Hi, On Tue, Sep 29, 2015 at 11:04 AM, Ganesh Ajjanagadde <gajja...@mit.edu> wrote:
> 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). 0x80000000U is fine. Ronald _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
