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 1ED3DC3F2CD for ; Wed, 4 Mar 2020 11:06:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2D972166E for ; Wed, 4 Mar 2020 11:06:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726440AbgCDLGJ (ORCPT ); Wed, 4 Mar 2020 06:06:09 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:51309 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729232AbgCDLGJ (ORCPT ); Wed, 4 Mar 2020 06:06:09 -0500 Received: from 79.184.237.41.ipv4.supernova.orange.pl (79.184.237.41) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.341) id 23ba990a84e430d4; Wed, 4 Mar 2020 12:06:06 +0100 From: "Rafael J. Wysocki" To: "Gustavo A. R. Silva" Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] powercap: idle_inject: Replace zero-length array with flexible-array member Date: Wed, 04 Mar 2020 12:06:06 +0100 Message-ID: <2823796.V19jU70VZq@kreacher> In-Reply-To: <20200227190721.GA19083@embeddedor> References: <20200227190721.GA19083@embeddedor> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thursday, February 27, 2020 8:07:21 PM CET 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] > > Lastly, fix the following checkpatch warning: > WARNING: Prefer 'unsigned long' over 'unsigned long int' as the int is unnecessary > + unsigned long int cpumask[]; > > 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/powercap/idle_inject.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c > index cd1270614cc6..e9bbd3c42eef 100644 > --- a/drivers/powercap/idle_inject.c > +++ b/drivers/powercap/idle_inject.c > @@ -67,7 +67,7 @@ struct idle_inject_device { > struct hrtimer timer; > unsigned int idle_duration_us; > unsigned int run_duration_us; > - unsigned long int cpumask[0]; > + unsigned long cpumask[]; > }; > > static DEFINE_PER_CPU(struct idle_inject_thread, idle_inject_thread); > Applied as 5.7 material, thanks!