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=-13.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 DEC04C433E0 for ; Thu, 21 May 2020 18:52:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C2D1D208C9 for ; Thu, 21 May 2020 18:52:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590087141; bh=22eFmN3PxHoXvV1xmhf23Ujh/olYK+FBaQOc/JWyKF4=; h=Date:From:To:Cc:Subject:List-ID:From; b=qM9uFw/5vV2J35H8u+BB272Mm+vUtsfPCTjhSQN3GLtz0BDmH00ddp6tXZSfd/e2B 52hc+40kmvZliMlsvbRsKhd+5NGTTYE+xEpAJdje8wmVTvAUYSoH6UYWscjpq5FbrX fYqz/CNkL1exrBIGCLnOVgjurtgN1yEAGrTu2Jok= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729891AbgEUSwT (ORCPT ); Thu, 21 May 2020 14:52:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:46768 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729691AbgEUSwS (ORCPT ); Thu, 21 May 2020 14:52:18 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1258720823; Thu, 21 May 2020 18:52:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590087138; bh=22eFmN3PxHoXvV1xmhf23Ujh/olYK+FBaQOc/JWyKF4=; h=Date:From:To:Cc:Subject:From; b=cyli121Xo8MCtetN7HlPeb5FuYJUdX9EgmVlj63DR/O2C7orp8cXW6DLqRFjve53v W+W2DB0x35sVsAD9+RkWhZItZKXVP56Pl03+NsfVPRAUiH6yxNMoxJCO8RzHG6SO5u 4zKoz/fekoxxLqds3tkaBugo+C9/smGpWiVN5+1U= Date: Thu, 21 May 2020 13:57:07 -0500 From: "Gustavo A. R. Silva" To: Geert Uytterhoeven Cc: linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] m68k: tools: Replace zero-length array with flexible-array member Message-ID: <20200521185707.GA3661@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-m68k-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-m68k@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 --- arch/m68k/tools/amiga/dmesg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/m68k/tools/amiga/dmesg.c b/arch/m68k/tools/amiga/dmesg.c index 7340f5b6cf6d..f8005a7efb0b 100644 --- a/arch/m68k/tools/amiga/dmesg.c +++ b/arch/m68k/tools/amiga/dmesg.c @@ -34,7 +34,7 @@ struct savekmsg { u_long magic2; /* SAVEKMSG_MAGIC2 */ u_long magicptr; /* address of magic1 */ u_long size; - char data[0]; + char data[]; }; -- 2.26.2