On Tue, Sep 29, 2015 at 9:24 AM, Hendrik Leppkes <h.lepp...@gmail.com> wrote: > On Sun, Sep 20, 2015 at 4:18 AM, Ganesh Ajjanagadde > <gajjanaga...@gmail.com> wrote: >> This fixes -Wshift-negative-value reported with clang 3.7+, e.g >> http://fate.ffmpeg.org/log.cgi?time=20150919172459&log=compile&slot=x86_64-darwin-clang-polly-notiling-3.7. >> Note that the patch crucially depends on int >= 32 bits, >> an assumption made in many places in the codebase. >> >> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> >> --- >> libavcodec/apedec.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c >> index 5536e0f..7b34d26 100644 >> --- a/libavcodec/apedec.c >> +++ b/libavcodec/apedec.c >> @@ -1281,7 +1281,7 @@ static void do_apply_filter(APEContext *ctx, int >> version, APEFilter *f, >> /* Update the adaption coefficients */ >> absres = FFABS(res); >> if (absres) >> - *f->adaptcoeffs = ((res & (-1<<31)) ^ (-1<<30)) >> >> + *f->adaptcoeffs = ((res & (-(1<<31))) ^ (-(1<<30))) >> >> (25 + (absres <= f->avg*3) + (absres <= >> f->avg*4/3)); >> else >> *f->adaptcoeffs = 0; >> -- >> 2.5.2 >> > > After this patch (GCC 5.2, x86) > > libavcodec/apedec.c: In function 'do_apply_filter': > libavcodec/apedec.c:1284:44: warning: integer overflow in expression > [-Woverflow] > *f->adaptcoeffs = ((res & (-(1<<31))) ^ (-(1<<30))) >>
Good catch - made an off by one error in my assumptions. I don't see a nice, clean way of dealing with -(1 << 31). I propose one of the following: 1. use INT32_MIN. 2. use an explicit binary/hexadecimal mask. 3. use e.g (-2)*(1<<30). I have no preference, and will post updated patch within the next few days, unless someone does the trivial fix and pushes before then. > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
