From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail27.static.mailgun.info ([104.130.122.27]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVsMS-00025i-S4 for ath10k@lists.infradead.org; Tue, 05 May 2020 07:51:30 +0000 MIME-Version: 1.0 Subject: Re: [PATCH] ath10k: Replace zero-length array with flexible-array From: Kalle Valo In-Reply-To: <20200504201108.GA32136@embeddedor> References: <20200504201108.GA32136@embeddedor> Message-Id: <20200505075126.C6D62C433D2@smtp.codeaurora.org> Date: Tue, 5 May 2020 07:51:26 +0000 (UTC) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "ath10k" Errors-To: ath10k-bounces+kvalo=adurom.com@lists.infradead.org To: "Gustavo A. R. Silva" Cc: netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, ath10k@lists.infradead.org, "David S. Miller" "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") > > Signed-off-by: Gustavo A. R. Silva Fails to apply, please rebase on top of ath.git master branch. error: patch failed: drivers/net/wireless/ath/ath10k/pci.h:182 error: drivers/net/wireless/ath/ath10k/pci.h: patch does not apply stg import: Diff does not apply cleanly Patch set to Changes Requested. -- https://patchwork.kernel.org/patch/11527635/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches _______________________________________________ ath10k mailing list ath10k@lists.infradead.org http://lists.infradead.org/mailman/listinfo/ath10k