From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755179Ab2ISD77 (ORCPT ); Tue, 18 Sep 2012 23:59:59 -0400 Received: from mail.active-venture.com ([67.228.131.205]:62134 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754474Ab2ISD76 (ORCPT ); Tue, 18 Sep 2012 23:59:58 -0400 X-Virus-Scan: Scanned by ClamAV 0.97.2 (no viruses); Tue, 18 Sep 2012 22:59:57 -0500 X-Originating-IP: 108.223.40.66 From: Guenter Roeck To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Jean Delvare , Mauro Carvalho Chehab , lm-sensors@lm-sensors.org, Guenter Roeck Subject: [PATCH] linux/kernel.h: Fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST Date: Tue, 18 Sep 2012 21:00:09 -0700 Message-Id: <1348027209-29710-1-git-send-email-linux@roeck-us.net> X-Mailer: git-send-email 1.7.9.7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After commit b6d86d3d (Fix DIV_ROUND_CLOSEST to support negative dividends), the following warning is seen if the kernel is compiled with W=1 (-Wextra): warning: comparison of unsigned expression >= 0 is always true The warning is due to the test '((typeof(x))-1) >= 0', which is used to detect if the variable type is unsigned. Research on the web suggests that the warning disappears if '>' instead of '>=' is used for the comparison. Tests after changing the macro along that line show that the warning is gone, and that the result is still correct: i=-4: DIV_ROUND_CLOSEST(i, 2)=-2 i=-3: DIV_ROUND_CLOSEST(i, 2)=-2 i=-2: DIV_ROUND_CLOSEST(i, 2)=-1 i=-1: DIV_ROUND_CLOSEST(i, 2)=-1 i=0: DIV_ROUND_CLOSEST(i, 2)=0 i=1: DIV_ROUND_CLOSEST(i, 2)=1 i=2: DIV_ROUND_CLOSEST(i, 2)=1 i=3: DIV_ROUND_CLOSEST(i, 2)=2 i=4: DIV_ROUND_CLOSEST(i, 2)=2 Code size is the same as before. Signed-off-by: Guenter Roeck --- include/linux/kernel.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 594b419..2451f1f 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -91,7 +91,7 @@ { \ typeof(x) __x = x; \ typeof(divisor) __d = divisor; \ - (((typeof(x))-1) >= 0 || (__x) >= 0) ? \ + (((typeof(x))-1) > 0 || (__x) > 0) ? \ (((__x) + ((__d) / 2)) / (__d)) : \ (((__x) - ((__d) / 2)) / (__d)); \ } \ -- 1.7.9.7