Re: [PATCH 2/2] Add warn_unused_result attr to AUD_register_card

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Nov 10, 2023 at 12:44:56PM +0200, Manos Pitsidianakis wrote:
> On Fri, 10 Nov 2023 12:21, Peter Maydell <peter.maydell@linaro.org> wrote:
> > This kind of thing is why Coverity's unused-result warning has a
> > lot of false positives. We shouldn't introduce extra code like
> > this to work around the fact that the tooling doesn't understand
> > our error-handling convention (i.e. error_fatal, and the way
> > that some functions report errors both via the return value and
> > also via the Error** argument).
> 
> I respect that :). But I personally believe that clinging to C's
> inadequacies, instead of preventing bugs statically just because it adds
> some lines of code, is misguided. Proper code should strive to make bugs
> impossible in the first place. At least that is my perspective and I would
> like there to be constructive discussions about different approaches in the
> mailing list. Perhaps something good might come out of it!

Your approach to the problem:

  if (!AUD_register_card("OMAP EAC", &s->codec.card, &error_fatal)) {
    exit(1);
  }

is adding dead-code because the exit(1) will never be reachable. So while
it lets you squelch the unused result warning, it is verbose and misleading
to anyone who sees it.

Perhaps a more viable option is to pull in gnulib's ignore_value macro

  #define ignore_value(x) \
    (__extension__ ({ __typeof__ (x) __x = (x); (void) __x; }))

and then we would have just this:

 ignore_value(AUD_register_card("OMAP EAC", &s->codec.card, &error_fatal));

With regards,
Daniel
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