this part of refptr.h (around line 214):

template <class T_CppObject>
 template <class T_CastFrom>
inline RefPtr<T_CppObject>::RefPtr(const RefPtr<T_CastFrom>& src)
:
 pCppObject_ (src.operator->())
{
 if(pCppObject_)
   pCppObject_->reference();
}

causes the Forte compiler to barf thus:

"../../glib/glibmm/refptr.h", line 214: Error: Cannot use const Gio::File* to initialize Gio::File*.

Removing the 'const' keyword results in this error instead:

"../../glib/glibmm/refptr.h", line 214: Error: Could not find a match for Glib::RefPtr<Glib::T_CppObject>::RefPtr(Glib::RefPtr<Glib::RefPtr<Glib::T_CppObject>::T_CastFrom>&).

Using pCppObject_ (const_cast<T_CppObject*>(src.operator->())), does allow compilation of glibmm to succeed.  But then gtkmm fails to compile with:

/usr/local/include/glibmm/refptr.h: In constructor 'Glib::RefPtr<T_CppObject>::RefPtr(const Glib::RefPtr<T_CastFrom>&) [with T_CastFrom = Gtk::ListStore, T_CppObject = Gtk::TreeModel]':
comboboxtext.cc:35:   instantiated from here
/usr/local/include/glibmm/refptr.h:214: error: invalid const_cast from type 'Gtk::ListStore*' to type 'Gtk::TreeModel*'