DOCUMENT:Q176641 12-NOV-1997 [vbwin] TITLE :BUG: Do Until Loop Evaluates "True" as -1 Exclusively PRODUCT :Microsoft Visual Basic for Windows PROD/VER:WINDOWS:5.0 OPER/SYS:WINDOWS KEYWORDS:vb5all VBKBVBA ====================================================================== --------------------------------------------------------------------- The information in this article applies to: - 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. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available. 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 that, in both cases, the loop that prints "B" should not execute. Additional query words: infinite loop iterate ====================================================================== Keywords : vb5all VBKBVBA Version : WINDOWS:5.0 Platform : WINDOWS Issue type : kbbug ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1997.