[FFmpeg-devel] [RFC] motion_est: avoid implicit truncation warnings

[Reimar Döffinger]

On Sun, Jun 27, 2010 at 12:12:49PM +0100, M?ns Rullg?rd wrote:
> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> 
> > Hello,
> > maybe a bit ugly to add an extra macro, but using the changed macro
> > everywhere produces very different code at least on x86_64.
> >
> > Index: libavcodec/motion_est.c
> > ===================================================================
> > --- libavcodec/motion_est.c	(revision 23819)
> > +++ libavcodec/motion_est.c	(working copy)
> > @@ -1476,6 +1476,7 @@
> >      const int xmax= c->xmax<<shift;
> >      const int ymax= c->ymax<<shift;
> >  #define HASH(fx,fy,bx,by) ((fx)+17*(fy)+63*(bx)+117*(by))
> > +#define HASH_CONST(fx,fy,bx,by) ((uint8_t)HASH(fx,fy,bx,by))
> 
> What is CONST supposed to signify here.  There is nothing const about
> the macro at all.  HASH8 would seem a better name.

As in "only suitable for values that are constant (and thus calculated
at compile time)".