From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754505AbaEHNSq (ORCPT ); Thu, 8 May 2014 09:18:46 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:46865 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754385AbaEHNSp (ORCPT ); Thu, 8 May 2014 09:18:45 -0400 Date: Thu, 8 May 2014 06:18:39 -0700 From: "Paul E. McKenney" To: Johannes Berg Cc: Andrew Morton , linux-kernel@vger.kernel.org, Peter Zijlstra , Daniel Santos Subject: Re: [PATCH] compiler.h: don't use temporary variable in __compiletime_assert() Message-ID: <20140508131839.GZ8754@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1399530685-7749-1-git-send-email-johannes@sipsolutions.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1399530685-7749-1-git-send-email-johannes@sipsolutions.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14050813-9332-0000-0000-000000BA1C4F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 08, 2014 at 08:31:25AM +0200, Johannes Berg wrote: > From: Johannes Berg > > Usually, BUG_ON and friends aren't even evaluated in sparse, but > recently compiletime_assert_atomic_type() was added, and that now > results in a sparse warning every time it is used. > > The reason turns out to be the temporary variable, after it sparse > no longer considers the value to be a constant, and results in a > warning and an error. The error is the more annoying part of this > as it suppresses any further warnings in the same file, hiding > other problems. > > Since this is all about compile time and the condition should be > side-effect free to start with, there's no downside (apart maybe > from a slight compilation time penalty?) to just duplicating it, > leaving sparse able to evaluate it at check time, getting rid of > the warning and error. > > Signed-off-by: Johannes Berg Acked-by: Paul E. McKenney > --- > include/linux/compiler.h | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 2472740d7ab2..38c0e00ddef8 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -324,11 +324,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); > > #define __compiletime_assert(condition, msg, prefix, suffix) \ > do { \ > - bool __cond = !(condition); \ > extern void prefix ## suffix(void) __compiletime_error(msg); \ > - if (__cond) \ > + if (!(condition)) \ > prefix ## suffix(); \ > - __compiletime_error_fallback(__cond); \ > + __compiletime_error_fallback(!(condition)); \ > } while (0) > > #define _compiletime_assert(condition, msg, prefix, suffix) \ > -- > 2.0.0.rc0 >