From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753744Ab2HCVsO (ORCPT ); Fri, 3 Aug 2012 17:48:14 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:38494 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753107Ab2HCVsL (ORCPT ); Fri, 3 Aug 2012 17:48:11 -0400 Date: Fri, 3 Aug 2012 14:48:06 -0700 From: Tejun Heo To: Sasha Levin Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org Subject: Re: [RFC v2 1/7] hashtable: introduce a small and naive hashtable Message-ID: <20120803214806.GM15477@google.com> References: <1344003788-1417-1-git-send-email-levinsasha928@gmail.com> <1344003788-1417-2-git-send-email-levinsasha928@gmail.com> <20120803171515.GH15477@google.com> <501C407D.9080900@gmail.com> <20120803213017.GK15477@google.com> <501C458E.7050000@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <501C458E.7050000@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Aug 03, 2012 at 11:41:34PM +0200, Sasha Levin wrote: > I forgot to comment on that one, sorry. > > If we put hash entries after struct hash_table we don't take the > bits field size into account, or did I miss something? So, if you do the following, struct { struct { int i; long ar[]; } B; long __ar_storage[32]; } A; It should always be safe to dereference A.B.ar[31]. I'm not sure whether this is something guaranteed by C tho. Maybe compilers are allowed to put members in reverse order but I think we already depend on the above. Thanks. -- tejun