From 41550fd519db25a69fb4f6baa59e5b00e4aeeefa Mon Sep 17 00:00:00 2001
From: Stefan Penner <stefan.penner@gmail.com>
Date: Tue, 31 Oct 2017 10:45:52 -0700
Subject: [PATCH] [LEAK FIX] Use Nan::ObjectWrap to handle memory management
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Nan::ObjectWrap Docs: https://github.com/nodejs/nan/blob/master/doc/object_wrappers.md#api_nan_object_wrap

Prior to this, all wrapper Objects would never be deleted, allowing memory to grow unbounded.

Example:
The following, would leak WrapperObjects, and never

```
while (true) {
  new sass.types.String(‘I LEAK’);
}
```
---
 src/custom_function_bridge.cpp      |  13 ++-
 src/sass_types/boolean.cpp          |  20 ++--
 src/sass_types/boolean.h            |   3 +-
 src/sass_types/color.cpp            |  16 +--
 src/sass_types/factory.cpp          |  11 +-
 src/sass_types/list.cpp             |  10 +-
 src/sass_types/map.cpp              |  15 +--
 src/sass_types/null.cpp             |   8 +-
 src/sass_types/number.cpp           |   8 +-
 src/sass_types/sass_value_wrapper.h | 152 +++++++++++-----------------
 src/sass_types/string.cpp           |   4 +-
 src/sass_types/value.h              |  29 +++++-
 12 files changed, 141 insertions(+), 148 deletions(-)

diff --git a/src/custom_function_bridge.cpp b/src/custom_function_bridge.cpp
index f0e49b6c8..f27c69545 100644
--- a/src/custom_function_bridge.cpp
+++ b/src/custom_function_bridge.cpp
@@ -4,10 +4,10 @@
 #include "sass_types/factory.h"
 #include "sass_types/value.h"
 
-Sass_Value* CustomFunctionBridge::post_process_return_value(v8::Local<v8::Value> val) const {
-  SassTypes::Value *v_;
-  if ((v_ = SassTypes::Factory::unwrap(val))) {
-    return v_->get_sass_value();
+Sass_Value* CustomFunctionBridge::post_process_return_value(v8::Local<v8::Value> _val) const {
+  SassTypes::Value *value = SassTypes::Factory::unwrap(_val);
+  if (value) {
+    return value->get_sass_value();
   } else {
     return sass_make_error("A SassValue object was expected.");
   }
@@ -17,7 +17,10 @@ std::vector<v8::Local<v8::Value>> CustomFunctionBridge::pre_process_args(std::ve
   std::vector<v8::Local<v8::Value>> argv = std::vector<v8::Local<v8::Value>>();
 
   for (void* value : in) {
-    argv.push_back(SassTypes::Factory::create(static_cast<Sass_Value*>(value))->get_js_object());
+    Sass_Value* x = static_cast<Sass_Value*>(value);
+    SassTypes::Value* y = SassTypes::Factory::create(x);
+
+    argv.push_back(y->get_js_object());
   }
 
   return argv;
diff --git a/src/sass_types/boolean.cpp b/src/sass_types/boolean.cpp
index 401ed14fb..2d4793238 100644
--- a/src/sass_types/boolean.cpp
+++ b/src/sass_types/boolean.cpp
@@ -6,7 +6,9 @@ namespace SassTypes
   Nan::Persistent<v8::Function> Boolean::constructor;
   bool Boolean::constructor_locked = false;
 
-  Boolean::Boolean(bool v) : value(v) {}
+  Boolean::Boolean(bool _value) {
+    value = sass_make_boolean(_value);
+  }
 
   Boolean& Boolean::get_singleton(bool v) {
     static Boolean instance_false(false), instance_true(true);
@@ -15,7 +17,7 @@ namespace SassTypes
 
   v8::Local<v8::Function> Boolean::get_constructor() {
     Nan::EscapableHandleScope scope;
-    v8::Local<v8::Function> conslocal; 
+    v8::Local<v8::Function> conslocal;
     if (constructor.IsEmpty()) {
       v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New);
 
@@ -42,16 +44,15 @@ namespace SassTypes
     return scope.Escape(conslocal);
   }
 
-  Sass_Value* Boolean::get_sass_value() {
-    return sass_make_boolean(value);
-  }
-
   v8::Local<v8::Object> Boolean::get_js_object() {
     return Nan::New(this->js_object);
   }
 
