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=-3.8 required=3.0 tests=BAYES_00, 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 94C8EC6379D for ; Wed, 25 Nov 2020 23:22:15 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 106A62083E for ; Wed, 25 Nov 2020 23:22:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 106A62083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=telegraphics.com.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.38151.70816 (Exim 4.92) (envelope-from ) id 1ki46q-0005zE-7T; Wed, 25 Nov 2020 23:22:00 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 38151.70816; Wed, 25 Nov 2020 23:22:00 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ki46q-0005z7-3r; Wed, 25 Nov 2020 23:22:00 +0000 Received: by outflank-mailman (input) for mailman id 38151; Wed, 25 Nov 2020 23:21:59 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ki46p-0005z2-Ht for xen-devel@lists.xenproject.org; Wed, 25 Nov 2020 23:21:59 +0000 Received: from kvm5.telegraphics.com.au (unknown [98.124.60.144]) by us1-rack-iad1.inumbo.com (Halon) with ESMTP id 3b4109bb-4bcd-4f48-b1da-519d2fd91930; Wed, 25 Nov 2020 23:21:58 +0000 (UTC) Received: from localhost (localhost.localdomain [127.0.0.1]) by kvm5.telegraphics.com.au (Postfix) with ESMTP id 414EA2A490; Wed, 25 Nov 2020 18:21:54 -0500 (EST) Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ki46p-0005z2-Ht for xen-devel@lists.xenproject.org; Wed, 25 Nov 2020 23:21:59 +0000 X-Inumbo-ID: 3b4109bb-4bcd-4f48-b1da-519d2fd91930 Received: from kvm5.telegraphics.com.au (unknown [98.124.60.144]) by us1-rack-iad1.inumbo.com (Halon) with ESMTP id 3b4109bb-4bcd-4f48-b1da-519d2fd91930; Wed, 25 Nov 2020 23:21:58 +0000 (UTC) Received: from localhost (localhost.localdomain [127.0.0.1]) by kvm5.telegraphics.com.au (Postfix) with ESMTP id 414EA2A490; Wed, 25 Nov 2020 18:21:54 -0500 (EST) Date: Thu, 26 Nov 2020 10:21:54 +1100 (AEDT) From: Finn Thain To: Nick Desaulniers cc: James Bottomley , Kees Cook , "Gustavo A. R. Silva" , Joe Perches , Jakub Kicinski , alsa-devel@alsa-project.org, linux-atm-general@lists.sourceforge.net, reiserfs-devel@vger.kernel.org, linux-iio@vger.kernel.org, linux-wireless , linux-fbdev@vger.kernel.org, dri-devel , LKML , Nathan Chancellor , linux-ide@vger.kernel.org, dm-devel@redhat.com, keyrings@vger.kernel.org, linux-mtd@lists.infradead.org, GR-everest-linux-l2@marvell.com, wcn36xx@lists.infradead.org, samba-technical@lists.samba.org, linux-i3c@lists.infradead.org, linux1394-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, usb-storage@lists.one-eyed-alien.net, drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, rds-devel@oss.oracle.com, linux-scsi@vger.kernel.org, linux-rdma@vger.kernel.org, oss-drivers@netronome.com, bridge@lists.linux-foundation.org, linux-security-module@vger.kernel.org, amd-gfx list , linux-stm32@st-md-mailman.stormreply.com, cluster-devel@redhat.com, linux-acpi@vger.kernel.org, coreteam@netfilter.org, intel-wired-lan@lists.osuosl.org, linux-input@vger.kernel.org, Miguel Ojeda , tipc-discussion@lists.sourceforge.net, linux-ext4@vger.kernel.org, linux-media@vger.kernel.org, linux-watchdog@vger.kernel.org, selinux@vger.kernel.org, linux-arm-msm , intel-gfx@lists.freedesktop.org, linux-geode@lists.infradead.org, linux-can@vger.kernel.org, linux-block@vger.kernel.org, linux-gpio@vger.kernel.org, op-tee@lists.trustedfirmware.org, linux-mediatek@lists.infradead.org, xen-devel@lists.xenproject.org, nouveau@lists.freedesktop.org, linux-hams@vger.kernel.org, ceph-devel@vger.kernel.org, virtualization@lists.linux-foundation.org, Linux ARM , linux-hwmon@vger.kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , linux-nfs@vger.kernel.org, GR-Linux-NIC-Dev@marvell.com, Linux Memory Management List , Network Development , linux-decnet-user@lists.sourceforge.net, linux-mmc@vger.kernel.org, Linux-Renesas , linux-sctp@vger.kernel.org, linux-usb@vger.kernel.org, netfilter-devel@vger.kernel.org, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , patches@opensource.cirrus.com, linux-integrity@vger.kernel.org, target-devel@vger.kernel.org, linux-hardening@vger.kernel.org, Jonathan Cameron , Greg KH Subject: Re: [Intel-wired-lan] [PATCH 000/141] Fix fall-through warnings for Clang In-Reply-To: Message-ID: References: <202011201129.B13FDB3C@keescook> <20201120115142.292999b2@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <202011220816.8B6591A@keescook> <9b57fd4914b46f38d54087d75e072d6e947cb56d.camel@HansenPartnership.com> <0147972a72bc13f3629de8a32dee6f1f308994b5.camel@HansenPartnership.com> <20201123130348.GA3119@embeddedor> <8f5611bb015e044fa1c0a48147293923c2d904e4.camel@HansenPartnership.com> <202011241327.BB28F12F6@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Wed, 25 Nov 2020, Nick Desaulniers wrote: > On Wed, Nov 25, 2020 at 1:33 PM Finn Thain > wrote: > > > > Or do you think that a codebase can somehow satisfy multiple checkers > > and their divergent interpretations of the language spec? > > Have we found any cases yet that are divergent? I don't think so. There are many implementations, so I think you are guaranteed to find more divergence if you look. That's because the spec is full of language like this: "implementations are encouraged not to emit a diagnostic" and "implementations are encouraged to issue a diagnostic". Some implementations will decide to not emit (under the premise that vast amounts of existing code would have to get patched until the compiler goes quiet) whereas other implementations will decide to emit (under the premise that the author is doing the checking and not the janitor or the packager). > It sounds to me like GCC's cases it warns for is a subset of Clang's. > Having additional coverage with Clang then should ensure coverage for > both. > If that claim were true, the solution would be simple. (It's not.) For the benefit of projects that enable -Werror and projects that nominated gcc as their preferred compiler, clang would simply need a flag to enable conformance with gcc by suppressing those additional warnings that clang would normally produce. This simple solution is, of course, completely unworkable, since it would force clang to copy some portion of gcc's logic (rewritten under LLVM's unique license) and then to track future changes to that portion of gcc indefinitely.