bpo-26579: Add object.__getstate__(). (GH-2821)

Copying and pickling instances of subclasses of builtin types
bytearray, set, frozenset, collections.OrderedDict, collections.deque,
weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes
implemented as slots.

Doc/library/pickle.rst

@@ -509,9 +509,8 @@ The following types can be pickled:
 
 * classes that are defined at the top level of a module
 
-* instances of such classes whose :attr:`~object.__dict__` or the result of
-  calling :meth:`__getstate__` is picklable  (see section :ref:`pickle-inst` for
-  details).
+* instances of such classes whose the result of calling :meth:`__getstate__`
+  is picklable  (see section :ref:`pickle-inst` for details).
 
 Attempts to pickle unpicklable objects will raise the :exc:`PicklingError`
 exception; when this happens, an unspecified number of bytes may have already
@@ -611,11 +610,31 @@ methods:
 
 .. method:: object.__getstate__()
 
-   Classes can further influence how their instances are pickled; if the class
-   defines the method :meth:`__getstate__`, it is called and the returned object
-   is pickled as the contents for the instance, instead of the contents of the
-   instance's dictionary.  If the :meth:`__getstate__` method is absent, the
-   instance's :attr:`~object.__dict__` is pickled as usual.
+   Classes can further influence how their instances are pickled by overriding
+   the method :meth:`__getstate__`.  It is called and the returned object
+   is pickled as the contents for the instance, instead of a default state.
+   There are several cases:
+
+   * For a class that has no instance :attr:`~object.__dict__` and no
+     :attr:`~object.__slots__`, the default state is ``None``.
+
+   * For a class that has an instance :attr:`~object.__dict__` and no
+     :attr:`~object.__slots__`, the default state is ``self.__dict__``.
+
+   * For a class that has an instance :attr:`~object.__dict__` and
+     :attr:`~object.__slots__`, the default state is a tuple consisting of two
+     dictionaries:  ``self.__dict__``, and a dictionary mapping slot
+     names to slot values.  Only slots that have a value are
+     included in the latter.
+
+   * For a class that has :attr:`~object.__slots__` and no instance
+     :attr:`~object.__dict__`, the default state is a tuple whose first item
+     is ``None`` and whose second item is a dictionary mapping slot names
+     to slot values described in the previous bullet.
+
+   .. versionchanged:: 3.11
+      Added the default implementation of the ``__getstate__()`` method in the
+      :class:`object` class.
 
 
 .. method:: object.__setstate__(state)

Doc/whatsnew/3.11.rst

@@ -187,6 +187,15 @@ Other Language Changes
   protocols correspondingly.
   (Contributed by Serhiy Storchaka in :issue:`12022`.)
 
+* Added :meth:`object.__getstate__` which provides the default
+  implementation of the ``__getstate__()`` method.  :mod:`Copying <copy>`
+  and :mod:`pickling <pickle>` instances of subclasses of builtin types
+  :class:`bytearray`, :class:`set`, :class:`frozenset`,
+  :class:`collections.OrderedDict`, :class:`collections.deque`,
+  :class:`weakref.WeakSet`, and :class:`datetime.tzinfo` now copies and
+  pickles instance attributes implemented as :term:`slots <__slots__>`.
+  (Contributed by Serhiy Storchaka in :issue:`26579`.)
+
 
 Other CPython Implementation Changes
 ====================================

Include/object.h

@@ -299,6 +299,11 @@ PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
 */
 PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
 
+/* Pickle support. */
+#ifndef Py_LIMITED_API
+PyAPI_FUNC(PyObject *) _PyObject_GetState(PyObject *);
+#endif
+
 
 /* Helpers for printing recursive container types */
 PyAPI_FUNC(int) Py_ReprEnter(PyObject *);

Lib/_weakrefset.py

@@ -80,8 +80,7 @@ class WeakSet:
         return wr in self.data
 
     def __reduce__(self):
-        return (self.__class__, (list(self),),
-                getattr(self, '__dict__', None))
+        return self.__class__, (list(self),), self.__getstate__()
 
     def add(self, item):
         if self._pending_removals:

