linux-kernel - Re: [PATCH] Documentation: Explain a second alternative for multi-line macros.

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Message-ID: <Pine.LNX.4.64.0701010322320.2935@localhost.localdomain>
Date:	Mon, 1 Jan 2007 03:26:02 -0500 (EST)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Segher Boessenkool <segher@...nel.crashing.org>
cc:	Muli Ben-Yehuda <muli@...ibm.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	trivial@...nel.org
Subject: Re: [PATCH] Documentation: Explain a second alternative for multi-line
 macros.

On Mon, 1 Jan 2007, Segher Boessenkool wrote:

> > > In this case, the second form
> > > should be used when the macro needs to return a value (and you can't
> > > use an inline function for whatever reason), whereas the first form
> > > should be used at all other times.
> >
> > that's a fair point, although it's certainly not the coding style
> > that's in play now.  for example,
> >
> >   #define setcc(cc) ({ \
> >     partial_status &= ~(SW_C0|SW_C1|SW_C2|SW_C3); \
> >     partial_status |= (cc) & (SW_C0|SW_C1|SW_C2|SW_C3); })
>
> This _does_ return a value though, bad example.

sigh ... you're right.  here's a thought.  my original patch
submission simply added an explanation for allowing the ({ }) notation
for defining a multi-line macro, without getting into recommending an
actual coding style.  at a minimum, something like that should be
added to the style document.

if someone wants to extend that explanation recommending *when* each
of those two styles should be used, feel free.  but a simple
decription of alternatives should *at least* be added, no?

rday
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