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Waits until the specified object is in the signaled state, an I/O completion routine or asynchronous procedure call (APC) is queued to the thread, or the time-out interval elapses.

To wait for multiple objects, use the WaitForMultipleObjectsEx.


DWORD WINAPI WaitForSingleObjectEx(
  _In_  HANDLE hHandle,
  _In_  DWORD dwMilliseconds,
  _In_  BOOL bAlertable


hHandle [in]
A handle to the object.
If this handle is closed while the wait is still pending, the function's behavior is undefined.
The handle must have the SYNCHRONIZE access right.
dwMilliseconds [in]
The time-out interval, in milliseconds. If a nonzero value is specified, the function waits until the object is signaled, an I/O completion routine or APC is queued, or the interval elapses. If dwMilliseconds is zero, the function does not enter a wait state if the criteria is not met; it always returns immediately. If dwMilliseconds is INFINITE, the function will return only when the object is signaled or an I/O completion routine or APC is queued.
bAlertable [in]
If this parameter is TRUE and the thread is in the waiting state, the function returns when the system queues an I/O completion routine or APC, and the thread runs the routine or function. Otherwise, the function does not return, and the completion routine or APC function is not executed.
A completion routine is queued when the ReadFileEx or WriteFileEx function in which it was specified has completed. The wait function returns and the completion routine is called only if bAlertable is TRUE, and the calling thread is the thread that initiated the read or write operation. An APC is queued when you call QueueUserAPC.

Return value

If the function succeeds, the return value indicates the event that caused the function to return. It can be one of the following values.

Return code/value Description

The specified object is a mutex object that was not released by the thread that owned the mutex object before the owning thread terminated. Ownership of the mutex object is granted to the calling thread and the mutex is set to nonsignaled.

If the mutex was protecting persistent state information, you should check it for consistency.

The wait was ended by one or more user-mode asynchronous procedure calls (APC) queued to the thread.
The state of the specified object is signaled.
The time-out interval elapsed, and the object's state is nonsignaled.
The function has failed. To get extended error information, call GetLastError.