The documentation says:
[quote]bool Thread::waitForThreadToExit ( int timeOutMilliseconds ) const
Waits for the thread to stop.
This will waits until isThreadRunning() is false or until a timeout expires.
timeOutMilliseconds the time to wait, in milliseconds. If this value is less than zero, it will wait forever.
true if the thread exits, or false if the timeout expires first.[/quote]
Since zero is not less than zero, waitForThreadToExit(0) should wait for 0ms—that is, just check and immediately return. But instead, it waits forever. If you look at the implementation, the problem is obvious:
if (timeOutMilliseconds > 0 && --count < 0).
I’m not sure whether there’s ever a good reason to directly call waitForThreadToExit(0). There could be a memory barrier or even synchronization that makes this more useful than just calling isThreadRunning(), but as of the current top of tree (and the oldest version I have around, too), there isn’t.
But it definitely comes up when you have other functions that take a timeout parameter and pass it along to waitForThreadToExit, expecting the usual “0 = try and return immediately” meaning.