rt: Make stack unwinding work more correctly with stack growth

src/rt/rust_task.cpp

@@ -131,6 +131,9 @@ rust_task::~rust_task()
     //   (ref_count == 1 && this == sched->root_task));
 
     // Delete all the stacks. There may be more than one if the task failed
+    // FIXME: This is not correct. During unwinding we need to delete
+    // the stacks and record the stack limit, otherwise the stack
+    // stack is corrupted when destructors are running.
     while (stk != NULL) {
         del_stk(this, stk);
     }

src/rt/rust_upcall.cpp

@@ -228,8 +228,8 @@ upcall_call_shim_on_c_stack(void *args, void *fn_ptr) {
     try {
         sched->c_context.call_shim_on_c_stack(args, fn_ptr);
     } catch (...) {
-        //task = rust_scheduler::get_task();
-        //task->record_stack_limit();
+        task = rust_scheduler::get_task();
+        task->record_stack_limit();
         throw;
     }
     task = rust_scheduler::get_task();

src/test/run-fail/morestack2.rs

@@ -0,0 +1,35 @@
+// xfail-test
+// error-pattern:explicit failure
+// compile-flags:--stack-growth
+
+// This time we're testing that the stack limits are restored
+// correctly after calling into the C stack and unwinding.
+// See the hack in upcall_call_shim_on_c_stack where it messes
+// with the stack limit.
+
+native mod rustrt {
+    fn pin_task();
+}
+
+fn getbig_call_c_and_fail(i: int) {
+    if i != 0 {
+        getbig_call_c_and_fail(i - 1);
+    } else {
+        rustrt::pin_task();
+        fail;
+    }
+}
+
+resource and_then_get_big_again(_i: ()) {
+    fn getbig(i: int) {
+        if i != 0 {
+            getbig(i - 1);
+        }
+    }
+    getbig(100000);
+}
+
+fn main() {
+    let r = and_then_get_big_again(());
+    getbig_call_c_and_fail(100000);
+}