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R. Silva" , LKML , alsa-devel@alsa-project.org, amd-gfx list , 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 , 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 , linux-arm-msm , linux-atm-general@lists.sourceforge.net, linux-block@vger.kernel.org, linux-can@vger.kernel.org, linux-cifs@vger.kernel.org, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , 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 Memory Management List , linux-mtd@lists.infradead.org, linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org, Linux-Renesas , 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 , Network Development , 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, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , xen-devel@lists.xenproject.org, linux-hardening@vger.kernel.org, Nathan Chancellor , Miguel Ojeda , Joe Perches Content-Type: text/plain; charset="UTF-8" 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 Sun, Nov 22, 2020 at 8:17 AM Kees Cook wrote: > > On Fri, Nov 20, 2020 at 11:51:42AM -0800, Jakub Kicinski wrote: > > 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. > > FWIW, this series has found at least one bug so far: > https://lore.kernel.org/lkml/CAFCwf11izHF=g1mGry1fE5kvFFFrxzhPSM6qKAO8gxSp=Kr_CQ@mail.gmail.com/ So looks like the bulk of these are: switch (x) { case 0: ++x; default: break; } I have a patch that fixes those up for clang: https://reviews.llvm.org/D91895 There's 3 other cases that don't quite match between GCC and Clang I observe in the kernel: switch (x) { case 0: ++x; default: goto y; } y:; switch (x) { case 0: ++x; default: return; } switch (x) { case 0: ++x; default: ; } Based on your link, and Nathan's comment on my patch, maybe Clang should continue to warn for the above (at least the `default: return;` case) and GCC should change? While the last case looks harmless, there were only 1 or 2 across the tree in my limited configuration testing; I really think we should just add `break`s for those. -- Thanks, ~Nick Desaulniers