Signals & Slots

[Lutger]

Lars Ivar Igesund wrote:

> It would be nice to have some actual
> evidence in this matter (either way, although I understand that complete
> thread safety may be impossible to prove for an efficient solution).
> 

The following hack resulted in a deadlock on my machine. I also found 
some access violations, this is perhaps a bug in sslot. A similar 
program for std.signals also gave deadlocks.
Well, this thread has reminded me I should remove the pretense that is 
multithreaded signals in sslot :)

import std.stdio;
import std.thread;
import std.gc;
import sslot = sslot.signal;

class Observer
{
     void watch(char[] msg, int i)
     {
         writefln("Observed msg '%s' and value %s", msg, i);
     }
     ~this()
     {
         writef("died...");
     }
}

sslot.SignalMT!(void, char[], int) signal;

class FooThread : Thread
{
     int run()
     {
         while(true)
         {
             Observer o = new Observer;
             signal ~= &o.watch;
             signal("message", 2);
             o = null;
             std.gc.fullCollect();
         }
         return 0;
     }
}

void main()
{
     std.gc.minimize();
     signal = new sslot.SignalMT!(void, char[], int);

     auto thread = new FooThread;
     thread.start();

     while(true)
         signal("message", 1);
}