FIX: NVL() Releases Object Ref and Causes Fatal Error C0000005

ID: Q221743

The information in this article applies to:

Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0

SYMPTOMS

Calling the NVL() function multiple times in Visual FoxPro 5.0 causes the following error message:

Property <property name> is not method or event.

If you click the Ignore button in the error dialog box and run the program again, you normally see the following error:

An application error has occurred and an application log is being generated.
VFP.exe
Exception: access violation (0x0000005), Address: <memory address>

In some instances, the first error message is skipped and the second error is displayed.

The following error can also occur:

The instruction at "0x00401e44" referenced memory at "0x010bb018". The memory could not be "read".

In Visual FoxPro 6.0, the following error often appears after calling the NVAL() function the third time:

Fatal error: Exception code: C0000005

CAUSE

The NVL() function saved the handle, but it released the object reference.

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:


ox = CreateObject("Lbltest")
ox.Test()
ox.Test()
ox.Test()

Define Class Lbltest as Label
 Procedure Test
 oObj = NVL(.NULL.,This)
 ?oObj.name
 EndProc
 
Enddefine

Run the program.

Additional query words:

Keywords : kberrmsg kbservicepack kbOOP kbVFp500abug kbVFp600 kbVFp600bug kbVS600sp2 kbVS600SP1 kbVS600sp3fix kbGrpFox
Version : WINDOWS:5.0,5.0a,6.0
Platform : WINDOWS
Issue type : kbbug