Return-Path: Received: from esgaroth.petrovitsch.at ([78.47.184.11]:4682 "EHLO esgaroth.tuxoid.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728270AbeJWCMC (ORCPT ); Mon, 22 Oct 2018 22:12:02 -0400 Subject: Re: [PATCH 1/2] Compiler Attributes: add support for __fallthrough (gcc >= 7.1) To: Miguel Ojeda , Dan Cc: "Ted Ts'o" , Greg KH , linux-kernel , Andreas Dilger , Masahiro Yamada , Michal Marek , Steven Rostedt , Mauro Carvalho Chehab , Olof Johansson , Konstantin Ryabitsev , David Miller , Andrey Ryabinin , Kees Cook , Thomas Gleixner , Ingo Molnar , Paul Lawrence , Sandipan Das , Andrey Konovalov , David Woodhouse , Will Deacon , Philippe Ombredanne , Paul Burton , David Rientjes , Willy Tarreau , Martin Sebor , Christopher Li , Jonathan Corbet , Geert Uytterhoeven , Rasmus Villemoes , Joe Perches , Arnd Bergmann , Dominique Martinet , Stefan Agner , Luc Van Oostenryck , Nick Desaulniers , Andrew Morton , Linus Torvalds , Linux Doc Mailing List , Ext4 Developers List , linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org, ndesaulniers@google.com References: <20181021171414.22674-1-miguel.ojeda.sandonis@gmail.com> <20181021171414.22674-2-miguel.ojeda.sandonis@gmail.com> <20181021222712.GI1617@thunk.org> <8fb78062-b6d4-6f2d-d943-44bec6b95ff0@petrovitsch.priv.at> <20181022102743.nua5fgbscyeymzal@mwanda> <1474d995-1b5a-2efb-f077-33eb4a5d9e31@petrovitsch.priv.at> <20181022105314.j6djkrpwbnokhai5@mwanda> From: Bernd Petrovitsch Message-ID: <3cbb5345-0270-5575-7563-6ad37d888e42@petrovitsch.priv.at> Date: Mon, 22 Oct 2018 19:49:21 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------4F428F195E06AF3B428EB1A0" Content-Language: en-US Sender: linux-ext4-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------4F428F195E06AF3B428EB1A0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi all! On 22/10/18 13:07, Miguel Ojeda wrote: > On Mon, Oct 22, 2018 at 12:54 PM Dan Carpenter wrote: >> >> Doing both is super ugly. Let's just do comments until Eclipse gets >> updated. Yes, "Eclipse" as the IDE. And yes but IMHO better super ugly than loosing the warning - YMMV. For the archives: I have Eclipse Photon/June 2016 here. And "no break" is the (default) string in a comment used by Eclipse (it can be customized and is actually a regexp but it must be in a comment). >> I had wanted to move to the attribute because that would simplify thin= gs >> in Smatch but it's not a huge deal to delay for another year. >=20 > I can re-send them later on, no problem. On the other hand, doing the > changes will push tools to get updated sooner ;-) >=20 > If tools were doing something as fancy as comment parsing for > diagnostics, they should have been updated with the attribute support > (either gcc's or C++17's) -- it has been more than a year now since > gcc 7.1 and the C++17 final draft. (Note that this does not apply for > things like clang, since they weren't doing comment parsing to begin > with.) That would be nice. And if they agree on the same texts (or accept per default all somewhat widely used and/or old ones). After stumbling over https://stackoverflow.com/questions/16935935/how-do-i-turn-off-a-static-c= ode-analysis-warning-on-a-line-by-line-warning-in-cd, looking into Eclipses Window -> Preferences -> C/C++ -> Code Analysis -> "No break at the end of case" screen (that's the screenshot there) and I tried various things: Preface: I have ---- snip ---- #define __fallthrough __attribute__((fallthrough)) ---- snip ---- for gcc >=3D 7 (because clang doesn't know it and I had also older gcc's in use before). So: - Adding a comment to the #define doesn't change anything for Eclipse. - Eclipse looks *only* in comments for the string/regexp given the warnings configuration (and that comment must be