-  NAN_METHOD(Boolean::New) {
+  v8::Local<v8::Boolean> Boolean::get_js_boolean() {
+    return sass_boolean_get_value(this->value) ? Nan::True() : Nan::False();
+  }
 
+  NAN_METHOD(Boolean::New) {
     if (info.IsConstructCall()) {
       if (constructor_locked) {
         return Nan::ThrowTypeError("Cannot instantiate SassBoolean");
@@ -67,9 +68,6 @@ namespace SassTypes
   }
 
   NAN_METHOD(Boolean::GetValue) {
-    Boolean *out;
-    if ((out = static_cast<Boolean*>(Factory::unwrap(info.This())))) { 
-      info.GetReturnValue().Set(Nan::New(out->value));
-    }
+    info.GetReturnValue().Set(Boolean::Unwrap<Boolean>(info.This())->get_js_boolean());
   }
 }
diff --git a/src/sass_types/boolean.h b/src/sass_types/boolean.h
index ac2a254ff..721a41c02 100644
--- a/src/sass_types/boolean.h
+++ b/src/sass_types/boolean.h
@@ -12,7 +12,6 @@ namespace SassTypes
       static Boolean& get_singleton(bool);
       static v8::Local<v8::Function> get_constructor();
 
-      Sass_Value* get_sass_value();
       v8::Local<v8::Object> get_js_object();
 
       static NAN_METHOD(New);
@@ -21,11 +20,11 @@ namespace SassTypes
     private:
       Boolean(bool);
 
-      bool value;
       Nan::Persistent<v8::Object> js_object;
 
       static Nan::Persistent<v8::Function> constructor;
       static bool constructor_locked;
+      v8::Local<v8::Boolean> get_js_boolean();
   };
 }
 
diff --git a/src/sass_types/color.cpp b/src/sass_types/color.cpp
index f484b196e..57efab3da 100644
--- a/src/sass_types/color.cpp
+++ b/src/sass_types/color.cpp
@@ -62,19 +62,19 @@ namespace SassTypes
   }
 
   NAN_METHOD(Color::GetR) {
-    info.GetReturnValue().Set(sass_color_get_r(unwrap(info.This())->value));
+    info.GetReturnValue().Set(sass_color_get_r(Color::Unwrap<Color>(info.This())->value));
   }
 
   NAN_METHOD(Color::GetG) {
-    info.GetReturnValue().Set(sass_color_get_g(unwrap(info.This())->value));
+    info.GetReturnValue().Set(sass_color_get_g(Color::Unwrap<Color>(info.This())->value));
   }
 
   NAN_METHOD(Color::GetB) {
-    info.GetReturnValue().Set(sass_color_get_b(unwrap(info.This())->value));
+    info.GetReturnValue().Set(sass_color_get_b(Color::Unwrap<Color>(info.This())->value));
   }
 
   NAN_METHOD(Color::GetA) {
-    info.GetReturnValue().Set(sass_color_get_a(unwrap(info.This())->value));
+    info.GetReturnValue().Set(sass_color_get_a(Color::Unwrap<Color>(info.This())->value));
   }
 
   NAN_METHOD(Color::SetR) {
@@ -86,7 +86,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a number");
     }
 
-    sass_color_set_r(unwrap(info.This())->value, Nan::To<double>(info[0]).FromJust());
+    sass_color_set_r(Color::Unwrap<Color>(info.This())->value, Nan::To<double>(info[0]).FromJust());
   }
 
   NAN_METHOD(Color::SetG) {
@@ -98,7 +98,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a number");
     }
 
-    sass_color_set_g(unwrap(info.This())->value, Nan::To<double>(info[0]).FromJust());
+    sass_color_set_g(Color::Unwrap<Color>(info.This())->value, Nan::To<double>(info[0]).FromJust());
   }
 
   NAN_METHOD(Color::SetB) {
@@ -110,7 +110,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a number");
     }
 
-    sass_color_set_b(unwrap(info.This())->value, Nan::To<double>(info[0]).FromJust());
+    sass_color_set_b(Color::Unwrap<Color>(info.This())->value, Nan::To<double>(info[0]).FromJust());
   }
 
   NAN_METHOD(Color::SetA) {
@@ -122,6 +122,6 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a number");
     }
 
-    sass_color_set_a(unwrap(info.This())->value, Nan::To<double>(info[0]).FromJust());
+    sass_color_set_a(Color::Unwrap<Color>(info.This())->value, Nan::To<double>(info[0]).FromJust());
   }
 }
diff --git a/src/sass_types/factory.cpp b/src/sass_types/factory.cpp
index 98bda5d58..c650710c3 100644
--- a/src/sass_types/factory.cpp
+++ b/src/sass_types/factory.cpp
@@ -61,11 +61,12 @@ namespace SassTypes
   }
 
