WaitForMultipleObjectsEx always return WAIT_FAILED in C++/CX

Question

Hi 

I created two event in C++/CX as following:

	endEvent[0] = CreateEventEx( NULL, L"e0", 0, 0);	
        endEvent[1] = CreateEventEx( NULL, L"e1", 0, 0);

then in main thread I want to wait for signaling for specific time.

	auto result = WaitForMultipleObjectsEx(
		2,
 		endEvent,
 		true,
 		2000,
		false);

but the result is always is WAIT_FAILED. Could anyone tell me what am I missing?

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Best Regards. Pooya Eimandar.

Answer 1

Check GetLastError; Do you executing your above code from UI thread?

If yes, you have to go into a different worker thread. Since, in windows store apps, UI always should be responsive and UI thread does not allow any blocking, any waiting/time consuming operation should belongs into worker thread.

Answer 2

Hi

Thanks for your reply.

I tested in both UI thread and worker thread, and nothing changed.

The GetLastError return error number 5, which means ERROR_ACCESS_DENIED. What is missing?

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Best Regards. Pooya Eimandar.

Answer 3

In case of Windows Store apps, always try to use Unicode version of APIs.

It seems to me that lack of permission in access on event object.

Try by setting EVENT_ALL_ACCESS as desired access mask for the event object.

CreateEventExW( NULL, NULL, NULL, EVENT_ALL_ACCESS );

For more details Synchronization Object Security and Access Rights

Answer 4

Thanks a lot. It works. ;)

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Best Regards. Pooya Eimandar.