Protect against uninitialized lexical variables at top-level.

src/ic/ic.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/base/bits.h"
@@ skipping 707 matching lines @@
 
   if (FLAG_harmony_scoping && object->IsGlobalObject() && name->IsString()) {
     // Look up in script context table.
     Handle<String> str_name = Handle<String>::cast(name);
     Handle<GlobalObject> global = Handle<GlobalObject>::cast(object);
     Handle<ScriptContextTable> script_contexts(
         global->native_context()->script_context_table());
 
     ScriptContextTable::LookupResult lookup_result;
     if (ScriptContextTable::Lookup(script_contexts, str_name, &lookup_result)) {
+      Handle<Object> result =
+          FixedArray::get(ScriptContextTable::GetContext(
+                              script_contexts, lookup_result.context_index),
+                          lookup_result.slot_index);
+      if (*result == *isolate()->factory()->the_hole_value()) {
+        // Do not install stubs and stay pre-monomorphic for
+        // uninitialized accesses.
+        return ReferenceError("not_defined", name);
+      }
+
       if (use_ic && LoadScriptContextFieldStub::Accepted(&lookup_result)) {
         LoadScriptContextFieldStub stub(isolate(), &lookup_result);
         PatchCache(name, stub.GetCode());
       }
-      return FixedArray::get(ScriptContextTable::GetContext(
-                                 script_contexts, lookup_result.context_index),
-                             lookup_result.slot_index);
+      return result;
     }
   }
 
   // Named lookup in the object.
   LookupIterator it(object, name);
   LookupForRead(&it);
 
   if (it.IsFound() || !IsUndeclaredGlobal(object)) {
     // Update inline cache and stub cache.
     if (use_ic) UpdateCaches(&it);
@@ skipping 2244 matching lines @@
 static const Address IC_utilities[] = {
 #define ADDR(name) FUNCTION_ADDR(name),
     IC_UTIL_LIST(ADDR) NULL
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) { return IC_utilities[id]; }
 }
 }  // namespace v8::internal