Lib/collections/__init__.py

@@ -271,10 +271,22 @@ class OrderedDict(dict):
 
     def __reduce__(self):
         'Return state information for pickling'
-        inst_dict = vars(self).copy()
-        for k in vars(OrderedDict()):
-            inst_dict.pop(k, None)
-        return self.__class__, (), inst_dict or None, None, iter(self.items())
+        state = self.__getstate__()
+        if state:
+            if isinstance(state, tuple):
+                state, slots = state
+            else:
+                slots = {}
+            state = state.copy()
+            slots = slots.copy()
+            for k in vars(OrderedDict()):
+                state.pop(k, None)
+                slots.pop(k, None)
+            if slots:
+                state = state, slots
+            else:
+                state = state or None
+        return self.__class__, (), state, None, iter(self.items())
 
     def copy(self):
         'od.copy() -> a shallow copy of od'

Lib/copyreg.py

@@ -89,6 +89,10 @@ def _reduce_ex(self, proto):
         except AttributeError:
             dict = None
     else:
+        if (type(self).__getstate__ is object.__getstate__ and
+            getattr(self, "__slots__", None)):
+            raise TypeError("a class that defines __slots__ without "
+                            "defining __getstate__ cannot be pickled")
         dict = getstate()
     if dict:
         return _reconstructor, args, dict

Lib/datetime.py

@@ -1169,15 +1169,7 @@ class tzinfo:
             args = getinitargs()
         else:
             args = ()
-        getstate = getattr(self, "__getstate__", None)
-        if getstate:
-            state = getstate()
-        else:
-            state = getattr(self, "__dict__", None) or None
-        if state is None:
-            return (self.__class__, args)
-        else:
-            return (self.__class__, args, state)
+        return (self.__class__, args, self.__getstate__())
 
 
 class IsoCalendarDate(tuple):

Lib/email/headerregistry.py

@@ -218,7 +218,7 @@ class BaseHeader(str):
                 self.__class__.__bases__,
                 str(self),
             ),
-            self.__dict__)
+            self.__getstate__())
 
     @classmethod
     def _reconstruct(cls, value):

Lib/test/datetimetester.py

@@ -139,8 +139,8 @@ class PicklableFixedOffset(FixedOffset):
     def __init__(self, offset=None, name=None, dstoffset=None):
         FixedOffset.__init__(self, offset, name, dstoffset)
 
-    def __getstate__(self):
-        return self.__dict__
+class PicklableFixedOffsetWithSlots(PicklableFixedOffset):
+    __slots__ = '_FixedOffset__offset', '_FixedOffset__name', 'spam'
 
 class _TZInfo(tzinfo):
     def utcoffset(self, datetime_module):
@@ -202,6 +202,7 @@ class TestTZInfo(unittest.TestCase):
         offset = timedelta(minutes=-300)
         for otype, args in [
             (PicklableFixedOffset, (offset, 'cookie')),
+            (PicklableFixedOffsetWithSlots, (offset, 'cookie')),
             (timezone, (offset,)),
             (timezone, (offset, "EST"))]:
             orig = otype(*args)
@@ -217,6 +218,7 @@ class TestTZInfo(unittest.TestCase):
                 self.assertIs(type(derived), otype)
                 self.assertEqual(derived.utcoffset(None), offset)
                 self.assertEqual(derived.tzname(None), oname)
+                self.assertFalse(hasattr(derived, 'spam'))
 
     def test_issue23600(self):
         DSTDIFF = DSTOFFSET = timedelta(hours=1)

Lib/test/pickletester.py

@@ -2382,9 +2382,11 @@ class AbstractPickleTests:
     def test_bad_getattr(self):
         # Issue #3514: crash when there is an infinite loop in __getattr__
         x = BadGetattr()
-        for proto in protocols:
+        for proto in range(2):
             with support.infinite_recursion():
                 self.assertRaises(RuntimeError, self.dumps, x, proto)
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            s = self.dumps(x, proto)
 
     def test_reduce_bad_iterator(self):
         # Issue4176: crash when 4th and 5th items of __reduce__()

