Implemented pure_virtual(...)

[SVN r19774]

include/boost/python/detail/nullary_function_adaptor.hpp

@@ -0,0 +1,41 @@
+// Copyright David Abrahams 2003. Permission to copy, use,
+// modify, sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+#ifndef NULLARY_FUNCTION_ADAPTOR_DWA2003824_HPP
+# define NULLARY_FUNCTION_ADAPTOR_DWA2003824_HPP
+
+namespace boost { namespace python { namespace detail { 
+
+// nullary_function_adaptor -- a class template which ignores its
+// arguments and calls a nullary function instead.  Used for building
+// error-reporting functions, c.f. pure_virtual
+template <class NullaryFunction>
+struct nullary_function_adaptor
+{
+    nullary_function_adaptor(NullaryFunction fn)
+      : m_fn(fn)
+    {}
+
+    void operator()() const { m_fn(); }
+
+# define BOOST_PP_LOCAL_MACRO(i)                                            \
+    template <BOOST_PP_ENUM_PARAMS_Z(1, i, class A)>                        \
+    void operator()(                                                        \
+        BOOST_PP_ENUM_BINARY_PARAMS_Z(1, i, A, const& BOOST_PP_INTERCEPT)   \
+    ) const                                                                 \
+    {                                                                       \
+        m_fn();                                                             \
+    }
+
+# define BOOST_PP_LOCAL_LIMITS (1, BOOST_PYTHON_MAX_ARITY)
+# include BOOST_PP_LOCAL_ITERATE()
+    
+ private:
+    NullaryFunction m_fn;
+};
+
+}}} // namespace boost::python::detail
+
+#endif // NULLARY_FUNCTION_ADAPTOR_DWA2003824_HPP

include/boost/python/pure_virtual.hpp

@@ -0,0 +1,127 @@
+// Copyright David Abrahams 2003. Permission to copy, use,
+// modify, sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+#ifndef PURE_VIRTUAL_DWA2003810_HPP
+# define PURE_VIRTUAL_DWA2003810_HPP
+
+# include <boost/python/def_visitor.hpp>
+# include <boost/python/default_call_policies.hpp>
+# include <boost/python/arg_from_python.hpp>
+# include <boost/mpl/push_front.hpp>
+# include <boost/mpl/pop_front.hpp>
+
+# include <boost/python/detail/nullary_function_adaptor.hpp>
+
+namespace boost { namespace python { 
+
+namespace detail
+{
+  //
+  // { Helpers for pure_virtual_visitor, below.
+  //
+  
+  // Raises a Python RuntimeError reporting that a pure virtual
+  // function was called.
+  void BOOST_PYTHON_DECL pure_virtual_called();
+
+  // Replace the two front elements of S with T1 and T2
+  template <class S, class T1, class T2>
+  struct replace_front2
+  {
+      // Metafunction forwarding seemed to confound vc6 
+      typedef typename mpl::push_front<
+          typename mpl::push_front<
+              typename mpl::pop_front<
+                  typename mpl::pop_front<
+                      S
+                  >::type
+              >::type
+            , T2
+          >::type
+        , T1
+      >::type type;
+  };
+
+  // Given an MPL sequence representing a signature, returns a new MPL
+  // sequence whose return type is replaced by void, and whose first
+  // argument is replaced by C&.
+  template <class C, class S>
+  typename replace_front2<S,void,C&>::type
+  error_signature(S BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(C))
+  {
+      typedef typename replace_front2<S,void,C&>::type r;
+      return r();
+  }
+
+  //
+  // } Helpers for pure_virtual_visitor
+  //
+
+  //
+  // A def_visitor which defines a method as usual, then adds a
+  // corresponding function which raises a "pure virtual called"
+  // exception unless it's been overridden.
+  //
+  template <class PointerToMemberFunction>
+  struct pure_virtual_visitor
+    : def_visitor<pure_virtual_visitor<PointerToMemberFunction> >
+  {
+      pure_virtual_visitor(PointerToMemberFunction pmf)
+        : m_pmf(pmf)
+      {}
+      
+   private:
+      friend class def_visitor_access;
+      
+      template <class C_, class Options>
+      void visit(C_& c, char const* name, Options& options) const
+      {
+          // This should probably be a nicer error message
+          BOOST_STATIC_ASSERT(!Options::has_default_implementation);
+
+          // Add the virtual function dispatcher
+          c.def(
+              name
+            , m_pmf
+            , options.doc()
+            , options.keywords()
+            , options.policies()
+          );
+
+          typedef BOOST_DEDUCED_TYPENAME C_::select_holder::held_type held_t;
+          
+          // Add the default implementation which raises the exception
+          c.def(
+              name
+            , detail::make_function_aux(
+                  detail::nullary_function_adaptor<void(*)()>(pure_virtual_called)
+                , default_call_policies()
+                , args_from_python()
+                , detail::error_signature<held_t>(detail::get_signature(m_pmf))
+              )
+          );
+      }
+      
+   private: // data members
+      PointerToMemberFunction m_pmf;
+  };
+}
+
+//
+// Passed a pointer to member function, generates a def_visitor which
+// creates a method that only dispatches to Python if the function has
+// been overridden, either in C++ or in Python, raising a "pure
+// virtual called" exception otherwise.
+//
+template <class PointerToMemberFunction>
+detail::pure_virtual_visitor<PointerToMemberFunction>
+pure_virtual(PointerToMemberFunction pmf)
+{
+    return detail::pure_virtual_visitor<PointerToMemberFunction>(pmf);
+}
+
+}} // namespace boost::python
+
+#endif // PURE_VIRTUAL_DWA2003810_HPP

