Q221702: FIX: C0000005 Fatal Error w/ ISBLANK( ) and Array Prop in Init

Article: Q221702
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0a,6.0
Operating System(s): 
Keyword(s): kbservicepack kbContainer kbCtrl kbOOP kbvfp500aBUG kbvfp600 kbvfp600bug kbXBase kbVS60
Last Modified: 20-MAY-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0a, 6.0 
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SYMPTOMS
========

Placing an ISBLANK() function in the Init of a form created programmatically
causes the following error in Visual FoxPro 6.0:

  Fatal Error C0000005

In Visual FoxPro 5.0x, the following error appears:

  An application has occurred
  and an application error log is being generated.
  VFP.exe
  Exception: access violation(0xc0000005); address: <memory location>

If the ISBLANK() function is in the Init event of a form create with the Form
Designer, no error occurs but the Show event of the form never fires. Therefore,
the form flashes and disappears.

RESOLUTION
==========

To work around this behavior, put parentheses around the array variable. In the
example below, this works:

  IIF(isblank((THISFORM.WorkerData[2]))

while this does not:

  IIF((isblank(THISFORM.WorkerData[2]))

In Steps to Reproduce Behavior below, comment and uncomment the specified lines
of code as indicated in the example and it operates as expected.

STATUS
======

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

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information
about Visual Studio service packs, please see the following articles in the
Microsoft Knowledge Base:

Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

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

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

1. Create a program that contains the following code:

  ***Code begins here
  PUBLIC oisblkerr
  oisblkerr=CREATEOBJECT("arrform")
  oisblkerr.SHOW
  READ EVENTS
  RELEASE oisblkerr
  RETURN

  DEFINE CLASS arrform AS FORM
     DIMENSION myar[3],larray[4,3]
     ADD OBJECT text1 AS TEXTBOX
     ADD OBJECT cmdexit AS COMMANDBUTTON
     cmdexit.TOP  = THISFORM.text1.TOP+THISFORM.text1.HEIGHT+10
     text1.width=150

     PROCEDURE init
  	  THISFORM.myar[1]="John"
  	  THISFORM.myar[2]="X."
  	  THISFORM.myar[3]="Smith"<BR/>
  * Comment this line below to prevent problem.
        THISFORM.text1.VALUE = ALLTRIM(THISFORM.myar[1])+" "+IIF(isblank(THISFORM.myar[2]),;
           "",THISFORM.myar[2])+ " "+RTRIM(THISFORM.myar[3])<BR/>
  * Uncomment these lines below for it to work properly
  *!*	      THISFORM.text1.VALUE = ALLTRIM(THISFORM.myar[1])+" "+IIF(isblank((THISFORM.myar[2])),;
  *!*	         "",THISFORM.myar[2])+ " "+RTRIM(THISFORM.myar[3])
     ENDPROC

     PROCEDURE cmdexit.CLICK
        THISFORM.RELEASE
        CLEAR EVENTS
        RETURN
     ENDPROC
  ENDDEFINE

2. Run the program.

  Depending on what code is commented, the form either appears or Visual FoxPro
  crashes with one of the errors mentioned in the Symptoms section.

To see the behavior in a form created with the Form Designer, follow these
steps:

1. Create a form.

2. Add the property "WorkerName" to the form. This will store the concatenated
  name.

3. Add the property "WorkerData[3]" to the form. This is an array to store the
  parts of the name.

4. In the Init event of the form, add the following code:

  THISFORM.WorkerData[1] = "JOHN"
  THISFORM.WorkerData[2] = "X"
  THISFORM.WorkerData[3] = "SMITH"

  * This code causes the error
  THISFORM.WorkerName = THISFORM.WorkerData[1] + ;
  	IIF((isblank(THISFORM.WorkerData[2])), " ", " " + THISFORM.WorkerData[2] + " ");
  	+ THISFORM.WorkerData[3]
  * This code does not cause the error
  *!*	THISFORM.WorkerName = THISFORM.WorkerData[1] + ;
  *!*		IIF(isblank((THISFORM.WorkerData[2])), " ", " " + THISFORM.WorkerData[2] + " ");
  *!*		+ THISFORM.WorkerData[3]

5. Save the form and run it. Notice that the form flashes and disappears.

6. Modify the form and edit the Init event. Comment the code that causes the
  error and uncomment the code that functions properly.

7. Run the form and notice that it appears on the screen.

Additional query words:

======================================================================
Keywords          : kbservicepack kbContainer kbCtrl kbOOP kbvfp500aBUG kbvfp600 kbvfp600bug kbXBase kbVS600sp2 kbVS600SP1 kbVS600sp3fix kbGrpDSFox 
Technology        : kbVFPsearch kbAudDeveloper kbVFP600 kbVFP500a
Version           : WINDOWS:5.0a,6.0
Issue type        : kbbug
Solution Type     : kbfix

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