From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id C10AE8E001A for ; Wed, 23 Jan 2019 10:44:46 -0500 (EST) Received: by mail-pg1-f198.google.com with SMTP id d71so1736169pgc.1 for ; Wed, 23 Jan 2019 07:44:46 -0800 (PST) Received: from mga06.intel.com (mga06.intel.com. [134.134.136.31]) by mx.google.com with ESMTPS id 1si19383796pld.239.2019.01.23.07.44.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Jan 2019 07:44:45 -0800 (PST) From: Jani Nikula Subject: RE: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches In-Reply-To: <000001d4b32a$845e06e0$8d1a14a0$@211mainstreet.net> References: <20190123110349.35882-1-keescook@chromium.org> <20190123110349.35882-2-keescook@chromium.org> <20190123115829.GA31385@kroah.com> <874l9z31c5.fsf@intel.com> <000001d4b32a$845e06e0$8d1a14a0$@211mainstreet.net> Date: Wed, 23 Jan 2019 17:46:14 +0200 Message-ID: <87va2f1int.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Edwin Zimmerman , 'Greg KH' , 'Kees Cook' Cc: dev@openvswitch.org, 'Ard Biesheuvel' , netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, intel-wired-lan@lists.osuosl.org, linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org, 'Laura Abbott' , linux-kbuild@vger.kernel.org, 'Alexander Popov' On Wed, 23 Jan 2019, Edwin Zimmerman wrote: > On Wed, 23 Jan 2019, Jani Nikula wrote: >> On Wed, 23 Jan 2019, Greg KH wrote: >> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote: >> >> Variables declared in a switch statement before any case statements >> >> cannot be initialized, so move all instances out of the switches. >> >> After this, future always-initialized stack variables will work >> >> and not throw warnings like this: >> >> >> >> fs/fcntl.c: In function =E2=80=98send_sigio_to_task=E2=80=99: >> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitc= h-unreachable] >> >> siginfo_t si; >> >> ^~ >> > >> > That's a pain, so this means we can't have any new variables in { } >> > scope except for at the top of a function? >> > >> > That's going to be a hard thing to keep from happening over time, as >> > this is valid C :( >>=20 >> Not all valid C is meant to be used! ;) > > Very true. The other thing to keep in mind is the burden of enforcing > a prohibition on a valid C construct like this. It seems to me that > patch reviewers and maintainers have enough to do without forcing them > to watch for variable declarations in switch statements. Automating > this prohibition, should it be accepted, seems like a good idea to me. Considering that the treewide diffstat to fix this is: 18 files changed, 45 insertions(+), 46 deletions(-) and using the gcc plugin in question will trigger the switch-unreachable warning, I think we're good. There'll probably be the occasional declarations that pass through, and will get fixed afterwards. BR, Jani. --=20 Jani Nikula, Intel Open Source Graphics Center