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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 57B65C10F27 for ; Tue, 10 Mar 2020 18:31:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3456421D56 for ; Tue, 10 Mar 2020 18:31:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727491AbgCJSbS (ORCPT ); Tue, 10 Mar 2020 14:31:18 -0400 Received: from relay1-d.mail.gandi.net ([217.70.183.193]:14679 "EHLO relay1-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726466AbgCJSbR (ORCPT ); Tue, 10 Mar 2020 14:31:17 -0400 X-Originating-IP: 91.224.148.103 Received: from localhost.localdomain (unknown [91.224.148.103]) (Authenticated sender: miquel.raynal@bootlin.com) by relay1-d.mail.gandi.net (Postfix) with ESMTPSA id C1BB4240008; Tue, 10 Mar 2020 18:31:13 +0000 (UTC) From: Miquel Raynal To: "Gustavo A. R. Silva" , Masahiro Yamada , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Liang Yang , Kevin Hilman , Xiaolei Li , Matthias Brugger , Maxime Ripard , Chen-Yu Tsai Cc: linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-mtd@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] mtd: rawnand: Replace zero-length array with flexible-array member Date: Tue, 10 Mar 2020 19:31:12 +0100 Message-Id: <20200310183112.18567-1-miquel.raynal@bootlin.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200226222722.GA18020@embeddedor> References: MIME-Version: 1.0 X-linux-mtd-patch-notification: thanks X-linux-mtd-patch-commit: 76d2f79cf5ae53bc5781903af98a1cb51ef12915 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-02-26 at 22:27:22 UTC, "Gustavo A. R. Silva" wrote: > 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 > Acked-by: Masahiro Yamada Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next, thanks. Miquel