Q176641: FIX: Do Until Loop Evaluates "True" as -1 Exclusively

Article: Q176641
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
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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.

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

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500 kbVB500
Issue type        : kbbug
Solution Type     : kbfix

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