From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 66871 invoked by alias); 13 Mar 2017 12:24:31 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 66797 invoked by uid 89); 13 Mar 2017 12:24:26 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.6 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW autolearn=no version=3.3.2 spammy=arnez, 21226, Arnez, HTo:U*palves X-HELO: mx0a-001b2d01.pphosted.com Received: from mx0a-001b2d01.pphosted.com (HELO mx0a-001b2d01.pphosted.com) (148.163.156.1) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 13 Mar 2017 12:24:25 +0000 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v2DCNaPN119845 for ; Mon, 13 Mar 2017 08:24:20 -0400 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0a-001b2d01.pphosted.com with ESMTP id 295st6vfw2-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 13 Mar 2017 08:24:20 -0400 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 13 Mar 2017 12:24:18 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (9.149.109.195) by e06smtp15.uk.ibm.com (192.168.101.145) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Mon, 13 Mar 2017 12:24:15 -0000 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v2DCOFiq17957246; Mon, 13 Mar 2017 12:24:15 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0067E4203F; Mon, 13 Mar 2017 12:23:59 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DB8E842049; Mon, 13 Mar 2017 12:23:58 +0000 (GMT) Received: from oc1027705133.ibm.com (unknown [9.152.212.162]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 13 Mar 2017 12:23:58 +0000 (GMT) From: Andreas Arnez To: Pedro Alves Cc: gdb-patches@sourceware.org Subject: Re: [PATCH] PR gdb/21226: Take DWARF stack value pieces from LSB end References: Date: Mon, 13 Mar 2017 12:24:00 -0000 In-Reply-To: (Pedro Alves's message of "Fri, 10 Mar 2017 19:29:18 +0000") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 17031312-0020-0000-0000-0000031D4C76 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17031312-0021-0000-0000-000040C0EE51 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-03-13_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1703130100 X-IsSubscribed: yes X-SW-Source: 2017-03/txt/msg00187.txt.bz2 On Fri, Mar 10 2017, Pedro Alves wrote: > On 03/08/2017 06:26 PM, Andreas Arnez wrote: > >> * pieces reaching outside the stack value bits are considered undefined, >> and a zero value can be used instead. > > I'm not exactly sure what that means, but doesn't "undefined" suggest > "optimized out" instead? For instance, consider a 20-byte piece from a stack value that is only 8 bytes wide. AFAIK, this is invalid DWARF. If we want to handle this case more gracefully, we could mark the upper 12 bytes optimzed out and still use the lower 8 bytes. Or we could treat it as an implementation-defined extension and perform zero- (or sign-) extension to the full piece size. But so far I didn't see it in the scope of this bug fix to add such logic, particularly since it doesn't exist for any other piece type either. -- Andreas