From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id Z6YDCv3zt1/iawAAWB0awg (envelope-from ) for ; Fri, 20 Nov 2020 11:51:09 -0500 Received: by simark.ca (Postfix, from userid 112) id 1C1811F08B; Fri, 20 Nov 2020 11:51:09 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: * X-Spam-Status: No, score=1.6 required=5.0 tests=DKIM_SIGNED,MAILING_LIST_MULTI, RCVD_IN_BL_SPAMCOP_NET,RDNS_NONE,T_DKIM_INVALID,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.2 Received: from sourceware.org (unknown [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id C46091E58F for ; Fri, 20 Nov 2020 11:51:08 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 42656384A018; Fri, 20 Nov 2020 16:51:08 +0000 (GMT) Received: from gateway32.websitewelcome.com (gateway32.websitewelcome.com [192.185.145.170]) by sourceware.org (Postfix) with ESMTPS id CDFE6384A018 for ; Fri, 20 Nov 2020 16:51:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org CDFE6384A018 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=tromey.com Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=tom@tromey.com Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway32.websitewelcome.com (Postfix) with ESMTP id 80ACBC5911A for ; Fri, 20 Nov 2020 10:51:01 -0600 (CST) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with SMTP id g9cjkI4zNfgo0g9cjkAzLR; Fri, 20 Nov 2020 10:51:01 -0600 X-Authority-Reason: nr=8 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=CunIxfKfUtcngiaVKmuAYdOpXWB82TRhmiYOmL28Pmg=; b=ab5XyeEaXS90QErzMtQT7As5QX JceQhPF7ouhP6Ua3tvYBQiellqaXOFtE97r9VuaS4rJfWsuy8g3dM5xeIsM/Bj/Tzb1Kcq+UAKKr1 hwkdWf4sIwbxutCBN5g4Q1Hb7; Received: from 97-122-89-243.hlrn.qwest.net ([97.122.89.243]:40094 helo=murgatroyd) by box5379.bluehost.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1kg9cj-0040UE-7T; Fri, 20 Nov 2020 09:51:01 -0700 From: Tom Tromey To: Tom de Vries Subject: Re: [PATCH] KFAIL variable-length array tests which fail with Clang References: <1605547055-25778-1-git-send-email-gbenson@redhat.com> <87mtzek5fv.fsf@tromey.com> <0a3f590c-2a76-e470-136f-e8f88aef1d17@suse.de> <87y2iwgh90.fsf@tromey.com> <55e92b95-8b3b-6c4f-a572-9d7f836a1758@suse.de> X-Attribution: Tom Date: Fri, 20 Nov 2020 09:51:00 -0700 In-Reply-To: <55e92b95-8b3b-6c4f-a572-9d7f836a1758@suse.de> (Tom de Vries's message of "Fri, 20 Nov 2020 17:30:02 +0100") Message-ID: <874klkgeff.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1.50 (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: 97.122.89.243 X-Source-L: No X-Exim-ID: 1kg9cj-0040UE-7T X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 97-122-89-243.hlrn.qwest.net (murgatroyd) [97.122.89.243]:40094 X-Source-Auth: tom+tromey.com X-Email-Count: 2 X-Source-Cap: ZWx5bnJvYmk7ZWx5bnJvYmk7Ym94NTM3OS5ibHVlaG9zdC5jb20= X-Local-Domain: yes 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: , Cc: Tom Tromey , Gary Benson via Gdb-patches Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" >> I don't really understand the is_reference stuff Tom> In case a dwarf expression is used for an DW_AT_location attribute, by Tom> default it represents an address, and needs to be dereferenced to get Tom> the value. Yeah, I guess I'd need to see some examples to understand why this decision is made here and not at the point of use. >> Anyway, gdb can't do this sort of check. It will fail if the expression >> has a different shape, which is completely allowed by the spec. Tom> AFAIU, the spec specifically says how to interpret a DW_OP_stack_value Tom> at the end of the dwarf expression which is used a location description, Tom> and the code in the patch follows that reasoning. ... Tom> So, for my understanding, can you give an example of the problem you're Tom> envisioning? Nothing prevents an expression from ending with some other DW_OP_* with 0x9f as an operand to the opcode. This would confuse this simple checker. Or to put it another way, nothing guarantees that the last byte of an expression is an opcode. I think it could even be both, depending on a runtime condition, because AFAIK nothing prevents a DWARF expression from branching to the middle of some other operation. Tom