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=-13.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 A5F70C47247 for ; Fri, 8 May 2020 23:29:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F0242184D for ; Fri, 8 May 2020 23:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728279AbgEHX3G (ORCPT ); Fri, 8 May 2020 19:29:06 -0400 Received: from mailout.easymail.ca ([64.68.200.34]:48862 "EHLO mailout.easymail.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727110AbgEHX3F (ORCPT ); Fri, 8 May 2020 19:29:05 -0400 Received: from localhost (localhost [127.0.0.1]) by mailout.easymail.ca (Postfix) with ESMTP id 3C6DB22477; Fri, 8 May 2020 23:29:04 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at emo06-pco.easydns.vpn Received: from mailout.easymail.ca ([127.0.0.1]) by localhost (emo06-pco.easydns.vpn [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qEFBl3V2kMAJ; Fri, 8 May 2020 23:29:04 +0000 (UTC) Received: from mail.gonehiking.org (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) by mailout.easymail.ca (Postfix) with ESMTPA id 21E132229D; Fri, 8 May 2020 23:29:01 +0000 (UTC) Received: from [192.168.1.4] (rhapsody.internal [192.168.1.4]) by mail.gonehiking.org (Postfix) with ESMTP id 262D93EEEE; Fri, 8 May 2020 17:29:01 -0600 (MDT) Subject: Re: [PATCH] pcdp: Replace zero-length array with flexible-array To: "Gustavo A. R. Silva" Cc: linux-kernel@vger.kernel.org References: <20200507190538.GA15601@embeddedor> From: Khalid Aziz Autocrypt: addr=khalid@gonehiking.org; prefer-encrypt=mutual; keydata= mQINBFA5V58BEADa1EDo4fqJ3PMxVmv0ZkyezncGLKX6N7Dy16P6J0XlysqHZANmLR98yUk4 1rpAY/Sj/+dhHy4AeMWT/E+f/5vZeUc4PXN2xqOlkpANPuFjQ/0I1KI2csPdD0ZHMhsXRKeN v32eOBivxyV0ZHUzO6wLie/VZHeem2r35mRrpOBsMLVvcQpmlkIByStXGpV4uiBgUfwE9zgo OSZ6m3sQnbqE7oSGJaFdqhusrtWesH5QK5gVmsQoIrkOt3Al5MvwnTPKNX5++Hbi+SaavCrO DBoJolWd5R+H8aRpBh5B5R2XbIS8ELGJZfqV+bb1BRKeo0kvCi7G6G4X//YNsgLv7Xl0+Aiw Iu/ybxI1d4AtBE9yZlyG21q4LnO93lCMJz/XqpcyG7DtrWTVfAFaF5Xl1GT+BKPEJcI2NnYn GIXydyh7glBjI8GAZA/8aJ+Y3OCQtVxEub5gyx/6oKcM12lpbztVFnB8+S/+WLbHLxm/t8l+ Rg+Y4jCNm3zB60Vzlz8sj1NQbjqZYBtBbmpy7DzYTAbE3P7P+pmvWC2AevljxepR42hToIY0 sxPAX00K+UzTUwXb2Fxvw37ibC5wk3t7d/IC0OLV+X29vyhmuwZ0K1+oKeI34ESlyU9Nk7sy c1WJmk71XIoxJhObOiXmZIvWaOJkUM2yZ2onXtDM45YZ8kyYTwARAQABtCNLaGFsaWQgQXpp eiA8a2hhbGlkQGdvbmVoaWtpbmcub3JnPokCOgQTAQgAJAIbAwULCQgHAwUVCgkICwUWAgMB AAIeAQIXgAUCUDlYcgIZAQAKCRDNWKGxftAz+mCdD/4s/LpQAYcoZ7TwwQnZFNHNZmVQ2+li 3sht1MnFNndcCzVXHSWd/fh00z2du3ccPl51fXU4lHbiG3ZyrjX2Umx48C20Xg8gbmdUBzq4 9+s12COrgwgsLyWZAXzCMWYXOn9ijPHeSQSq1XYj8p2w4oVjMa/QfGueKiJ5a14yhCwye2AM f5o8uDLf+UNPgJIYAGJ46fT6k5OzXGVIgIGmMZCbYPhhSAvLKBfLaIFd5Bu6sPjp0tJDXJd8 pG831Kalbqxk7e08FZ76opzWF9x/ZjLPfTtr4xiVvx+f9g/5E83/A5SvgKyYHdb3Nevz0nvn MqQIVfZFPUAQfGxdWgRsFCudl6i9wEGYTcOGe00t7JPbYolLlvdn+tA+BCE5jW+4cFg3HmIf YFchQtp+AGxDXG3lwJcNwk0/x+Py3vwlZIVXbdxXqYc7raaO/+us8GSlnsO+hzC3TQE2E/Hy n45FDXgl51rV6euNcDRFUWGE0d/25oKBXGNHm+l/MRvV8mAdg3iTiy2+tAKMYmg0PykiNsjD b3P5sMtqeDxr3epMO+dO6+GYzZsWU2YplWGGzEKI8sn1CrPsJzcMJDoWUv6v3YL+YKnwSyl1 