Re-enabled join.

src/lib/task.rs

@@ -1,6 +1,7 @@
 native "rust" mod rustrt {
     fn task_sleep(uint time_in_us);
     fn task_yield();
+    fn task_join(task t);
 }
 
 /**
@@ -17,8 +18,7 @@ fn yield() {
 }
 
 fn join(task t) {
-    // TODO: figure out how to pass tasks to the runtime and call the builtin
-    // join.
+    ret rustrt::task_join(t);
 }
 
 // Local Variables:

src/rt/rust_builtin.cpp

@@ -361,7 +361,12 @@ task_yield(rust_task *task) {
 
 extern "C" CDECL void
 task_join(rust_task *task, rust_task *join_task) {
-    // TODO
+    // If the other task is already dying, we don't have to wait for it.
+    if (join_task->dead() == false) {
+        join_task->tasks_waiting_to_join.push(task);
+        task->block(join_task, "joining local task");
+        task->yield(2);
+    }
 }
 
 /* Debug builtins for std.dbg. */

src/rt/rust_upcall.cpp

@@ -509,8 +509,6 @@ upcall_new_task(rust_task *spawner, rust_vec *name) {
     return task;
 }
 
-// TODO: This is copied from rust_task.cpp. Both copies should be moved to a
-// common location.
 static uintptr_t
 align_down(uintptr_t sp)
 {

src/test/run-pass/join.rs

@@ -0,0 +1,18 @@
+// xfail-stage0
+// -*- rust -*-
+
+use std;
+
+import std::task::*;
+
+fn main() {
+  auto other = spawn child();
+  log_err "1";
+  yield();
+  join(other);
+  log_err "3";
+}
+
+fn child() {
+  log_err "2";
+}