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=-13.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 A38E6C3F2CD for ; Mon, 2 Mar 2020 22:42:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6AF9F208C3 for ; Mon, 2 Mar 2020 22:42:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="sYfDK+07" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726843AbgCBWmG (ORCPT ); Mon, 2 Mar 2020 17:42:06 -0500 Received: from gateway33.websitewelcome.com ([192.185.145.24]:40471 "EHLO gateway33.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726755AbgCBWmF (ORCPT ); Mon, 2 Mar 2020 17:42:05 -0500 Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway33.websitewelcome.com (Postfix) with ESMTP id 413F31F4371 for ; Mon, 2 Mar 2020 16:42:01 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 8tlBjOjLvXVkQ8tlBjizBJ; Mon, 02 Mar 2020 16:42:01 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=+FgTF4phqPQ4ev03UWJ01rP2KoU5/XHfnR9gkSeBOIY=; b=sYfDK+070JjWhlFJJ9K6P3u3Nx jQ6q1CnoMZwikhHwcFTg/Cr/z1QvHKDPBgnE7I9k+X6yEu8UFrFaVqrhh1OJosylY6DEqW6fllWru lQFRbc3t79PRdrR/KRoZGUcwt/kdPk9gzUYZqDYKo5K2fHigNuNAzDnpUgGPsqo8jnmr66bJ2HkAq N0ED36f27/Smi+sKuWnzF25dI0fOLPAiM0IF/FpK5OAMCyIs2ZAk63eD8Jqfso9ZRzuLGjNe5uh+W y5vZwHfU1SeksgkJPNpl10+MsmaN1f44r8f+3z6fufuwTd634z8bZr/5S2JCEOvkSGt//eAp8tEz0 qaecbRXQ==; Received: from [201.166.169.236] (port=1308 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j8tl9-000sUo-A4; Mon, 02 Mar 2020 16:41:59 -0600 Date: Mon, 2 Mar 2020 16:45:01 -0600 From: "Gustavo A. R. Silva" To: Peter Oberparleiter , Andrew Morton Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] gcov: gcc_3_4: Replace zero-length array with flexible-array member Message-ID: <20200302224501.GA14175@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 201.166.169.236 X-Source-L: No X-Exim-ID: 1j8tl9-000sUo-A4 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.166.169.236]:1308 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- kernel/gcov/gcc_3_4.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/gcov/gcc_3_4.c b/kernel/gcov/gcc_3_4.c index 801ee4b0b969..acb83558e5df 100644 --- a/kernel/gcov/gcc_3_4.c +++ b/kernel/gcov/gcc_3_4.c @@ -38,7 +38,7 @@ static struct gcov_info *gcov_info_head; struct gcov_fn_info { unsigned int ident; unsigned int checksum; - unsigned int n_ctrs[0]; + unsigned int n_ctrs[]; }; /** @@ -78,7 +78,7 @@ struct gcov_info { unsigned int n_functions; const struct gcov_fn_info *functions; unsigned int ctr_mask; - struct gcov_ctr_info counts[0]; + struct gcov_ctr_info counts[]; }; /** @@ -352,7 +352,7 @@ struct gcov_iterator { unsigned int count; int num_types; - struct type_info type_info[0]; + struct type_info type_info[]; }; static struct gcov_fn_info *get_func(struct gcov_iterator *iter) -- 2.25.0