From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32719C433FF for ; Mon, 29 Jul 2019 10:24:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0576B2075C for ; Mon, 29 Jul 2019 10:24:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728191AbfG2KYa convert rfc822-to-8bit (ORCPT ); Mon, 29 Jul 2019 06:24:30 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:49549 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728150AbfG2KYa (ORCPT ); Mon, 29 Jul 2019 06:24:30 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-234-VJwiHrKHPaOBTCMo7rm5ew-1; Mon, 29 Jul 2019 11:24:28 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 29 Jul 2019 11:24:27 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 29 Jul 2019 11:24:27 +0100 From: David Laight To: "'Moore, Robert'" , Qian Cai , "Wysocki, Rafael J" CC: "Schmauss, Erik" , "jkim@FreeBSD.org" , "lenb@kernel.org" , "ndesaulniers@google.com" , "linux-acpi@vger.kernel.org" , "devel@acpica.org" , "clang-built-linux@googlegroups.com" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2] acpica: fix -Wnull-pointer-arithmetic warnings Thread-Topic: [PATCH v2] acpica: fix -Wnull-pointer-arithmetic warnings Thread-Index: AQHVPaHylXmfzBauvEybJLDaugeeCqbdV0WAgAQb46A= Date: Mon, 29 Jul 2019 10:24:27 +0000 Message-ID: References: <20190718194846.1880-1-cai@lca.pw> <94F2FBAB4432B54E8AACC7DFDE6C92E3B9661CBD@ORSMSX110.amr.corp.intel.com> In-Reply-To: <94F2FBAB4432B54E8AACC7DFDE6C92E3B9661CBD@ORSMSX110.amr.corp.intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: VJwiHrKHPaOBTCMo7rm5ew-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Moore, Robert > Sent: 26 July 2019 20:36 ... > This is because pointer arithmetic > on a pointer not pointing to an array is an undefined behavior (C11 6.5.6, constraint 8). ... The standards committee as smoking dope again :-) If that is enforced as a compiler warning/error a lot of code 'breaks'. Anything that does: struct foo *foo = ...; struct bar *bar = (void *)(foo + 1); suddenly becomes 'invalid'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)