mostly documentation, some playing around with weak_ptr but it doesn't seem to be properly working

include/cereal/details/polymorphic_impl.hpp

@@ -74,10 +74,18 @@ namespace cereal
     struct binding_name {};
 
     //! A structure holding a map from type_indices to output serializer functions
+    /*! A static object of this map should be created for each registered archive
+        type, containing entries for every registered type that describe how to
+        properly cast the type to its real type in polymorphic scenarios for
+        shared_ptr, weak_ptr, and unique_ptr. */
     template <class Archive>
     struct OutputBindingMap
     {
       //! A serializer function
+      /*! Serializer functions return nothing and take an archive as
+          their first parameter (will be cast properly inside the function,
+          and a pointer to actual data (contents of smart_ptr's get() function)
+          as their second parameter */
       typedef std::function<void(void*, void const *)> Serializer;
 
       //! Struct containing the serializer functions for all pointer types
@@ -92,11 +100,21 @@ namespace cereal
     };
 
     //! A structure holding a map from type name strings to input serializer functions
+    /*! A static object of this map should be created for each registered archive
+        type, containing entries for every registered type that describe how to
+        properly cast the type to its real type in polymorphic scenarios for
+        shared_ptr, weak_ptr, and unique_ptr. */
     template <class Archive>
     struct InputBindingMap
     {
-      //! A serializer function
+      //! Shared ptr serializer function
+      /*! Serializer functions return nothing and take an archive as
+          their first parameter (will be cast properly inside the function,
+          and a shared_ptr (or unique_ptr for the unique case) of any base
+          type.  Internally it will properly be loaded and cast to the
+          correct type. */
       typedef std::function<void(void*, std::shared_ptr<void> & )> SharedSerializer;
+      //! Unique ptr serializer function
       typedef std::function<void(void*, std::unique_ptr<void> & )> UniqueSerializer;
 
       //! Struct containing the serializer functions for all pointer types
@@ -113,11 +131,18 @@ namespace cereal
     //! An empty noop deleter
     template<class T> struct EmptyDeleter { void operator()(T *) const {} };
 
+    // forward decls for archives from cereal.hpp
     struct InputArchiveBase;
     struct OutputArchiveBase;
 
+    //! Creates a binding (map entry) between an input archive type and a polymorphic type
+    /*! Bindings are made when types are registered, assuming that at least one
+        archive has already been registered.  When this struct is created,
+        it will insert (at run time) an entry into a map that properly handles
+        casting for serializing polymorphic objects */
     template <class Archive, class T> struct InputBindingCreator
     {
+      //! Initialize the binding
       InputBindingCreator()
       {
         typename InputBindingMap<Archive>::Serializers serializers;
@@ -148,8 +173,14 @@ namespace cereal
       }
     };
 
+    //! Creates a binding (map entry) between an output archive type and a polymorphic type
+    /*! Bindings are made when types are registered, assuming that at least one
+        archive has already been registered.  When this struct is created,
+        it will insert (at run time) an entry into a map that properly handles
+        casting for serializing polymorphic objects */
     template <class Archive, class T> struct OutputBindingCreator
     {
+      //! Writes appropriate metadata to the archive for this polymorphic type
       static void writeMetadata(Archive & ar)
       {
         // Register the polymorphic type name with the archive, and get the id
@@ -167,11 +198,11 @@ namespace cereal
         }
       }
 
+      //! Initialize the binding
       OutputBindingCreator()
       {
         typename OutputBindingMap<Archive>::Serializers serializers;
 
-
         serializers.shared_ptr =
           [](void * arptr, void const * dptr)
           {
@@ -243,6 +274,7 @@ namespace cereal
       typedef instantiate_function<instantiate> unused;
     };
 
+    // instantiate implementation
     template <class Archive, class T>
     void polymorphic_serialization_support<Archive,T>::instantiate()
     {

include/cereal/types/polymorphic.hpp

@@ -31,7 +31,7 @@
 #include <cereal/types/memory.hpp>
 #include <cereal/details/polymorphic_impl.hpp>
 #include <cereal/details/util.hpp>
-
+#include <iostream>
 //! Registers a polymorphic type with cereal
 /*! Polymorphic types must be registered before pointers
     to them can be serialized.  This also assumes that
@@ -152,13 +152,9 @@ namespace cereal
   typename std::enable_if<std::is_polymorphic<T>::value, void>::type
   save( Archive & ar, std::weak_ptr<T> const & ptr )
   {
-    if(!ptr)
-    {
-      // same behavior as nullptr in memory implementation
-      ar( std::uint32_t(0) );
-      return;
-    }
-
+    std::cout << "poly weak" << std::endl;
+    auto sptr = ptr.lock();
+    ar( sptr );
   }
 
   //! Loading std::weak_ptr for polymorphic types
@@ -166,6 +162,9 @@ namespace cereal
   typename std::enable_if<std::is_polymorphic<T>::value, void>::type
   load( Archive & ar, std::weak_ptr<T> & ptr )
   {
+    std::shared_ptr<T> sptr;
+    ar( sptr );
+    ptr = sptr;
   }
 
   //! Saving std::unique_ptr for polymorphic types

sandbox_rtti.cpp

@@ -96,10 +96,12 @@ int main()
     std::shared_ptr<Base> ptr1 = std::make_shared<MyType>();
     std::shared_ptr<Base> ptr2 = std::make_shared<YourType>();
     std::unique_ptr<Base> ptr3(new MyType);
+    std::weak_ptr<Base>   ptr4 = ptr2;
 
     oarchive(ptr1);
     oarchive(ptr2);
     oarchive(ptr3);
+    oarchive(ptr4);
   }
 
 
@@ -111,10 +113,12 @@ int main()
     std::shared_ptr<Base> ptr1;
     std::shared_ptr<Base> ptr2;
     std::unique_ptr<Base> ptr3;
+    std::weak_ptr<Base>   ptr4;
 
     iarchive(ptr1);
     iarchive(ptr2);
     iarchive(ptr3);
+    iarchive(ptr4);
   }
 
 }