- More use of pre-allocated read-only handles.

runtime/vm/isolate.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "lib/mirrors.h"
@@ skipping 91 matching lines @@
   StartIsolateScope start_scope(isolate_);
   StackZone zone(isolate_);
   HandleScope handle_scope(isolate_);
 
   // If the message is in band we lookup the receive port to dispatch to.  If
   // the receive port is closed, we drop the message without deserializing it.
   Object& receive_port = Object::Handle();
   if (!message->IsOOB()) {
     receive_port = DartLibraryCalls::LookupReceivePort(message->dest_port());
     if (receive_port.IsError()) {
-      return ProcessUnhandledException(Instance::Handle(),
+      return ProcessUnhandledException(Object::null_instance(),
                                        Error::Cast(receive_port));
     }
     if (receive_port.IsNull()) {
       delete message;
       return true;
     }
   }
 
   // Parse the message.
   SnapshotReader reader(message->data(), message->len(),
                         Snapshot::kMessage, Isolate::Current());
   const Object& msg_obj = Object::Handle(reader.ReadObject());
   if (msg_obj.IsError()) {
     // An error occurred while reading the message.
-    return ProcessUnhandledException(Instance::Handle(), Error::Cast(msg_obj));
+    return ProcessUnhandledException(Object::null_instance(),
+                                     Error::Cast(msg_obj));
   }
   if (!msg_obj.IsNull() && !msg_obj.IsInstance()) {
     // TODO(turnidge): We need to decide what an isolate does with
     // malformed messages.  If they (eventually) come from a remote
     // machine, then it might make sense to drop the message entirely.
     // In the case that the message originated locally, which is
     // always true for now, then this should never occur.
     UNREACHABLE();
   }
 
@@ skipping 1049 matching lines @@
   return func.raw();
 }
 
 
 void IsolateSpawnState::Cleanup() {
   SwitchIsolateScope switch_scope(isolate());
   Dart::ShutdownIsolate();
 }
 
 }  // namespace dart