Q1Dlo+K9FeALqBE5FTDlwWPh2SSIlRtHEf8EynUqLSCjOtRhykmqAn+mzIQk+hIy6a0to9iX uLRdVbkCDQRQOVefARAAsdGTEi98RDUGFrxK5ai2R2t9XukLLRbRmwyYYx7sc7eYp7W4zbnI W6J+hKv3aQsk0C0Em4QCHf9vXOH7dGrgkfpvG6aQlTMRWnmiVY99V9jTZGwK619fpmFXgdAt WFPMeNKVGkYzyMMjGQ4YbfDcy04BSH2fEok0jx7Jjjm0U+LtSJL8fU4tWhlkKHtO1oQ9Y9HH Uie/D/90TYm1nh7TBlEn0I347zoFHw1YwRO13xcTCh4SL6XaQuggofvlim4rhwSN/I19wK3i YwAm3BTBzvJGXbauW0HiLygOvrvXiuUbyugMksKFI9DMPRbDiVgCqe0lpUVW3/0ynpFwFKeR FyDouBc2gOx8UTbcFRceOEew9eNMhzKJ2cvIDqXqIIvwEBrA+o92VkFmRG78PleBr0E8WH2/ /H/MI3yrHD4F4vTRiPwpJ1sO/JUKjOdfZonDF6Hu/Beb0U5coW6u7ENKBmaQ/nO1pHrsqZp+ 2ErG02yOHF5wDWxxgbd4jgcNTKJiY9F1cdKP+NbWW/rnJgem8qYI3a4VkIkFT5BE2eYLvZlR cIzWc/ve/RoQh6jzXD0T08whoajZ1Y3yFQ8oyLSFt8ybxF0b5XryL2RVeHQTkE8NKwoGVYTn ER+o7x2sUGbIkjHrE4Gq2cooEl9lMv6I5TEkvP1E5hiZFJWYYnrXa/cAEQEAAYkCHwQYAQgA CQUCUDlXnwIbDAAKCRDNWKGxftAz+reUEACQ+rz2AlVZZcUdMxWoiHqJTb5JnaF7RBIBt6Ia LB9triebZ7GGW+dVPnLW0ZR1X3gTaswo0pSFU9ofHkG2WKoYM8FbzSR031k2NNk/CR0lw5Bh whAUZ0w2jgF4Lr+u8u6zU7Qc2dKEIa5rpINPYDYrJpRrRvNne7sj5ZoWNp5ctl8NBory6s3b bXvQ8zlMxx42oF4ouCcWtrm0mg3Zk3SQQSVn/MIGCafk8HdwtYsHpGmNEVn0hJKvUP6lAGGS uDDmwP+Q+ThOq6b6uIDPKZzYSaa9TmL4YIUY8OTjONJ0FLOQl7DsCVY9UIHF61AKOSrdgCJm N3d5lXevKWeYa+v6U7QXxM53e1L+6h1CSABlICA09WJP0Fy7ZOTvVjlJ3ApO0Oqsi8iArScp fbUuQYfPdk/QjyIzqvzklDfeH95HXLYEq8g+u7nf9jzRgff5230YW7BW0Xa94FPLXyHSc85T E1CNnmSCtgX15U67Grz03Hp9O29Dlg2XFGr9rK46Caph3seP5dBFjvPXIEC2lmyRDFPmw4yw KQczTkg+QRkC4j/CEFXw0EkwR8tDAPW/NVnWr/KSnR/qzdA4RRuevLSK0SYSouLQr4IoxAuj nniu8LClUU5YxbF57rmw5bPlMrBNhO5arD8/b/XxLx/4jGQrcYM+VrMKALwKvPfj20mB6A== Message-ID: <15a0454b-7913-fe76-c39a-fb0ab315360d@gonehiking.org> Date: Fri, 8 May 2020 17:29:01 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200507190538.GA15601@embeddedor> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/7/20 1:05 PM, Gustavo A. R. Silva wrote: > 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, which > 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 operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] > > sizeof(flexible-array-member) triggers a warning because flexible array > members have incomplete type[1]. There are some instances of code in > which the sizeof operator is being incorrectly/erroneously applied to > zero-length arrays and the result is zero. Such instances may be hiding > some bugs. So, this work (flexible-array member conversions) will also > help to get completely rid of those sorts of issues. > > 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/firmware/pcdp.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/pcdp.h b/drivers/firmware/pcdp.h > index ce75d1da9e84..e02540571c52 100644 > --- a/drivers/firmware/pcdp.h > +++ b/drivers/firmware/pcdp.h > @@ -103,6 +103,6 @@ struct pcdp { > u8 creator_id[4]; > u32 creator_rev; > u32 num_uarts; > - struct pcdp_uart uart[0]; /* actual size is num_uarts */ > + struct pcdp_uart uart[]; /* actual size is num_uarts */ > /* remainder of table is pcdp_device structures */ > } __attribute__((packed)); > Loks good to me. Acked-by: Khalid Aziz