   Value* Factory::unwrap(v8::Local<v8::Value> obj) {
-    // Todo: non-SassValue objects could easily fall under that condition, need to be more specific.
-    if (!obj->IsObject() || obj.As<v8::Object>()->InternalFieldCount() != 1) {
+      if (obj->IsObject()) {
+          v8::Local<v8::Object> v8_obj = obj.As<v8::Object>();
+          if (v8_obj->InternalFieldCount() == 1) {
+              return SassTypes::Value::Unwrap<Value>(v8_obj);
+          }
+      }
       return NULL;
-    }
-
-    return static_cast<Value*>(Nan::GetInternalFieldPointer(obj.As<v8::Object>(), 0));
   }
 }
diff --git a/src/sass_types/list.cpp b/src/sass_types/list.cpp
index cc94729a3..4c946ec90 100644
--- a/src/sass_types/list.cpp
+++ b/src/sass_types/list.cpp
@@ -47,7 +47,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied index should be an integer");
     }
 
-    Sass_Value* list = unwrap(info.This())->value;
+    Sass_Value* list = List::Unwrap<List>(info.This())->value;
     size_t index = Nan::To<uint32_t>(info[0]).FromJust();
 
 
@@ -73,14 +73,14 @@ namespace SassTypes
 
     Value* sass_value = Factory::unwrap(info[1]);
     if (sass_value) {
-      sass_list_set_value(unwrap(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
+      sass_list_set_value(List::Unwrap<List>(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
     } else {
       Nan::ThrowTypeError("A SassValue is expected as the list item");
     }
   }
 
   NAN_METHOD(List::GetSeparator) {
-    info.GetReturnValue().Set(sass_list_get_separator(unwrap(info.This())->value) == SASS_COMMA);
+    info.GetReturnValue().Set(sass_list_get_separator(List::Unwrap<List>(info.This())->value) == SASS_COMMA);
   }
 
   NAN_METHOD(List::SetSeparator) {
@@ -92,10 +92,10 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a boolean");
     }
 
-    sass_list_set_separator(unwrap(info.This())->value, Nan::To<bool>(info[0]).FromJust() ? SASS_COMMA : SASS_SPACE);
+    sass_list_set_separator(List::Unwrap<List>(info.This())->value, Nan::To<bool>(info[0]).FromJust() ? SASS_COMMA : SASS_SPACE);
   }
 
   NAN_METHOD(List::GetLength) {
-    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_list_get_length(unwrap(info.This())->value)));
+    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_list_get_length(List::Unwrap<List>(info.This())->value)));
   }
 }
diff --git a/src/sass_types/map.cpp b/src/sass_types/map.cpp
index ad147e6f9..ae4a260bf 100644
--- a/src/sass_types/map.cpp
+++ b/src/sass_types/map.cpp
@@ -37,7 +37,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied index should be an integer");
     }
 
-    Sass_Value* map = unwrap(info.This())->value;
+    Sass_Value* map = Map::Unwrap<Map>(info.This())->value;
     size_t index = Nan::To<uint32_t>(info[0]).FromJust();
 
 
@@ -63,14 +63,13 @@ namespace SassTypes
 
     Value* sass_value = Factory::unwrap(info[1]);
     if (sass_value) {
-      sass_map_set_value(unwrap(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
+      sass_map_set_value(Map::Unwrap<Map>(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
     } else {
       Nan::ThrowTypeError("A SassValue is expected as a map value");
     }
   }
 
   NAN_METHOD(Map::GetKey) {
-
     if (info.Length() != 1) {
       return Nan::ThrowTypeError("Expected just one argument");
     }
@@ -79,7 +78,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied index should be an integer");
     }
 
-    Sass_Value* map = unwrap(info.This())->value;
+    Sass_Value* map = Map::Unwrap<Map>(info.This())->value;
     size_t index = Nan::To<uint32_t>(info[0]).FromJust();
 
 
@@ -87,7 +86,9 @@ namespace SassTypes
       return Nan::ThrowRangeError(Nan::New("Out of bound index").ToLocalChecked());
     }
 