on the line directly before the "case"). - Eclipse understands [[fallthrough]] out-of-the-box though (which is C++11 AFAIK) as does g++-7 (I use -std=3Dgnu++17 - most of the sources are C++, but not all) and clang++-6 (all the current standard Ubuntu-18.06/Bionic packages). Eclipse "accepts" [[fallthrough]] only in C++ sources (and not in C sources). - Neither gcc nor clang understand [[fallthrough]] (so it's probably a no-go for the Kernel with C89 anyways). MfG, Bernd PS: clang++ errors with "fallthrough annotation in unreachable code" if [[fallthrough]] is after an assert(). clang-devs there, please, the fallthrough doesn't really generated code (I hope;-). I have lots of switch()es which catch undefined values (for enums et. al.) with "default"+assert() and fall through to the most safe case (for the deployed version). --=20 "I dislike type abstraction if it has no real reason. And saving on typing is not a good reason - if your typing speed is the main issue when you're coding, you're doing something seriously wrong." - Linus Torvalds --------------4F428F195E06AF3B428EB1A0 Content-Type: application/pgp-keys; name="pEpkey.asc" Content-Transfer-Encoding: quoted-printable Content-Disposition: attachment; filename="pEpkey.asc" -----BEGIN PGP PUBLIC KEY BLOCK----- mQGNBFss+8cBDACpXlq0ZC9Qp8R+iFPx5vDPu12FpnmbbV8CwexVDchdizF2qz+A PFh12RrkE6yudI0r7peAIRePiSVYqv8XT82TpJM+tbTYk/MSQaPhcmz8jl1HaKv0 q8g5nKtr42qRsswU7Q2Sa6mWXaIdOisPYZ9eLZC9BDBhI/YrgdAwszyYJ1HUwNkp Dw5i4wW/SsIKrotCboYzbBjZfHbmDJr4dFYSoMg5jQVHD2Yz8fqNSoRyd7i/oicn 1bH/DjEkrmIu9YuptuHYmblpCRo5dLww7kgszNw12j8Iljp64uJ/uz5+asBUmRZM mGey82BB1DnIvy1v+GnbGWFIYy79/HeqdN+KbOgO/sXoqYKS5KJ6aSqWOLTQk6sv AnDN2PNF5jOB9ROCNwoQSH/YNEfMd/mQ5pGB0UJ4ykD0UnjW7DdXbVOwvwWzfHF7 HaZXB1NMpBzHxold3W19DThd4HECvXYZ6Au6p0WE8IfABS11CzbX7KJuD5Ua+xKG 3W05fMg5i0td2aMAEQEAAbQtQmVybmQgUGV0cm92aXRzY2ggPGJlcm5kQHBldHJv dml0c2NoLnByaXYuYXQ+iQHUBBMBCgA+FiEEgDWyyHEwksebo557hUq7AhBHKGYF Alss+/wCGwMFCQHhM4AFCwkIBwMFFQoJCAsFFgMCAQACHgECF4AACgkQhUq7AhBH KGa5Hgv7BKXf7BKtA/2Awa/UW5mA+6FU/kcQCHptKDZqFEleDPiUOoU+nbz1FMNu zs84cJxTUWl+lqFEDlvId+K8948OgIi2ImQgg/FeGjywmB3GOzaMGKZjSzLGnnAf RqamHIsoQMGHwI0dh0obnx2sjqXghu4bs2DVEV0oUGFNhclSoWNUucg/tOSG3QCM ViUqfCGADaLG8zavRC093423m51ea9IVJkaTtdi59EKWjY6UqlRTOWXh3E/yF8NK T1SWztTs0jWPeISx063/TzkfbEAtGPOSHP136ZpI1WR3c+6Y3gXrgTYN1QilRM9m daep4/Fsoc8pwCtfKXND4v4kbuJnEaeTU+5XF9fCB0nHXX+ToqaOxZOO8KZ6XY+p 9nJgt2zBudKnT2oWzlqOROOHlckxYwEHeDhX3U8nIuDwYsnD/nB40oDiXjauv/Op 25Ej0BMSDSsTZ2/q7bjXwsV10ML7h6C0SRx8Hr6coGbvbP0BMrlV3Nphi24qvXZp iCc+G6wnuQGNBFss+8kBDADRASin2ms38GGbHv5HcWkVWDtPQo08ceO5ULrtA3G3 lQrv08pbKfSw91n5cIOCDvcCY29GrVZ/lcSGov855zu6tFZ/T+d68zth3aWZzR5d Brz6Nb6DclyEMkfKX2xYT7tGoN9XgBboG4yWgTMKvlu6yKxxJM4AM5AjpHodsXwP txvzqnmfgIQ4k0idqB7c7khiFsraUM1+f0/Bn+p+RPhqg+C33Ui38IWdwtNgck+G U7+WYQi3LxD2mu8BC0NIYJMiFTUPC0a4FTQtKCXno5Stys5wYG6OXiGOw3sTbs3v qy95H5/cVa6mf81OiNZP1liXnm0cBrT+UbFgtZk/OnoekzS7RPCdCuMZyxMqPTLl +EjNyejmSN3cnGLNDa+Jh/eSIUZzvihuNFxdtQQfuD+nqoPanfSfrWaDABMU7Daf 6vZI10D3d473WzCplWR4A+Rdm8ysi2haas7KZnL+ajcEo2jCghW83BQPBD57fEtl UWLXihAFcEiSx0i2AUAXYOcAEQEAAYkBvAQYAQoAJhYhBIA1sshxMJLHm6Oee4VK uwIQRyhmBQJbLPvJAhsMBQkB4TOAAAoJEIVKuwIQRyhmrGIL/3rsdQqaO3umXj9X Ts4nAme/2DVsEyGUFzeDllbzOKH7PsjJhbEsQRRE+kDk0tp2xbpVzNZ73wFhXFL+ zqa8tdMhYEjLUZ4ry/bg83yZH2bNj/jTii32AkvmL2zcYf0/knuAAAypdfTM4K6S PVlwOo09Drkiz/SDXyvpSG9GdCZLVR/HbQpsob0JddcouWwliATRrnUETb/MN6MO WI4687r1wi4Kn28CHydWA5YONvFyb7BJZRHiLQnJwlh7dgBtOSCeZClrKfhIBFB2 YgfBcgmHnpYkzyBGdUTnrrlmiMeuxZqG2SzwswRMACYqUFoe+3E7RZQX5ym17oUP Kat5L8uZbd2+TlbICXnxwTadBKDvk8qxjLSwzthoHlmM6zeFekQdq67aiBWfa9oV 6tljJtvE9QREo+hDjQaiVmzHqeB8pMGVHWzAGJzvxFuXMaKzUI8vWDH5jaht0Sqn xHyhVz8+rEsLoB67PBuY3GLecTeQ3rr52BVMzfNRPdSyVHESzw=3D=3D =3Dv2Yn -----END PGP PUBLIC KEY BLOCK----- --------------4F428F195E06AF3B428EB1A0--