From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755467AbZLTQxT (ORCPT ); Sun, 20 Dec 2009 11:53:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755411AbZLTQxT (ORCPT ); Sun, 20 Dec 2009 11:53:19 -0500 Received: from one.firstfloor.org ([213.235.205.2]:38086 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755375AbZLTQxS (ORCPT ); Sun, 20 Dec 2009 11:53:18 -0500 Date: Sun, 20 Dec 2009 17:53:15 +0100 From: Andi Kleen To: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, jbeulich@novell.com, rusty@rustcorp.com.au, rguenther@suse.de Cc: arnd@arndb.de Subject: [PATCH] Fix BUILD_BUG_ON in fs/compat_ioctl.c to build with gcc 4.5 snapshot Message-ID: <20091220165315.GA13208@basil.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fix BUILD_BUG_ON in fs/compat_ioctl.c to build with gcc 4.5 snapshot The BUILD_BUG_ON in compat_ioctl_check_table() fails with a recent gcc mainline snapshot (gcc version 4.5.0 20091219) (GCC)), even though it works with older compilers. const int max = ARRAY_SIZE(ioctl_pointer) - 1; BUILD_BUG_ON(max >= (1 << 16)); I replaced the BUILD_BUG_ON with a old style extern reference and that works. That shows that the actual expression is evaluated ok and something must be wrong with the BUILD_BUG_ON macro itself. Maybe Rusty's rework will fix that (I haven't tried but it's probably worth investigating) I filed a bug on the compiler too http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42439 According to Joseph Myers the problem is that even when declared with const "max" is not a constant expression in the C standard sense, so the code is indeed incorrect. Anyways with this workaround a relatively standard defconfig like configuration and a 64bit allyes configuration builds again with gcc 4.5 Cc: jbeulich@novell.com Cc: rusty@rustcorp.com.au Cc: rguenther@suse.de Signed-off-by: Andi Kleen --- fs/compat_ioctl.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) Index: linux-2.6.33-rc1-ak/fs/compat_ioctl.c =================================================================== --- linux-2.6.33-rc1-ak.orig/fs/compat_ioctl.c +++ linux-2.6.33-rc1-ak/fs/compat_ioctl.c @@ -1649,8 +1649,10 @@ static int compat_ioctl_check_table(unsi { int i; const int max = ARRAY_SIZE(ioctl_pointer) - 1; + extern void __ioctl_pointer_too_large(void); - BUILD_BUG_ON(max >= (1 << 16)); + if (max >= (1 << 16)) + __ioctl_pointer_too_large(); /* guess initial offset into table, assuming a normalized distribution */