Date: Sun, 30 Jan 2011 22:37:07 +0000 From: Alexander Best <arundel@freebsd.org> To: Gary Jennejohn <gljennjohn@googlemail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: empty function macros Message-ID: <20110130223707.GA40378@freebsd.org> In-Reply-To: <20110130201142.09f4b998@ernst.jennejohn.org> References: <20110130172941.GA10701@freebsd.org> <20110130201142.09f4b998@ernst.jennejohn.org>
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On Sun Jan 30 11, Gary Jennejohn wrote:
> On Sun, 30 Jan 2011 17:29:41 +0000
> Alexander Best <arundel@freebsd.org> wrote:
>
> > hi there,
> >
> > i noticed freebsd has a few of the following macros:
> >
> > #define FUNC(sb)
> >
> > when you do something like
> >
> > if (cond)
> > FUNC(i)
> >
> > the compiler complains about an if statement with an empty body. any sensible
> > way of dealing with this issue?
> >
> > i saw some reiserfs code which does the following to silence compilers:
> >
> > #define FUNC(sb) do { } while (0)
> >
>
> What happens if you treat it like a real function call and put ';'
> after it?
sorry this was my fault. it should have actually been:
if (cond)
FUNC(i);
basically, since FUNC evaluates to nothing this results in
if (cond)
;
while gcc doesn't complain, clang does.
cheers.
alex
>
> --
> Gary Jennejohn (gj@)
--
a13x
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