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=-11.8 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 7145DC433DF for ; Tue, 19 May 2020 18:44:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 530D5207D3 for ; Tue, 19 May 2020 18:44:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727844AbgESSoX (ORCPT ); Tue, 19 May 2020 14:44:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726903AbgESSoT (ORCPT ); Tue, 19 May 2020 14:44:19 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCDFCC08C5C0; Tue, 19 May 2020 11:44:18 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jb7Dr-0006cq-FS; Tue, 19 May 2020 20:44:15 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 1C3F31C047E; Tue, 19 May 2020 20:44:15 +0200 (CEST) Date: Tue, 19 May 2020 18:44:15 -0000 From: "tip-bot2 for Gustavo A. R. Silva" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Replace zero-length array with flexible-array Cc: "Gustavo A. R. Silva" , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <20200507192141.GA16183@embeddedor> References: <20200507192141.GA16183@embeddedor> MIME-Version: 1.0 Message-ID: <158991385502.17951.1325330133750697343.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 04f5c362ec6d3ff0e14f1c05230b550da7f528a4 Gitweb: https://git.kernel.org/tip/04f5c362ec6d3ff0e14f1c05230b550da7f528a4 Author: Gustavo A. R. Silva AuthorDate: Thu, 07 May 2020 14:21:41 -05:00 Committer: Peter Zijlstra CommitterDate: Tue, 19 May 2020 20:34:14 +02:00 sched/fair: Replace zero-length array with flexible-array 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200507192141.GA16183@embeddedor --- kernel/sched/fair.c | 2 +- kernel/sched/sched.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 44b0c8e..01f94cf 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1094,7 +1094,7 @@ struct numa_group { * more by CPU use than by memory faults. */ unsigned long *faults_cpu; - unsigned long faults[0]; + unsigned long faults[]; }; /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 21416b3..2bd2a22 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1462,7 +1462,7 @@ struct sched_group { * by attaching extra space to the end of the structure, * depending on how many CPUs the kernel has booted up with) */ - unsigned long cpumask[0]; + unsigned long cpumask[]; }; static inline struct cpumask *sched_group_span(struct sched_group *sg)