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 A137CC2BA1A for ; Tue, 7 Apr 2020 03:11:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 58AB620716 for ; Tue, 7 Apr 2020 03:11:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="SukrHK2T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 58AB620716 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 0B49D8E009B; Mon, 6 Apr 2020 23:11:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 040CD8E0062; Mon, 6 Apr 2020 23:11:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DAC5F8E009B; Mon, 6 Apr 2020 23:11:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0195.hostedemail.com [216.40.44.195]) by kanga.kvack.org (Postfix) with ESMTP id BF2FA8E0062 for ; Mon, 6 Apr 2020 23:11:57 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 80950181AC217 for ; Tue, 7 Apr 2020 03:11:57 +0000 (UTC) X-FDA: 76679584674.27.army11_1111f8655de3c X-HE-Tag: army11_1111f8655de3c X-Filterd-Recvd-Size: 3694 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Tue, 7 Apr 2020 03:11:57 +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 4EED22072F; Tue, 7 Apr 2020 03:11:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586229116; bh=hArNhSo98xhg/I+bcFw6MElchg8Z18nFWE70kScNNNs=; h=Date:From:To:Subject:In-Reply-To:From; b=SukrHK2T4r9pqkUGPXJzgghAtHBnuG5Po9kV3CssQLTUKJQdNBNFpA3n65iWH7zH3 j2yhACkADnqqfl7sCOejjXNfJKgwt2epCB2tAFQyZOt4xBa2sQnU7Rw6qFmC7opEEx JhvHDYhg7XniX/0QnIvM+lx3j7U/AfSquB7/eapg= Date: Mon, 06 Apr 2020 20:11:55 -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 148/166] gcov: gcc_3_4: replace zero-length array with flexible-array member Message-ID: <20200407031155.sjtwHB7DK%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_3_4: 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/20200302224501.GA14175@embeddedor Signed-off-by: Gustavo A. R. Silva Cc: Peter Oberparleiter Signed-off-by: Andrew Morton --- kernel/gcov/gcc_3_4.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/kernel/gcov/gcc_3_4.c~gcov-gcc_3_4-replace-zero-length-array-with-flexible-array-member +++ a/kernel/gcov/gcc_3_4.c @@ -38,7 +38,7 @@ static struct gcov_info *gcov_info_head; struct gcov_fn_info { unsigned int ident; unsigned int checksum; - unsigned int n_ctrs[0]; + unsigned int n_ctrs[]; }; /** @@ -78,7 +78,7 @@ struct gcov_info { unsigned int n_functions; const struct gcov_fn_info *functions; unsigned int ctr_mask; - struct gcov_ctr_info counts[0]; + struct gcov_ctr_info counts[]; }; /** @@ -352,7 +352,7 @@ struct gcov_iterator { unsigned int count; int num_types; - struct type_info type_info[0]; + struct type_info type_info[]; }; static struct gcov_fn_info *get_func(struct gcov_iterator *iter) _