From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gproxy1-pub.mail.unifiedlayer.com (gproxy1-pub.mail.unifiedlayer.com [69.89.25.95]) by sourceware.org (Postfix) with ESMTPS id 251A13858406 for ; Tue, 20 Sep 2022 19:08:05 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 251A13858406 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=tromey.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tromey.com Received: from cmgw12.mail.unifiedlayer.com (unknown [10.0.90.127]) by progateway3.mail.pro1.eigbox.com (Postfix) with ESMTP id 3802C10046968 for ; Tue, 20 Sep 2022 19:07:49 +0000 (UTC) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with ESMTP id aiayo6pYf9QuVaiayoEYHC; Tue, 20 Sep 2022 19:07:49 +0000 X-Authority-Reason: nr=8 X-Authority-Analysis: v=2.4 cv=eIrWMFl1 c=1 sm=1 tr=0 ts=632a0f85 a=ApxJNpeYhEAb1aAlGBBbmA==:117 a=ApxJNpeYhEAb1aAlGBBbmA==:17 a=dLZJa+xiwSxG16/P+YVxDGlgEgI=:19 a=xOM3xZuef0cA:10:nop_rcvd_month_year a=Qbun_eYptAEA:10:endurance_base64_authed_username_1 a=CCpqsmhAAAAA:8 a=5I0PTW1_t2ExDCA6U7EA:9 a=ul9cdbp4aOFLsgKbc677:22 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date:References :Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=c2sctEll3iSytBoDkfmkPhk8Cqy/CY7Dnhn2uGRtpiM=; b=yj7om5swz5A8lrTjPj+bOflsZ0 8Ns/UWxww8UISzfCkGia5pkLox6wc1RP+mOSezCDUySB8uJfNSGKNvhPOtG2bWE/+AnotAjQ813P4 f1CYb+XYgs8T9noNzJxs1hPPl; Received: from 71-211-160-49.hlrn.qwest.net ([71.211.160.49]:56502 helo=murgatroyd) by box5379.bluehost.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1oaiay-0034pi-0T; Tue, 20 Sep 2022 13:07:48 -0600 From: Tom Tromey To: Magne Hov via Gdb-patches Subject: Re: [PATCH] gdb/source.c: Fix undefined behaviour dereferencing empty string References: <20220915183141.3484234-1-mhov@undo.io> X-Attribution: Tom Date: Tue, 20 Sep 2022 13:07:42 -0600 In-Reply-To: <20220915183141.3484234-1-mhov@undo.io> (Magne Hov via Gdb-patches's message of "Thu, 15 Sep 2022 19:31:41 +0100") Message-ID: <87mtat6f0h.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - box5379.bluehost.com X-AntiAbuse: Original Domain - sourceware.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tromey.com X-BWhitelist: no X-Source-IP: 71.211.160.49 X-Source-L: No X-Exim-ID: 1oaiay-0034pi-0T X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 71-211-160-49.hlrn.qwest.net (murgatroyd) [71.211.160.49]:56502 X-Source-Auth: tom+tromey.com X-Email-Count: 1 X-Source-Cap: ZWx5bnJvYmk7ZWx5bnJvYmk7Ym94NTM3OS5ibHVlaG9zdC5jb20= X-Local-Domain: yes X-Spam-Status: No, score=-3022.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, JMQ_SPF_NEUTRAL, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Sep 2022 19:08:08 -0000 >>>>> "Magne" == Magne Hov via Gdb-patches writes: Magne> When a source file's dirname is solely made up of directory separators Magne> we end up trying to dereference the last character of an empty string Magne> with std::string::back, which results in undefined behaviour. A typical Magne> use case where this can happen is when the root directory "/" is used as Magne> a compilation directory. ... Magne> Fix this by checking for the empty string. I wonder if this code should be changed to use path_join instead. That function doesn't seem to have this bug: if (!ret.empty () && !IS_DIR_SEPARATOR (ret.back ())) ret += '/'; thanks, Tom