Subj : Re: Main thread going away but worker threads executing?
To   : comp.programming.threads
From : doug
Date : Tue Jul 19 2005 12:42 am


"Kev" <krr@user.doma.in> wrote in message 
news:Pine.SOL.4.63.0507181045340.12475@conquest.OCF.Berkeley.EDU...
>
> I've noticed that in a managed environment (such as C#), even if the main 
> thread that spawns worker threads dies, the worker threads themselves 
> continue to execute until they reach completion.
>
> Example:
>    Main Thread
>          Start Thread 0
>          Start Thread 1
>          Start Thread 2
>          End Main Thread immediately without waiting on Threads 0,1,2
>
>
> Does the same thing happen in unmanaged environments such as C and C++? If 
> yes, is there any difference in the basic treatment of threads between 
> unmanaged and managed environments at all?
>
> I have been under the impression that this behavior is expected in C# but 
> that the opposite is true in C. (If the main thread dies, everything 
> dies.)
>
> Thanks in advance!
> Kevin
>

Crikey, I've had a nightmare of a time with my computers lately.  Bad disk 
sectors, fried network interfaces and cables, and an exploding router.  In 
Scotland it just rains.  Down here in London it positively *thunderstikes*.

I sent a post a wee while ago, but there's a chance my new router ate it 
(it's been a difficult evening).  So, since everyting appears to be stable, 
let me crack open a beer.  So here goes again.

In these managed environments (such as C#), threads usually run within an 
'engine' process - be it a JVM, a CLR runtime instance, etc.  These 
environments have defined threading semantics - and all threads are created 
equal*.  Your main thread is not special.

With *nix using pthreads, the opposite is true.  pthreads is a library, and 
is not part of the C or C++ spec (which has no real notion of threads). 
Look at the manpages for pthread_exit() - they state that if the main thread 
exits without calling pthread_exit, the process exits.  Calling 
pthread_exit() in your main thread will make it exit like any other thread 
(and it can even be joined on some platforms).

Doug

* Pedant notice: if you create them with default attributes**.
** I don't like pedants.











































*** There is no ***.  Go away.

.