FIX: Do Until Loop Evaluates "True" as -1 Exclusively

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

A Do Until loop that uses a literal or a variable of type Integer as a conditional will execute endlessly if the value is not -1.

RESOLUTION

Use a variable of type Variant or Long as the conditional argument for the loop.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Basic 6.0.

MORE INFORMATION

Visual Basic defines "True" to mean "non-zero." Any value that is not zero should be evaluated as True. The Do Until loop in Visual Basic 5.0, however, evaluates only -1 as True if a literal value or a variable of type integer is used for the conditional argument.

Steps to Reproduce Behavior

1. Place the following code on a CommandButton on a Visual Basic 5.0 form:

   
         Debug.Print "A"
         Do Until 3
            Debug.Print "B"
         Loop
         Debug.Print "C" 




2. Click the button. This loop will print "B" endlessly. (Press CTRL-BRK to stop execution.)

1. Place the following code on a CommandButton on a Visual Basic 5.0 form:

   
         Dim i As Integer
         i = 3
         Debug.Print "A"
         Do Until i
            Debug.Print "B"
         Loop
         Debug.Print "C" 




2. Click on the button. This loop will print "B" endlessly. (Press CTRL-BRK to stop execution.)
   
   NOTE: In both cases, the loop that prints "B" should not execute.

Additional query words: infinite loop iterate kbVBp500bug kbVBp600fix kbVBp kbdsd kbDSupport kbVBA

Keywords : kbGrpVB
Version :
Platform : WINDOWS
Issue type : kbbug