DOCUMENT:Q199848  19-APR-2001  [foxpro]
TITLE   :BUG: Fatal Error When Releasing a Converted FoxPro 2.x Form
PRODUCT :Microsoft FoxPro
PROD/VER::3.0,3.0b,5.0,5.0a,6.0
OPER/SYS:
KEYWORDS:kbContainer kbCtrl kbvfp300bBUG kbvfp300BUG kbvfp500aBUG kbvfp500bug kbvfp600bug

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

 - Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

Visual FoxPro terminates when you release a converted FoxPro 2.x form. Depending
on the version of Visual FoxPro, one of the following error messages appear:

Visual FoxPro 6.0 displays the following message:

    Fatal Error: Exception Code=C0000005

Visual FoxPro 3.x and Visual FoxPro 5.x, display a message box captioned "VFP.EXE
APPLICATION ERROR" that contains a message similar to the following:

   The instruction at "0x0046ae8e" referenced memory at "0x00000020".
   The memory count not be "read".<BR/>

-or-

Visual FoxPro 3.0 and Visual FoxPro 5.0x produce this error:

   VFP caused an invalid page fault in module VFP.EXE at 0137:0045e07a.

-or-

Visual FoxPro hangs and does not close. The Visual FoxPro session or the
executable created with Visual FoxPro then terminates.

CAUSE
=====

This behavior may occur in forms that have been functionally converted from
screens created using FoxPro 2.x and an attempt is made to release the converted
formset from memory while an @ ... GET statement is active.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

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

With earlier versions of FoxPro, there are some conditions in which a developer
may have found it desirable to include @ ... GET statements in the ERROR,
MESSAGE, VALID, or WHEN clause of certain controls.

When screens created with FoxPro 2.x are functionally converted to Visual FoxPro
forms, @ ... GET statements, used to generate a FoxPro 2.x screen, are converted
to a corresponding Visual FoxPro control. Likewise, any code contained in any of
the clauses of the control is copied to a corresponding Visual FoxPro form
method. If the ERROR, MESSAGE, VALID, or WHEN clause of a FoxPro 2.x screen
contains an @ ... GET statement, then the @ ... GET statement is copied into the
Visual FoxPro as code and is not treated as a form control.

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

1. Using FoxPro 2.6 create a quick screen named ztest.

2. Add the following code to the screen SETUP:

      STORE "This is a test" to test_var

3. Add a Get field to the screen.

4. In the Valid Clause of the Get field, add the following code:

      @ 1, 15 GET test_var

5. Add a push button to the screen. Set the variable to "test", and then set it
   to Terminate Read.

6. Save the form.

7. From Visual FoxPro, modify the form and select functional conversion.

8. In the Command window type:

      DO ZTEST.SPR

9. Click the command button.

The following Visual FoxPro code illustrates the error that occurs.

NOTE: The memory error may not occur under Visual FoxPro 3.0x when running the
.spr file created in the conversion process. However, Visual FoxPro 5.0x and 6.0
do produce the problem.

WARNING: To minimize the risk of corruption associated with abnormal program
termination, it is recommended that any open databases and tables be closed
before running the following code.

1. Create a program called "Showtest.prg" using the following code:

      *!* Begin Code
      DO TEST
      RELEASE ox

      PROCEDURE TEST
      PUBLIC ox
      ox=CREATEOBJECT('testset')
      ox.SHOW

      DEFINE CLASS testset AS FORMSET
            AUTORELEASE =.t.
            WINDOWTYPE  = 2

         ADD OBJECT form1 AS test1 WITH ;
            TOP    = 0, ;
            LEFT   = 0, ;
            HEIGHT = 250, ;
            WIDTH  = 375
      ENDDEFINE

      DEFINE CLASS test1 AS FORM
         DOCREATE = .T.
         CAPTION  = "Form1"
         NAME     = "Form1"

         PROCEDURE activate
            m.cust_id="this is a test"
            @ 10,1 GET m.cust_id ;
               SIZE 1, 25
         ENDPROC

         ADD OBJECT command1 AS COMMANDBUTTON WITH ;
            TOP = 192, ;
            LEFT = 48, ;
            HEIGHT = 25, ;
            WIDTH = 241, ;
            CAPTION = "E\<xit", ;
            TERMINATEREAD=.t., ;
            NAME = "Command1"

         PROCEDURE command1.CLICK
            RELEASE THISFORM
         ENDPROC
      ENDDEFINE
      *!* End Code

2. At the command prompt type:

      DO SHOWTEST

3. Click the command button labeled "Exit"

4. Depending on the version of Visual FoxPro, one of the following occurs:
   Visual FoxPro 6.0 displays the following message:

      Fatal Error: Exception Code=C0000005

   Visual FoxPro 3.x and Visual FoxPro 5.x, display a message box captioned
   "VFP.EXE APPLICATION ERROR" that has a message similar to the following:

     The instruction at <memory address> referenced memory at <memory address>.

     The memory count not be "read".

   -or-

   Visual FoxPro 3.0 and Visual FoxPro 5.0x produce this error:

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

   -or-

   Visual FoxPro hangs and does not close.

REFERENCES
==========

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by John R.
Desch, Microsoft Corporation.


Additional query words: kbDSupport kbDSE

======================================================================
Keywords          : kbContainer kbCtrl kbvfp300bBUG kbvfp300BUG kbvfp500aBUG kbvfp500bug kbvfp600bug 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : :3.0,3.0b,5.0,5.0a,6.0
Issue type        : kbbug
Solution Type     : kbnofix

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

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 2001.