From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751827AbaJ0FdL (ORCPT ); Mon, 27 Oct 2014 01:33:11 -0400 Received: from smtprelay0174.hostedemail.com ([216.40.44.174]:49524 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750855AbaJ0FdK (ORCPT ); Mon, 27 Oct 2014 01:33:10 -0400 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,joe@perches.com,:::::,RULES_HIT:41:355:379:541:800:960:973:982:988:989:1260:1277:1311:1313:1314:1345:1373:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2197:2199:2393:2553:2559:2562:2828:3138:3139:3140:3141:3142:3352:3653:3865:3866:3871:3874:4321:5007:6120:6261:7901:8957:10004:10400:10848:11026:11473:11658:11914:12043:12517:12519:12555:13069:13311:13357:14394:21080,0,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: cloud27_8fc9839bb3a06 X-Filterd-Recvd-Size: 1770 Message-ID: <1414387986.15751.28.camel@perches.com> Subject: [PATCH] checkpatch: Try to avoid mask and shift errors From: Joe Perches To: Andrew Morton Cc: Andy Whitcroft , LKML Date: Sun, 26 Oct 2014 22:33:06 -0700 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 Shift has a higher precedence that mask so warn when a mask then shift operation is done without parentheses around the mask. This test works well for a right shift, but the left shift is pretty commonly done correctly so only warn on the right shift. Signed-off-by: Joe Perches --- scripts/checkpatch.pl | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index d94f5d8..9b474d5 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -4478,6 +4478,14 @@ sub process { } } +# check for mask then right shift without a parentheses + if ($^V && $^V ge 5.10.0 && + $line =~ /$LvalOrFunc\s*\&\s*($LvalOrFunc)\s*>>/ && + $4 !~ /^\&/) { # $LvalOrFunc may be &foo, ignore if so + WARN("MASK_THEN_SHIFT", + "Possible precedence defect with mask then right shift - may need parentheses\n" . $herecurr); + } + # check for bad placement of section $InitAttribute (e.g.: __initdata) if ($line =~ /(\b$InitAttribute\b)/) { my $attr = $1;