Fix -Wstrict-aliasing warnings.

src/serialize.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 1136 matching lines @@
        i++) {
     Object* entry = isolate->serialize_partial_snapshot_cache()[i];
     if (entry == heap_object) return i;
   }
 
   // We didn't find the object in the cache.  So we add it to the cache and
   // then visit the pointer so that it becomes part of the startup snapshot
   // and we can refer to it from the partial snapshot.
   int length = isolate->serialize_partial_snapshot_cache_length();
   isolate->PushToPartialSnapshotCache(heap_object);
-  startup_serializer_->VisitPointer(reinterpret_cast<Object**>(&heap_object));
+
+  // Avoid type-punning compiler warnings.
+  union {
+    HeapObject** in;
+    Object** out;
+  } u;
+  u.in = &heap_object;
+  startup_serializer_->VisitPointer(u.out);
+
   // We don't recurse from the startup snapshot generator into the partial
   // snapshot generator.
   ASSERT(length == isolate->serialize_partial_snapshot_cache_length() - 1);
   return length;
 }
 
 
 int Serializer::RootIndex(HeapObject* heap_object, HowToCode from) {
   Heap* heap = HEAP;
   if (heap->InNewSpace(heap_object)) return kInvalidRootIndex;
@@ skipping 455 matching lines @@
 
 bool SnapshotByteSource::AtEOF() {
   if (0u + length_ - position_ > 2 * sizeof(uint32_t)) return false;
   for (int x = position_; x < length_; x++) {
     if (data_[x] != SerializerDeserializer::nop()) return false;
   }
   return true;
 }
 
 } }  // namespace v8::internal