PRB: Object Instances Are Not Freed from Memory

MORE INFORMATION

Steps to Reproduce Behavior

1. Start a new project in Visual Basic. Form1 is created by default.
2. Add three command buttons (Command1, Command2, and Command3) to Form1.
3. Add the following code to the general declarations of Form1:

      Sub addx(y As Class1)
         Dim x As New Class1
         Set y.v = x
      End Sub
   
      Sub CircularRef()
         Dim x As New Class1
         Set x.v = x
         Set x.v1 = x
         Set x.v2 = x
         Set x.v3 = x
         Set x.v4 = x
         Set x.v5 = x
         Set x.v6 = x
         Set x.v7 = x
         Set x.v8 = x
         Set x.v9 = x
         Set x.v10 = x
         Set x.v11 = x
         Set x.v12 = x
         Set x.v13 = x
         Set x.v14 = x
         Set x.v15 = x
         Set x.v16 = x
         Set x.v17 = x
         Set x.v18 = x
         Set x.v19 = x
         Set x.v20 = x
         Set x = Nothing
      End Sub
   						

4. Add the following code to the Command1_Click event procedure:

      Private Sub Command1_Click()
      #If Win32 Then
         Dim ut As MEMORYSTATUS
         ut.dwLength = 32
         GlobalMemoryStatus ut
         Print ut.dwAvailPhys
      #Else
         Dim fspace As Long
         fspace = GetFreeSpace(0)
         Print fspace
      #End If
      End Sub
   						

5. Add the following code to the Command2_Click event procedure:

      Private Sub Command2_Click()
         Dim y As New Class1
         Dim x As Class1
         Dim i As Integer
   
         For i = 1 To 1000
            addx y
            Set y = y.v
         Next
      End Sub
   						

6. Add the following code to the Command3_Click event procedure:

      Private Sub Command3_Click()
         Dim i As Integer
         For i = 1 To 1000
            CircularRef
         Next
      End Sub
   						

7. From the Insert menu, choose Module to add Module1 to the project.
8. Add the following code to the general declarations section of Module1:

      #If Win32 Then
         Public Type MEMORYSTATUS
            dwLength As Long
            dwMemoryLoad As Long   ' percent of memory in use
            dwTotalPhys As Long    ' bytes of physical memory
            dwAvailPhys  As Long   ' free physical memory bytes
            dwTotalPageFile As Long ' bytes of paging file
            dwAvailPageFile As Long ' free bytes of paging file
            dwTotalVirtual As Long ' user bytes of address space
            dwAvailVirtual As Long ' free user bytes
         End Type
   
         Declare Sub GlobalMemoryStatus Lib "kernel32" (lpBuffer As _
            MEMORYSTATUS)
      #Else
         Declare Function GetFreeSpace Lib "Kernel" (ByVal wFlags As Integer)_
            As Long
      #End If
   						

9. From the Insert menu, choose Class Module to add Class1 to the project.
10. Add the following code to the general declarations section of Class1:

       Public v As Variant
       Public v1 As Variant
       Public v2 As Variant
       Public v3 As Variant
       Public v4 As Variant
       Public v5 As Variant
       Public v6 As Variant
       Public v7 As Variant
       Public v8 As Variant
       Public v9 As Variant
       Public v10 As Variant
       Public v11 As Variant
       Public v12 As Variant
       Public v13 As Variant
       Public v14 As Variant
       Public v15 As Variant
       Public v16 As Variant
       Public v17 As Variant
       Public v18 As Variant
       Public v19 As Variant
       Public v20 As Variant
    						

11. Run the program. Press the Command1 button to print the initial free memory. Press the Command2 button to create a linked list. Press the Command1 button again, and notice that the free memory is the same. Then press Command3 to create a circular list. Press the Command1 button again, and notice that the available free memory has dropped.