[FFmpeg-cvslog] av_memcpy_backptr: avoid an infinite loop for back = 0

[Reimar Döffinger]

On Sun, Feb 24, 2013 at 12:27:55PM +0100, Anton Khirnov wrote:
> ffmpeg | branch: master | Anton Khirnov <anton at khirnov.net> | Wed Feb 13 21:36:25 2013 +0100| [f935aca44c674d30e3ed940ef73bbad1228a5855] | committer: Anton Khirnov
> 
> av_memcpy_backptr: avoid an infinite loop for back = 0
> 
> CC:libav-stable at libav.org
> 
> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f935aca44c674d30e3ed940ef73bbad1228a5855
> ---
> 
>  libavutil/mem.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/libavutil/mem.c b/libavutil/mem.c
> index 3a4433d..391eb7d 100644
> --- a/libavutil/mem.c
> +++ b/libavutil/mem.c
> @@ -252,6 +252,9 @@ static void fill32(uint8_t *dst, int len)
>  void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
>  {
>      const uint8_t *src = &dst[-back];
> +    if (!back)
> +        return;

This will leave dst uninitialized.
Either this is an expected case, then it should work
properly and use memset like the == 1 case (of course not
with *src but e.g. 0).
Or this is not expected then an assert would be more appropriate.