MSVC variant support

AzothAmmo · Oct 23, 2019 · df229ce · df229ce
1 parent 32f71b1
commit df229ce
Showing 1 changed file with 41 additions and 18 deletions.
diff --git a/include/cereal/types/boost_variant.hpp b/include/cereal/types/boost_variant.hpp
@@ -60,16 +60,6 @@ namespace cereal
       Archive & ar;
     };
 
-    //! @internal
-    template<class T, class Variant, class Archive>
-    typename std::enable_if<std::is_default_constructible<T>::value>::type
-    load_variant(Archive & ar, Variant & variant)
-    {
-      T value;
-      ar( CEREAL_NVP_("data", value) );
-      variant = std::move(value);
-    }
-
     //! @internal
     template <class Archive, class T>
     struct LoadAndConstructLoadWrapper
@@ -98,15 +88,48 @@ namespace cereal
     };
 
     //! @internal
-    template<class T, class Variant, class Archive>
-    typename std::enable_if<!std::is_default_constructible<T>::value>::type
-    load_variant(Archive & ar, Variant & variant)
+    template <class T> struct load_variant_wrapper;
+
+    //! Avoid serializing variant void_ type
+    /*! @internal */
+    template <>
+    struct load_variant_wrapper<boost::detail::variant::void_>
     {
-      LoadAndConstructLoadWrapper<Archive, T> loadWrapper;
+      template <class Variant, class Archive>
+      static void load_variant( Archive &, Variant & )
+      { }
+    };
 
-      ar( CEREAL_NVP_("data", loadWrapper) );
-      variant = std::move(*loadWrapper.construct.ptr());
-    }
+    //! @internal
+    template <class T>
+    struct load_variant_wrapper
+    {
+      // default constructible
+      template <class Archive, class Variant>
+      static void load_variant_impl( Archive & ar, Variant & variant, std::true_type )
+      {
+        T value;
+        ar( CEREAL_NVP_("data", value) );
+        variant = std::move(value);
+      }
+
+      // not default constructible
+      template<class Variant, class Archive>
+      static void load_variant_impl(Archive & ar, Variant & variant, std::false_type )
+      {
+        LoadAndConstructLoadWrapper<Archive, T> loadWrapper;
+
+        ar( CEREAL_NVP_("data", loadWrapper) );
+        variant = std::move(*loadWrapper.construct.ptr());
+      }
+
+      //! @internal
+      template<class Variant, class Archive>
+      static void load_variant(Archive & ar, Variant & variant)
+      {
+        load_variant_impl( ar, variant, typename std::is_default_constructible<T>::type() );
+      }
+    };
   } // namespace boost_variant_detail
 
   //! Saving for boost::variant
@@ -127,7 +150,7 @@ namespace cereal
     ar( CEREAL_NVP_("which", which) );
 
     using LoadFuncType = void(*)(Archive &, boost::variant<VariantTypes...> &);
-    CEREAL_CONSTEXPR_LAMBDA LoadFuncType loadFuncArray[] = {&boost_variant_detail::load_variant<VariantTypes>...};
+    CEREAL_CONSTEXPR_LAMBDA LoadFuncType loadFuncArray[] = {&boost_variant_detail::load_variant_wrapper<VariantTypes>::load_variant...};
 
     if(which >= int32_t(sizeof(loadFuncArray)/sizeof(loadFuncArray[0])))
       throw Exception("Invalid 'which' selector when deserializing boost::variant");