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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 BE180C0650F for ; Tue, 30 Jul 2019 11:13:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DE5420693 for ; Tue, 30 Jul 2019 11:13:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564485206; bh=9tf7pyyGFyjMsbo4saqBU7or8vExlKNzfa5rBM69Tw0=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=MQnbG8cBj7PzpzjVEzZNhO7Ys2AWS8pgnEkWqjLeKOtw9g84+nBKG656OYqiSsMQ+ 6I7ndxIQMOPs2kBi0Tdm6ZmYETCuNSuRlUeWxbqVgXcIpo/hcHzrKgkjZMkvo/TSUr 0c2vD6cDjOZUS7Dr2+534qmoQVk6zNkOL56D0LBc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728172AbfG3LNZ (ORCPT ); Tue, 30 Jul 2019 07:13:25 -0400 Received: from foss.arm.com ([217.140.110.172]:59424 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726267AbfG3LNY (ORCPT ); Tue, 30 Jul 2019 07:13:24 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 30C42344; Tue, 30 Jul 2019 04:13:24 -0700 (PDT) Received: from [10.1.197.61] (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B4D813F575; Tue, 30 Jul 2019 04:13:23 -0700 (PDT) Subject: Re: [PATCH 05/12] genirq/debugfs: Replace strncmp with str_has_prefix To: Chuhong Yuan , Thomas Gleixner Cc: LKML References: <20190729151435.9498-1-hslester96@gmail.com> From: Marc Zyngier Organization: Approximate Message-ID: <708d8d79-6464-fbd3-6a62-853c29b32cc3@kernel.org> Date: Tue, 30 Jul 2019 12:13:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/07/2019 11:58, Chuhong Yuan wrote: > Thomas Gleixner 于2019年7月30日周二 下午5:17写道： >> >> On Mon, 29 Jul 2019, Chuhong Yuan wrote: >> >>> strncmp(str, const, len) is error-prone. >>> We had better use newly introduced >>> str_has_prefix() instead of it. >> >> Can you please provide a proper explanation why the below strncmp() is >> error prone? >> > > If the size is less than 7, for example, 2, then even if buf is "tr", the > result will still be true. This is an error. > strncmp(str, const, len) is error-prone mainly because the len is easy > to be wrong. > >> Just running a script and copying some boiler plate changelog saying >> 'strncmp() is error prone' does not cut it. >> >>> - if (!strncmp(buf, "trigger", size)) { >>> + if (str_has_prefix(buf, "trigger")) { >> >> Especially when the resulting code is not equivalent. >> > > I think here the semantic is the comparison should only return true > when buf is "trigger". Not quite. It will satisfy the condition for 't', 'tr', 'trig', 'trigger', and of course 'triggerthissillyinterruptwhichImdebugging'. I agree that the semantic is a bit bizarre and maybe not quite expected, but still... You seem to be changing the semantic without any justification other than "this is safer". Thanks, M. -- Jazz is not dead, it just smells funny...