Microsoft KB Archive/171472

= FIX: Toggling PortOpen w/MSCOMM32.OCX Leaks Memory on Win95/98 =

Article ID: 171472

Article Last Modified on 5/12/2003

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APPLIES TO


 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition

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This article was previously published under Q171472



SYMPTOMS
When using the PortOpen method of the MSCOMM32.OCX control, continuous or multiple uses of this method will produce a memory drain. The exact amount of memory and resources lost varies with different port drivers installed.



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 Studio 97 Service Pack 2.

For more information on the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base:

170365 : INFO: Visual Studio 97 Service Packs - What, Where, and Why

For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base:

171554 : INFO: Visual Basic 5.0 Fixes in Visual Studio 97 Service Pack 2



Steps to Reproduce Behavior
 Create a new Standard EXE project. Add an instance of the mscomm32.ocx control to Form1.  Add the following code to Form1. Sub Form_Load Show While True MSComm1.Settings = "9600, N, 8, 1" MSComm1.PortOpen = True x = Timer Do While x + 0.25 > Timer DoEvents: DoEvents: DoEvents Loop MSComm1.PortOpen = False x = Timer Do While x + 0.25 > Timer DoEvents: DoEvents: DoEvents Loop Wend End Sub  Run the application by pressing the F5 Key.

After about 100 iterations, memory will be reduced by about 4k.

Additional query words: com port

Keywords: kbbug kbfix kbvbp500sp2fix kbvs97sp3fix kbvs97fix kbctrl KB171472

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