-    info.GetReturnValue().Set(Factory::create(sass_map_get_key(map, Nan::To<uint32_t>(info[0]).FromJust()))->get_js_object());
+    SassTypes::Value* obj = Factory::create(sass_map_get_key(map, Nan::To<uint32_t>(info[0]).FromJust()));
+    v8::Local<v8::Object> js_obj = obj->get_js_object();
+    info.GetReturnValue().Set(js_obj);
   }
 
   NAN_METHOD(Map::SetKey) {
@@ -105,13 +106,13 @@ namespace SassTypes
 
     Value* sass_value = Factory::unwrap(info[1]);
     if (sass_value) {
-      sass_map_set_key(unwrap(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
+      sass_map_set_key(Map::Unwrap<Map>(info.This())->value, Nan::To<uint32_t>(info[0]).FromJust(), sass_value->get_sass_value());
     } else {
       Nan::ThrowTypeError("A SassValue is expected as a map key");
     }
   }
 
   NAN_METHOD(Map::GetLength) {
-    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_map_get_length(unwrap(info.This())->value)));
+    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_map_get_length(Map::Unwrap<Map>(info.This())->value)));
   }
 }
diff --git a/src/sass_types/null.cpp b/src/sass_types/null.cpp
index 766cdf935..69f4c216d 100644
--- a/src/sass_types/null.cpp
+++ b/src/sass_types/null.cpp
@@ -6,7 +6,9 @@ namespace SassTypes
   Nan::Persistent<v8::Function> Null::constructor;
   bool Null::constructor_locked = false;
 
-  Null::Null() {}
+  Null::Null() {
+      value = sass_make_null();
+  }
 
   Null& Null::get_singleton() {
     static Null singleton_instance;
@@ -37,10 +39,6 @@ namespace SassTypes
     return scope.Escape(conslocal);
   }
 
-  Sass_Value* Null::get_sass_value() {
-    return sass_make_null();
-  }
-
   v8::Local<v8::Object> Null::get_js_object() {
     return Nan::New(this->js_object);
   }
diff --git a/src/sass_types/number.cpp b/src/sass_types/number.cpp
index d74a0d14d..d8d303ee0 100644
--- a/src/sass_types/number.cpp
+++ b/src/sass_types/number.cpp
@@ -41,11 +41,11 @@ namespace SassTypes
   }
 
   NAN_METHOD(Number::GetValue) {
-    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_number_get_value(unwrap(info.This())->value)));
+    info.GetReturnValue().Set(Nan::New<v8::Number>(sass_number_get_value(Number::Unwrap<Number>(info.This())->value)));
   }
 
   NAN_METHOD(Number::GetUnit) {
-    info.GetReturnValue().Set(Nan::New<v8::String>(sass_number_get_unit(unwrap(info.This())->value)).ToLocalChecked());
+    info.GetReturnValue().Set(Nan::New<v8::String>(sass_number_get_unit(Number::Unwrap<Number>(info.This())->value)).ToLocalChecked());
   }
 
   NAN_METHOD(Number::SetValue) {
@@ -58,7 +58,7 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a number");
     }
 
-    sass_number_set_value(unwrap(info.This())->value, Nan::To<double>(info[0]).FromJust());
+    sass_number_set_value(Number::Unwrap<Number>(info.This())->value, Nan::To<double>(info[0]).FromJust());
   }
 
   NAN_METHOD(Number::SetUnit) {
@@ -70,6 +70,6 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a string");
     }
 
-    sass_number_set_unit(unwrap(info.This())->value, create_string(info[0]));
+    sass_number_set_unit(Number::Unwrap<Number>(info.This())->value, create_string(info[0]));
   }
 }
diff --git a/src/sass_types/sass_value_wrapper.h b/src/sass_types/sass_value_wrapper.h
index 54eb16a02..52a351187 100644
--- a/src/sass_types/sass_value_wrapper.h
+++ b/src/sass_types/sass_value_wrapper.h
@@ -12,122 +12,90 @@ namespace SassTypes
   // Include this in any SassTypes::Value subclasses to handle all the heavy lifting of constructing JS
   // objects and wrapping sass values inside them
   template <class T>
-  class SassValueWrapper : public SassTypes::Value {
-    public:
-      static char const* get_constructor_name() { return "SassValue"; }
+    /* class SassValueWrapper : public SassTypes::Value { */
+    class SassValueWrapper : public SassTypes::Value  {
+      public:
+        static char const* get_constructor_name() { return "SassValue"; }
 
-      SassValueWrapper(Sass_Value*);
-      virtual ~SassValueWrapper();
+        SassValueWrapper(Sass_Value* v) : Value(v) { }
+        v8::Local<v8::Object> get_js_object();
 
