From patchwork Thu May 7 18:57:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 11534723 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 34A6C14B4 for ; Thu, 7 May 2020 18:53:20 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 052272495E for ; Thu, 7 May 2020 18:53:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="FSQeULZO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 052272495E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id ADA63117F2780; Thu, 7 May 2020 11:51:20 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=gustavoars@kernel.org; receiver= Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 4FD5B117E5ADE for ; Thu, 7 May 2020 11:51:19 -0700 (PDT) Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8828424960; Thu, 7 May 2020 18:53:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877598; bh=qD1YTu45POQi4xsMj+gdlSVCGKp5j89OYm2p2pPtKh4=; h=Date:From:To:Cc:Subject:From; b=FSQeULZOf97JknZWY5LLJLQT/B28yD4GV5UeqoNuLVRKkxweMPCE3bj9Ix6zBiXZG SkK2rXUmNi8iocLO2FpUJfFio+NqcvdSBhbGk6cfmwEwR3nhnNDUrEwSblam8VUPu8 tKEbXqXjoojLcnrP4v7c2q3FxuHkngwmGz6OeIH8= Date: Thu, 7 May 2020 13:57:44 -0500 From: "Gustavo A. R. Silva" To: Dan Williams , Vishal Verma , Dave Jiang , Ira Weiny Subject: [PATCH] tools/testing/nvdimm: Replace zero-length array with flexible-array Message-ID: <20200507185744.GA14974@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Message-ID-Hash: NXBJ3SLK7FN5RUTE2QHOPYQ7NWLDF33Q X-Message-ID-Hash: NXBJ3SLK7FN5RUTE2QHOPYQ7NWLDF33Q X-MailFrom: gustavoars@kernel.org X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: 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 --- tools/testing/nvdimm/test/nfit_test.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/testing/nvdimm/test/nfit_test.h b/tools/testing/nvdimm/test/nfit_test.h index db3c07beb9d1..b5f7a996c4d0 100644 --- a/tools/testing/nvdimm/test/nfit_test.h +++ b/tools/testing/nvdimm/test/nfit_test.h @@ -51,7 +51,7 @@ struct nd_cmd_translate_spa { __u32 nfit_device_handle; __u32 _reserved; __u64 dpa; - } __packed devices[0]; + } __packed devices[]; } __packed; @@ -74,7 +74,7 @@ struct nd_cmd_ars_err_inj_stat { struct nd_error_stat_query_record { __u64 err_inj_stat_spa_range_base; __u64 err_inj_stat_spa_range_length; - } __packed record[0]; + } __packed record[]; } __packed; #define ND_INTEL_SMART 1 @@ -180,7 +180,7 @@ struct nd_intel_fw_send_data { __u32 context; __u32 offset; __u32 length; - __u8 data[0]; + __u8 data[]; /* this field is not declared due ot variable data from input */ /* __u32 status; */ } __packed;