Update hash_value for pointers to handle the case when uintptr_t is larger than size_t

include/boost/container_hash/hash.hpp

@@ -26,9 +26,7 @@
 #include <boost/type_traits/is_floating_point.hpp>
 #include <boost/type_traits/is_signed.hpp>
 #include <boost/type_traits/is_unsigned.hpp>
-#include <boost/type_traits/make_signed.hpp>
 #include <boost/type_traits/make_unsigned.hpp>
-#include <boost/type_traits/conditional.hpp>
 #include <boost/type_traits/enable_if.hpp>
 #include <boost/type_traits/conjunction.hpp>
 #include <boost/cstdint.hpp>
@@ -40,10 +38,6 @@
 #include <climits>
 #include <cstring>
 
-#if !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
-# include <type_traits>
-#endif
-
 #if !defined(BOOST_NO_CXX11_SMART_PTR)
 # include <memory>
 #endif
@@ -169,17 +163,21 @@ namespace boost
     typename boost::enable_if_<boost::is_enum<T>::value, std::size_t>::type
         hash_value( T v )
     {
-#if !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
+        // This should in principle return the equivalent of
+        //
+        // boost::hash_value( to_underlying(v) );
+        //
+        // However, the C++03 implementation of underlying_type,
+        //
+        // conditional<is_signed<T>, make_signed<T>, make_unsigned<T>>::type::type
+        //
+        // generates a legitimate -Wconversion warning in is_signed,
+        // because -1 is not a valid enum value when all the enumerators
+        // are nonnegative.
+        //
+        // So the legacy implementation will have to do for now.
 
-        typedef typename std::underlying_type<T>::type U;
-
-#else
-
-        typedef typename boost::conditional< boost::is_signed<T>::value, boost::make_signed<T>, boost::make_unsigned<T> >::type::type U;
-
-#endif
-
-        return boost::hash_value( static_cast<U>( v ) );
+        return static_cast<std::size_t>( v );
     }
 
     // floating point types
@@ -346,12 +344,11 @@ namespace boost
 
     // pointer types
 
-    // Implementation by Alberto Barbati and Dave Harris.
+    // `x + (x >> 3)` adjustment by Alberto Barbati and Dave Harris.
     template <class T> std::size_t hash_value( T* const& v )
     {
-        std::size_t x = static_cast<std::size_t>(
-           reinterpret_cast<boost::uintptr_t>(v));
-        return x + (x >> 3);
+        boost::uintptr_t x = reinterpret_cast<boost::uintptr_t>( v );
+        return boost::hash_value( x + (x >> 3) );
     }
 
     // array types