-      Sass_Value* get_sass_value();
-      v8::Local<v8::Object> get_js_object();
+        static v8::Local<v8::Function> get_constructor();
+        static v8::Local<v8::FunctionTemplate> get_constructor_template();
+        static NAN_METHOD(New);
+        static Sass_Value *fail(const char *, Sass_Value **);
 
-      static v8::Local<v8::Function> get_constructor();
-      static v8::Local<v8::FunctionTemplate> get_constructor_template();
-      static NAN_METHOD(New);
-      static Sass_Value *fail(const char *, Sass_Value **);
-
-    protected:
-      Sass_Value* value;
-      static T* unwrap(v8::Local<v8::Object>);
-
-    private:
-      static Nan::Persistent<v8::Function> constructor;
-      Nan::Persistent<v8::Object> js_object;
-  };
+        /* private: */
+        static Nan::Persistent<v8::Function> constructor;
+    };
 
   template <class T>
-  Nan::Persistent<v8::Function> SassValueWrapper<T>::constructor;
+    Nan::Persistent<v8::Function> SassValueWrapper<T>::constructor;
 
   template <class T>
-  SassValueWrapper<T>::SassValueWrapper(Sass_Value* v) {
-    this->value = sass_clone_value(v);
-  }
-
-  template <class T>
-  SassValueWrapper<T>::~SassValueWrapper() {
-    this->js_object.Reset();
-    sass_delete_value(this->value);
-  }
+    v8::Local<v8::Object> SassValueWrapper<T>::get_js_object() {
+      if (this->persistent().IsEmpty()) {
+        v8::Local<v8::Object> wrapper = Nan::NewInstance(T::get_constructor()).ToLocalChecked();
+        this->Wrap(wrapper);
+      }
 
-  template <class T>
-  Sass_Value* SassValueWrapper<T>::get_sass_value() {
-    return sass_clone_value(this->value);
-  }
+      return this->handle();
+    }
 
   template <class T>
-  v8::Local<v8::Object> SassValueWrapper<T>::get_js_object() {
-    if (this->js_object.IsEmpty()) {
-      v8::Local<v8::Object> wrapper = Nan::NewInstance(T::get_constructor()).ToLocalChecked();
-      delete static_cast<T*>(Nan::GetInternalFieldPointer(wrapper, 0));
-      Nan::SetInternalFieldPointer(wrapper, 0, this);
-      this->js_object.Reset(wrapper);
+    v8::Local<v8::FunctionTemplate> SassValueWrapper<T>::get_constructor_template() {
+      Nan::EscapableHandleScope scope;
+      v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New);
+      tpl->SetClassName(Nan::New<v8::String>(T::get_constructor_name()).ToLocalChecked());
+      tpl->InstanceTemplate()->SetInternalFieldCount(1);
+      T::initPrototype(tpl);
+
+      return scope.Escape(tpl);
     }
 
-    return Nan::New(this->js_object);
-  }
-
   template <class T>
-  v8::Local<v8::FunctionTemplate> SassValueWrapper<T>::get_constructor_template() {
-    Nan::EscapableHandleScope scope;
-    v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New);
-    tpl->SetClassName(Nan::New<v8::String>(T::get_constructor_name()).ToLocalChecked());
-    tpl->InstanceTemplate()->SetInternalFieldCount(1);
-    T::initPrototype(tpl);
-
-    return scope.Escape(tpl);
-  }
+    v8::Local<v8::Function> SassValueWrapper<T>::get_constructor() {
+      if (constructor.IsEmpty()) {
+        constructor.Reset(Nan::GetFunction(T::get_constructor_template()).ToLocalChecked());
+      }
 
-  template <class T>
-  v8::Local<v8::Function> SassValueWrapper<T>::get_constructor() {
-    if (constructor.IsEmpty()) {
-      constructor.Reset(Nan::GetFunction(T::get_constructor_template()).ToLocalChecked());
+      return Nan::New(constructor);
     }
 
-    return Nan::New(constructor);
-  }
-
   template <class T>
-  NAN_METHOD(SassValueWrapper<T>::New) {
-    std::vector<v8::Local<v8::Value>> localArgs(info.Length());
+    NAN_METHOD(SassValueWrapper<T>::New) {
+      std::vector<v8::Local<v8::Value>> localArgs(info.Length());
 
