Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964941AbVITJDF (ORCPT ); Tue, 20 Sep 2005 05:03:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964944AbVITJDF (ORCPT ); Tue, 20 Sep 2005 05:03:05 -0400 Received: from relay.rost.ru ([80.254.111.11]:52632 "EHLO smtp.rost.ru") by vger.kernel.org with ESMTP id S964941AbVITJDE convert rfc822-to-8bit (ORCPT ); Tue, 20 Sep 2005 05:03:04 -0400 Date: Tue, 20 Sep 2005 13:02:52 +0400 To: Vadim Lobanov Cc: colin , linux-kernel@vger.kernel.org Subject: Re: CONFIG_PRINTK doesn't makes size smaller Message-ID: <20050920090252.GC20363@pazke> Mail-Followup-To: Vadim Lobanov , colin , linux-kernel@vger.kernel.org References: <01bf01c5bdaa$9e8b81c0$106215ac@realtek.com.tw> <20050920063805.GB20363@pazke> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: X-Uname: Linux 2.6.11-pazke i686 User-Agent: Mutt/1.5.9i From: Andrey Panin Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1582 Lines: 43 On 263, 09 20, 2005 at 12:48:59AM -0700, Vadim Lobanov wrote: > 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...? do-while loop eliminates "statement with no effect" warnings from gcc4. > #define printk(...) ({ 0; }) > -- Andrey Panin | Linux and UNIX system administrator pazke@donpac.ru | PGP key: wwwkeys.pgp.net - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/