---

yaml
---
r: 23776
b: refs/heads/master
c: 3405c54
h: refs/heads/master
v: v3

Author: Elliott Slaughter

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 9ea4afe5daf359c7022057774f943645d0d32043
+refs/heads/master: 3405c548e8f65c9955dfc89188f3cd9db4432bba
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: cd6f24f9d14ac90d167386a56e7a6ac1f0318195
 refs/heads/try: ffbe0e0e00374358b789b0037bcb3a577cd218be

trunk/src/libcore/gc.rs

@@ -102,6 +102,12 @@ unsafe fn walk_gc_roots(mem: Memory, visitor: Visitor) {
                 match sp {
                   Some(sp_info) => {
                     for walk_safe_point(frame.fp, sp_info) |root, tydesc| {
+                        // Skip null pointers, which can occur when a
+                        // unique pointer has already been freed.
+                        if ptr::is_null(*root) {
+                            again;
+                        }
+
                         if ptr::is_null(tydesc) {
                             // Root is a generic box.
                             let refcount = **root;