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+#ifndef BOOST_TYPE_TRAITS_DETAIL_COMPOSITE_POINTER_TYPE_HPP_INCLUDED
+#define BOOST_TYPE_TRAITS_DETAIL_COMPOSITE_POINTER_TYPE_HPP_INCLUDED
+
+//
+//  Copyright 2015 Peter Dimov
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//  See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt
+//
+
+#include <boost/type_traits/copy_cv.hpp>
+#include <boost/type_traits/remove_cv.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/is_void.hpp>
+#include <boost/type_traits/is_base_of.hpp>
+#include <boost/config.hpp>
+#include <cstddef>
+
+namespace boost
+{
+
+namespace type_traits_detail
+{
+
+template<class T, class U> struct composite_pointer_type;
+
+// same type
+
+template<class T> struct composite_pointer_type<T*, T*>
+{
+    typedef T* type;
+};
+
+// nullptr_t
+
+#if !defined( BOOST_NO_CXX11_NULLPTR )
+
+#if !defined( BOOST_NO_CXX11_DECLTYPE ) && ( ( defined( __clang__ ) && !defined( _LIBCPP_VERSION ) ) || defined( __INTEL_COMPILER ) )
+
+template<class T> struct composite_pointer_type<T*, decltype(nullptr)>
+{
+    typedef T* type;
+};
+
+template<class T> struct composite_pointer_type<decltype(nullptr), T*>
+{
+    typedef T* type;
+};
+
+template<> struct composite_pointer_type<decltype(nullptr), decltype(nullptr)>
+{
+    typedef decltype(nullptr) type;
+};
+
+#else
+
+template<class T> struct composite_pointer_type<T*, std::nullptr_t>
+{
+    typedef T* type;
+};
+
+template<class T> struct composite_pointer_type<std::nullptr_t, T*>
+{
+    typedef T* type;
+};
+
+template<> struct composite_pointer_type<std::nullptr_t, std::nullptr_t>
+{
+    typedef std::nullptr_t type;
+};
+
+#endif
+
+#endif // !defined( BOOST_NO_CXX11_NULLPTR )
+
+namespace detail
+{
+
+template<class T, class U> struct has_common_pointee
+{
+private:
+
+    typedef typename boost::remove_cv<T>::type T2;
+    typedef typename boost::remove_cv<U>::type U2;
+
+public:
+
+    BOOST_STATIC_CONSTANT( bool, value =
+        (boost::is_same<T2, U2>::value)
+        || boost::is_void<T2>::value
+        || boost::is_void<U2>::value
+        || (boost::is_base_of<T2, U2>::value)
+        || (boost::is_base_of<U2, T2>::value) );
+};
+
+template<class T, class U> struct common_pointee
+{
+private:
+
+    typedef typename boost::remove_cv<T>::type T2;
+    typedef typename boost::remove_cv<U>::type U2;
+
+public:
+
+    typedef typename boost::conditional<
+
+        boost::is_same<T2, U2>::value || boost::is_void<T2>::value || boost::is_base_of<T2, U2>::value,
+        typename boost::copy_cv<T, U>::type,
+        typename boost::copy_cv<U, T>::type
+
+    >::type type;
+};
+
+template<class T, class U> struct composite_pointer_impl
+{
+private:
+
+    typedef typename boost::remove_cv<T>::type T2;
+    typedef typename boost::remove_cv<U>::type U2;
+
+public:
+
+    typedef typename boost::copy_cv<typename boost::copy_cv<typename composite_pointer_type<T2, U2>::type const, T>::type, U>::type type;
+};
+
+//Old compilers like MSVC-7.1 have problems using boost::conditional in
+//composite_pointer_type. Partially specializing on has_common_pointee<T, U>::value
+//seems to make their life easier
+template<class T, class U, bool = has_common_pointee<T, U>::value >
+struct composite_pointer_type_dispatch
+   : common_pointee<T, U>
+{};
+
+template<class T, class U>
+struct composite_pointer_type_dispatch<T, U, false>
+   : composite_pointer_impl<T, U>
+{};
+
+
+} // detail
+
+
+template<class T, class U> struct composite_pointer_type<T*, U*>
+{
+    typedef typename detail::composite_pointer_type_dispatch<T, U>::type* type;
+};
+
+} // namespace type_traits_detail
+
+} // namespace boost
+
+#endif // #ifndef BOOST_TYPE_TRAITS_DETAIL_COMPOSITE_POINTER_TYPE_HPP_INCLUDED