Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 28 Mar 2002 08:36:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 28 Mar 2002 08:36:00 -0500 Received: from rwcrmhc52.attbi.com ([216.148.227.88]:58287 "EHLO rwcrmhc52.attbi.com") by vger.kernel.org with ESMTP id ; Thu, 28 Mar 2002 08:35:43 -0500 Message-ID: <3CA31BF6.7030609@didntduck.org> Date: Thu, 28 Mar 2002 08:34:46 -0500 From: Brian Gerst User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.9) Gecko/20020311 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andrew Morton CC: linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [patch] ext2_fill_super breakage In-Reply-To: <3CA2C68E.5B8C4176@zip.com.au> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > In 2.5.7 there is a thinko in the allocation and initialisation > of the fs-private superblock for ext2. It's passing the wrong type > to the sizeof operator (which of course gives the wrong size) > when allocating and clearing the memory. > > Lesson for the day: this is one of the reasons why this idiom: > > some_type *p; > > p = malloc(sizeof(*p)); > ... > memset(p, 0, sizeof(*p)); > > is preferable to > > some_type *p; > > p = malloc(sizeof(some_type)); > ... > memset(p, 0, sizeof(some_type)); > > I checked the other filesystems. They're OK (but idiomatically > impure). I've added a couple of defensive memsets where > they were missing. I'm not sure I follow you here. Compiling this code (gcc 2.96): int foo1(void) { return sizeof(struct ext2_sb_info); } int foo2(struct ext2_sb_info *sbi) { return sizeof(*sbi); } yields: 00000b70 : b70: b8 dc 00 00 00 mov $0xdc,%eax b75: c3 ret 00000b80 : b80: b8 dc 00 00 00 mov $0xdc,%eax b85: c3 ret The sizes are the same, so unless it makes a difference with another version of gcc then this is just a cosmetic change. -- Brian Gerst - 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/