linux-kernel - Re: [PATCH] omap2/omapfb: make DBG() more resistant in if-else constructions

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Date:	Tue, 10 May 2011 11:42:01 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Niels de Vos <ndevos@...hat.com>
Cc:	linux-omap@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] omap2/omapfb: make DBG() more resistant in if-else constructions

On Tue, May 10, 2011 at 11:20, Niels de Vos <ndevos@...hat.com> wrote:
> When DBG() is used in a simple if-else, the resulting code path
> currently depends on the definition of DBG(). Inserting the statement in
> a "do { ... } while (0)" prevents this possible misuse.
>
> Signed-off-by: Niels de Vos <ndevos@...hat.com>

> --- a/drivers/video/omap2/omapfb/omapfb.h
> +++ b/drivers/video/omap2/omapfb/omapfb.h
> @@ -34,8 +34,10 @@
>  #ifdef DEBUG
>  extern unsigned int omapfb_debug;
>  #define DBG(format, ...) \
> -       if (omapfb_debug) \
> -               printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__)
> +       do { \
> +               if (omapfb_debug) \
> +                       printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__); \
> +       while (0)

Where's the closing '}'?

>  #else
>  #define DBG(format, ...)

BTW, no printf()-style format checking here.

>  #endif

What about using the standard pr_debug()/dev_dbg() instead?
With dynamic debug, it can be enabled at run time.
As a bonus, you get printf()-style format checking if debugging is disabled.


Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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