src/object/function.cpp

@@ -627,7 +627,7 @@ handle<> function_handle_impl(py_function const& f)
             new function(f, 0, 0)));
 }
 
-}
+} // namespace objects
 
 namespace detail
 {
@@ -639,6 +639,11 @@ namespace detail
           f
           , keyword_range(&k,&k));
   }
+  void BOOST_PYTHON_DECL pure_virtual_called()
+  {
+      PyErr_SetString(PyExc_RuntimeError, "Pure virtual function called");
+      throw_error_already_set();
+  }
 }
 
-}} // namespace boost::python::objects
+}} // namespace boost::python

test/polymorphism.cpp

@@ -9,6 +9,7 @@
 #include <boost/python/manage_new_object.hpp>
 #include <boost/python/reference_existing_object.hpp>
 #include <boost/python/call_method.hpp>
+#include <boost/python/pure_virtual.hpp>
 #include <boost/python/def.hpp>
 #include <boost/utility.hpp>
 
@@ -20,6 +21,27 @@ struct Callback
     PyObject* mSelf;
 };
 
+struct P
+{
+    virtual ~P(){}
+    virtual std::string f() = 0;
+};
+
+struct PCallback : P, Callback
+{
+    PCallback (PyObject* self) : Callback(self) {}
+    
+    std::string f()
+    {
+        return call_method<std::string>(mSelf, "f");
+    }
+};
+
+struct Q : P
+{
+    std::string f() { return "Q::f()"; } 
+};
+
 struct A
 {
     virtual ~A(){}
@@ -44,7 +66,7 @@ struct ACallback :  A,  Callback
 
 struct B : A
 {
-    virtual std::string f() { return "B::f()"; }
+    virtual std::string f() { return "B::f()"; } 
 };
 
 struct C : A
@@ -127,6 +149,13 @@ BOOST_PYTHON_MODULE_INIT(polymorphism_ext)
     def("factory", factory, return_value_policy<manage_new_object>());
 
     def("call_f", call_f);
+
+    class_<P,boost::noncopyable,PCallback>("P")
+        .def("f", pure_virtual(&P::f))
+        ;
+
+    class_<Q, bases<P> >("Q")
+        ;
 }
 
 //#include "module_tail.cpp"

test/polymorphism.py

@@ -46,7 +46,22 @@ class PolymorphTest(unittest.TestCase):
    def test_wrapper_downcast(self):
       a = pass_a(D())
       self.failUnlessEqual('D::g()', a.g())
-   
+
+   def test_pure_virtual(self):
+      p = P()
+      self.assertRaises(RuntimeError, p.f)
+      
+      q = Q()
+      self.failUnlessEqual ('Q::f()', q.f())
+      
+      class R(P):
+         def f(self):
+            return 'R.f'
+
+      r = R()
+      self.failUnlessEqual ('R.f', r.f())
+      
+                        
 if __name__ == "__main__":
    
    # remove the option which upsets unittest