HeapProfiler: Make strings unique in HeapProfile.

src/heap-snapshot-generator.h

 // Copyright 2013 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 610 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotGenerator);
 };
 
 class OutputStreamWriter;
 
 class HeapSnapshotJSONSerializer {
  public:
   explicit HeapSnapshotJSONSerializer(HeapSnapshot* snapshot)
       : snapshot_(snapshot),
-        strings_(ObjectsMatch),
+        strings_(StringsMatch),
         next_node_id_(1),
         next_string_id_(1),
         writer_(NULL) {
   }
   void Serialize(v8::OutputStream* stream);
 
  private:
-  INLINE(static bool ObjectsMatch(void* key1, void* key2)) {
-    return key1 == key2;
+  INLINE(static bool StringsMatch(void* key1, void* key2)) {
+    return strcmp(reinterpret_cast<char*>(key1),
+                  reinterpret_cast<char*>(key2)) == 0;
   }
 
-  INLINE(static uint32_t ObjectHash(const void* key)) {
-    return ComputeIntegerHash(
-        static_cast<uint32_t>(reinterpret_cast<uintptr_t>(key)),
-        v8::internal::kZeroHashSeed);
+  INLINE(static uint32_t StringHash(const void* string)) {
+    const char* s = reinterpret_cast<const char*>(string);
+    uint32_t len = strlen(s);

[alph, 2013/09/16 08:23:49]

Would be nice to have a type cast here. Otherwise it might cause error/warning
on x64 (Win64 in particular).

Also consider using int instead as HashSequentialString accepts int.

+    return StringHasher::HashSequentialString(
+        s, len, v8::internal::kZeroHashSeed);
   }
 
   int GetStringId(const char* s);
   int entry_index(HeapEntry* e) { return e->index() * kNodeFieldsCount; }
   void SerializeEdge(HeapGraphEdge* edge, bool first_edge);
   void SerializeEdges();
   void SerializeImpl();
   void SerializeNode(HeapEntry* entry);
   void SerializeNodes();
   void SerializeSnapshot();
@@ skipping 14 matching lines @@
   friend class HeapSnapshotJSONSerializerIterator;
 
   DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_SNAPSHOT_GENERATOR_H_