[DP-112] spawn may leak messages when interrupted

[Imported from JIRA. Reported by Facundo Dominguez @facundominguez) as DP-112 on 2015-06-02 19:03:28]
{{spawn}} is waiting for some messages, but if it is interrupted, the messages may arrive at the mailbox without nobody ever reading them.

{code}
spawn :: NodeId -> Closure (Process ()) -> Process ProcessId
spawn nid proc = do
us <- getSelfPid
mRef <- monitorNode nid
sRef <- spawnAsync nid (cpDelayed us proc)
receiveWait [
matchIf ((DidSpawn ref _) -> ref == sRef) $ (DidSpawn _ pid) -> do
unmonitor mRef
send pid ()
return pid
, matchIf ((NodeMonitorNotification ref _ _) -> ref == mRef) $ _ ->
return (nullProcessId nid)
]
{code}

The only fix I see so far is to wrap the {{spawn}} definition with {{callLocal}}.

Start with the spawn definition shown in the issue and read the callLocal approach it identifies as a possible fix. Trace the interruption and message-waiting behavior, then verify that an interrupted spawn cannot leave messages in the mailbox without a reader.