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Tue, 24 Nov 2020 17:58:15 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 82340F8016C; Fri, 20 Nov 2020 20:51:56 +0100 (CET) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id A9111F800C5 for ; Fri, 20 Nov 2020 20:51:50 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz A9111F800C5 Authentication-Results: alsa1.perex.cz; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0HJ898xk" 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 ADA4D206B6; Fri, 20 Nov 2020 19:51:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605901908; bh=RBzOhaxiAPO90htsWQNreeN48VhmFALIIs8F+S8F2tg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0HJ898xky9A4AiX47c8E/kv2vloKTCLDsa1B08r0Ns0UI6ViLC8sEEmzvLmSWmHDR rh+QM7asV5JMfRqDaW/zMVHUMAG8pWVLOHT3LXTHM6aAp9QNwMcpVcVlrfF8wRUqJ9 pWgdeTKSVxQ+8c5KHivLBQCp2OjpIRpNZteZuQdk= Date: Fri, 20 Nov 2020 11:51:42 -0800 From: Jakub Kicinski To: Kees Cook Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang Message-ID: <20201120115142.292999b2@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: <202011201129.B13FDB3C@keescook> References: <20201120105344.4345c14e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <202011201129.B13FDB3C@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Tue, 24 Nov 2020 17:58:08 +0100 Cc: alsa-devel@alsa-project.org, linux-atm-general@lists.sourceforge.net, reiserfs-devel@vger.kernel.org, linux-iio@vger.kernel.org, linux-wireless@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, 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, Nick Desaulniers , 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@lists.freedesktop.org, 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@vger.kernel.org, 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-kernel@lists.infradead.org, linux-hwmon@vger.kernel.org, x86@kernel.org, linux-nfs@vger.kernel.org, GR-Linux-NIC-Dev@marvell.com, linux-mm@kvack.org, netdev@vger.kernel.org, linux-decnet-user@lists.sourceforge.net, linux-mmc@vger.kernel.org, "Gustavo A. R. Silva" , linux-renesas-soc@vger.kernel.org, linux-sctp@vger.kernel.org, linux-usb@vger.kernel.org, netfilter-devel@vger.kernel.org, linux-crypto@vger.kernel.org, patches@opensource.cirrus.com, Joe Perches , linux-integrity@vger.kernel.org, target-devel@vger.kernel.org, linux-hardening@vger.kernel.org X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Fri, 20 Nov 2020 11:30:40 -0800 Kees Cook wrote: > On Fri, Nov 20, 2020 at 10:53:44AM -0800, Jakub Kicinski wrote: > > 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?! > > It's certainly a place where the intent is not always clear. I think > this makes all the cases unambiguous, and doesn't impact the machine > code, since the compiler will happily optimize away any behavioral > redundancy. If none of the 140 patches here fix a real bug, and there is no change to machine code then it sounds to me like a W=2 kind of a warning. I think clang is just being annoying here, but if I'm the only one who feels this way chances are I'm wrong :)