Q97759: Starting Heap Walker Results in a GP Fault

Article: Q97759
Product(s): Microsoft Windows Software Development Kit
Version(s): 3.0,3.1
Operating System(s): 
Keyword(s): kbfile
Last Modified: 23-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

When the Microsoft Windows Heap Walker application (HEAPWALK.EXE) that is
shipped with the Microsoft Windows versions 3.0 and 3.1 SDK is started or if
another application is started after Heap Walker is running, a general
protection (GP) fault may occur with the following message:

  HEAPWALK caused a general Protection Fault in module HEAPWALK.EXE at
  xxxx.xxxx.

If Dr. Watson is running, it reports the fault as:

  'Exceed Segment Bounds (Write)' fault at HEAPWALK xxxx:xxxx

There is a bug in the Heap Walker application that results in a GP fault when
there are too many objects in the global heap. This problem happens more often
when many applications are running in the system. The problem can also happen,
however, when only a few applications are running in the system but some of them
are allocating a number of global memory blocks. Do one of the following to
resolve this problem:

- Do not run the Heap Walker application when many applications are running in
  the system. If the GP fault occurs, exit and restart Windows, and run Heap
  Walker only when a few applications are running.

-or-

- Use the updated version of the Heap Walker application available in the
  Microsoft Download Center. The updated version, called Newheap.exe, corrects
  the GP fault problem.

MORE INFORMATION
================

The following file is available for download from the Microsoft Download
Center:

  Newheap.exe

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.

When the Heap Walker application is started, it tries to list all the objects in
the global heap in its main window. It uses the Toolhelp Library to walk the
global heap, and it keeps track of all these objects in a linked list. If there
are a large number of objects in the global heap, the linked list would grow
beyond a 64K segment. Any global object that grows larger than a 64K segment
must be accessed using huge pointers, otherwise an error will occur. In the Heap
Walker application, the linked list is being accessed using far pointers instead
of huge pointers. This results in a GP fault.

The updated version of Heap Walker corrects this problem by using huge pointers
instead of far pointers to access the linked list.

Additional query words: crash gpf gp-fault heapwalker

======================================================================
Keywords          : kbfile 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : :3.0,3.1

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.