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 D89EAC38A24 for ; Thu, 7 May 2020 18:53:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0CB32495D for ; Thu, 7 May 2020 18:53:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877599; bh=qD1YTu45POQi4xsMj+gdlSVCGKp5j89OYm2p2pPtKh4=; h=Date:From:To:Cc:Subject:List-ID:From; b=DKTeS8X1s/Lq5i1KizLew9mFmrww/sLWO6lIIGIIYXjPAqgNMefy6TpjfMN2PUZn9 zmvmnp6hGzTyWlq/z7fOm/S1/mW33c9vfi8rynUioufUHECue9xGlPD50wXzQU427Y 2PAocHoLkaXy/hv0Tps8d6IyBQGKPCL3n5LvRqFs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728660AbgEGSxT (ORCPT ); Thu, 7 May 2020 14:53:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:54736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728451AbgEGSxS (ORCPT ); Thu, 7 May 2020 14:53:18 -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 8828424960; Thu, 7 May 2020 18:53:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588877598; bh=qD1YTu45POQi4xsMj+gdlSVCGKp5j89OYm2p2pPtKh4=; h=Date:From:To:Cc:Subject:From; b=FSQeULZOf97JknZWY5LLJLQT/B28yD4GV5UeqoNuLVRKkxweMPCE3bj9Ix6zBiXZG SkK2rXUmNi8iocLO2FpUJfFio+NqcvdSBhbGk6cfmwEwR3nhnNDUrEwSblam8VUPu8 tKEbXqXjoojLcnrP4v7c2q3FxuHkngwmGz6OeIH8= Date: Thu, 7 May 2020 13:57:44 -0500 From: "Gustavo A. R. Silva" To: Dan Williams , Vishal Verma , Dave Jiang , Ira Weiny Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: [PATCH] tools/testing/nvdimm: Replace zero-length array with flexible-array Message-ID: <20200507185744.GA14974@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 --- tools/testing/nvdimm/test/nfit_test.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/testing/nvdimm/test/nfit_test.h b/tools/testing/nvdimm/test/nfit_test.h index db3c07beb9d1..b5f7a996c4d0 100644 --- a/tools/testing/nvdimm/test/nfit_test.h +++ b/tools/testing/nvdimm/test/nfit_test.h @@ -51,7 +51,7 @@ struct nd_cmd_translate_spa { __u32 nfit_device_handle; __u32 _reserved; __u64 dpa; - } __packed devices[0]; + } __packed devices[]; } __packed; @@ -74,7 +74,7 @@ struct nd_cmd_ars_err_inj_stat { struct nd_error_stat_query_record { __u64 err_inj_stat_spa_range_base; __u64 err_inj_stat_spa_range_length; - } __packed record[0]; + } __packed record[]; } __packed; #define ND_INTEL_SMART 1 @@ -180,7 +180,7 @@ struct nd_intel_fw_send_data { __u32 context; __u32 offset; __u32 length; - __u8 data[0]; + __u8 data[]; /* this field is not declared due ot variable data from input */ /* __u32 status; */ } __packed;