[FFmpeg-devel] Unix "fileno" libavformat module

mark cox markcox
Thu Jul 12 00:56:35 CEST 2007

On 11/07/07, M?ns Rullg?rd <mans at mansr.com> wrote:
> William Ahern <william at 25thandClement.com> writes:
> >> > +        (void)memcpy(buf, s->rbuf.r.pos, size);
> >>
> >> why this cast ?
> >
> > Its not an uncommon style to "cast away" a return value for the purposes
> of
> > inline documentation. The intent is to say, "I am willfully ignoring the
> > return value". The sense becomes clearer for things like close(), and,
> > especially, snprintf(). WIN32 snprintf() returns -1 on overflow, and
> notably
> > does not guarantee null-termination for this condition (effectively the
> > complete opposite of C99 snprintf()). I've noticed this in some of the
> > ffmpeg code. A (void) cast in such a situation would (or should) serve
> to
> > document that the author understood the behavior and implications.
> All I've ever seen such casts indicate is the author using compiler
> (or worse, lint tool) giving warnings unless those casts were added.
> If done often enough, it could well become an unconscious habit.
> In the memcpy() case, I can't recall having ever seen the return value
> being used.

I also use (void) in this way as a documentation tool. It is useful, but in
this case i think for common fn's like malloc and memcpy it is not useful.

> M?ns Rullg?rd
> mans at mansr.com
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel

More information about the ffmpeg-devel mailing list