Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753645AbaB0Pxa (ORCPT ); Thu, 27 Feb 2014 10:53:30 -0500 Received: from terminus.zytor.com ([198.137.202.10]:56312 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752639AbaB0PtS (ORCPT ); Thu, 27 Feb 2014 10:49:18 -0500 Message-ID: <530F5E53.5070208@zytor.com> Date: Thu, 27 Feb 2014 07:48:35 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: "Theodore Ts'o" , Borislav Petkov , Joe Perches , Ben Pfaff , Christopher Li , Josh Triplett , linux-sparse@vger.kernel.org, Linux Kernel Mailing List Subject: Re: [PATCH V2] sparse: Allow override of sizeof(bool) warning References: <530E8C2E.7080307@zytor.com> <1393466619.24588.65.camel@joe-AO722> <20140227022857.GC23659@thin> <1393469594.24588.71.camel@joe-AO722> <20140227025845.GA25145@thin> <530EB103.5070406@zytor.com> <1393472326.24588.82.camel@joe-AO722> <60797a1a-1a83-468e-9629-abf4e8712d65@email.android.com> <20140227082529.GA18210@pd.tnic> <20140227152435.GA7982@thunk.org> In-Reply-To: <20140227152435.GA7982@thunk.org> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/27/2014 07:24 AM, Theodore Ts'o wrote: > On Thu, Feb 27, 2014 at 07:10:25AM -0800, H. Peter Anvin wrote: >> Keep in mind, too, that for the kernel we don't care about the full >> C standard but a subset. We rely on extrastandard behavior all over >> the place. For all ABIs supported by the kernel, sizeof(_Book) == 1 >> and so everything is sane. > > Do we have a fairly comprehensive list of what these extrastandard > requirements / assumptions are? It might be a good idea to have one > that we can point to, so that (a) people who are trying to define a > new architecture knows what they need to handle, (b) and so we can > give a list of things that static code analyzers like smatch and > coverity and sparse should be able to suppress (perhaps in a Linux > kernel-only mode). > No, but I think we can certainly make a list... a lot of it right now sits in various people's heads. Here are a couple: - Bytes are 8 bits - Signed integers will be 2's complement - sizeof char, short, int, long, and long long will be 1, 2, 4, 4, 8 or 1, 2, 4, 8, 8 on 32- and 64-bit processors, respectively. - sizeof(long) == sizeof(void *) - NULL is represented by all zero - Structures will not add padding as long as all the members are naturally aligned. Someone want to set up a collaborative document of some kind and collect more? -hpa -- 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/