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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 B231DC433ED for ; Tue, 27 Apr 2021 16:28:44 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2A01561182 for ; Tue, 27 Apr 2021 16:28:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A01561182 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.118730.224969 (Exim 4.92) (envelope-from ) id 1lbQZf-00019w-DU; Tue, 27 Apr 2021 16:28:35 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 118730.224969; Tue, 27 Apr 2021 16:28:35 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lbQZf-00019p-AR; Tue, 27 Apr 2021 16:28:35 +0000 Received: by outflank-mailman (input) for mailman id 118730; Tue, 27 Apr 2021 16:28:34 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lbQZe-00019j-8r for xen-devel@lists.xenproject.org; Tue, 27 Apr 2021 16:28:34 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lbQZc-0003FA-GB; Tue, 27 Apr 2021 16:28:32 +0000 Received: from 54-240-197-235.amazon.com ([54.240.197.235] helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lbQZc-0007vt-8k; Tue, 27 Apr 2021 16:28:32 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=StjzRaZfN+kNWl72qIf7AbhfCy0WcOXJl0Cq4/uXr1Q=; b=Z3iWNztLdJQm3Qm40DeeyBcnQM RKLsebhYzRWHTZ9h8CFVX/kJQ6GTHVt4/849DADBibmhucEC07AVo/iOMFCIEEqwGplFxCBYEysFi 9BXGOAb2eZ7L2lnTOd3CU2n2cd7DH965vgch9aLvvGpX+WFElh1vXmihHxbCk3LNneSQ=; Subject: Re: [PATCH 07/14] tools/xl: Use const whenever we point to literal strings To: Anthony PERARD Cc: xen-devel@lists.xenproject.org, Julien Grall , Ian Jackson , Wei Liu References: <20210405155713.29754-1-julien@xen.org> <20210405155713.29754-8-julien@xen.org> From: Julien Grall Message-ID: <7bda03dd-d943-98c5-e2e8-69f6a9677da0@xen.org> Date: Tue, 27 Apr 2021 17:28:30 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Anthony, On 27/04/2021 17:04, Anthony PERARD wrote: > On Mon, Apr 05, 2021 at 04:57:06PM +0100, Julien Grall wrote: >> From: Julien Grall >> >> literal strings are not meant to be modified. So we should use const >> char * rather than char * when we want to store a pointer to them. >> >> Signed-off-by: Julien Grall >> --- >> diff --git a/tools/xl/xl.h b/tools/xl/xl.h >> index 137a29077c1e..3052e3db0072 100644 >> --- a/tools/xl/xl.h >> +++ b/tools/xl/xl.h >> @@ -21,13 +21,13 @@ >> #include >> >> struct cmd_spec { >> - char *cmd_name; >> + const char *cmd_name; >> int (*cmd_impl)(int argc, char **argv); >> int can_dryrun; >> int modifies; >> - char *cmd_desc; >> - char *cmd_usage; >> - char *cmd_option; >> + const char *cmd_desc; >> + const char *cmd_usage; >> + const char *cmd_option; >> }; > > Those const in cmd_spec feels almost the wrong things to do, but it is > also unlikely that we would want to modify the strings in a cmd_spec so > I guess that's fine. May I ask why you think it feels wrong things to do? Using char * to point to literal string is a recipe for disaster because the compiler will not warn you if you end up to write in them. Instead, you will get a runtime error. xl only deals with a single domain, so the consequences will not be too bad, but for other piece of the userspace (e.g. libxl, xenstored) this would be a nice host DoS. Both GCC and Clang provide an option (see -Wwrite-strings) to throw an error at compile time if char * points to literal string. I would like to enable it because it will harden our code. The price to pay to use const char * for some fo the field. This is not that bad compare to the other options (e.g strdup(), casting...) or the potential fallout with the existing code. > > I'm thinking that `cmd_table` should be const as well (I mean > const struct cmd_spec cmd_table[];) as there is no reason to modify the > entries once they are in the table. I'll send a patch. > > > The rest looks good. > Reviewed-by: Anthony PERARD Thanks. Cheers, -- Julien Grall