Date: Tue, 20 Sep 2005 00:48:59 -0700 (PDT)
From: Vadim Lobanov <vlobanov@speakeasy.net>
To: Andrey Panin <pazke@donpac.ru>
cc: colin <colin@realtek.com.tw>, linux-kernel@vger.kernel.org
Subject: Re: CONFIG_PRINTK doesn't makes size smaller
In-Reply-To: <20050920063805.GB20363@pazke>
Message-ID: <Pine.LNX.4.58.0509200047120.3173@shell2.speakeasy.net>
References: <01bf01c5bdaa$9e8b81c0$106215ac@realtek.com.tw> <20050920063805.GB20363@pazke>
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On Tue, 20 Sep 2005, Andrey Panin wrote:

> On 263, 09 20, 2005 at 02:14:55PM +0800, colin wrote:
> >
> > Hi there,
> > I tried to make kernel with CONFIG_PRINTK off. I considered it should become
> > smaller, but it didn't because it actually isn't an empty function, and
> > there are many copies of it in vmlinux, not just one. Here is its
> > definition:
> >     static inline int printk(const char *s, ...) { return 0; }
> >
> > I change the definition to this and it can greatly reduce the size by about
> > 5%:
> >     #define printk(...) do {} while (0)
> > However, this definition would lead to error in some situations. For
> > example:
> >     1. (printk)
> >     2. ret = printk
> >
> > I hope someone could suggest a better definition of printk that can both
> > make printk smaller and eliminate errors.
>
> What about the macro below ?
>
> #define printk(...) ({ do { } while(0); 0; })

So what does the do-while loop give us in the above case? In other
words, why not just do the following...?

#define printk(...) ({ 0; })

-VadimL
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