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=-11.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 02350C38A2A for ; Thu, 7 May 2020 20:08:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D30DE21582 for ; Thu, 7 May 2020 20:08:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728045AbgEGUIp convert rfc822-to-8bit (ORCPT ); Thu, 7 May 2020 16:08:45 -0400 Received: from mga07.intel.com ([134.134.136.100]:50154 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGUIo (ORCPT ); Thu, 7 May 2020 16:08:44 -0400 IronPort-SDR: vHNozOPniD9IXduQ3g977zM8LzOGG69RxENbCHdtLGfdYbfmBb8Zt6bIqEfPI8bQLsLUx8mfxW Y6FyNzGsBIhg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2020 13:08:43 -0700 IronPort-SDR: kNBmpPTiIIT3xUKaY76vFUH7TgihcmBZxesy2tUDROkzb6YlRrOZj1162qnp/LLTSQ4pr3gdkf ubUjilR2rcwQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,365,1583222400"; d="scan'208";a="370223059" Received: from fmsmsx103.amr.corp.intel.com ([10.18.124.201]) by fmsmga001.fm.intel.com with ESMTP; 07 May 2020 13:08:43 -0700 Received: from hasmsx603.ger.corp.intel.com (10.184.107.143) by FMSMSX103.amr.corp.intel.com (10.18.124.201) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 7 May 2020 13:08:43 -0700 Received: from hasmsx602.ger.corp.intel.com (10.184.107.142) by HASMSX603.ger.corp.intel.com (10.184.107.143) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Thu, 7 May 2020 23:08:41 +0300 Received: from hasmsx602.ger.corp.intel.com ([10.184.107.142]) by HASMSX602.ger.corp.intel.com ([10.184.107.142]) with mapi id 15.01.1713.004; Thu, 7 May 2020 23:08:41 +0300 From: "Winkler, Tomas" To: "Gustavo A. R. Silva" CC: "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] treewide: Replace zero-length array with flexible-array Thread-Topic: [PATCH] treewide: Replace zero-length array with flexible-array Thread-Index: AQHWJKBOJSsbWiWaH0mmen9kZErTsqidDUCQ Date: Thu, 7 May 2020 20:08:40 +0000 Message-ID: <7cf79b41ef1e479196f0a644b55ff67b@intel.com> References: <20200507185413.GA14583@embeddedor> In-Reply-To: <20200507185413.GA14583@embeddedor> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.2.0.6 x-originating-ip: [10.184.70.1] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Gustavo A. R. Silva > Sent: Thursday, May 07, 2020 21:54 > To: Winkler, Tomas > Cc: linux-kernel@vger.kernel.org > Subject: [PATCH] treewide: Replace zero-length array with flexible-array Ack. > > 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 > --- > samples/mei/mei-amt-version.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/samples/mei/mei-amt-version.c b/samples/mei/mei-amt-version.c > index 32234481ad7d..ad3e56042f96 100644 > --- a/samples/mei/mei-amt-version.c > +++ b/samples/mei/mei-amt-version.c > @@ -267,7 +267,7 @@ struct amt_host_if_msg_header { struct > amt_host_if_resp_header { > struct amt_host_if_msg_header header; > uint32_t status; > - unsigned char data[0]; > + unsigned char data[]; > } __attribute__((packed)); > > const uuid_le MEI_IAMTHIF = UUID_LE(0x12f80028, 0xb4b7, 0x4b2d, \