Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932447AbYCEMbQ (ORCPT ); Wed, 5 Mar 2008 07:31:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757414AbYCEMa5 (ORCPT ); Wed, 5 Mar 2008 07:30:57 -0500 Received: from wf-out-1314.google.com ([209.85.200.168]:10571 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757196AbYCEMaz (ORCPT ); Wed, 5 Mar 2008 07:30:55 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=lIQfh8g5QBt5Yf6flp65wyWpm/wfGHbjE9g0y51gzUAnI2xJEZIX1h1mv4ON1VYH6ILe+NpXAfjMQscxe2BV6F4yx8+m+s2t9VCeY0hQZzDZsbwzX3BV8KheqozIP4DOwvJOFOhGuyntHUd0/y74a1Cwu3LHlOp2NsAiaVlCQ6Q= Message-ID: Date: Wed, 5 Mar 2008 13:30:54 +0100 From: "Bart Van Assche" To: "Ingo Molnar" Subject: Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and & 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" In-Reply-To: <20080305122010.GA999@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080305063842.GA24495@elte.hu> <70318cbf0803042249j57d7f3a3j7666961a9132b10b@mail.gmail.com> <20080305070201.GA32434@elte.hu> <20080305122010.GA999@elte.hu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 30 On Wed, Mar 5, 2008 at 1:20 PM, Ingo Molnar wrote: > > * Julia Lawall wrote: > > > There are some legitimate uses of !x & y which are actually of the > > form !x & !y, where x and y are function calls. That is a not > > particularly elegant way of getting both x and y to be evaluated and > > then combining the results using "and". If such code is considered > > acceptable, then perhaps the sparse patch should be more complicated. > > i tend to be of the opinion that the details in C source code should be > visually obvious and should be heavily simplified down from what is > 'possible' language-wise - with most deviations and complications that > depart from convention considered an error. I'd consider "!fn1() & > !fn2()" a borderline coding style violation in any case - and it costs > nothing to change it to "!fn1() && !fn2()". 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. Bart Van Assche. -- 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/