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Wed, 25 Nov 2020 14:09:40 -0800 (PST) MIME-Version: 1.0 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> In-Reply-To: From: Nick Desaulniers Date: Wed, 25 Nov 2020 14:09:29 -0800 Message-ID: Subject: Re: [Intel-wired-lan] [PATCH 000/141] Fix fall-through warnings for Clang To: Finn Thain 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 Content-Type: text/plain; charset="UTF-8" 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. 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. > > This is not a shiny new warning; it's already on for GCC and has existed > > in both compilers for multiple releases. > > > > Perhaps you're referring to the compiler feature that lead to the > ill-fated, tree-wide /* fallthrough */ patch series. > > When the ink dries on the C23 language spec and the implementations figure > out how to interpret it then sure, enforce the warning for new code -- the > cost/benefit analysis is straight forward. However, the case for patching > existing mature code is another story. I don't think we need to wait for the ink to dry on the C23 language spec to understand that implicit fallthrough is an obvious defect of the C language. While the kernel is a mature codebase, it's not immune to bugs. And its maturity has yet to slow its rapid pace of development. -- Thanks, ~Nick Desaulniers