BUG: Fatal Error When Releasing a Converted FoxPro 2.x Form

    Fatal Error: Exception Code=C0000005
				

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

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.