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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 ABA87C63777 for ; Fri, 20 Nov 2020 18:53:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1220324101 for ; Fri, 20 Nov 2020 18:53:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="y6BwGzsU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1220324101 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1E9AD6B006E; Fri, 20 Nov 2020 13:53:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1733B6B0070; Fri, 20 Nov 2020 13:53:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 013306B0071; Fri, 20 Nov 2020 13:53:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0186.hostedemail.com [216.40.44.186]) by kanga.kvack.org (Postfix) with ESMTP id BC5256B006E for ; Fri, 20 Nov 2020 13:53:51 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 650591F0A for ; Fri, 20 Nov 2020 18:53:51 +0000 (UTC) X-FDA: 77505695862.27.beast03_3a0e4502734d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 43D343D663 for ; Fri, 20 Nov 2020 18:53:51 +0000 (UTC) X-HE-Tag: beast03_3a0e4502734d X-Filterd-Recvd-Size: 4905 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Nov 2020 18:53:50 +0000 (UTC) Received: from kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com (unknown [163.114.132.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D19712242B; Fri, 20 Nov 2020 18:53:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605898429; bh=RlEnelajx5E1UvOiu4TwGuYZq41CYqRzy+OE2vpEZwM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=y6BwGzsUDu1zr4tV0nGpfLuqNb1AQVwTl3HIlZXKXQmalkVaXzcKTw6PaiYzn6cs4 cCrQcjpmBltf5qc0pbll6lEfWSr4jv5MMDA/VHBdadKQQtZqXFk9pYOspqu5FdKf1A HiIo+vycYYhwL3jW0KIV5eL5D/2xlLalPiHVxUuA= Date: Fri, 20 Nov 2020 10:53:44 -0800 From: Jakub Kicinski To: "Gustavo A. R. Silva" Cc: linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org, amd-gfx@lists.freedesktop.org, bridge@lists.linux-foundation.org, ceph-devel@vger.kernel.org, cluster-devel@redhat.com, coreteam@netfilter.org, devel@driverdev.osuosl.org, dm-devel@redhat.com, drbd-dev@lists.linbit.com, dri-devel@lists.freedesktop.org, GR-everest-linux-l2@marvell.com, GR-Linux-NIC-Dev@marvell.com, intel-gfx@lists.freedesktop.org, intel-wired-lan@lists.osuosl.org, keyrings@vger.kernel.org, linux1394-devel@lists.sourceforge.net, linux-acpi@vger.kernel.org, linux-afs@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-atm-general@lists.sourceforge.net, linux-block@vger.kernel.org, linux-can@vger.kernel.org, linux-cifs@vger.kernel.org, linux-crypto@vger.kernel.org, linux-decnet-user@lists.sourceforge.net, linux-ext4@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-geode@lists.infradead.org, linux-gpio@vger.kernel.org, linux-hams@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-i3c@lists.infradead.org, linux-ide@vger.kernel.org, linux-iio@vger.kernel.org, linux-input@vger.kernel.org, linux-integrity@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-media@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-sctp@vger.kernel.org, linux-security-module@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-usb@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, nouveau@lists.freedesktop.org, op-tee@lists.trustedfirmware.org, oss-drivers@netronome.com, patches@opensource.cirrus.com, rds-devel@oss.oracle.com, reiserfs-devel@vger.kernel.org, samba-technical@lists.samba.org, selinux@vger.kernel.org, target-devel@vger.kernel.org, tipc-discussion@lists.sourceforge.net, usb-storage@lists.one-eyed-alien.net, virtualization@lists.linux-foundation.org, wcn36xx@lists.infradead.org, x86@kernel.org, xen-devel@lists.xenproject.org, linux-hardening@vger.kernel.org, Nick Desaulniers , Nathan Chancellor , Miguel Ojeda , Joe Perches , Kees Cook Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang Message-ID: <20201120105344.4345c14e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 20 Nov 2020 12:21:39 -0600 Gustavo A. R. Silva wrote: > This series aims to fix almost all remaining fall-through warnings in > order to enable -Wimplicit-fallthrough for Clang. > > In preparation to enable -Wimplicit-fallthrough for Clang, explicitly > add multiple break/goto/return/fallthrough statements instead of just > letting the code fall through to the next case. > > Notice that in order to enable -Wimplicit-fallthrough for Clang, this > change[1] is meant to be reverted at some point. So, this patch helps > to move in that direction. > > Something important to mention is that there is currently a discrepancy > between GCC and Clang when dealing with switch fall-through to empty case > statements or to cases that only contain a break/continue/return > statement[2][3][4]. Are we sure we want to make this change? Was it discussed before? Are there any bugs Clangs puritanical definition of fallthrough helped find? IMVHO compiler warnings are supposed to warn about issues that could be bugs. Falling through to default: break; can hardly be a bug?!