FIX: Do Until Loop Evaluates "True" as -1 Exclusively (176641)


The information in this article applies to:

  • Microsoft Visual Basic Learning Edition for Windows 5.0
  • Microsoft Visual Basic Professional Edition for Windows 5.0
  • Microsoft Visual Basic Enterprise Edition for Windows 5.0
This article was previously published under Q176641

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

Method 1:

  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.)
Method 2:

  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.
Modification Type:MajorLast Reviewed:11/18/2003
Keywords:kbbug kbfix KB176641
©2003 Microsoft Corporation. All rights reserved.