Re: [PATCH] Documentation: Explain a second alternative for multi-linemacros.
From: Robert P. J. Day
Date: Mon Jan 01 2007 - 09:33:42 EST
On Mon, 1 Jan 2007, Christoph Hellwig wrote:
> On Sun, Dec 31, 2006 at 02:32:25PM -0500, Robert P. J. Day wrote:
> > + (a) Enclose those statements in a do - while block:
> > +
> > + #define macrofun(a, b, c) \
> > + do { \
> > + if (a == 5) \
> > + do_this(b, c); \
> > + } while (0)
>
> nitpick, please don't add an indentaion level for the do {. Do this
> should look like:
>
> #define macrofun(a, b, c) \
> do { \
> if (a == 5) \
> do_this(b, c); \
> } while (0)
the former is the way it's presented in CodingStyle currently, it
wasn't my personal opinion on the subject. i was just reproducing
what was already there.
> > + (b) Use the gcc extension that a compound statement enclosed in
> > + parentheses represents an expression:
> > +
> > + #define macrofun(a, b, c) ({ \
> > if (a == 5) \
> > do_this(b, c); \
> > - } while (0)
> > + })
>
> I'd rather document to not use this - it makes the code far less
> redable. And it's a non-standard extension, something we only
> use if it provides us a benefit which it doesn't here.
it might be a bit late to put a cork in *that* bottle:
$ grep -r "#define.*({" *
rday
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