> > I'll look into this idea, but some of what my processChunk() does are
> > calls into an external library that I can't control so my options are
> > limited there. As far as I can tell, this is an issue for any code that 
> > just takes
> a long time.
> Yes, if this it's a call into an external API that provides no mechanism to 
> cancel
> the call prematurely, you have no option for graceful shutdown and have to
> kill the threads forcefully.
> I guess in the code handling your application exit, you can wait a little bit 
> for
> all threads in the pool, and after an "unreasonable"
> amount of time has passed (half a second?), kill them all forcefully.
> Bit of a big hammer, but I don't know of any way to query for the threads
> currently used by a specific ::map call (maybe someone else does though).

Yeah, and that seems to be the rub with the QtConcurrent functions, I don't
get any sort of handle to the threads it is spawning off, unless maybe I can get
at them via the global thread pool? I'm just starting to look at that. Other 
trying to call cancel() on the associated QFutureWatcher, which does work
eventually as long as your function called by map() actually returns, there 
seem to be a way to stop those concurrent threads.

With the way my code exists at the moment, I've got the main application running
in the UI thread. I intentionally spawn off Thread A and move my 
object over to that thread, and when that object gets a processing request, it  
QtConcurrent::map() which spawns off Threads B, C, D, etc... and I don't seem 
to have
any control over those threads. I know when I had the infinite loop bug in my
processChunk() call, killing off Thread A (the processingManager's thread) and 
the processingManager itself didn't seem to forcefully terminate Threads B 
whatever - they just kept on running forever. I'm going to try writing up a 
small test app to
double check this. I was doing all this in the main application, which has a 
whole lot of
other stuff going on, so maybe my issue was somewhere else...

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