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,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 07D41C352A4 for ; Wed, 12 Feb 2020 19:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0BC321569 for ; Wed, 12 Feb 2020 19:31:12 +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="SO0RE1gr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728930AbgBLTbM (ORCPT ); Wed, 12 Feb 2020 14:31:12 -0500 Received: from gateway32.websitewelcome.com ([192.185.145.101]:34067 "EHLO gateway32.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727361AbgBLTbL (ORCPT ); Wed, 12 Feb 2020 14:31:11 -0500 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway32.websitewelcome.com (Postfix) with ESMTP id B4D0E607B87 for ; Wed, 12 Feb 2020 13:31:10 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 1xj4j0knLRP4z1xj4jSNtQ; Wed, 12 Feb 2020 13:31:10 -0600 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=qVT3JEBGacGB2ITpJDbesv5hNV8nBdRWBrUKUxTwmPU=; b=SO0RE1grbeu4rE7C9/5vgBTS9v K+ivX9nq4nObO5gnVyWWT0j5krix2wwszSD9HtfY7xNU83Ao1JIqSDAcivueHllxK5q5NjlumO/9x lAkWMdQtrLxYO0DsEm2ozZ2D/WyOlP32QTmLnBGrNxsm51sc9eiIcBkCLbzAB9YxV2lslJvU/CBDK JBy1DJsGvdL4CdSrL13a6+iARyCiqeFtU6ZhV1jTHmbBX1u+VO8A+gG1QuEH5wC5WyfukIx26BZYM uOGnBXi930Jwk5WOrLliqaaVy4DpJ73ipH895mNAE+lTfv3eMlLKmUFgijJ0BD7C9/TeKFSumIaWP xKngX4VQ==; Received: from [201.144.174.25] (port=10240 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j1xj3-0017cN-2B; Wed, 12 Feb 2020 13:31:09 -0600 Date: Wed, 12 Feb 2020 13:33:44 -0600 From: "Gustavo A. R. Silva" To: Dave Airlie , Gerd Hoffmann , David Airlie , Daniel Vetter Cc: virtualization@lists.linux-foundation.org, spice-devel@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] drm/qxl: replace zero-length array with flexible-array member Message-ID: <20200212193344.GA27929@embeddedor> 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: 201.144.174.25 X-Source-L: No X-Exim-ID: 1j1xj3-0017cN-2B X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.144.174.25]:10240 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 24 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 inadvertenly 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/gpu/drm/qxl/qxl_cmd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/qxl/qxl_cmd.c b/drivers/gpu/drm/qxl/qxl_cmd.c index ef09dc6bc635..d1086b2a6892 100644 --- a/drivers/gpu/drm/qxl/qxl_cmd.c +++ b/drivers/gpu/drm/qxl/qxl_cmd.c @@ -36,7 +36,7 @@ static int qxl_reap_surface_id(struct qxl_device *qdev, int max_to_reap); struct ring { struct qxl_ring_header header; - uint8_t elements[0]; + uint8_t elements[]; }; struct qxl_ring { -- 2.25.0