- Provisional support for pickling new-style objects. (*)

- Made cls.__module__ writable.

- Ensure that obj.__dict__ is returned as {}, not None, even upon first
  reference; it simply springs into life when you ask for it.

(*) The pickling support is provisional for the following reasons:

- It doesn't support classes with __slots__.

- It relies on additional support in copy_reg.py: the C method
  __reduce__, defined in the object class, really calls calling
  copy_reg._reduce(obj).  Eventually the Python code in copy_reg.py
  needs to be migrated to C, but I'd like to experiment with the
  Python implementation first.  The _reduce() code also relies on an
  additional helper function, _reconstructor(), defined in
  copy_reg.py; this should also be reimplemented in C.

Lib/copy_reg.py

@@ -33,3 +33,32 @@ def pickle_complex(c):
     return complex, (c.real, c.imag)
 
 pickle(type(1j), pickle_complex, complex)
+
+# Support for picking new-style objects
+
+_dummy_classes = {}
+
+def _reconstructor(cls, base, state):
+    dummy = _dummy_classes.get(base)
+    if dummy is None:
+        class dummy(base): pass
+        _dummy_classes[base] = dummy
+    obj = dummy(state)
+    obj._foo = 1; del obj._foo # hack to create __dict__
+    obj.__class__ = cls
+    return obj
+_reconstructor.__safe_for_unpickling__ = 1
+
+_HEAPTYPE = 1<<9
+
+def _reduce(self):
+    for base in self.__class__.__mro__:
+        if not base.__flags__ & _HEAPTYPE:
+            break
+    else:
+        base = object # not really reachable
+    if base is object:
+        state = None
+    else:
+        state = base(self)
+    return _reconstructor, (self.__class__, base, state), self.__dict__