Microsoft KB Archive/221580

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BUG: Concurrent access of ToolbarWindow32 window class causes lockup when using Active Accessibility

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Q221580

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The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK), on platform(s):
 * the operating system: Microsoft Windows NT
 * the operating system: Microsoft Windows 95
 * the operating system: Microsoft Windows 98

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SYMPTOMS
Multi-threaded Active Accessibility client applications that concurrently access the ToolbarWindow32 window class result in system lockup.

CAUSE
This behavior is a result of the fact that calling AccessibleObjectFromEvent and AccessibleObjectFromWindow results in a call to SendMessage. This causes concurrent access problems for multi-threaded clients that can call these APIs from more than one of their threads.

STATUS
This has been identified as a problem in Microsoft Active Accessibility version 1.x. It will be fixed in a future version of Microsoft Active Accessibility.