Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757910AbXE0PFa (ORCPT ); Sun, 27 May 2007 11:05:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754168AbXE0PFX (ORCPT ); Sun, 27 May 2007 11:05:23 -0400 Received: from mailer.gwdg.de ([134.76.10.26]:49332 "EHLO mailer.gwdg.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701AbXE0PFW (ORCPT ); Sun, 27 May 2007 11:05:22 -0400 Date: Sun, 27 May 2007 17:02:10 +0200 (MEST) From: Jan Engelhardt To: Stefan Richter cc: Auke Kok , randy.dunlap@oracle.com, Linux Kernel Mailing List , Scott Preece Subject: Re: [PATCH] [condingstyle] Add chapter on tests In-Reply-To: <4659978D.6020802@s5r6.in-berlin.de> Message-ID: References: <20070525172509.5138.56430.stgit@localhost.localdomain> <20070525172515.5138.13652.stgit@localhost.localdomain> <4659978D.6020802@s5r6.in-berlin.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Report: Content analysis: 0.0 points, 6.0 required _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2375 Lines: 90 On May 27 2007 16:37, Stefan Richter wrote: >Jan Engelhardt wrote: >> + if (is_prime(number) == true) >> + return 0; >> + if (is_prime(number) == false) >> + return 1; >> + >> +should be: >> + >> + if (is_prime(number)) >> + return 0; >> + if (!is_prime(number)) >> + return 1; >> + >> +As far as pointers or functions returning an integer are concerned, >> +using long form tests helps to distinguish between pointers and bools >> +or functions returning boolean or integer, respectively. >> +Examples are: >> + >> + if (p == NULL) >> + return 1; >> + if (!p) >> + return 0; >> + >> + if (strcmp(haystack, needle) == 0) >> + return 1; >> + if (!strcmp(haystack, needle)) >> + return 0; > >The latter two examples seem odd. Didn't you mean the following? See how much confusion it all makes! Right, it was intended -- first the long form is shown and then the shorter one (and "long form tests help to distinguish"): if (p == NULL) /* this way please */ return 1; if (!p) /* Everytime you shorten it, God kills a kitten */ return 0; /* so perhaps don't do it if you love animals or know someone who does. */ I seem to have forgotten more comments/explanation. > if (p == NULL) > return 1; > if (p) > return 0; > > if (strcmp(haystack, needle) == 0) > return 1; > if (strcmp(haystack, needle)) > return 0; > >Perhaps better: > > if (p == NULL) > return NO_MEMORY; > if (p) > return MEMORY; > > if (strcmp(haystack, needle) == 0) > return IS_SAME; > if (strcmp(haystack, needle)) > return IS_DIFFERENT; > >However, to follow your argument about non-boolean expressions, the >following would be more consequently going into your direction: > >I.e., why do the explicit comparison with 0 or NULL only when it is >tested for equality, but not when testing for inequality? > >However, I agree with Scott Preece that these rules should be left out >of CodingStyle because they are contentious. > >(Disclosure: I am personally used to "if (p)" and "if (!p)" tests of >pointers and many integer expressions, but I tend to the longer form in >less obvious cases like "if (strcmp(a, b) != 0)".) Jan -- - 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/