Guard against undefined fields in global context.

src/deoptimizer.cc

Index: src/deoptimizer.cc
diff --git a/src/deoptimizer.cc b/src/deoptimizer.cc
index 108e547f2b95e6197a6d282bb432f7d06dde5ca2..b6df432322dfdb7c9ed11ba97cecd775cac7e9b4 100644
--- a/src/deoptimizer.cc
+++ b/src/deoptimizer.cc
@@ -264,11 +264,14 @@ void Deoptimizer::VisitAllOptimizedFunctions(
   AssertNoAllocation no_allocation;
 
   // Run through the list of all global contexts and deoptimize.
-  Object* global = Isolate::Current()->heap()->global_contexts_list();
-  while (!global->IsUndefined()) {
-    VisitAllOptimizedFunctionsForGlobalObject(Context::cast(global)->global(),
-                                              visitor);
-    global = Context::cast(global)->get(Context::NEXT_CONTEXT_LINK);
+  Object* context = Isolate::Current()->heap()->global_contexts_list();
+  while (!context->IsUndefined()) {
+    Object* global = Context::cast(context)->get(Context::GLOBAL_INDEX);

[ulan, 2011/12/12 19:11:16]

Do we need check here? Is global object always defined?

[Vyacheslav Egorov (Chromium), 2011/12/13 12:26:20]

I think we need it. Judging from the control flow inside Genesis::Genesis we can
get GC before set_global was called. 

Please add a comment about this here (so people reading the code will know that
GC can happen when context is in the list but not yet fully initialized).

[ulan, 2011/12/13 13:02:58]

Done.

+    if (!global->IsUndefined()) {
+      VisitAllOptimizedFunctionsForGlobalObject(JSObject::cast(global),
+                                                visitor);
+    }
+    context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
   }
 }