[FFmpeg-devel] [PATCH] Avoid undefined behavior when start_time_text is -1<<63

[Michael Niedermayer]

On Tue, Jul 17, 2018 at 02:37:55PM -0700, Fredrik Hubinette wrote:
> 

>  utils.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> e69f1a3a447e331cad7ea85e28c0ed13e48ce33c  0001-Avoid-undefined-behavior-when-start_time_text-is-1-6.patch
> From d7bd55c3d280c10b990577003a985296f10a2b59 Mon Sep 17 00:00:00 2001
> From: Fredrik Hubinette <hubbe at google.com>
> Date: Tue, 17 Jul 2018 14:35:55 -0700
> Subject: [PATCH] Avoid undefined behavior when start_time_text is -1<<63
> 
> ---
>  libavformat/utils.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index c9cdd2b470..5b83ed7872 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -2666,7 +2666,7 @@ static void update_stream_timings(AVFormatContext *ic)
>                  duration = FFMAX(duration, duration1);
>          }
>      }
> -    if (start_time == INT64_MAX || (start_time > start_time_text && start_time - start_time_text < AV_TIME_BASE))
> +    if (start_time == INT64_MAX || (start_time > start_time_text && start_time - AV_TIME_BASE < start_time_text ))

Casting to uint64_t should be a more complete fix.

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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