Allow users of the V8 API to distinguish between unset and undefined HiddenValues

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 13362 matching lines @@
 
 
 // Retrieve the stack trace.  This could be the raw stack trace collected
 // on stack overflow or the already formatted stack trace string.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_GetOverflowedStackTrace) {
   HandleScope scope(isolate);
   ASSERT_EQ(args.length(), 1);
   CONVERT_ARG_CHECKED(JSObject, error_object, 0);
   String* key = isolate->heap()->hidden_stack_trace_string();
   Object* result = error_object->GetHiddenProperty(key);
+  if (result->IsTheHole()) result = isolate->heap()->undefined_value();
   RUNTIME_ASSERT(result->IsJSArray() ||
                  result->IsString() ||
                  result->IsUndefined());
   return result;
 }
 
 
 // Set or clear the stack trace attached to an stack overflow error object.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_SetOverflowedStackTrace) {
   HandleScope scope(isolate);
@@ skipping 529 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal