[FFmpeg-devel] [PATCH] avformat/movenc: suppress -Wstrict-overflow warnings

[Ronald S. Bultje]

Hi,

On Sat, Sep 26, 2015 at 7:19 PM, Ganesh Ajjanagadde <gajjanag at mit.edu>
wrote:

> On Sat, Sep 26, 2015 at 7:11 PM, Michael Niedermayer <michaelni at gmx.at>
> wrote:
> > On Fri, Sep 18, 2015 at 05:15:50PM -0400, Ganesh Ajjanagadde wrote:
> >> This patch results in identical behavior of movenc, and suppresses
> -Wstrict-overflow
> >> warnings observed in GCC 5.2.
> >> I have manually checked that all usages are safe, and overflow
> possibility does
> >> not exist with this expression rewrite.
> >>
> >> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> >> ---
> >>  libavformat/movenc.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> >> index af03d1e..6e4a1a6 100644
> >> --- a/libavformat/movenc.c
> >> +++ b/libavformat/movenc.c
> >> @@ -854,7 +854,7 @@ static int get_cluster_duration(MOVTrack *track,
> int cluster_idx)
> >>  {
> >>      int64_t next_dts;
> >>
> >> -    if (cluster_idx >= track->entry)
> >> +    if (cluster_idx - track->entry >= 0)
> >
> > i do not understand what this fixes or why
> > also plese quote the actual warnings which are fixed in the commit
> > message
>
> I have posted v2 with a more detailed commit message. It should be
> self explanatory.


Even with the new message, it's still not clear to me what's being fixed.
What does the warning check for? What is the problem in the initial
expression?

Ronald