Knowledge Base

BUG: Memory Leak Using UBound or LBound When Returning Array

Article ID: 197190

Article Last Modified on 5/13/2003

Microsoft Visual Basic 6.0 Learning Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q197190

SYMPTOMS

When you use a function that returns an array as a parameter to the UBound or LBound functions, the memory allocated for the array is not released.

CAUSE

The array is copied to temporary return storage, but the temporary storage is not released until the application ends.

RESOLUTION

To avoid this problem, assign the return value to a local variable before using UBound or LBound. For example:

   vntReturn = ArryFunc()
   iAryLen = UBound(vntReturn)

STATUS

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

MORE INFORMATION

Steps to Reproduce Behavior

Create a New Standard EXE project in Visual Basic. Form1 is created by default.
Add a CommandButton (Command1) to Form1.

Add the following code to Form1:

      Public Sub Command1_Click()
         iAryLen = UBound(ArryFunc())
      End Sub

Add a standard Module to the project and add the following code:

      Public Function ArryFunc() as Long ()
         Dim x(100000) as Long
         ArryFunc = x
      End Function

Run the project.

RESULT: When you click the button, it leaks ~400k with each click.

Keywords: kbbug kbpending KB197190