Prohibit default pickling of classes with non-Python-convertable members.

Cython/Compiler/ParseTreeTransforms.py

@@ -1568,12 +1568,31 @@ if VALUE is not None:
         return node
 
     def _inject_pickle_methods(self, node):
+        env = self.current_env()
         all_members = []
         cls = node.entry.type
         while cls is not None:
             all_members.extend(cls.scope.var_entries)
             cls = cls.base_type
             all_members.sort(key=lambda e: e.name)
+
+        non_py = [
+            e for e in all_members
+            if not e.type.is_pyobject and (not e.type.create_from_py_utility_code(env)
+                                           or not e.type.create_to_py_utility_code(env))]
+
+        if non_py:
+            msg = "%s cannot be converted to a Python object" % ','.join("self.%s" % e.name for e in non_py)
+            pickle_func = TreeFragment(u"""
+                def __reduce__(self):
+                    raise TypeError("%s")
+                """ % msg,
+                level='c_class', pipeline=[NormalizeTree(None)]).substitute({})
+            pickle_func.analyse_declarations(node.scope)
+            self.visit(pickle_func)
+            node.body.stats.append(pickle_func)
+
+        else:
             all_members_names = [e.name for e in all_members]
             unpickle_func_name = '__pyx_unpickle_%s' % node.class_name
 

tests/run/reduce_pickle.pyx

@@ -96,3 +96,14 @@ cdef class DefaultReduceSubclass(DefaultReduce):
 
     def __repr__(self):
         return "DefaultReduceSubclass(i=%s, s=%r, x=%s)" % (self.i, self.s, self.x)
+
+
+cdef class NoReduceDueToIntPtr(object):
+    """
+    >>> import pickle
+    >>> pickle.dumps(NoReduceDueToIntPtr())
+    Traceback (most recent call last):
+    ...
+    TypeError: self.int_ptr cannot be converted to a Python object
+    """
+    cdef int* int_ptr