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Sat, 17 Oct 2020 19:00:10 +0000 (UTC) Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay08.hostedemail.com (Postfix) with ESMTP id 15895182CED2A; Sat, 17 Oct 2020 19:00:10 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: jewel08_4005cbe27228 X-Filterd-Recvd-Size: 5179 Received: from XPS-9350.home (unknown [47.151.133.149]) (Authenticated sender: joe@perches.com) by omf01.hostedemail.com (Postfix) with ESMTPA; Sat, 17 Oct 2020 19:00:02 +0000 (UTC) Message-ID: <503af4a57ca6daeb3e42a9be136dcd21e6d6e23d.camel@perches.com> Subject: Re: [Cocci] [RFC] treewide: cleanup unreachable breaks From: Joe Perches To: Julia Lawall Cc: trix@redhat.com, linux-kernel@vger.kernel.org, cocci , alsa-devel@alsa-project.org, clang-built-linux@googlegroups.com, linux-iio@vger.kernel.org, nouveau@lists.freedesktop.org, storagedev@microchip.com, dri-devel@lists.freedesktop.org, virtualization@lists.linux-foundation.org, keyrings@vger.kernel.org, linux-mtd@lists.infradead.org, ath10k@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, usb-storage@lists.one-eyed-alien.net, linux-watchdog@vger.kernel.org, devel@driverdev.osuosl.org, linux-samsung-soc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, amd-gfx@lists.freedesktop.org, linux-acpi@vger.kernel.org, intel-wired-lan@lists.osuosl.org, industrypack-devel@lists.sourceforge.net, linux-pci@vger.kernel.org, spice-devel@lists.freedesktop.org, MPT-FusionLinux.pdl@broadcom.com, linux-media@vger.kernel.org, linux-serial@vger.kernel.org, linux-nfc@lists.01.org, linux-pm@vger.kernel.org, linux-can@vger.kernel.org, linux-block@vger.kernel.org, linux-gpio@vger.kernel.org, xen-devel@lists.xenproject.org, linux-amlogic@lists.infradead.org, openipmi-developer@lists.sourceforge.net, platform-driver-x86@vger.kernel.org, linux-integrity@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, linux-security-module@vger.kernel.org, linux-crypto@vger.kernel.org, patches@opensource.cirrus.com, bpf@vger.kernel.org, ocfs2-devel@oss.oracle.com, linux-power@fi.rohmeurope.com Date: Sat, 17 Oct 2020 12:00:01 -0700 In-Reply-To: References: <20201017160928.12698-1-trix@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.4-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit On Sat, 2020-10-17 at 20:21 +0200, Julia Lawall wrote: > On Sat, 17 Oct 2020, Joe Perches wrote: > > On Sat, 2020-10-17 at 09:09 -0700, trix@redhat.com wrote: > > > From: Tom Rix > > > > > > This is a upcoming change to clean up a new warning treewide. > > > I am wondering if the change could be one mega patch (see below) or > > > normal patch per file about 100 patches or somewhere half way by collecting > > > early acks. > > > > > > clang has a number of useful, new warnings see > > > https://clang.llvm.org/docs/DiagnosticsReference.html > > > > > > This change cleans up -Wunreachable-code-break > > > https://clang.llvm.org/docs/DiagnosticsReference.html#wunreachable-code-break > > > for 266 of 485 warnings in this week's linux-next, allyesconfig on x86_64. > > > > Early acks/individual patches by subsystem would be good. > > Better still would be an automated cocci script. > > Coccinelle is not especially good at this, because it is based on control > flow, and a return or goto diverts the control flow away from the break. > A hack to solve the problem is to put an if around the return or goto, but > that gives the break a meaningless file name and line number. I collected > the following list, but it only has 439 results, so fewer than clang. But > maybe there are some files that are not considered by clang in the x86 > allyesconfig configuration. > > Probably checkpatch is the best solution here, since it is not > configuration sensitive and doesn't care about control flow. Likely the clang compiler is the best option here. It might be useful to add -Wunreachable-code-break to W=1 or just always enable it if it isn't already enabled. diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index 95e4cdb94fe9..3819787579d5 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -32,6 +32,7 @@ KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable) KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned) KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) +KBUILD_CFLAGS += $(call cc-option, -Wunreachable-code-break) # The following turn off the warnings enabled by -Wextra KBUILD_CFLAGS += -Wno-missing-field-initializers KBUILD_CFLAGS += -Wno-sign-compare (and thank you Tom for pushing this forward) checkpatch can't find instances like: case FOO: if (foo) return 1; else return 2; break; As it doesn't track flow and relies on the number of tabs to be the same for any goto/return and break; checkpatch will warn on: case FOO: ... goto bar; break;