From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E21DC10F28 for ; Mon, 9 Mar 2020 07:49:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14C3720675 for ; Mon, 9 Mar 2020 07:49:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726451AbgCIHtz (ORCPT ); Mon, 9 Mar 2020 03:49:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:53410 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726403AbgCIHty (ORCPT ); Mon, 9 Mar 2020 03:49:54 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 8A072AD48; Mon, 9 Mar 2020 07:49:50 +0000 (UTC) Subject: Re: [PATCH][next] drm: Replace zero-length array with flexible-array member To: "Gustavo A. R. Silva" , Jani Nikula , Lucas Stach , Russell King , Christian Gmeiner , David Airlie , Daniel Vetter , Patrik Jakobsson , Joonas Lahtinen , Rodrigo Vivi , Rob Clark , Sean Paul , Dave Airlie , Gerd Hoffmann , Hans de Goede , Eric Anholt , VMware Graphics , Thomas Hellstrom , Maarten Lankhorst , Maxime Ripard Cc: etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, virtualization@lists.linux-foundation.org, spice-devel@lists.freedesktop.org References: <20200225140347.GA22864@embeddedor> <87a756sqdc.fsf@intel.com> <138ff691-94b3-1ce5-e7fa-e6d7c436bf8e@embeddedor.com> From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= mQENBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAG0J1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPokBVAQTAQgAPhYh BHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJbOdLgAhsDBQkDwmcABQsJCAcCBhUKCQgLAgQWAgMB Ah4BAheAAAoJEGgNwR1TC3ojR80H/jH+vYavwQ+TvO8ksXL9JQWc3IFSiGpuSVXLCdg62AmR irxW+qCwNncNQyb9rd30gzdectSkPWL3KSqEResBe24IbA5/jSkPweJasgXtfhuyoeCJ6PXo clQQGKIoFIAEv1s8l0ggPZswvCinegl1diyJXUXmdEJRTWYAtxn/atut1o6Giv6D2qmYbXN7 mneMC5MzlLaJKUtoH7U/IjVw1sx2qtxAZGKVm4RZxPnMCp9E1MAr5t4dP5gJCIiqsdrVqI6i KupZstMxstPU//azmz7ZWWxT0JzgJqZSvPYx/SATeexTYBP47YFyri4jnsty2ErS91E6H8os Bv6pnSn7eAq5AQ0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRH UE9eosYbT6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgT RjP+qbU63Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+R dhgATnWWGKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zb ehDda8lvhFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r 12+lqdsAEQEAAYkBPAQYAQgAJhYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJbOdLgAhsMBQkD wmcAAAoJEGgNwR1TC3ojpfcIAInwP5OlcEKokTnHCiDTz4Ony4GnHRP2fXATQZCKxmu4AJY2 h9ifw9Nf2TjCZ6AMvC3thAN0rFDj55N9l4s1CpaDo4J+0fkrHuyNacnT206CeJV1E7NYntxU n+LSiRrOdywn6erjxRi9EYTVLCHcDhBEjKmFZfg4AM4GZMWX1lg0+eHbd5oL1as28WvvI/uI aMyV8RbyXot1r/8QLlWldU3NrTF5p7TMU2y3ZH2mf5suSKHAMtbE4jKJ8ZHFOo3GhLgjVrBW HE9JXO08xKkgD+w6v83+nomsEuf6C6LYrqY/tsZvyEX6zN8CtirPdPWu/VXNRYAl/lat7lSI 3H26qrE= Message-ID: <67c46a2b-8127-a4b7-c825-8cba6f28db8c@suse.de> Date: Mon, 9 Mar 2020 08:49:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <138ff691-94b3-1ce5-e7fa-e6d7c436bf8e@embeddedor.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Ul1CrpBm5H0rrZlYhdIfEA75XDUYdEO4y" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Ul1CrpBm5H0rrZlYhdIfEA75XDUYdEO4y Content-Type: multipart/mixed; boundary="0DgKy29qpwpTjPxx9ZHosYzYcoKck294a"; protected-headers="v1" From: Thomas Zimmermann To: "Gustavo A. R. Silva" , Jani Nikula , Lucas Stach , Russell King , Christian Gmeiner , David Airlie , Daniel Vetter , Patrik Jakobsson , Joonas Lahtinen , Rodrigo Vivi , Rob Clark , Sean Paul , Dave Airlie , Gerd Hoffmann , Hans de Goede , Eric Anholt , VMware Graphics , Thomas Hellstrom , Maarten Lankhorst , Maxime Ripard Cc: etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, virtualization@lists.linux-foundation.org, spice-devel@lists.freedesktop.org Message-ID: <67c46a2b-8127-a4b7-c825-8cba6f28db8c@suse.de> Subject: