From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752360AbbIOBGE (ORCPT ); Mon, 14 Sep 2015 21:06:04 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:33895 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751959AbbIOBFh (ORCPT ); Mon, 14 Sep 2015 21:05:37 -0400 From: John Stultz To: LKML Cc: John Stultz , Andrew Morton , Ingo Molnar , "Steven Rostedt (Red Hat)" , Peter Zijlstra , Masami Hiramatsu , Michal Nazarewicz Subject: [RFC][PATCH 5/5] abs(): Provide build error on passing 64bit value to abs() Date: Mon, 14 Sep 2015 18:05:24 -0700 Message-Id: <1442279124-7309-6-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442279124-7309-1-git-send-email-john.stultz@linaro.org> References: <1442279124-7309-1-git-send-email-john.stultz@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As noted in the comment above abs(): "abs() should not be used for 64-bit types (s64, u64, long long) - use abs64() for those." Unfortunately, its quite easy to pass 64-bit values to abs() accidentally, and the compiler provides no warning when the returned value is erroniously capped at 32-bits. So this patch tries to make it easier to detect when 64-bit values are passed to abs() by generating a build error. Obviously, since this causes build errors, this patch is last in the series, and I tried to fix up all of the issues I ran into in my build testing. But there are likely still some out there. Cc: Andrew Morton Cc: Ingo Molnar Cc: "Steven Rostedt (Red Hat)" Cc: Peter Zijlstra Cc: Masami Hiramatsu Cc: Michal Nazarewicz Signed-off-by: John Stultz --- include/linux/kernel.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 5582410..6f01151 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -208,6 +208,9 @@ extern int _cond_resched(void); */ #define abs(x) ({ \ long ret; \ + compiletime_assert( \ + !(sizeof(typeof(x)) > sizeof(long)), \ + "abs() should not be used for 64-bit types - use abs64()");\ if (sizeof(x) == sizeof(long)) { \ long __x = (x); \ ret = (__x < 0) ? -__x : __x; \ -- 1.9.1