From patchwork Thu May 7 19:25:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 11534793 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3949592A for ; Thu, 7 May 2020 19:21:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21EBB208D6 for ; Thu, 7 May 2020 19:21:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879262; bh=hzZ3BRJHxK/0iJNH5rKEuCwWUFrZiZMlsFx+KFOhD6E=; h=Date:From:To:Cc:Subject:List-ID:From; b=gAW16XUG0eS/FA/tCvdeXJzbw0h04WlDpdXileGSye7hftKGq5MwTi161x2DI5Hw9 euEo55UsQJucbQUynSSYhX63QmUl7Zx2afpZLyDnyhp856LuORAxEupt1TYsdw9Yvc nMtnNmc/MWQ26GaklmwNgyGb/bXvKw8Bsp9saYdU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728634AbgEGTU6 (ORCPT ); Thu, 7 May 2020 15:20:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:42516 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727837AbgEGTU6 (ORCPT ); Thu, 7 May 2020 15:20:58 -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 970BF208D6; Thu, 7 May 2020 19:20:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879258; bh=hzZ3BRJHxK/0iJNH5rKEuCwWUFrZiZMlsFx+KFOhD6E=; h=Date:From:To:Cc:Subject:From; b=Tq/MIkKsUFJuC5zOBIHBid/OytqD/3C8lK0sI37YnFdE9Amxy9nluQqghi/muFfKZ BF4iKukLDB9U57ZGGH6UfZuoAFFZ5Hi4i1N6ORzbWoRO4BAO3+eQIZ2qZDT4SvJG7F U+f3cF7Vh/2r/QiCpMT3QrufbXDQO5SvogLjygv0= Date: Thu, 7 May 2020 14:25:24 -0500 From: "Gustavo A. R. Silva" To: Andreas Noever , Michael Jamet , Mika Westerberg , Yehezkel Bernat Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] thunderbolt: Replace zero-length array with flexible-array Message-ID: <20200507192524.GA16580@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@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] 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 --- include/linux/thunderbolt.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h index ece782ef5466..ff397c0d5c07 100644 --- a/include/linux/thunderbolt.h +++ b/include/linux/thunderbolt.h @@ -80,7 +80,7 @@ struct tb { int index; enum tb_security_level security_level; size_t nboot_acl; - unsigned long privdata[0]; + unsigned long privdata[]; }; extern struct bus_type tb_bus_type;