From mboxrd@z Thu Jan 1 00:00:00 1970 From: joe@perches.com (Joe Perches) Date: Thu, 13 Nov 2014 22:12:38 -0800 Subject: [Cocci] spatch for trivial pointer comparison style? In-Reply-To: References: <1415908529.4223.11.camel@perches.com> Message-ID: <1415945558.5912.10.camel@perches.com> To: cocci@systeme.lip6.fr List-Id: cocci@systeme.lip6.fr On Fri, 2014-11-14 at 07:06 +0100, Julia Lawall wrote: > On Thu, 13 Nov 2014, Joe Perches wrote: > > > I added a checkpatch entry for this. > > Maybe some cocci test like this would be useful? > > > > @@ > > type t; > > t *p; > > @@ > > - p == NULL > > + !p > > > > @@ > > type t; > > t *p; > > @@ > > - p != NULL > > + p > > > > @@ > > type t; > > t *p; > > @@ > > - NULL == p > > + !p > > > > @@ > > type t; > > t *p; > > @@ > > - NULL != p > > + p > > This was discussed many years ago. I don't think that the change is > desirable in all cases. There are functions like kmalloc where NULL means > failure and !p seems like the reasonable choice. But there maybe other > cases where NULL is somehow a meaningful value. > > Here is a link to the part of the discussion: > > https://lkml.org/lkml/2007/7/27/103 Yes, I agree with some of the things Al Viro said there, but isn't 'type t; t *p;' a subset of "expression *e"? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754437AbaKNGMm (ORCPT ); Fri, 14 Nov 2014 01:12:42 -0500 Received: from smtprelay0114.hostedemail.com ([216.40.44.114]:55831 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751146AbaKNGMl (ORCPT ); Fri, 14 Nov 2014 01:12:41 -0500 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Spam-Summary: 50,0,0,,d41d8cd98f00b204,joe@perches.com,:::::,RULES_HIT:41:355:379:541:599:967:973:988:989:1260:1277:1311:1313:1314:1345:1359:1373:1437:1515:1516:1518:1534:1540:1593:1594:1711:1730:1747:1777:1792:2393:2525:2553:2560:2563:2682:2685:2828:2859:2899:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3353:3622:3865:3866:3867:3868:3870:3871:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4250:4321:5007:6261:7904:9025:10004:10400:10848:11232:11658:11914:12043:12517:12519:12740:13019:13069:13161:13229:13311:13357:14096:14097:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: cub16_51691095c0f30 X-Filterd-Recvd-Size: 1859 Message-ID: <1415945558.5912.10.camel@perches.com> Subject: Re: [Cocci] spatch for trivial pointer comparison style? From: Joe Perches To: Julia Lawall Cc: cocci , LKML Date: Thu, 13 Nov 2014 22:12:38 -0800 In-Reply-To: References: <1415908529.4223.11.camel@perches.com> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.12.7-0ubuntu1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-11-14 at 07:06 +0100, Julia Lawall wrote: > On Thu, 13 Nov 2014, Joe Perches wrote: > > > I added a checkpatch entry for this. > > Maybe some cocci test like this would be useful? > > > > @@ > > type t; > > t *p; > > @@ > > - p == NULL > > + !p > > > > @@ > > type t; > > t *p; > > @@ > > - p != NULL > > + p > > > > @@ > > type t; > > t *p; > > @@ > > - NULL == p > > + !p > > > > @@ > > type t; > > t *p; > > @@ > > - NULL != p > > + p > > This was discussed many years ago. I don't think that the change is > desirable in all cases. There are functions like kmalloc where NULL means > failure and !p seems like the reasonable choice. But there maybe other > cases where NULL is somehow a meaningful value. > > Here is a link to the part of the discussion: > > https://lkml.org/lkml/2007/7/27/103 Yes, I agree with some of the things Al Viro said there, but isn't 'type t; t *p;' a subset of "expression *e"?