Task links, failure trapping.

[graydon]

Presently task failure just fails parent task. Need trap / link mechanism.

[graydon]

probably something like:

io obj failure_guard(chan[tid] c) {  
    drop {
        if (sys.failing()) {
            c <| sys.gettid();
            sys.flush(c);
        }
    }
}

fn trap(chan[tid] c, (fn () -> ()) thunk) {
  auto guard = failure_guard(c);
  sys.unlink();
  thunk();
}

will do.

[graydon]

Some of this landed in b1eeb9b but there's' still more to do.

[brson]

I'm going to go ahead and close this. We have all the ingredients, but it looks a lot different:

#[test]
fn test_join_chan_fail() {
    fn failer() { task::unsupervise(); fail }

    let p = comm::port();
    let f = failer;
    task::spawn_notify(f, comm::chan(p));
    let s = comm::recv(p);
    log_err "received task status message";
    log_err s;
    alt s {
      task::exit(_, task::tr_failure.) {/* yay! */ }
      _ { fail "invalid task status received" }
    }
}