From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751905AbaANLoL (ORCPT ); Tue, 14 Jan 2014 06:44:11 -0500 Received: from plane.gmane.org ([80.91.229.3]:51540 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451AbaANLoJ (ORCPT ); Tue, 14 Jan 2014 06:44:09 -0500 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Rasmus Villemoes Subject: Re: [PATCH 1/2] lib/lcm.c: Ensure correct result whenever it fits Date: Tue, 14 Jan 2014 12:43:51 +0100 Organization: D03 Message-ID: <87y52i94aw.fsf@rasmusvillemoes.dk> References: <1387291572-12348-1-git-send-email-linux@rasmusvillemoes.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: pool-17.imf.au.dk User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux) Cancel-Lock: sha1:N8G+J6dExsto36qfAh1tM5IdRbY= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rasmus Villemoes writes: Ping... > Ensure that lcm(a,b) returns the mathematically correct result, > provided it fits in an unsigned long. The current version returns > garbage if a*b overflows, even if the final result would fit. > > Signed-off-by: Rasmus Villemoes > --- > There are of course still plenty of cases where the return value is > wrong. > > lib/lcm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/lcm.c b/lib/lcm.c > index b9c8de4..01b3aa9 100644 > --- a/lib/lcm.c > +++ b/lib/lcm.c > @@ -7,7 +7,7 @@ > unsigned long lcm(unsigned long a, unsigned long b) > { > if (a && b) > - return (a * b) / gcd(a, b); > + return (a / gcd(a, b)) * b; > else if (b) > return b;