[D-runtime] druntime commit, revision 483

[Sean Kelly]

This commit also fixes a race issue between newly created threads and the GC.  I have one remaining issue to sort out, but not being able to debug on OSX is somewhat of a problem.  I'll look into it more on Linux this weekend, with luck.  The issue is that when I run the following app, sometimes I get a bus error, it hangs, I get a segfault, or there's no output.  It's something within std.concurrency, but it's hard to say what without a debugger.  Here's the code:

import std.concurrency;
import core.stdc.stdio;

void thr() {
  scope(failure) printf( "failure\n" );
  receive(
    (OwnerTerminated)
    {
        printf( "received\n" );
    }
 );
 printf( "done\n" );
}

void main() {
spawn(&thr);
}

And here's a backtrace:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x00000074
[Switching to process 4169]
0x000025af in D3std11concurrency10MessageBox48__T3getTDFC3std11concurrency15OwnerTerminatedZvZ3getMFDFC3std11concurrency15OwnerTerminatedZvZb13onLinkDeadMsgMFKS3std11concurrency7MessageZb ()
(gdb) bt
#0  0x000025af in D3std11concurrency10MessageBox48__T3getTDFC3std11concurrency15OwnerTerminatedZvZ3getMFDFC3std11concurrency15OwnerTerminatedZvZb13onLinkDeadMsgMFKS3std11concurrency7MessageZb ()
#1  0x0000278b in D3std11concurrency10MessageBox48__T3getTDFC3std11concurrency15OwnerTerminatedZvZ3getMFDFC3std11concurrency15OwnerTerminatedZvZb12onControlMsgMFKS3std11concurrency7MessageZb ()
#2  0x00002800 in D3std11concurrency10MessageBox48__T3getTDFC3std11concurrency15OwnerTerminatedZvZ3getMFDFC3std11concurrency15OwnerTerminatedZvZb4scanMFKS3std11concurrency36__T4ListTS3std11concurrency7MessageZ4ListZb ()
#3  0x0000248d in D3std11concurrency10MessageBox48__T3getTDFC3std11concurrency15OwnerTerminatedZvZ3getMFDFC3std11concurrency15OwnerTerminatedZvZb ()
#4  0x00002346 in D3std11concurrency52__T7receiveTDFC3std11concurrency15OwnerTerminatedZvZ7receiveFDFC3std11concurrency15OwnerTerminatedZvZv ()
#5  0x0000229b in D3xxx3thrFZv ()
#6  0x00004138 in D3std11concurrency11__T6_spawnZ6_spawnFbPFZvZS3std11concurrency3Tid4execMFZv ()
#7  0x0000c5a6 in D4core6thread6Thread3runMFZv ()
#8  0x0000bb20 in thread_entryPoint ()
#9  0x960277fd in _pthread_start ()
#10 0x96027682 in thread_start ()

 Seems like I'm passing a NULL into the ctor for Message, but I don't see where.  That this appears to be timing related is even weirder.  Hopefully a real debugger will turn something up.