Lib/test/test_bytes.py

@@ -1940,28 +1940,30 @@ class SubclassTest:
     def test_pickle(self):
         a = self.type2test(b"abcd")
         a.x = 10
-        a.y = self.type2test(b"efgh")
+        a.z = self.type2test(b"efgh")
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             b = pickle.loads(pickle.dumps(a, proto))
             self.assertNotEqual(id(a), id(b))
             self.assertEqual(a, b)
             self.assertEqual(a.x, b.x)
-            self.assertEqual(a.y, b.y)
+            self.assertEqual(a.z, b.z)
             self.assertEqual(type(a), type(b))
-            self.assertEqual(type(a.y), type(b.y))
+            self.assertEqual(type(a.z), type(b.z))
+            self.assertFalse(hasattr(b, 'y'))
 
     def test_copy(self):
         a = self.type2test(b"abcd")
         a.x = 10
-        a.y = self.type2test(b"efgh")
+        a.z = self.type2test(b"efgh")
         for copy_method in (copy.copy, copy.deepcopy):
             b = copy_method(a)
             self.assertNotEqual(id(a), id(b))
             self.assertEqual(a, b)
             self.assertEqual(a.x, b.x)
-            self.assertEqual(a.y, b.y)
+            self.assertEqual(a.z, b.z)
             self.assertEqual(type(a), type(b))
-            self.assertEqual(type(a.y), type(b.y))
+            self.assertEqual(type(a.z), type(b.z))
+            self.assertFalse(hasattr(b, 'y'))
 
     def test_fromhex(self):
         b = self.type2test.fromhex('1a2B30')
@@ -1994,6 +1996,9 @@ class SubclassTest:
 class ByteArraySubclass(bytearray):
     pass
 
+class ByteArraySubclassWithSlots(bytearray):
+    __slots__ = ('x', 'y', '__dict__')
+
 class BytesSubclass(bytes):
     pass
 
@@ -2014,6 +2019,9 @@ class ByteArraySubclassTest(SubclassTest, unittest.TestCase):
         x = subclass(newarg=4, source=b"abcd")
         self.assertEqual(x, b"abcd")
 
+class ByteArraySubclassWithSlotsTest(SubclassTest, unittest.TestCase):
+    basetype = bytearray
+    type2test = ByteArraySubclassWithSlots
 
 class BytesSubclassTest(SubclassTest, unittest.TestCase):
     basetype = bytes

Lib/test/test_deque.py

@@ -781,6 +781,9 @@ class TestVariousIteratorArgs(unittest.TestCase):
 class Deque(deque):
     pass
 
+class DequeWithSlots(deque):
+    __slots__ = ('x', 'y', '__dict__')
+
 class DequeWithBadIter(deque):
     def __iter__(self):
         raise TypeError
@@ -810,40 +813,28 @@ class TestSubclass(unittest.TestCase):
         self.assertEqual(len(d), 0)
 
     def test_copy_pickle(self):
+        for cls in Deque, DequeWithSlots:
+            for d in cls('abc'), cls('abcde', maxlen=4):
+                d.x = ['x']
+                d.z = ['z']
 
-        d = Deque('abc')
+                e = d.__copy__()
+                self.assertEqual(type(d), type(e))
+                self.assertEqual(list(d), list(e))
 
-        e = d.__copy__()
-        self.assertEqual(type(d), type(e))
-        self.assertEqual(list(d), list(e))
+                e = cls(d)
+                self.assertEqual(type(d), type(e))
+                self.assertEqual(list(d), list(e))
 
