From patchwork Tue Apr 7 03:11:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11477469 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 A54B592A for ; Tue, 7 Apr 2020 03:12:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 72D3820769 for ; Tue, 7 Apr 2020 03:12:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="PZLfullQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72D3820769 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1A0E98E009C; Mon, 6 Apr 2020 23:12:01 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 0B3CA8E0062; Mon, 6 Apr 2020 23:12:01 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F0C378E009C; Mon, 6 Apr 2020 23:12:00 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0241.hostedemail.com [216.40.44.241]) by kanga.kvack.org (Postfix) with ESMTP id D1D928E0062 for ; Mon, 6 Apr 2020 23:12:00 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9AE82180AD806 for ; Tue, 7 Apr 2020 03:12:00 +0000 (UTC) X-FDA: 76679584800.02.arm62_11842471f9128 X-Spam-Summary: 2,0,0,bacb98366ec4fe05,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:355:379:800:960:967:973:988:989:1260:1263:1345:1359:1381:1431:1437:1534:1541:1711:1730:1747:1777:1792:2194:2198:2199:2200:2393:2525:2553:2559:2565:2682:2685:2693:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3352:3865:3866:3867:3868:3870:3871:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4321:4605:5007:6117:6261:6653:7576:7903:8599:9025:9545:10004:10913:11658:11914:12043:12048:12296:12297:12517:12519:12555:12679:12696:12737:12783:12986:13069:13161:13229:13255:13311:13357:14094:14181:14384:14721:14849:21067:21080:21451:21524:21627:21939:21972:30029:30054:30070:30090,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-62.2.0.100 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:2,LUA_SUMMARY:none X-HE-Tag: arm62_11842471f9128 X-Filterd-Recvd-Size: 3212 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Tue, 7 Apr 2020 03:12:00 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 628F820801; Tue, 7 Apr 2020 03:11:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586229119; bh=y8oAJJX6nszOGnMGpNq2e+oIjeVtN1YA1O8X5x1xYAQ=; h=Date:From:To:Subject:In-Reply-To:From; b=PZLfullQ5hiRKRTefHYGBbouuuCxFokEt9Bw4OEdjJW7Y3i3zYtccFaYof3goH5c4 8eHjEVnx77molbWLSqMbGFqG+rKE0O1v3ovTidQOuy7h2Ybctj5YensaYkeOjlnkNO XoFwkzh7yFafctc+so++YHmOdWNB+bthU9Z9pizs= Date: Mon, 06 Apr 2020 20:11:58 -0700 From: Andrew Morton To: akpm@linux-foundation.org, gustavo@embeddedor.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, oberpar@linux.ibm.com, torvalds@linux-foundation.org Subject: [patch 149/166] kernel/gcov/fs.c: replace zero-length array with flexible-array member Message-ID: <20200407031158.wkhb-ywcR%akpm@linux-foundation.org> In-Reply-To: <20200406200254.a69ebd9e08c4074e41ddebaf@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: "Gustavo A. R. Silva" Subject: kernel/gcov/fs.c: replace zero-length array with flexible-array member 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") Link: http://lkml.kernel.org/r/20200302224851.GA26467@embeddedor Signed-off-by: Gustavo A. R. Silva Cc: Peter Oberparleiter Signed-off-by: Andrew Morton --- kernel/gcov/fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/gcov/fs.c~gcov-fs-replace-zero-length-array-with-flexible-array-member +++ a/kernel/gcov/fs.c @@ -58,7 +58,7 @@ struct gcov_node { struct dentry *dentry; struct dentry **links; int num_loaded; - char name[0]; + char name[]; }; static const char objtree[] = OBJTREE;