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=-6.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 EB8BEC433E0 for ; Wed, 13 May 2020 15:06:11 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 105E22220D for ; Wed, 13 May 2020 14:56:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="VtnF10ti"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="l4mRGFNZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 105E22220D 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-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=qoNcJV167+qIORZq5skNtK8PzNI0f9RUzRsJppSLv4w=; b=VtnF10tiGms9nU pS6bZKIUG3UYTJ1piivF2vXV/TUDCMPzK6qzYxHp9uSDF1Nr9l2inHxRXOz4+nZIYznMubwCv90gZ 2Htl1Z0Y3N0Pz1fDpIzGMLfUjrOJ8qGrWFkDxRTK7B0EviF7j0Dr8663O4v5PZWJOXC/xXa+CaiI9 LorbDGIMm7iGmucv3l5K36cUJymjDZHbXYYkhr8sanfTLQZpo00AWCTyUzp6EMedq3E1ydE8qSfgs Bg+ZylI9o/x2H79LHjWV3jTZDo4A0OW6Cec4qu5rtz0Uh2wByakNRbWhXAPLjTiXp9dFF7weAR+fR KW0tr8d7A+CuknezGD2A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYsoG-0003I3-3k; Wed, 13 May 2020 14:56:36 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYso8-0003EJ-IE for linux-arm-kernel@lists.infradead.org; Wed, 13 May 2020 14:56:30 +0000 Received: from localhost (unknown [106.200.233.149]) (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 8B1EE221E6; Wed, 13 May 2020 14:56:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589381788; bh=8SmbnrZ5qW6mVaqqlcGDrJ3tZhpY+ZYEC2ysujal7jE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=l4mRGFNZDs1RO7j/ngnkH16aePO1WvI/3rJkpo0/bOqGBn+zq90/znJcuC3NGZKTu qNSI7KkiyyzXV4E6Yg1UrgZMXzyeIrvdG/iStQWx+x7Wz+aQnWosrPzMIp73qeck4f eRdMLpxjBQ3RWdNMW0mCsJ6Abq7tMpCUQi1rnv5U= Date: Wed, 13 May 2020 20:26:24 +0530 From: Vinod Koul To: "Gustavo A. R. Silva" Subject: Re: [PATCH] dmaengine: at_xdmac: Replace zero-length array with flexible-array Message-ID: <20200513145624.GM14092@vkoul-mobl> References: <20200507190046.GA15298@embeddedor> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200507190046.GA15298@embeddedor> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200513_075628_616725_DE1DEB69 X-CRM114-Status: GOOD ( 14.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dmaengine@vger.kernel.org, Ludovic Desroches , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 07-05-20, 14:00, 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") Applied, thanks -- ~Vinod _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel