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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 D915BC3F68F for ; Thu, 13 Feb 2020 14:46:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0BC024650 for ; Thu, 13 Feb 2020 14:46:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581605199; bh=W82GgC4McSrXk1Q92M7zOg/KKPxsVJA4PeYnPwzdY1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ME8vhtA9Gb0HW1R9HQhnyqSZoLzrxKWmelHFBiT04bnOfHzdsIHnS9mEbdlTVjU+F 0cQNhVN7boTfcL18lAysvrOQmwQ0/S9H7Yevy4om3jK6KTaCHPYr6eyBDjOAEbAEAV tYYEVocmQ5kF6CRym8fWYTXwXYGmiyJ4KTXVP7pk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727433AbgBMOqj (ORCPT ); Thu, 13 Feb 2020 09:46:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:58076 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727076AbgBMOqj (ORCPT ); Thu, 13 Feb 2020 09:46:39 -0500 Received: from localhost (unknown [106.201.58.38]) (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 A4EC22073C; Thu, 13 Feb 2020 14:46:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581605198; bh=W82GgC4McSrXk1Q92M7zOg/KKPxsVJA4PeYnPwzdY1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=d2tVYJDW0otBDp/xIhPuC5x72IbITOGml3006xOnvsRGafUYR6VDozarGzriLQcT0 phXNBZtxsPqirxMOs8JQiLv2Sfx8uBcfbDQBB3MYu5Eb028FFGOLgNTGYlOHdFDIv9 XY/nzzWTa9rEOIBq8Znfs0p3DF6FdasLsWkiCb9A= Date: Thu, 13 Feb 2020 20:16:32 +0530 From: Vinod Koul To: "Gustavo A. R. Silva" Cc: Dan Williams , Masahiro Yamada , dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dmaengine: uniphier-mdmac: replace zero-length array with flexible-array member Message-ID: <20200213144632.GL2618@vkoul-mobl> References: <20200213003535.GA3269@embeddedor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200213003535.GA3269@embeddedor.com> Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On 12-02-20, 18:35, 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] > > 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