Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645AbaAQN6R (ORCPT ); Fri, 17 Jan 2014 08:58:17 -0500 Received: from mail-wi0-f173.google.com ([209.85.212.173]:61585 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751920AbaAQN6M (ORCPT ); Fri, 17 Jan 2014 08:58:12 -0500 MIME-Version: 1.0 In-Reply-To: References: Date: Fri, 17 Jan 2014 14:58:10 +0100 Message-ID: Subject: Re: Why is (2 < 2) true? Is it a gcc bug? From: Richard Weinberger To: "Dorau, Lukasz" Cc: "linux-kernel@vger.kernel.org" , "linux-scsi@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 17, 2014 at 2:37 PM, Dorau, Lukasz wrote: > Hi > > My story is very simply... > I applied the following patch: > > diff --git a/drivers/scsi/isci/init.c b/drivers/scsi/isci/init.c > --- a/drivers/scsi/isci/init.c > +++ b/drivers/scsi/isci/init.c > @@ -698,8 +698,11 @@ static int isci_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) > if (err) > goto err_host_alloc; > > - for_each_isci_host(i, isci_host, pdev) > + for_each_isci_host(i, isci_host, pdev) { > + pr_err("(%d < %d) == %d\n",\ > + i, SCI_MAX_CONTROLLERS, (i < SCI_MAX_CONTROLLERS)); > scsi_scan_host(to_shost(isci_host)); > + } > > return 0; > > -- > 1.8.3.1 > > Then I issued the command 'modprobe isci' on platform with two SCU controllers (Patsburg D or T chipset) > and received the following, very strange, output: > > (0 < 2) == 1 > (1 < 2) == 1 > (2 < 2) == 1 > > Can anyone explain why (2 < 2) is true? Is it a gcc bug? > > (The kernel was compiled using gcc version 4.8.2.) > Can you reproduce this using a standalone test? I.e: #include int main() { assert(2 < 2 != 1); return 0; } -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/