KB113031 - FIX: ActiveControl Property of Screen Object Loses Memory

Article ID: 113031

Article Last Modified on 10/29/2003

Microsoft Visual Basic 3.0 Professional Edition
Microsoft Visual Basic 3.0 Professional Edition

This article was previously published under Q113031

SYMPTOMS

It is possible to receive an "Out of Memory" error when using the ActiveControl property of the Visual Basic Screen object.

CAUSE

The ActiveControl property of the screen object can leak memory when used with the Is operator.

RESOLUTION

Use a temporary variable to work around the problem. For example, change the command click event in the code listed in the More Information section below to this code:

Sub Command1_Click ()
   Dim ctr As Long
   Dim ActControl As control
   Do
      ctr = ctr + 1
      Text1.Text = ctr
      ' Use a temporary object variable
      Set ActControl = Screen.ActiveControl
      If ActControl Is Command1 Then
      End If
   Loop
End Sub

This code should run indefinitely.

STATUS

Microsoft has confirmed this to be a bug in Visual Basic version 3.0 for Windows. This problem has been corrected in Visual Basic version 4.0.

MORE INFORMATION

Steps to Reproduce Problem

Start a new project in Visual Basic. Form1 is created by default.
Put a command button (Command1) and a text box (Text1) on the form.

Add the following code to the command button's click event:

   Sub Command1_Click ()
      Dim ctr As Long
      Do
         ctr = ctr + 1
         Text1.Text = ctr
         If Screen.ActiveControl Is Command1 Then
         End If
      Loop
   End Sub

Run the program, and you will receive an "Out of Memory" error eventually.

Additional query words: buglist3.00 3.00 MemLeak fixlist4.00

Keywords: kbbug kbfix KB113031