From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-376735-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 32287 invoked by alias); 12 Dec 2011 21:56:01 -0000
Received: (qmail 32278 invoked by uid 22791); 12 Dec 2011 21:56:00 -0000
X-SWARE-Spam-Status: No, hits=-2.9 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 12 Dec 2011 21:55:39 +0000
From: "nikolay at totalviewtech dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug debug/51517] New: [4.4 regression ] Wrong debug information for pointers with negative strides.
Date: Mon, 12 Dec 2011 21:58:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: debug
X-Bugzilla-Keywords:
X-Bugzilla-Severity: major
X-Bugzilla-Who: nikolay at totalviewtech dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-51517-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2011-12/txt/msg01301.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51517

             Bug #: 51517
           Summary: [4.4 regression ] Wrong debug information for pointers
                    with negative strides.
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: nikolay@totalviewtech.com


Created attachment 26062
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26062
Example to demostrate

Consider attached examples, pointer ip: 
integer, dimension (:), pointer :: ip

If you associate it twice for two variables, 
.....
ip   => it  (10:1:-2)
.... 
ip    => unpleasant%small_pad

than stride calculated as zero
 <2><b2>: Abbrev Number: 7 (DW_TAG_variable)
     DW_AT_name        : ip    
     DW_AT_decl_file   : 1    
     DW_AT_decl_line   : 8    
     DW_AT_type        : <165>    
     DW_AT_location    : 3 byte block: 91 b0 7e     (DW_OP_fbreg: -208)
 <1><165>: Abbrev Number: 15 (DW_TAG_array_type)
     DW_AT_data_location: 2 byte block: 97 6     (DW_OP_push_object_address;
DW_OP_deref)
     DW_AT_associated  : 4 byte block: 97 6 30 2e    
(DW_OP_push_object_address; DW_OP_deref; DW_OP_lit0; DW_OP_ne)
     DW_AT_type        : <60>    
     DW_AT_sibling     : <189>
 <2><176>: Abbrev Number: 14 (DW_TAG_subrange_type)
     DW_AT_lower_bound : 4 byte block: 97 23 20 6    
(DW_OP_push_object_address; DW_OP_plus_uconst: 32; DW_OP_deref)
     DW_AT_upper_bound : 4 byte block: 97 23 28 6    
(DW_OP_push_object_address; DW_OP_plus_uconst: 40; DW_OP_deref)
     DW_AT_stride      : 6 byte block: 97 23 18 6 30 1e    
(DW_OP_push_object_address; DW_OP_plus_uconst: 24; DW_OP_deref; DW_OP_lit0;
DW_OP_mul)

I think error is in: DW_OP_lit0. Should be something like DW_OP_lit2

This is regression from 4.4 and is broken in 4.5 and 4.6

I have attached an example that you can compile and verify.