-        e = Deque(d)
-        self.assertEqual(type(d), type(e))
-        self.assertEqual(list(d), list(e))
-
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            s = pickle.dumps(d, proto)
-            e = pickle.loads(s)
-            self.assertNotEqual(id(d), id(e))
-            self.assertEqual(type(d), type(e))
-            self.assertEqual(list(d), list(e))
-
-        d = Deque('abcde', maxlen=4)
-
-        e = d.__copy__()
-        self.assertEqual(type(d), type(e))
-        self.assertEqual(list(d), list(e))
-
-        e = Deque(d)
-        self.assertEqual(type(d), type(e))
-        self.assertEqual(list(d), list(e))
-
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            s = pickle.dumps(d, proto)
-            e = pickle.loads(s)
-            self.assertNotEqual(id(d), id(e))
-            self.assertEqual(type(d), type(e))
-            self.assertEqual(list(d), list(e))
+                for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+                    s = pickle.dumps(d, proto)
+                    e = pickle.loads(s)
+                    self.assertNotEqual(id(d), id(e))
+                    self.assertEqual(type(d), type(e))
+                    self.assertEqual(list(d), list(e))
+                    self.assertEqual(e.x, d.x)
+                    self.assertEqual(e.z, d.z)
+                    self.assertFalse(hasattr(e, 'y'))
 
     def test_pickle_recursive(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):

Lib/test/test_descrtut.py

@@ -181,6 +181,7 @@ You can get the information from the list type:
      '__ge__',
      '__getattribute__',
      '__getitem__',
+     '__getstate__',
      '__gt__',
      '__hash__',
      '__iadd__',

Lib/test/test_ordered_dict.py

@@ -287,6 +287,8 @@ class OrderedDictTests:
         # and have a repr/eval round-trip
         pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]
         od = OrderedDict(pairs)
+        od.x = ['x']
+        od.z = ['z']
         def check(dup):
             msg = "\ncopy: %s\nod: %s" % (dup, od)
             self.assertIsNot(dup, od, msg)
@@ -295,13 +297,27 @@ class OrderedDictTests:
             self.assertEqual(len(dup), len(od))
             self.assertEqual(type(dup), type(od))
         check(od.copy())
-        check(copy.copy(od))
-        check(copy.deepcopy(od))
+        dup = copy.copy(od)
+        check(dup)
+        self.assertIs(dup.x, od.x)
+        self.assertIs(dup.z, od.z)
+        self.assertFalse(hasattr(dup, 'y'))
+        dup = copy.deepcopy(od)
+        check(dup)
+        self.assertEqual(dup.x, od.x)
+        self.assertIsNot(dup.x, od.x)
+        self.assertEqual(dup.z, od.z)
+        self.assertIsNot(dup.z, od.z)
+        self.assertFalse(hasattr(dup, 'y'))
         # pickle directly pulls the module, so we have to fake it
         with replaced_module('collections', self.module):
             for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                 with self.subTest(proto=proto):
-                    check(pickle.loads(pickle.dumps(od, proto)))
+                    dup = pickle.loads(pickle.dumps(od, proto))
+                    check(dup)
+                    self.assertEqual(dup.x, od.x)
+                    self.assertEqual(dup.z, od.z)
+                    self.assertFalse(hasattr(dup, 'y'))
         check(eval(repr(od)))
         update_test = OrderedDict()
         update_test.update(od)
@@ -846,6 +862,23 @@ class CPythonOrderedDictSubclassTests(CPythonOrderedDictTests):
         pass
 
 
+class PurePythonOrderedDictWithSlotsCopyingTests(unittest.TestCase):
+
+    module = py_coll
+    class OrderedDict(py_coll.OrderedDict):
+        __slots__ = ('x', 'y')
+    test_copying = OrderedDictTests.test_copying
+
+
+@unittest.skipUnless(c_coll, 'requires the C version of the collections module')
+class CPythonOrderedDictWithSlotsCopyingTests(unittest.TestCase):
+
+    module = c_coll
+    class OrderedDict(c_coll.OrderedDict):
+        __slots__ = ('x', 'y')
+    test_copying = OrderedDictTests.test_copying
+
+
 class PurePythonGeneralMappingTests(mapping_tests.BasicTestMappingProtocol):
 
