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 18B73C433DF for ; Tue, 19 May 2020 18:44:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E079A20849 for ; Tue, 19 May 2020 18:44:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726899AbgESSoQ (ORCPT ); Tue, 19 May 2020 14:44:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726528AbgESSoP (ORCPT ); Tue, 19 May 2020 14:44:15 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 139DEC08C5C1; Tue, 19 May 2020 11:44:15 -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 1jb7Dn-0006af-SZ; Tue, 19 May 2020 20:44:12 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 6C11B1C047E; Tue, 19 May 2020 20:44:11 +0200 (CEST) Date: Tue, 19 May 2020 18:44:11 -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: perf/core] perf/x86: Replace zero-length array with flexible-array Cc: "Gustavo A. R. Silva" , "Peter Zijlstra (Intel)" , x86 , LKML In-Reply-To: <20200511200911.GA13149@embeddedor> References: <20200511200911.GA13149@embeddedor> MIME-Version: 1.0 Message-ID: <158991385134.17951.17648363671247069672.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 perf/core branch of tip: Commit-ID: 8ac7571a8cd3c11da24c3c3555f6e40e33049609 Gitweb: https://git.kernel.org/tip/8ac7571a8cd3c11da24c3c3555f6e40e33049609 Author: Gustavo A. R. Silva AuthorDate: Mon, 11 May 2020 15:09:11 -05:00 Committer: Peter Zijlstra CommitterDate: Tue, 19 May 2020 20:34:16 +02:00 perf/x86: 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/20200511200911.GA13149@embeddedor --- arch/x86/events/intel/bts.c | 2 +- arch/x86/events/intel/uncore.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c index 6a3b599..731dd8d 100644 --- a/arch/x86/events/intel/bts.c +++ b/arch/x86/events/intel/bts.c @@ -58,7 +58,7 @@ struct bts_buffer { local_t head; unsigned long end; void **data_pages; - struct bts_phys buf[0]; + struct bts_phys buf[]; }; static struct pmu bts_pmu; diff --git a/arch/x86/events/intel/uncore.h b/arch/x86/events/intel/uncore.h index 0da4a46..b469ddd 100644 --- a/arch/x86/events/intel/uncore.h +++ b/arch/x86/events/intel/uncore.h @@ -130,7 +130,7 @@ struct intel_uncore_box { struct list_head list; struct list_head active_list; void __iomem *io_addr; - struct intel_uncore_extra_reg shared_regs[0]; + struct intel_uncore_extra_reg shared_regs[]; }; /* CFL uncore 8th cbox MSRs */