diff --git a/hphp/runtime/base/memory/memory_manager.h b/hphp/runtime/base/memory/memory_manager.h
index 3dd511812..a09af464a 100644
--- a/hphp/runtime/base/memory/memory_manager.h
+++ b/hphp/runtime/base/memory/memory_manager.h
@@ -398,6 +398,22 @@ void* smart_calloc(size_t count, size_t bytes);
 void* smart_realloc(void* ptr, size_t nbytes);
 void  smart_free(void* ptr);
 
+namespace smart {
+namespace do_not_use_directly {
+/*
+ * We are deriving from the std::collection classes to get
+ * smart::collection classes that use smart allocation.
+ * To avoid the various issues involved with deriving
+ * from value types, we want to make sure that there are
+ * no references to std::collection<...,SmartStlAlloc<>>
+ * other than the ones below. That way we know that
+ * a pointer to a smart::collection can never decay
+ * to a pointer to a std::collection.
+ *
+ * The namespace do_not_use_directly should remind us
+ * of that.
+ *
+ */
 template <class T>
 class SmartStlAlloc {
  public:
@@ -460,21 +476,50 @@ bool operator!= (const SmartStlAlloc<T1>&,
   return false;
 }
 
-namespace smart {
-template <class Key, class T, class Compare = std::less<Key>,
-          class Alloc = HPHP::SmartStlAlloc<std::pair<const Key, T> > >
-class map : public std::map<Key, T, Compare, Alloc> {};
-
-template <class T, class Alloc = HPHP::SmartStlAlloc<T> >
-class deque : public std::deque<T, Alloc> {};
-
-template <class T, class Alloc = HPHP::SmartStlAlloc<T> >
-class vector : public std::vector<T, Alloc> {};
-
-template <class T, class Container = deque<T> >
-class queue : public std::queue<T, Container> {};
 }
+/*
+ * Derivation from value types is generally bad.
+ * Here, we derive from classes that do not exist anywhere
+ * else in the code base (see comments above).
+ *
+ * We also add no functionality to the derived class. Your
+ * code will not get past code review if you try to do so.
+ */
+template <class Key, class T, class Compare = std::less<Key> >
+class map : public std::map<
+  Key, T, Compare,
+  do_not_use_directly::SmartStlAlloc<std::pair<const Key, T> > > {};
 
+template <class T>
+class deque : public std::deque<T, do_not_use_directly::SmartStlAlloc<T> > {};
+
+template <class T>
+class vector : public std::vector<T, do_not_use_directly::SmartStlAlloc<T> > {};
+
+template <class T>
+class list : public std::list<T, do_not_use_directly::SmartStlAlloc<T> > {};
+
+template <class T>
+class queue : public std::queue<T, deque<T> > {};
+
+template <class _T, class _U,
+          class _V = hphp_hash<_T>,class _W = std::equal_to<_T> >
+struct hash_map : std::tr1::unordered_map<
+  _T, _U, _V, _W, do_not_use_directly::SmartStlAlloc<std::pair<_T, _U> > > {
+  hash_map() : std::tr1::unordered_map<
+    _T, _U, _V, _W, do_not_use_directly::SmartStlAlloc<std::pair<_T, _U> >
+    >(0) {}
+};
+
+template <class _T,
+          class _V = hphp_hash<_T>,class _W = std::equal_to<_T> >
+struct hash_set : std::tr1::unordered_set<
+  _T, _V, _W, do_not_use_directly::SmartStlAlloc<_T> > {
+  hash_set() : std::tr1::unordered_set<
+    _T, _V, _W, do_not_use_directly::SmartStlAlloc<_T> >(0) {}
+};
+
+}
 ///////////////////////////////////////////////////////////////////////////////
 }
 
diff --git a/hphp/runtime/base/variable_serializer.cpp b/hphp/runtime/base/variable_serializer.cpp
index 24adf151c..8ff001f56 100644
--- a/hphp/runtime/base/variable_serializer.cpp
+++ b/hphp/runtime/base/variable_serializer.cpp
@@ -45,7 +45,7 @@ VariableSerializer::VariableSerializer(Type type, int option /* = 0 */,
     m_levelDebugger(0) {
   m_maxLevelDebugger = g_context->getDebuggerPrintLevel();
   if (type == Serialize || type == APCSerialize || type == DebuggerSerialize) {
-    m_arrayIds = new PointerCounterMap();
+    m_arrayIds = new SmartPtrCtrMap();
   } else {
     m_arrayIds = nullptr;
   }
@@ -477,7 +477,7 @@ void VariableSerializer::writeOverflow(void* ptr, bool isObject /* = false */) {
   case APCSerialize:
     {
       assert(m_arrayIds);
-      PointerCounterMap::const_iterator iter = m_arrayIds->find(ptr);
+      SmartPtrCtrMap::const_iterator iter = m_arrayIds->find(ptr);
       assert(iter != m_arrayIds->end());
       int id = iter->second;
       if (isObject) {
diff --git a/hphp/runtime/base/variable_serializer.h b/hphp/runtime/base/variable_serializer.h
index 6fbfe5357..5aee04916 100644
--- a/hphp/runtime/base/variable_serializer.h
+++ b/hphp/runtime/base/variable_serializer.h
@@ -108,12 +108,13 @@ public:
   void getResourceInfo(String &rsrcName, int &rsrcId);
   Type getType() const { return m_type; }
 private:
+  typedef smart::hash_map<void*, int, pointer_hash<void> > SmartPtrCtrMap;
   Type m_type;
   int m_option;                  // type specific extra options
   StringBuffer *m_buf;
   int m_indent;
-  PointerCounterMap m_counts;    // counting seen arrays for recursive levels
-  PointerCounterMap *m_arrayIds; // reference ids for objs/arrays
+  SmartPtrCtrMap m_counts;       // counting seen arrays for recursive levels
+  SmartPtrCtrMap *m_arrayIds;    // reference ids for objs/arrays
   int m_valueCount;              // Current ref index
   bool m_referenced;             // mark current array element as reference
   int m_refCount;                // current variable's reference count
@@ -132,7 +133,7 @@ private:
     bool first_element; // whether this is first array element
     int  indent_delta;  // the extra indent to serialize this object
   };
-  std::vector<ArrayInfo> m_arrayInfos;
+  smart::vector<ArrayInfo> m_arrayInfos;
 
   void writePropertyKey(CStrRef prop);
 };
diff --git a/hphp/runtime/base/variable_unserializer.h b/hphp/runtime/base/variable_unserializer.h
index 6d4553edf..e3f436616 100644
--- a/hphp/runtime/base/variable_unserializer.h
+++ b/hphp/runtime/base/variable_unserializer.h
@@ -120,8 +120,8 @@ public:
   Type m_type;
   const char *m_buf;
   const char *m_end;
-  std::vector<RefInfo> m_refs;
-  std::list<Variant> m_vars;
+  smart::vector<RefInfo> m_refs;
+  smart::list<Variant> m_vars;
   bool m_unknownSerializable;
 
   void check() {