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=-13.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 2B07FC4332B for ; Fri, 20 Mar 2020 23:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05F1B20732 for ; Fri, 20 Mar 2020 23:08:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584745704; bh=qygH61ppjWPqCHNvMFYMcBRUJgDDlw/mHEY83m/hSpo=; h=Date:From:To:cc:Subject:In-Reply-To:References:List-ID:From; b=WY7kzhofcaJQVFAeknrFQw/a1EXeqsnTydMHIw+dDkTjTigxTi/zSWvH4Nk+b5ZYS d6XQr8NfS4RJmj9laAdT21IfFjsk86SRnIhlbcajklrqI7OiTqxw9lDiFuyJsTqxSa 4q28lHaw1XNOMWjUCVuVomczVKLNUewEk8w5YSNg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727640AbgCTXIX (ORCPT ); Fri, 20 Mar 2020 19:08:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:37112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727635AbgCTXIX (ORCPT ); Fri, 20 Mar 2020 19:08:23 -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 84B0E2072C; Fri, 20 Mar 2020 23:08:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584745702; bh=qygH61ppjWPqCHNvMFYMcBRUJgDDlw/mHEY83m/hSpo=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=1E2eG+cYq1q4R9KID+6MD4CGq6HsQJzQVEm6grvE0AOHGbm5PdyNmeqSV7BHi218O 88DE5SQnqKUGKMHHAwT3b66IBe+TZEEc+6XdOOgmduGJjvLi04E1zFEfBFuK1i3LaS 4oC2VzASGw4uqz3gJXuNSd+M/PztU5pTbRGHjlPU= Date: Sat, 21 Mar 2020 00:08:19 +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: hbm.h: Replace zero-length array with flexible-array member In-Reply-To: <20200319212950.GA9155@embeddedor.com> Message-ID: References: <20200319212950.GA9155@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-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@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 > --- > drivers/hid/intel-ish-hid/ishtp/hbm.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/hid/intel-ish-hid/ishtp/hbm.h b/drivers/hid/intel-ish-hid/ishtp/hbm.h > index bb85985b1620..7c445b203f2a 100644 > --- a/drivers/hid/intel-ish-hid/ishtp/hbm.h > +++ b/drivers/hid/intel-ish-hid/ishtp/hbm.h > @@ -82,7 +82,7 @@ struct ishtp_msg_hdr { > > struct ishtp_bus_message { > uint8_t hbm_cmd; > - uint8_t data[0]; > + uint8_t data[]; > } __packed; > > /** Applied this one too, thanks Gustavo. -- Jiri Kosina SUSE Labs