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=-10.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 E9DAEC4332D for ; Fri, 20 Mar 2020 23:08:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC1792072D for ; Fri, 20 Mar 2020 23:08:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584745689; bh=U26CY0BQGcpUtPuH/7HtSD84yz0NB/7PRIZLpRdJOoA=; h=Date:From:To:cc:Subject:In-Reply-To:References:List-ID:From; b=b/oLVorf84328xexhT8wXXaNf7gytBqlmARpv8wH8JRo+zcZDrkiUVzuLilXLBew1 gTgz+NvxLdOBNd8NYJzRh5o6VXPR/dAFJzfb1TfMJE2k+2c9kGHCfl6XMbh5rWyO7x chQc+k/ugorePooD/zC1CVNbA3qjl4myT1WLQB/w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727629AbgCTXII (ORCPT ); Fri, 20 Mar 2020 19:08:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:37038 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727550AbgCTXII (ORCPT ); Fri, 20 Mar 2020 19:08:08 -0400 Received: from pobox.suse.cz (prg-ext-pat.suse.com [213.151.95.130]) (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 060122072C; Fri, 20 Mar 2020 23:08:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584745688; bh=U26CY0BQGcpUtPuH/7HtSD84yz0NB/7PRIZLpRdJOoA=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=mIY8xyMYxhFbdVAAr8V0NjP439UxHAwqqKMAk5ZJKQuUeAhobURyBW76+2wqPo2BU DLefhhg3oeoONuOTMS9gAp1Bfu27Lv5brDztYrzpSDGSzyaqa5CySnrMI5fBe3vWpA bU81cEDTcHC+7lMIfM0nlhMF49uOjyqD31VtU7I8= Date: Sat, 21 Mar 2020 00:08:05 +0100 (CET) From: Jiri Kosina To: "Gustavo A. R. Silva" cc: Srinivas Pandruvada , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH][next] intel-ish-hid: ishtp: ishtp-dev.h: Replace zero-length array with flexible-array member In-Reply-To: <20200319213108.GA9320@embeddedor.com> Message-ID: References: <20200319213108.GA9320@embeddedor.com> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 19 Mar 2020, 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") > > Signed-off-by: Gustavo A. R. Silva Applied, thanks. -- Jiri Kosina SUSE Labs