KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q162553: FIX: ALEN() Function Causes Illegal Operation in Debug Window

Article: Q162553
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b
Operating System(s): 
Keyword(s): kbvfp kbvfp300bBUG kbvfp500fixkbbuglist kbfixlist
Last Modified: 24-MAR-2000

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

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

Using the ALEN() function in the Debug window to reference an array that does
not exist in a form causes Visual FoxPro 3.0 for Windows to shut down. The
following error message appears in Windows 95 after the form closes:

  This program has performed an illegal operation and will be shut down.

Clicking Details reveals the following message:

  VFP caused an invalid page fault in module <module name> at <memory
  address>.

In Windows NT 4.0, the following error appears:

  An application error has occurred and an application error log is being
  generated.

  VFP.exe
  Exception: access violation <error number>, Address: <memory
  address>.

The operating system then closes Visual FoxPro.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual FoxPro 5.0 for
Windows.

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

Steps to Reproduce Behavior
---------------------------

1. Create a form called ztest.scx.

2. Add a command button to the form. In the Click event of the button, place the
  following code:

        ThisForm.Release

3. Save the form.

4. Invoke the Debug window, type the following line, and press the Enter key:

  " ALEN(ThisForm.atest) " (without the quotation marks)

  This references a nonexistent array.

5. Run the form and click the command button to close the form.

6. The error occurs and Visual FoxPro shuts down.

Additional query words:

======================================================================
Keywords          : kbvfp kbvfp300bBUG kbvfp500fix kbbuglist kbfixlist
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version           : WINDOWS:3.0,3.0b
Issue type        : kbbug
Solution Type     : kbfix

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

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.