-    for (auto i = 0; i < info.Length(); ++i) {
-      localArgs[i] = info[i];
-    }
-    if (info.IsConstructCall()) {
-      Sass_Value* value;
-      if (T::construct(localArgs, &value) != NULL) {
-        T* obj = new T(value);
-        sass_delete_value(value);
-
-        Nan::SetInternalFieldPointer(info.This(), 0, obj);
-        obj->js_object.Reset(info.This());
-      } else {
-        return Nan::ThrowError(Nan::New<v8::String>(sass_error_get_message(value)).ToLocalChecked());
+      for (auto i = 0; i < info.Length(); ++i) {
+        localArgs[i] = info[i];
       }
-    } else {
-      v8::Local<v8::Function> cons = T::get_constructor();
-      v8::Local<v8::Object> inst;
-      if (Nan::NewInstance(cons, info.Length(), &localArgs[0]).ToLocal(&inst)) {
-        info.GetReturnValue().Set(inst);
+      if (info.IsConstructCall()) {
+        Sass_Value* value;
+        if (T::construct(localArgs, &value) != NULL) {
+          T* obj = new T(value);
+          sass_delete_value(value);
+
+          obj->Wrap(info.This());
+          info.GetReturnValue().Set(info.This());
+        } else {
+          return Nan::ThrowError(Nan::New<v8::String>(sass_error_get_message(value)).ToLocalChecked());
+        }
       } else {
-        info.GetReturnValue().Set(Nan::Undefined());
+        v8::Local<v8::Function> cons = T::get_constructor();
+        v8::Local<v8::Object> inst;
+        if (Nan::NewInstance(cons, info.Length(), &localArgs[0]).ToLocal(&inst)) {
+          info.GetReturnValue().Set(inst);
+        } else {
+          info.GetReturnValue().Set(Nan::Undefined());
+        }
       }
     }
-  }
 
   template <class T>
-  T* SassValueWrapper<T>::unwrap(v8::Local<v8::Object> obj) {
-    /* This maybe NULL */
-    return static_cast<T*>(Factory::unwrap(obj));
-  }
-
-  template <class T>
-  Sass_Value *SassValueWrapper<T>::fail(const char *reason, Sass_Value **out) {
-    *out = sass_make_error(reason);
-    return NULL;
-  }
+    Sass_Value *SassValueWrapper<T>::fail(const char *reason, Sass_Value **out) {
+      *out = sass_make_error(reason);
+      return NULL;
+    }
 }
 
-
 #endif
diff --git a/src/sass_types/string.cpp b/src/sass_types/string.cpp
index 9235f9e02..c6f2c48fc 100644
--- a/src/sass_types/string.cpp
+++ b/src/sass_types/string.cpp
@@ -31,7 +31,7 @@ namespace SassTypes
   }
 
   NAN_METHOD(String::GetValue) {
-    info.GetReturnValue().Set(Nan::New<v8::String>(sass_string_get_value(unwrap(info.This())->value)).ToLocalChecked());
+    info.GetReturnValue().Set(Nan::New<v8::String>(sass_string_get_value(String::Unwrap<String>(info.This())->value)).ToLocalChecked());
   }
 
   NAN_METHOD(String::SetValue) {
@@ -43,6 +43,6 @@ namespace SassTypes
       return Nan::ThrowTypeError("Supplied value should be a string");
     }
 
-    sass_string_set_value(unwrap(info.This())->value, create_string(info[0]));
+    sass_string_set_value(String::Unwrap<String>(info.This())->value, create_string(info[0]));
   }
 }
diff --git a/src/sass_types/value.h b/src/sass_types/value.h
index c1cfdaff1..fa4703cb3 100644
--- a/src/sass_types/value.h
+++ b/src/sass_types/value.h
@@ -7,10 +7,35 @@
 namespace SassTypes
 {
   // This is the interface that all sass values must comply with
-  class Value {
+  class Value : public Nan::ObjectWrap {
+
     public:
-      virtual Sass_Value* get_sass_value() =0;
       virtual v8::Local<v8::Object> get_js_object() =0;
+
+      Value() {
+
+      }
+
+      Sass_Value* get_sass_value() {
+        return sass_clone_value(this->value);
+      }
+
+    protected:
+
+      Sass_Value* value;
+
+      Value(Sass_Value* v) {
+        this->value = sass_clone_value(v);
+      }
+
+      ~Value() {
+        sass_delete_value(this->value);
+      }
+
+      static Sass_Value* fail(const char *reason, Sass_Value **out) {
+        *out = sass_make_error(reason);
+        return NULL;
+      }
   };
 }