Re: [PATCH][next] drm: Replace zero-length array with flexible-array member References: <20200225140347.GA22864@embeddedor> <87a756sqdc.fsf@intel.com> <138ff691-94b3-1ce5-e7fa-e6d7c436bf8e@embeddedor.com> In-Reply-To: <138ff691-94b3-1ce5-e7fa-e6d7c436bf8e@embeddedor.com> --0DgKy29qpwpTjPxx9ZHosYzYcoKck294a Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Hi Gustavo Am 03.03.20 um 19:20 schrieb Gustavo A. R. Silva: >=20 >=20 > On 2/25/20 08:17, Jani Nikula wrote: >> On Tue, 25 Feb 2020, "Gustavo A. R. Silva" wr= ote: >>> The current codebase makes use of the zero-length array language >>> extension to the C90 standard, but the preferred mechanism to declare= >>> variable-length types such as these ones is a flexible array member[1= ][2], >>> introduced in C99: >>> >>> struct foo { >>> int stuff; >>> struct boo array[]; >>> }; >>> >>> By making use of the mechanism above, we will get a compiler warning >>> in case the flexible array does not occur last in the structure, whic= h >>> will help us prevent some kind of undefined behavior bugs from being >>> inadvertently introduced[3] to the codebase from now on. >>> >>> Also, notice that, dynamic memory allocations won't be affected by >>> this change: >>> >>> "Flexible array members have incomplete type, and so the sizeof opera= tor >>> may not be applied. As a quirk of the original implementation of >>> zero-length arrays, sizeof evaluates to zero."[1] >>> >>> This issue was found with the help of Coccinelle. >>> >>> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html >>> [2] https://github.com/KSPP/linux/issues/21 >>> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") >>> >>> Signed-off-by: Gustavo A. R. Silva >>> --- >>> drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +- >>> drivers/gpu/drm/gma500/intel_bios.h | 2 +- >>> drivers/gpu/drm/i915/display/intel_vbt_defs.h | 4 ++-- >>> drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +- >>> drivers/gpu/drm/i915/i915_gpu_error.h | 2 +- >> >> Please split out the i915 changes to a separate patch. >> >=20 > Sure thing. I can do that. I think each driver deserves it's own patch. Makes backporting easier. Best regards Thomas >=20 >>> drivers/gpu/drm/msm/msm_gem.h | 2 +- >>> drivers/gpu/drm/qxl/qxl_cmd.c | 2 +- >>> drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +- >>> drivers/gpu/drm/vc4/vc4_drv.h | 2 +- >>> drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 2 +- >>> drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 2 +- >>> include/drm/bridge/mhl.h | 4 ++-- >>> include/drm/drm_displayid.h | 2 +- >>> include/uapi/drm/i915_drm.h | 4 ++-- >> >> Not sure it's worth touching uapi headers. They're full of both [0] an= d >> []. Again, please at least split it to a separate patch to be decided >> separately. >> >=20 > Yeah, it's worth it; the purpose of these patches is to replace [0] wit= h [] across > the whole tree. >=20 > Thanks > -- > Gustavo >=20 --=20 Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 N=C3=BCrnberg, Germany (HRB 36809, AG N=C3=BCrnberg) Gesch=C3=A4ftsf=C3=BChrer: Felix Imend=C3=B6rffer --0DgKy29qpwpTjPxx9ZHosYzYcoKck294a-- --Ul1CrpBm5H0rrZlYhdIfEA75XDUYdEO4y Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEchf7rIzpz2NEoWjlaA3BHVMLeiMFAl5l9RkACgkQaA3BHVML eiNGUQgAgjKSCBND55SWYJrmDfa3irwlGfO6EKxH9F6r/W+oYNLwfa7Re8zDiRjN oMHZLY2a2iKckXvawizS65l/0mqLfNQ11BfXFGBr6RAgxWt7Ac2pw1wP9FaVQ3HN PSksqH6ASJUhgDm9hfZSRu9fZDLV1AGIWdTE/pHRcJ8inzEV543+SffD2ddPFjwV m+hBDC678jVfSux+/aBkp40Mv9VryJTVN4TyQNRuUtmciIWSoVvoiJxk5d+0Ykcn McM6bm+GmCvvUmjlLa7LNv8Fv9zr17XF3Q2Nv2v8Gn+sYDXY2S8RU8BXlV05XZVE xLoQ88iIqzrGQjmARyUf0W4vvek8XQ== =9S1h -----END PGP SIGNATURE----- --Ul1CrpBm5H0rrZlYhdIfEA75XDUYdEO4y--