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

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Date:	Sat, 24 May 2008 21:38:35 +0100
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Tom Spink <tspink@...il.com>
CC:	Vegard Nossum <vegard.nossum@...il.com>,
	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

Tom Spink wrote:
> A thought occurred to me that we may be able to used some preprocessor
> magic and do this:
>
> #define config_defined(x) CFGVAL_## x
>
> Which means that, if we get Kconfig to produce:
>
> #define CFGVAL_CONFIG_FOO 0
> #define CFGVAL_CONFIG_VALUE_BAR 1
> #define CFGVAL_CONFIG_VALUE_BAZ_MODULE 1
>
> We can use this:
>
> if (config_defined(CONFIG_FOO) && some_expr) {
>    panic("Oh no.");
> }

Well, in that case you could use Willy's magic hack:

#define config_defined(x)      (x - 0)

Which isn't a bad alternative to defining a whole pile of new symbols...

    J
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