From patchwork Tue May 10 09:20:49 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Niels de Vos X-Patchwork-Id: 773662 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id p4A9Lhx2006108 for ; Tue, 10 May 2011 09:21:44 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753185Ab1EJJVT (ORCPT ); Tue, 10 May 2011 05:21:19 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:46632 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751796Ab1EJJVR (ORCPT ); Tue, 10 May 2011 05:21:17 -0400 Received: by wwa36 with SMTP id 36so6653840wwa.1 for ; Tue, 10 May 2011 02:21:15 -0700 (PDT) Received: by 10.227.160.69 with SMTP id m5mr2099165wbx.97.1305019275512; Tue, 10 May 2011 02:21:15 -0700 (PDT) Received: from localhost.localdomain (cpc3-glfd3-0-0-cust917.6-2.cable.virginmedia.com [86.17.251.150]) by mx.google.com with ESMTPS id ed10sm4265810wbb.66.2011.05.10.02.21.14 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 10 May 2011 02:21:14 -0700 (PDT) From: Niels de Vos To: linux-omap@vger.kernel.org Cc: linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Niels de Vos Subject: [PATCH] omap2/omapfb: make DBG() more resistant in if-else constructions Date: Tue, 10 May 2011 10:20:49 +0100 Message-Id: <1305019249-9898-1-git-send-email-ndevos@redhat.com> X-Mailer: git-send-email 1.7.4.4 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Tue, 10 May 2011 09:21:44 +0000 (UTC) When DBG() is used in a simple if-else, the resulting code path currently depends on the definition of DBG(). Inserting the statement in a "do { ... } while (0)" prevents this possible misuse. Signed-off-by: Niels de Vos --- Note, I have not found any offenders, but a mistake can easily be made. The following example shows what can go wrong if little intention is paid to the definition of the DBG() macro. Example: if something_went_wrong() DBG("oh no, something went wrong!\n"); else printk("all went fine\n"); Old result where the else is placed inside the first if-statment: if something_went_wrong() { if (omapfb_debug) { printk(KERN_DEBUG "oh no, something went wrong!\n"); } else { printk("all went fine\n"); } } New result where the else is an alternative to the first if-statement: if something_went_wrong() { do { if (omapfb_debug) printk(KERN_DEBUG "oh no, something went wrong!\n"); } while (0); } else { printk("all went fine\n"); } --- drivers/video/omap2/omapfb/omapfb.h | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/video/omap2/omapfb/omapfb.h b/drivers/video/omap2/omapfb/omapfb.h index 1305fc9..a01b0bb 100644 --- a/drivers/video/omap2/omapfb/omapfb.h +++ b/drivers/video/omap2/omapfb/omapfb.h @@ -34,8 +34,10 @@ #ifdef DEBUG extern unsigned int omapfb_debug; #define DBG(format, ...) \ - if (omapfb_debug) \ - printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__) + do { \ + if (omapfb_debug) \ + printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__); \ + while (0) #else #define DBG(format, ...) #endif