From 4dd23f24d65e05169594bfcb45b84adfe4e52516 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Thu, 25 Aug 2011 17:13:06 -0700
Subject: [PATCH] rt: Null check in walk_obj_contents. Prevents marking from
 crashing when calling object constructors.

---
 src/rt/rust_shape.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/rt/rust_shape.h b/src/rt/rust_shape.h
index e8a30d5874a8..060dd7fed406 100644
--- a/src/rt/rust_shape.h
+++ b/src/rt/rust_shape.h
@@ -903,6 +903,8 @@ data<T,U>::walk_obj_contents(bool align, ptr &dp) {
     type_desc *subtydesc =
         *reinterpret_cast<type_desc **>(box_ptr + sizeof(void *));
     ptr obj_closure_dp(box_ptr + sizeof(void *));
+    if (!box_ptr)   // Null check.
+        return;
 
     arena arena;
     type_param *params = type_param::from_obj_shape(subtydesc->shape,