Modify task::join to indicate how the task terminated

This involves sticking yet another field into the task structure

Author: brson

src/lib/task.rs

@@ -1,7 +1,7 @@
 native "rust" mod rustrt {
     fn task_sleep(uint time_in_us);
     fn task_yield();
-    fn task_join(task t);
+    fn task_join(task t) -> int;
     fn task_unsupervise();
     fn pin_task();
     fn unpin_task();
@@ -20,8 +20,16 @@ fn yield() {
     ret rustrt::task_yield();
 }
 
-fn join(task t) {
-    ret rustrt::task_join(t);
+tag task_result {
+    tr_success;
+    tr_failure;
+}
+
+fn join(task t) -> task_result {
+    alt (rustrt::task_join(t)) {
+        0 { tr_success }
+        _ { tr_failure }
+    }
 }
 
 fn unsupervise() {

src/rt/rust_builtin.cpp

@@ -410,7 +410,7 @@ task_yield(rust_task *task) {
     task->yield(1);
 }
 
-extern "C" CDECL void
+extern "C" CDECL intptr_t
 task_join(rust_task *task, rust_task *join_task) {
     // If the other task is already dying, we don't have to wait for it.
     join_task->lock.lock();
@@ -423,6 +423,11 @@ task_join(rust_task *task, rust_task *join_task) {
     else {
         join_task->lock.unlock();
     }
+    if (!join_task->failed) {
+        return 0;
+    } else {
+        return -1;
+    }
 }
 
 extern "C" CDECL void

src/rt/rust_task.cpp

@@ -82,7 +82,8 @@ rust_task::rust_task(rust_scheduler *sched, rust_task_list *state,
     running_on(-1),
     pinned_on(-1),
     local_region(&sched->srv->local_region),
-    _on_wakeup(NULL)
+    _on_wakeup(NULL),
+    failed(false)
 {
     LOGPTR(sched, "new task", (uintptr_t)this);
     DLOG(sched, task, "sizeof(task) = %d (0x%x)", sizeof *this, sizeof *this);
@@ -230,6 +231,7 @@ rust_task::fail() {
     // FIXME: implement unwinding again.
     if (this == sched->root_task)
         sched->fail();
+    failed = true;
 }
 
 void

src/rt/rust_task.h

@@ -89,6 +89,9 @@ rust_task : public maybe_proxy<rust_task>,
 
     wakeup_callback *_on_wakeup;
 
+    // Indicates that the task ended in failure
+    bool failed;
+
     lock_and_signal lock;
 
     // Only a pointer to 'name' is kept, so it must live as long as this task.

src/test/run-pass/lib-task.rs

@@ -15,8 +15,27 @@ fn test_unsupervise() {
   spawn f();
 }
 
+fn test_join() {
+  fn winner() {
+  }
+
+  auto wintask = spawn winner();
+
+  assert task::join(wintask) == task::tr_success;
+
+  fn failer() {
+    task::unsupervise();
+    fail;
+  }
+
+  auto failtask = spawn failer();
+
+  assert task::join(failtask) == task::tr_failure;
+}
+
 fn main() {
   // FIXME: Why aren't we running this?
   //test_sleep();
   test_unsupervise();
+  test_join();
 }

src/test/run-pass/spawn.rs

@@ -5,7 +5,7 @@ use std;
 
 fn main() {
     auto t = spawn child(10);
-    std::task::join(t)
+    std::task::join(t);
 }
 
 fn child(int i) {