linux-kernel - Re: [PATCH 00/12] scsi/NCR5380: fix debugging macros and #include structure

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Date:	Wed, 19 Mar 2014 12:46:16 +1100 (EST)
From:	Finn Thain <fthain@...egraphics.com.au>
To:	Joe Perches <joe@...ches.com>
cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	scsi <linux-scsi@...r.kernel.org>, Sam Creasey <sammy@...my.net>,
	Russell King <linux@....linux.org.uk>,
	Michael Schmitz <schmitz@...ian.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux/m68k <linux-m68k@...r.kernel.org>
Subject: Re: [PATCH 00/12] scsi/NCR5380: fix debugging macros and #include
 structure


On Tue, 18 Mar 2014, Joe Perches wrote:

> But using "if (0)" prevents the no_printk from occurring at all so there 
> would be no side-effects and the format & args would still be verified 
> by the compiler.

I'd prefer this (for symmetry and clarity):

#if NDEBUG
#define dprintk(flg, fmt, ...) \
        do { if ((NDEBUG) & (flg)) pr_debug(fmt, ## __VA_ARGS__); } while (0)
#else
#define dprintk(flg, fmt, ...) \
        do { if (0) pr_debug(fmt, ## __VA_ARGS__); } while (0)
#endif

But you seem to be asking for this instead:

#if NDEBUG
#define dprintk(flg, fmt, ...) \
        do { if ((NDEBUG) & (flg)) pr_debug(fmt, ## __VA_ARGS__); } while (0)
#else
#define dprintk(flg, fmt, ...) \
        do { if (0) no_printk(fmt, ## __VA_ARGS__); } while (0)
#endif

Why is that better?

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