Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933473AbYCEMh1 (ORCPT ); Wed, 5 Mar 2008 07:37:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759617AbYCEMhG (ORCPT ); Wed, 5 Mar 2008 07:37:06 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:46615 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753691AbYCEMhE (ORCPT ); Wed, 5 Mar 2008 07:37:04 -0500 Date: Wed, 5 Mar 2008 13:36:42 +0100 From: Ingo Molnar To: Bart Van Assche Cc: Julia Lawall , Christopher Li , yi.zhu@intel.com, linux-wireless@vger.kernel.org, ipw3945-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Harvey Harrison , Alexander Viro , linux-sparse@vger.kernel.org, Josh Triplett Subject: Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and & Message-ID: <20080305123641.GA2365@elte.hu> References: <20080305063842.GA24495@elte.hu> <70318cbf0803042249j57d7f3a3j7666961a9132b10b@mail.gmail.com> <20080305070201.GA32434@elte.hu> <20080305122010.GA999@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 975 Lines: 28 * Bart Van Assche wrote: > If someone writes (!x & !y) instead of (!x && !y) because both x and y > have to be evaluated, this means that both x and y have side effects. > Please keep in mind that the C language does not specify whether x or > y has to be evaluated first, so if x and y have to be evaluated in > that order, an expression like (!x & !y) can be the cause of very > subtle bugs. I prefer readability above brevity. such expressions _must_ be written as: ret1 = x(); ret2 = y(); if (ret1 && ret2) ... any side-effects are totally un-obvious when they are in expressions and someone doing cleanups later on could easily change the '&' to '&&' and introduce a bug. Ingo -- 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/