linux-kernel - Re: kernel coding style for if ... else which cross #ifdef

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Date:	Sat, 24 May 2008 16:46:27 +0200
From:	Willy Tarreau <w@....eu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Sam Ravnborg <sam@...nborg.org>, "H. Peter Anvin" <hpa@...or.com>,
	Steve French <smfrench@...il.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: kernel coding style for if ... else which cross #ifdef

On Sat, May 24, 2008 at 03:41:21PM +0100, Jeremy Fitzhardinge wrote:
> Willy Tarreau wrote:
> >You still have the possibility to use the "-0" trick :
> >
> > 	if (CFG_THINGY_LIMIT && x > (CONFIG_THINGY_LIMIT-0)) {...}
> >  
> 
> Oh, that's cute in a vile way.  I hadn't seen it before.

I use it in some of my code (but moderately). It's particularly useful
for limit checking such as above. It's useful too when you want to use
the config value as an offset or a bit shift. Eg:

    p = malloc(buf_size << (CONFIG_SHIFT-0));

Willy

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