_t *buf8;

    int32_t cola =
        (color->b << 24) |
        (color->g << 16) |
        (color->r << 8) |
        (color->b);
    int32_t colb =
        (color->g << 24) |
        (color->r << 16) |
        (color->b << 8) |
        (color->g);
    int32_t colc =
        (color->r << 24) |
        (color->b << 16) |
        (color->g << 8) |
        (color->r);

    for (y = 0; y < video->height; y++) {
        buf = (uint32_t *) rbuf; // warning is for this line

        for (x = video->width; x >= video->bpp; x -= video->bpp) {
            *(buf++) = cola;
            *(buf++) = colb;
            *(buf++) = colc;
        }

        buf8 = (uint8_t *) buf;
        *(buf8++) = color->b;
        *(buf8++) = color->g;
        *(buf8++) = color->r;


        rbuf += video->pitch;
    }

    return VISUAL_OK;
}

Answer 1

I’m not sure you can. That function might return color array unaligned. You can’t do anything to be able to read word from there.
You will have to read color by components (uint8_t) and then construct uint32_t from these by adding and shifting.