[Spice-devel] [spice-server PATCH v1 4/12] mjpeg_encoder: fix alignment warnings (pixel_converter)

[Christophe Fergeau]

Hey,

In this case, we are going to pass unaligned data to pixel_converter(),
so I'd say the warning is legit and we are just papering over it:

uint8_t *row;
for (x = 0; x < image_width; x++) {
    encoder->pixel_converter(src_pixels, row);
    row += 3;
    src_pixels += encoder->bytes_per_pixel;
}

Christophe

On Wed, Aug 05, 2015 at 02:23:18PM +0200, Victor Toso wrote:
> As the input line could be uint8_t*, uint16_t*, uint32_t*, changing the
> default from uint8_t* to void* to deal with upcasting warnings.
> 
> from clang:
> mjpeg_encoder.c:260:23: error: cast from 'uint8_t *'
> (aka 'unsigned char *') to 'uint16_t *' (aka 'unsigned short *')
> increases required alignment from 1 to 2 [-Werror,-Wcast-align]
>   uint16_t pixel = *(uint16_t *)src;
>                     ^~~~~~~~~~~~~~~
> ---
>  server/mjpeg_encoder.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/server/mjpeg_encoder.c b/server/mjpeg_encoder.c
> index 9a41ef3..1d1f167 100644
> --- a/server/mjpeg_encoder.c
> +++ b/server/mjpeg_encoder.c
> @@ -162,7 +162,7 @@ struct MJpegEncoder {
>      struct jpeg_error_mgr jerr;
>  
>      unsigned int bytes_per_pixel; /* bytes per pixel of the input buffer */
> -    void (*pixel_converter)(uint8_t *src, uint8_t *dest);
> +    void (*pixel_converter)(void *src, uint8_t *dest);
>  
>      MJpegEncoderRateControl rate_control;
>      MJpegEncoderRateControlCbs cbs;
> @@ -238,15 +238,16 @@ uint8_t mjpeg_encoder_get_bytes_per_pixel(MJpegEncoder *encoder)
>  
>  #ifndef JCS_EXTENSIONS
>  /* Pixel conversion routines */
> -static void pixel_rgb24bpp_to_24(uint8_t *src, uint8_t *dest)
> +static void pixel_rgb24bpp_to_24(void *src_ptr, uint8_t *dest)
>  {
> +    uint8_t *src = src_ptr;
>      /* libjpegs stores rgb, spice/win32 stores bgr */
>      *dest++ = src[2]; /* red */
>      *dest++ = src[1]; /* green */
>      *dest++ = src[0]; /* blue */
>  }
>  
> -static void pixel_rgb32bpp_to_24(uint8_t *src, uint8_t *dest)
> +static void pixel_rgb32bpp_to_24(void *src, uint8_t *dest)
>  {
>      uint32_t pixel = *(uint32_t *)src;
>      *dest++ = (pixel >> 16) & 0xff;
> @@ -255,7 +256,7 @@ static void pixel_rgb32bpp_to_24(uint8_t *src, uint8_t *dest)
>  }
>  #endif
>  
> -static void pixel_rgb16bpp_to_24(uint8_t *src, uint8_t *dest)
> +static void pixel_rgb16bpp_to_24(void *src, uint8_t *dest)
>  {
>      uint16_t pixel = *(uint16_t *)src;
>      *dest++ = ((pixel >> 7) & 0xf8) | ((pixel >> 12) & 0x7);
> -- 
> 2.4.3
> 
> _______________________________________________
> Spice-devel mailing list
> Spice-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/spice-devel
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