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 3A45AC38A24 for ; Thu, 7 May 2020 18:48:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0185124956 for ; Thu, 7 May 2020 18:48:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877328; bh=DT6pf4s8Z+o8NdUVi2jciKOH7+SzyKg9SeNRFT3XikQ=; h=Date:From:To:Cc:Subject:List-ID:From; b=fBe+NBpfXdZQZSw8FwaTBCX4Z2d/+rJWra+GlXv+ZfxSnPErXX242qxZuuSgVUMrY ffUm3bO0UaW9iM1pR10CsSiMEgcfXGCwPbW20ZEzHs/HorNvHd5sFt3opnt6Vfhkau nOS8RE+lZgGCcKum3qxRV+Dq3yM/XAzzSIg6E8Kg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728632AbgEGSsr (ORCPT ); Thu, 7 May 2020 14:48:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:49878 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728166AbgEGSsq (ORCPT ); Thu, 7 May 2020 14:48:46 -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 3AD5124955; Thu, 7 May 2020 18:48:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877326; bh=DT6pf4s8Z+o8NdUVi2jciKOH7+SzyKg9SeNRFT3XikQ=; h=Date:From:To:Cc:Subject:From; b=NFjpeG2clblm3YEQEa2Jh77GUhDQCVQ3tU1sq58gS1/AxxDnOwLWyLH+nXsKqYeLE UELbd3+57tHlw45RXPcCWTTmqUCDMevrd1h8/b9CQZvS6c03iyBuK95MWEE+oOhUBp iyR/SdW+uXBH1oY5yzD2EVgFh63cPfUi2kiscyyU= Date: Thu, 7 May 2020 13:53:13 -0500 From: "Gustavo A. R. Silva" To: Johan Hovold Cc: linux-kernel@vger.kernel.org Subject: [PATCH] treewide: Replace zero-length array with flexible-array Message-ID: <20200507185313.GA14373@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/gnss/serial.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gnss/serial.h b/drivers/gnss/serial.h index 980ffdc86c2a..621953f7821d 100644 --- a/drivers/gnss/serial.h +++ b/drivers/gnss/serial.h @@ -16,7 +16,7 @@ struct gnss_serial { struct gnss_device *gdev; speed_t speed; const struct gnss_serial_ops *ops; - unsigned long drvdata[0]; + unsigned long drvdata[]; }; enum gnss_serial_pm_state {