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=-13.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 19963C4332B for ; Thu, 19 Mar 2020 23:07:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DEF2B20658 for ; Thu, 19 Mar 2020 23:07:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="O2K0uP9L" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727649AbgCSXHl (ORCPT ); Thu, 19 Mar 2020 19:07:41 -0400 Received: from gateway31.websitewelcome.com ([192.185.143.38]:22178 "EHLO gateway31.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727377AbgCSXHl (ORCPT ); Thu, 19 Mar 2020 19:07:41 -0400 Received: from cm16.websitewelcome.com (cm16.websitewelcome.com [100.42.49.19]) by gateway31.websitewelcome.com (Postfix) with ESMTP id DED9677FE for ; Thu, 19 Mar 2020 18:07:39 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id F4GJjZw5B8vkBF4GJjQxVi; Thu, 19 Mar 2020 18:07:39 -0500 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=10e20ftHbNBtdbV6audFvzsWbL3yXsySetTvF2M/Lq8=; b=O2K0uP9L/sLPmqZfto8eZ9Auuz 3wwFpugnOnD//3aPNsBC2Yfrzs9P6q6SVPUTEmkWvRkFqr4geqD9awCrpXtgP7er9l3St8GVs32Hu 11vLzovX1rQ/e+aP/2W7gAwQsVwPOL7QP/w7UlC8fD817SuFG+J3gBHp2Hwc6UcQUO21Ve7FkVTB8 0LjnIhDC4DjjHNmIREHMNIJd7TRB5yDDzrEv5VJzOTWZTqXsKI7ISNA0pqQvKivZSC2Z6iEJ1DzPg knO42HE5DxsaCGw4WkYv3bYFHwApBAfTf3it+gbpU39jgYutPu98w1QiP748MluBFdyIXYhrALmwp bAt84OQA==; Received: from cablelink-189-218-116-241.hosts.intercable.net ([189.218.116.241]:54038 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jF4GI-002PZ0-A4; Thu, 19 Mar 2020 18:07:38 -0500 Date: Thu, 19 Mar 2020 18:07:37 -0500 From: "Gustavo A. R. Silva" To: Dan Williams , Vishal Verma , Dave Jiang , Ira Weiny Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] nvdimm: label.h: Replace zero-length array with flexible-array member Message-ID: <20200319230737.GA16452@embeddedor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.218.116.241 X-Source-L: No X-Exim-ID: 1jF4GI-002PZ0-A4 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: cablelink-189-218-116-241.hosts.intercable.net (embeddedor) [189.218.116.241]:54038 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 16 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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] 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/nvdimm/label.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/nvdimm/label.h b/drivers/nvdimm/label.h index 4c7b775c2811..956b6d1bd8cc 100644 --- a/drivers/nvdimm/label.h +++ b/drivers/nvdimm/label.h @@ -62,7 +62,7 @@ struct nd_namespace_index { __le16 major; __le16 minor; __le64 checksum; - u8 free[0]; + u8 free[]; }; /** -- 2.23.0