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 2C1EEC3B186 for ; Wed, 12 Feb 2020 19:50:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 00B6824671 for ; Wed, 12 Feb 2020 19:50:01 +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="bJr9lPFU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729048AbgBLTuA (ORCPT ); Wed, 12 Feb 2020 14:50:00 -0500 Received: from gateway22.websitewelcome.com ([192.185.47.179]:34487 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729018AbgBLTt7 (ORCPT ); Wed, 12 Feb 2020 14:49:59 -0500 Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway22.websitewelcome.com (Postfix) with ESMTP id 6C441411A for ; Wed, 12 Feb 2020 13:49:57 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 1y1Fj6jghAGTX1y1FjIuwh; Wed, 12 Feb 2020 13:49:57 -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=TtzHE9bt3EsnQaUgQbettd2dBBa+zgbK1XhwIh6LAZ8=; b=bJr9lPFUVcqwf7A5m+kbN5zfIQ ZM5QxBS1BMjGSLSBomD228kTD9jX8NFst6tcdo0H8OOBMysEt/yfLe0V3JuZlIKLiMAxVBrf2Jftg aX/AjrSQvqADKCSXHxae5RMnUuB2Dn7nP6PSpaqixfsJFt3vdWqVuMDpNUMp8AcGxA7jCZrdWVw+E BsE7mcIZubgYGTw/aPAM3kxXqxXqAv5w6E+2Vk2CruwQoaw+q5UNpm7N2vw6fZe6q30bsiRxk7CkL VyjaijJHlHZnEEO3nei1AgRqHhQFsOCjMEW/dTKBVIa2Vgd2qYFI0V9O0Di0pWd6QSBNZQsw32X5b RjEGWtQA==; Received: from [201.144.174.25] (port=3740 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j1y1D-001GNE-QC; Wed, 12 Feb 2020 13:49:56 -0600 Date: Wed, 12 Feb 2020 13:52:31 -0600 From: "Gustavo A. R. Silva" To: Miguel Ojeda Sandonis Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] auxdisplay: charlcd: replace zero-length array with flexible-array member Message-ID: <20200212195231.GA2867@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: 1j1y1D-001GNE-QC X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.144.174.25]:3740 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 48 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/auxdisplay/charlcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index 874c259a8829..c0da3820454b 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -88,7 +88,7 @@ struct charlcd_priv { int len; } esc_seq; - unsigned long long drvdata[0]; + unsigned long long drvdata[]; }; #define charlcd_to_priv(p) container_of(p, struct charlcd_priv, lcd) -- 2.25.0