     @classmethod

Lib/test/test_set.py

@@ -227,14 +227,17 @@ class TestJointOps:
 
     def test_pickling(self):
         for i in range(pickle.HIGHEST_PROTOCOL + 1):
+            if type(self.s) not in (set, frozenset):
+                self.s.x = ['x']
+                self.s.z = ['z']
             p = pickle.dumps(self.s, i)
             dup = pickle.loads(p)
             self.assertEqual(self.s, dup, "%s != %s" % (self.s, dup))
             if type(self.s) not in (set, frozenset):
-                self.s.x = 10
-                p = pickle.dumps(self.s, i)
-                dup = pickle.loads(p)
                 self.assertEqual(self.s.x, dup.x)
+                self.assertEqual(self.s.z, dup.z)
+                self.assertFalse(hasattr(self.s, 'y'))
+                del self.s.x, self.s.z
 
     def test_iterator_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
@@ -808,6 +811,21 @@ class TestFrozenSetSubclass(TestFrozenSet):
         # All empty frozenset subclass instances should have different ids
         self.assertEqual(len(set(map(id, efs))), len(efs))
 
+
+class SetSubclassWithSlots(set):
+    __slots__ = ('x', 'y', '__dict__')
+
+class TestSetSubclassWithSlots(unittest.TestCase):
+    thetype = SetSubclassWithSlots
+    setUp = TestJointOps.setUp
+    test_pickling = TestJointOps.test_pickling
+
+class FrozenSetSubclassWithSlots(frozenset):
+    __slots__ = ('x', 'y', '__dict__')
+
+class TestFrozenSetSubclassWithSlots(TestSetSubclassWithSlots):
+    thetype = FrozenSetSubclassWithSlots
+
 # Tests taken from test_sets.py =============================================
 
 empty_set = set()

Lib/test/test_weakset.py

@@ -1,5 +1,6 @@
 import unittest
 from weakref import WeakSet
+import copy
 import string
 from collections import UserString as ustr
 from collections.abc import Set, MutableSet
@@ -15,6 +16,12 @@ class RefCycle:
     def __init__(self):
         self.cycle = self
 
+class WeakSetSubclass(WeakSet):
+    pass
+
+class WeakSetWithSlots(WeakSet):
+    __slots__ = ('x', 'y')
+
 
 class TestWeakSet(unittest.TestCase):
 
@@ -447,6 +454,30 @@ class TestWeakSet(unittest.TestCase):
         self.assertIsInstance(self.s, Set)
         self.assertIsInstance(self.s, MutableSet)
 
+    def test_copying(self):
+        for cls in WeakSet, WeakSetWithSlots:
+            s = cls(self.items)
+            s.x = ['x']
+            s.z = ['z']
+
+            dup = copy.copy(s)
+            self.assertIsInstance(dup, cls)
+            self.assertEqual(dup, s)
+            self.assertIsNot(dup, s)
+            self.assertIs(dup.x, s.x)
+            self.assertIs(dup.z, s.z)
+            self.assertFalse(hasattr(dup, 'y'))
+
+            dup = copy.deepcopy(s)
+            self.assertIsInstance(dup, cls)
+            self.assertEqual(dup, s)
+            self.assertIsNot(dup, s)
+            self.assertEqual(dup.x, s.x)
+            self.assertIsNot(dup.x, s.x)
+            self.assertEqual(dup.z, s.z)
+            self.assertIsNot(dup.z, s.z)
+            self.assertFalse(hasattr(dup, 'y'))
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_xml_etree.py

@@ -2524,8 +2524,7 @@ class BasicElementTest(ElementTestCase, unittest.TestCase):
                     <group><dogs>4</dogs>
                     </group>"""
                 e1 = dumper.fromstring(XMLTEXT)
-                if hasattr(e1, '__getstate__'):
-                    self.assertEqual(e1.__getstate__()['tag'], 'group')
+                self.assertEqual(e1.__getstate__()['tag'], 'group')
                 e2 = self.pickleRoundTrip(e1, 'xml.etree.ElementTree',
                                           dumper, loader, proto)
                 self.assertEqual(e2.tag, 'group')

