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

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Message-ID: <BANLkTim0Wao+dX-+GpKxdsHtg96DF1bHyw@mail.gmail.com>
Date:	Tue, 10 May 2011 11:57:18 +0100
From:	Niels de Vos <ndevos@...hat.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	linux-omap@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, "Premi, Sanjeev" <premi@...com>
Subject: Re: [PATCH] omap2/omapfb: make DBG() more resistant in if-else constructions

On Tue, May 10, 2011 at 10:42 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> 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 '}'?

Good catch! That's in a "fixup!" that I forgot to squash :-/
I'll post an update version in a bit.


>>  #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.

I think removing DBG() and the omapfb_debug module-parameter is surely
a good thing. Unfortunately DBG() is used quite a bit in the code and
replacing them 'll take some more time. I don't know yet when I find
some time to do and test that.

Thanks for the pointers,
Niels


> 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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