Re: do { } while (0) question

[Jiri Slaby <jirislaby@gmail.com>]

Peter Zijlstra wrote:
> On Tue, 2006-08-01 at 02:03 -0700, Hua Zhong wrote:
> > > #if KILLER == 1
> > > #define MACRO
> > > #else
> > > #define MACRO do { } while (0)
> > > #endif
> > >
> > > {
> > > 	if (some_condition)
> > > 		MACRO
> > >
> > > 	if_this_is_not_called_you_loose_your_data();
> > > }
> > >
> > > How do you want to define KILLER, 0 or 1? I personally choose 0.
> > Really? Does it compile?
>
> No, and that is the whole point.
>
> The empty 'do {} while (0)' makes the missing semicolon a syntax error.

Bulls^WNope, it was a bad example (we don't want to break the compilation, just 
not want to emit a warn or an err).

I can't emit an error with the thing like that, only a warning, but we are not 
using -Werror to get err from a warn. Thing such this would emit empty-statement 
warn if define KILLER as 1:
#if KILLER == 1
#define MACRO
#else
#define MACRO do { } while (0)
#endif

{
 	if (some_condition)
 		MACRO;
	else
		do_something();
}

regards,
--
<a href="http://www.fi.muni.cz/~xslaby/";>Jiri Slaby</a>
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E
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