Re: Comparing thread handles

Hi!

I have a simple scenario where a service thread calls some callbacks.
One of the things I must avoid is that the callback tries to turn off
the service thread because this then leads to a
WaitForSingleObject(service_thread) which of course never works, the
thread is blocked waiting for itself to terminate. :(

Now, what I thought was that I'd check that I'm not running in the
context of the service thread:

 assert( service_thread != GetCurrentThread());

However, this won't work because GetCurrentThread() returns a "pseudo
handle" that is just a symbolic alias for the current thread's
handle. If anyone could tell me how to perhaps fix the comparison
above, I would be happy, too, but there's one more attempt I made:

 assert( GetThreadId(service_thread) != GetCurrentThreadId());

Alas, while this might have worked, GetThreadId() requires MS Windows
Vista, Longhorn or Server 2003. Okay, I thought, we'll have to take
the complicated way:

 HANDLE h = OpenThread( THREAD_ALL_ACCESS, FALSE,
 GetCurrentThreadId()); assert(h!=NULL);
 assert(h!=service_thread);
 CloseHandle(h);

Three more lines than I wanted, but this method must be bullet proof.
Well, in case you didn't guess it already, it isn't. Even though I
got two handles referring to the same thread, those handles had
different values and we're back at step 1 (i.e. how to implement the
comparison properly).

Of course, my last way out would be to store the thread ID along with
the waitable handle and compare that when shutting down, but I don't
need the ID otherwise and I don't want to waste that storage without
need.

Any better ideas anyone?