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=-8.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 E9302C54E8D for ; Mon, 11 May 2020 13:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7BDB207FF for ; Mon, 11 May 2020 13:01:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="IDnyOjLh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729993AbgEKNBR (ORCPT ); Mon, 11 May 2020 09:01:17 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:26693 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729937AbgEKNBP (ORCPT ); Mon, 11 May 2020 09:01:15 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1589202075; h=Date: Message-Id: Cc: To: References: In-Reply-To: From: Subject: Content-Transfer-Encoding: MIME-Version: Content-Type: Sender; bh=DDYrY47HSTYss32CprtbeYo3Xm5nNQMfOh6XX4YKxGc=; b=IDnyOjLhjqkdm9SdanmC1/l3M1X51HXYMnI/cLoi7c30g+4fM5mr3GDs0Ya+Y8bawNlwXBPI 50/Mxo1eiWj1Q7vs/0iRsT/itnAmCY2i2E15LCogKSzeq/Xe+D8Lotb4Uor+awMV6P30fHSb KXuzVdYxsjioxqUUiAznD2k3ids= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI3YTAwOSIsICJsaW51eC13aXJlbGVzc0B2Z2VyLmtlcm5lbC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5eb94c70.7f8434bba0d8-smtp-out-n03; Mon, 11 May 2020 13:00:32 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 7E203C44798; Mon, 11 May 2020 13:00:32 +0000 (UTC) Received: from potku.adurom.net (88-114-240-156.elisa-laajakaista.fi [88.114.240.156]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: kvalo) by smtp.codeaurora.org (Postfix) with ESMTPSA id E7DFCC44792; Mon, 11 May 2020 13:00:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org E7DFCC44792 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=kvalo@codeaurora.org Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [PATCH] carl9170: Replace zero-length array with flexible-array From: Kalle Valo In-Reply-To: <20200507185132.GA14046@embeddedor> References: <20200507185132.GA14046@embeddedor> To: "Gustavo A. R. Silva" Cc: Christian Lamparter , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org User-Agent: pwcli/0.1.0-git (https://github.com/kvalo/pwcli/) Python/3.5.2 Message-Id: <20200511130032.7E203C44798@smtp.codeaurora.org> Date: Mon, 11 May 2020 13:00:32 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org "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 This was sent twice so I'm dropping this version. Patch set to Superseded. -- https://patchwork.kernel.org/patch/11534683/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches