linux-kernel - Re: [PATCH] Documentation/CodingStyle: Mention multi-line macros using expressions

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Date:	Fri, 13 Jul 2012 08:43:51 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Joe Perches <joe@...ches.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Documentation/CodingStyle: Mention multi-line macros
 using expressions

On Wed, 11 Jul 2012, Joe Perches wrote:

> On Wed, 2012-07-11 at 13:32 -0400, Robert P. J. Day wrote:
> []
> > diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
> []
> > +A newer technique is to use the GCC extension of being able to place
> > +statements and declarations in an expression, as with this example from
> > +the <linux/kernel.h> header file:
> > +
> > +#define roundup(x, y) (				\
> > +{						\
> > +        const typeof(y) __y = y;		\
> > +        (((x) + (__y - 1)) / __y) * __y;	\
> > +}						\
> > +)
>
> Hi Robert.
>
> How about the phrase "GCC's statement expression extension"
> or maybe give a link like:
> http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html

  ok, i'll do that later today.

> Please put the opening ({ and closing )} on a single line.
> It's shorter and makes grep easier.
>
> #define statement_expression(args)		\
> ({						\
> 	etc					\
> })

  i was simply transcribing what was in kernel.h verbatim, but i'll
tuck it together for brevity.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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