[FFmpeg-devel] [PATCH 1/4] avcodec/startcode: Use AV_RN due to UBSan warning about unaligned access

[Andreas Rheinhardt]

Andreas Rheinhardt:
> when directly accessing a buffer via a pointer to uint8_t cast to a
> pointer to uint64_t/uint32_t. This happened only if HAVE_FAST_UNALIGNED
> was set, so it was ok, but UBSan nevertheless complained about unaligned
> accesses. So simply use AV_RNxx to read the buffer; this also improves
> readability.
> 
> This affected many FATE-tests (namely 228 of them; e.g. the cbs-h264
> tests) and it has also been reported in tickets #8138 and #8485.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavcodec/startcode.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/startcode.c b/libavcodec/startcode.c
> index 9efdffe8c6..d84f326521 100644
> --- a/libavcodec/startcode.c
> +++ b/libavcodec/startcode.c
> @@ -25,6 +25,7 @@
>   * @author Michael Niedermayer <michaelni at gmx.at>
>   */
>  
> +#include "libavutil/intreadwrite.h"
>  #include "startcode.h"
>  #include "config.h"
>  
> @@ -38,14 +39,14 @@ int ff_startcode_find_candidate_c(const uint8_t *buf, int size)
>       */
>  #if HAVE_FAST_64BIT
>      while (i < size &&
> -            !((~*(const uint64_t *)(buf + i) &
> -                    (*(const uint64_t *)(buf + i) - 0x0101010101010101ULL)) &
> +            !((~AV_RN64(buf + i) &
> +                    (AV_RN64(buf + i) - 0x0101010101010101ULL)) &
>                      0x8080808080808080ULL))
>          i += 8;
>  #else
>      while (i < size &&
> -            !((~*(const uint32_t *)(buf + i) &
> -                    (*(const uint32_t *)(buf + i) - 0x01010101U)) &
> +            !((~AV_RN32(buf + i) &
> +                    (AV_RN32(buf + i) - 0x01010101U)) &
>                      0x80808080U))
>          i += 4;
>  #endif
> 
Ping for this and the other unmerged patches of this patchset.

- Andreas