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=-8.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D9331C2BA80 for ; Tue, 7 Apr 2020 03:11:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9BDF520769 for ; Tue, 7 Apr 2020 03:11:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="e0Nf2dwv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BDF520769 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 DAC0E8E009A; Mon, 6 Apr 2020 23:11:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D5F508E0062; Mon, 6 Apr 2020 23:11:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C74268E009A; Mon, 6 Apr 2020 23:11:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0069.hostedemail.com [216.40.44.69]) by kanga.kvack.org (Postfix) with ESMTP id AAD728E0062 for ; Mon, 6 Apr 2020 23:11:54 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 79909281F for ; Tue, 7 Apr 2020 03:11:54 +0000 (UTC) X-FDA: 76679584548.15.duck07_10a07637b4454 X-HE-Tag: duck07_10a07637b4454 X-Filterd-Recvd-Size: 3245 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Tue, 7 Apr 2020 03:11:54 +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 424D8206B8; Tue, 7 Apr 2020 03:11:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586229113; bh=VRvMSgLd5U80T70bgwb0zIP0psVgZ15vvIRqcUXYZ4w=; h=Date:From:To:Subject:In-Reply-To:From; b=e0Nf2dwvzh5iFwrfy2KDZd2kZnAlXzK4p4ut/YeB64X614J1Id5jx8Ootk5HmRhCZ Q45u/jHmjmRbvs457qzy3rbqCJjzGWhjz0SlWxqT4sbjEYMMwxLh1Lcsl3WrlK+ep6 6iKQKwX49dvX6w6aAu3utbpLrGMtC1g0O0tJOwmk= Date: Mon, 06 Apr 2020 20:11:52 -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 147/166] gcov: gcc_4_7: replace zero-length array with flexible-array member Message-ID: <20200407031152.5DFUMTlhw%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: gcov: gcc_4_7: 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/20200213152241.GA877@embeddedor Signed-off-by: Gustavo A. R. Silva Acked-by: Peter Oberparleiter Signed-off-by: Andrew Morton --- kernel/gcov/gcc_4_7.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/gcov/gcc_4_7.c~gcov-gcc_4_7-replace-zero-length-array-with-flexible-array-member +++ a/kernel/gcov/gcc_4_7.c @@ -68,7 +68,7 @@ struct gcov_fn_info { unsigned int ident; unsigned int lineno_checksum; unsigned int cfg_checksum; - struct gcov_ctr_info ctrs[0]; + struct gcov_ctr_info ctrs[]; }; /** _