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=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 DBA7BC38A24 for ; Thu, 7 May 2020 19:20:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3B1E208D6 for ; Thu, 7 May 2020 19:20:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879236; bh=uXi39PQvaKDfT68j1+BxFLuUBBa53fIwGeidQwFDQog=; h=Date:From:To:Cc:Subject:List-ID:From; b=KDyFnuBC+M4MsZeQO5dOLOb9IcE5mFmyFuseW1d8gmtJioCvwfHjoDoofdN2afgeP MY0+L7S1bfHxRrtV28hFPOByYSDc8CuLAMo2gcCMmmXSM6Erz2caTYIgHaIGwZDWqL ve1lNcA6dP+13UIq94wqNqcfDU3XTO9FGKlT+cL4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728468AbgEGTUf (ORCPT ); Thu, 7 May 2020 15:20:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:42214 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728391AbgEGTUf (ORCPT ); Thu, 7 May 2020 15:20:35 -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 B785F208D6; Thu, 7 May 2020 19:20:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879235; bh=uXi39PQvaKDfT68j1+BxFLuUBBa53fIwGeidQwFDQog=; h=Date:From:To:Cc:Subject:From; b=GnfrXSO3O3Uth1ANWH7AgHHNxrQE6cvAFWkKtM6gDk0xlsOGOGzMAE1kp+iDksEMn +3l/CRAN2t0sGhoKkYSGCCS7kQrWA/6i9fsgmlNFEdvLaMTnF8XqK0fXXA7wQAmtS9 ihdBaO3F0X7VkPiVE4WRC9MJUaS/8hWtf6dJJQQI= Date: Thu, 7 May 2020 14:25:01 -0500 From: "Gustavo A. R. Silva" To: Alexander Shishkin Cc: linux-kernel@vger.kernel.org Subject: [PATCH] stm class: Replace zero-length array with flexible-array Message-ID: <20200507192501.GA16491@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-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] 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 --- drivers/hwtracing/stm/policy.c | 2 +- drivers/hwtracing/stm/stm.h | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c index 4f932a419752..603b4a9969d3 100644 --- a/drivers/hwtracing/stm/policy.c +++ b/drivers/hwtracing/stm/policy.c @@ -34,7 +34,7 @@ struct stp_policy_node { unsigned int first_channel; unsigned int last_channel; /* this is the one that's exposed to the attributes */ - unsigned char priv[0]; + unsigned char priv[]; }; void *stp_policy_node_priv(struct stp_policy_node *pn) diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h index 3569439d53bb..a9be49fc7a6b 100644 --- a/drivers/hwtracing/stm/stm.h +++ b/drivers/hwtracing/stm/stm.h @@ -23,7 +23,7 @@ void *stp_policy_node_priv(struct stp_policy_node *pn); struct stp_master { unsigned int nr_free; - unsigned long chan_map[0]; + unsigned long chan_map[]; }; struct stm_device { @@ -42,7 +42,7 @@ struct stm_device { const struct config_item_type *pdrv_node_type; /* master allocation */ spinlock_t mc_lock; - struct stp_master *masters[0]; + struct stp_master *masters[]; }; #define to_stm_device(_d) \