From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30254 invoked by alias); 20 Mar 2009 15:02:58 -0000 Received: (qmail 30035 invoked by uid 22791); 20 Mar 2009 15:02:56 -0000 X-SWARE-Spam-Status: No, hits=-1.7 required=5.0 tests=AWL,BAYES_00,KAM_STOCKGEN X-Spam-Check-By: sourceware.org Received: from rock.gnat.com (HELO rock.gnat.com) (205.232.38.15) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 20 Mar 2009 15:02:50 +0000 Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id D1D4A2BABFC; Fri, 20 Mar 2009 11:02:48 -0400 (EDT) Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id fwoTUNuRG5LN; Fri, 20 Mar 2009 11:02:48 -0400 (EDT) Received: from joel.gnat.com (localhost.localdomain [127.0.0.1]) by rock.gnat.com (Postfix) with ESMTP id BCF372BABF1; Fri, 20 Mar 2009 11:02:48 -0400 (EDT) Received: by joel.gnat.com (Postfix, from userid 1000) id 4D2AFF5CFA; Fri, 20 Mar 2009 11:02:48 -0400 (EDT) Date: Fri, 20 Mar 2009 15:17:00 -0000 From: Joel Brobecker To: Jan Kratochvil Cc: gdb-patches@sourceware.org Subject: Re: [patch/rfc] Recognize non-DW_AT_location symbols Message-ID: <20090320150248.GA12530@adacore.com> References: <20090316202040.GA27070@host0.dyn.jankratochvil.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090316202040.GA27070@host0.dyn.jankratochvil.net> User-Agent: Mutt/1.5.18 (2008-05-17) 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 X-SW-Source: 2009-03/txt/msg00408.txt.bz2 Hi Jan, > * zero-length DW_AT_location should be the same as missing DW_AT_location. > https://fedorahosted.org/pipermail/elfutils-devel/2009-March/000180.html I agree. I have been trying to understand what is going on in this patch, so can you bear with me? The first observation is that dwarf2read treats zero-length DW_AT_location lists as LOC_OPTIMIZED_OUT. See var_decode_location: /* A DW_AT_location attribute with no contents indicates that a variable has been optimized away. */ if (attr_form_is_block (attr) && DW_BLOCK (attr)->size == 0) { SYMBOL_CLASS (sym) = LOC_OPTIMIZED_OUT; return; } I'll see if I can reproduce using the testcase you provided (I don't have gcc-4.4 handy, so I can't use the C example you gave). -- Joel