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

ID: Q221702

The information in this article applies to:

Microsoft Visual FoxPro for Windows, versions 5.0a, 6.0

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

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

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:

Create a form.

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

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

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]

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

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

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 kbGrpFox
Version : WINDOWS:5.0a,6.0
Platform : WINDOWS
Issue type : kbbug