Microsoft KB Archive/153808

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FIX: Transforms Used in ExtCreateRegion Cause Leak

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Q153808

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), included with:
 * Microsoft Windows NT Server version 3.51
 * Microsoft Windows NT Workstation version 3.51

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SYMPTOMS
Calling ExtCreateRegion with a transformation matrix in the XForm parameter causes a small leak in system resources.

This can be viewed by watching the Private Bytes reported by the Performance Monitor (perfmon.exe) for the CSRSS process. Each call to ExtCreateRegion results in a slight increase to the allocated private bytes for CSRSS that are not returned to the system, even when the application exits. Several thousand calls to ExtCreateRegion are necessary before the leak is evident in the Performance Monitor.

RESOLUTION
To work around the problem, do not call ExtCreateRegion with a transformation. Always call this function with a NULL parameter for XForm. Similar functionality can be achieved by creating the region without a transformation and then setting a World Transformation with the SetWorldTransform function prior to using the Region.

If the goal is a transformed region without altering World Transformations, the application performs the necessary matrix calculations to transform region data prior to its creation.

STATUS
Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article.

Additional query words: 3.51

Keywords : kbOSWinNT351bug kbOSWinNT400fix kbSDKWin32 kbDSupport

Issue type : kbbug

Technology : kbAudDeveloper kbWin32sSearch kbWin32API