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=-11.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 840BBC47255 for ; Mon, 11 May 2020 05:47:43 +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 5493E20735 for ; Mon, 11 May 2020 05:47:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WYNhEt8b" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5493E20735 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=microchip.com 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=k9vAHsEcl4aT4T2N0rDN6wvWtB33Gik1/Md9/4aTDKg=; b=WYNhEt8bhqdui4 JE0rnb6HgDA0uKlHWT6x/ya9aogOBleymJ3U9VkLlZf+RgU6W7VEvz/zAnG2gW+Bh7bT6TJ22I8Tw CnjVaD6zptkZMjlHeN+ge7LowsEiXsIk6LYQq8A8sTT3Kqu1mJ/QFTKcjhBlQKOZBEEOpTEOth1A1 kTi6y9Zv5Ptikgt31QuccNqRZ2ka/mUqEqP/kFYlcdoA5wDOWlqyzQ4ncaXrxV9No8Gfac9LCEQB/ a69VJ59bjMJf/cNRyy4uXkWIJgNfAAS093JdIxLAaum22o2eyP6UUXXJTgBchLM3KLrh4WO9ukbLF Rg/KTX0/8k98pqhRcydA==; 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 1jY1Hy-0006iC-AQ; Mon, 11 May 2020 05:47:42 +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 1jY1Hv-0006hO-Tt for linux-arm-kernel@lists.infradead.org; Mon, 11 May 2020 05:47:41 +0000 Received: from sekiro (amontpellier-556-1-155-96.w109-210.abo.wanadoo.fr [109.210.131.96]) (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 326EF20735; Mon, 11 May 2020 05:47:35 +0000 (UTC) Date: Mon, 11 May 2020 07:47:30 +0200 From: Ludovic Desroches To: "Gustavo A. R. Silva" Subject: Re: [PATCH] dmaengine: at_hdmac: Replace zero-length array with flexible-array Message-ID: <20200511054730.pfsavov2onak4nf6@sekiro> References: <20200507190038.GA15272@embeddedor> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200507190038.GA15272@embeddedor> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200510_224739_983731_B7C0345E X-CRM114-Status: GOOD ( 20.89 ) 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, 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 Thu, May 07, 2020 at 02:00:38PM -0500, Gustavo A. R. Silva wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > 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 Acked-by: Ludovic Desroches Thanks > --- > drivers/dma/at_hdmac_regs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h > index 397692e937b3..80fc2fe8c77e 100644 > --- a/drivers/dma/at_hdmac_regs.h > +++ b/drivers/dma/at_hdmac_regs.h > @@ -331,7 +331,7 @@ struct at_dma { > struct dma_pool *dma_desc_pool; > struct dma_pool *memset_pool; > /* AT THE END channels table */ > - struct at_dma_chan chan[0]; > + struct at_dma_chan chan[]; > }; > > #define dma_readl(atdma, name) \ > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel