Extend sign bit before serializing it.

runtime/vm/snapshot.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "vm/allocation.h"
 #include "vm/assert.h"
 #include "vm/bitfield.h"
@@ skipping 337 matching lines @@
 
   // Writes raw data to the stream (basic type).
   // sizeof(T) must be in {1,2,4,8}.
   template <typename T>
   void Write(T value) {
     WriteStream::Raw<sizeof(T), T>::Write(&stream_, value);
   }
 
   // Writes an intptr_t type value out.
   void WriteIntptrValue(intptr_t value) {
-    Write<int64_t>(value);
+    Write<int64_t>(static_cast<int64_t>(value));

[siva, 2012/01/03 22:55:17]

Is this cast necessary, isn't there an implicit cast from intptr_t to int64_t?

   }
 
   // Write an object that is serialized as an Id (singleton, object store,
   // or an object that was already serialized before).
   void WriteIndexedObject(intptr_t object_id) {
     WriteSerializationMarker(kObjectId, object_id);
   }
 
   // Write out object header value.
   void WriteObjectHeader(intptr_t class_id, intptr_t tags) {
@@ skipping 140 matching lines @@
 
  private:
   SnapshotWriter* writer_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_