Are spawn'ed threads waited automatically?

[Ali Çehreli]

On 06/06/2011 12:07 PM, Steven Schveighoffer wrote:
> On Mon, 06 Jun 2011 14:09:25 -0400, Ali Çehreli <acehreli at yahoo.com> wrote:
>
>> First, the answer may be as simple as "use
>> core.thread.thread_joinAll". Is that the proper way of waiting for all
>> threads?
>
> main (the C main, not D main) does this already:
>
> https://github.com/D-Programming-Language/druntime/blob/master/src/rt/dmain2.d#L512
>
>
> But note that "daemonized" threads will not be included:
>
> http://www.digitalmars.com/d/2.0/phobos/core_thread.html#isDaemon
>
> -Steve

Thank you but it doesn't explain the inconsistent behavior. It seems 
like thread_joinAll() has a different idea at different times. Now I 
also print the result of isDaemon():

import std.stdio;
import std.concurrency;
import core.thread;

void tell_daemon_state(string name)
{
     writeln(name, " isDaemon: ", Thread.getThis.isDaemon);
}

void foo()
{
     tell_daemon_state("foo");

     foreach (i; 0 .. 5) {
         Thread.sleep(dur!"msecs"(500));
         writeln(i, " foo");
     }
}

void intermediate()
{
     tell_daemon_state("intermediate");

     spawn(&foo);
     writeln("intermediate done");
}

void main()
{
     tell_daemon_state("main");

     spawn(&intermediate);
     writeln("main done");
}

I see that only the main thread is a daemon:

main isDaemon: true
main done
intermediate isDaemon: false
intermediate done
foo isDaemon: false
0 foo
1 foo
2 foo
3 foo
4 foo

That makes sense.

There is a race condition: Just because I added the printing of the 
isDaemon state, now foo() runs to completion seemingly everytime I start 
the program. When I remove the printing AND run the program under 
'time', I get inconsistent behavior.

The following are two consecutive runs:

$ time ./deneme
main done
intermediate done
0 foo                    <--- foo()'s output is present
1 foo
2 foo
3 foo
4 foo

real	0m2.504s
user	0m0.000s
sys	0m0.000s

$ time ./deneme
main done
intermediate done        <--- foo()'s output is missing

real	0m0.003s
user	0m0.000s
sys	0m0.000s

As if thread_joinAll() misses the fact that there is still the 
non-daemon foo() thread.

Note that it's not failing to flush stdout either. The program runs 
shorter in the case where foo()'s output is missing.

Thank you,
Ali