---

yaml
---
r: 23779
b: refs/heads/master
c: 578b036
h: refs/heads/master
i:
  23777: 6a35a1e
  23775: c4839f7
v: v3

Author: Elliott Slaughter

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 7823ad8586f52bcd6277965277bd15ff15674219
+refs/heads/master: 578b036f9b0415852aae0af9286ff53630fa1c56
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: cd6f24f9d14ac90d167386a56e7a6ac1f0318195
 refs/heads/try: ffbe0e0e00374358b789b0037bcb3a577cd218be

trunk/src/libcore/gc.rs

@@ -167,18 +167,33 @@ fn RootSet() -> RootSet {
     LinearMap()
 }
 
+#[cfg(gc)]
+fn expect_sentinel() -> bool { true }
+
+#[cfg(nogc)]
+fn expect_sentinel() -> bool { false }
+
 // This should only be called from fail, as it will drop the roots
 // which are *live* on the stack, rather than dropping those that are
 // dead.
 fn cleanup_stack_for_failure() {
     unsafe {
-        // Leave a sentinel on the stack to mark the current
-        // frame. The stack walker will ignore any frames above the
-        // sentinel, thus avoiding collecting any memory being used by
-        // the stack walker itself.
+        // Leave a sentinel on the stack to mark the current frame. The
+        // stack walker will ignore any frames above the sentinel, thus
+        // avoiding collecting any memory being used by the stack walker
+        // itself.
+        //
+        // However, when core itself is not compiled with GC, then none of
+        // the functions in core will have GC metadata, which means we
+        // won't be able to find the sentinel root on the stack. In this
+        // case, we can safely skip the sentinel since we won't find our
+        // own stack roots on the stack anyway.
         let sentinel_box = ~0;
-        let sentinel: **Word =
-            unsafe::reinterpret_cast(&ptr::addr_of(sentinel_box));
+        let sentinel: **Word = if expect_sentinel() {
+            unsafe::reinterpret_cast(&ptr::addr_of(sentinel_box))
+        } else {
+            ptr::null()
+        };
 
         let mut roots = ~RootSet();
         for walk_gc_roots(need_cleanup, sentinel) |root, tydesc| {