Misc/NEWS.d/next/Core and Builtins/2017-07-23-11-28-45.bpo-26579.lpCY8R.rst

@@ -0,0 +1,7 @@
+Added ``object.__getstate__`` which provides the default implementation of
+the ``__getstate__()`` method.
+
+Copying and pickling instances of subclasses of builtin types bytearray,
+set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet,
+and datetime.tzinfo now copies and pickles instance attributes implemented as
+slots.

Modules/_collectionsmodule.c

@@ -1347,27 +1347,24 @@ deque_traverse(dequeobject *deque, visitproc visit, void *arg)
 static PyObject *
 deque_reduce(dequeobject *deque, PyObject *Py_UNUSED(ignored))
 {
-    PyObject *dict, *it;
+    PyObject *state, *it;
 
-    if (_PyObject_LookupAttr((PyObject *)deque, &_Py_ID(__dict__), &dict) < 0) {
+    state = _PyObject_GetState((PyObject *)deque);
+    if (state == NULL) {
         return NULL;
     }
-    if (dict == NULL) {
-        dict = Py_None;
-        Py_INCREF(dict);
-    }
 
     it = PyObject_GetIter((PyObject *)deque);
     if (it == NULL) {
-        Py_DECREF(dict);
+        Py_DECREF(state);
         return NULL;
     }
 
     if (deque->maxlen < 0) {
-        return Py_BuildValue("O()NN", Py_TYPE(deque), dict, it);
+        return Py_BuildValue("O()NN", Py_TYPE(deque), state, it);
     }
     else {
-        return Py_BuildValue("O(()n)NN", Py_TYPE(deque), deque->maxlen, dict, it);
+        return Py_BuildValue("O(()n)NN", Py_TYPE(deque), deque->maxlen, state, it);
     }
 }
 

Modules/_datetimemodule.c

@@ -3736,9 +3736,8 @@ static PyObject *
 tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *args, *state;
-    PyObject *getinitargs, *getstate;
+    PyObject *getinitargs;
     _Py_IDENTIFIER(__getinitargs__);
-    _Py_IDENTIFIER(__getstate__);
 
     if (_PyObject_LookupAttrId(self, &PyId___getinitargs__, &getinitargs) < 0) {
         return NULL;
@@ -3754,34 +3753,13 @@ tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
         return NULL;
     }
 
-    if (_PyObject_LookupAttrId(self, &PyId___getstate__, &getstate) < 0) {
+    state = _PyObject_GetState(self);
+    if (state == NULL) {
         Py_DECREF(args);
         return NULL;
     }
-    if (getstate != NULL) {
-        state = PyObject_CallNoArgs(getstate);
-        Py_DECREF(getstate);
-        if (state == NULL) {
-            Py_DECREF(args);
-            return NULL;
-        }
-    }
-    else {
-        PyObject **dictptr;
-        state = Py_None;
-        dictptr = _PyObject_GetDictPtr(self);
-        if (dictptr && *dictptr && PyDict_GET_SIZE(*dictptr)) {
-            state = *dictptr;
-        }
-        Py_INCREF(state);
-    }
 
-    if (state == Py_None) {
-        Py_DECREF(state);
-        return Py_BuildValue("(ON)", Py_TYPE(self), args);
-    }
-    else
-        return Py_BuildValue("(ONN)", Py_TYPE(self), args, state);
+    return Py_BuildValue("(ONN)", Py_TYPE(self), args, state);
 }
 
 static PyMethodDef tzinfo_methods[] = {

Objects/bytearrayobject.c

@@ -2122,35 +2122,26 @@ bytearray_hex_impl(PyByteArrayObject *self, PyObject *sep, int bytes_per_sep)
 static PyObject *
 _common_reduce(PyByteArrayObject *self, int proto)
 {
-    PyObject *dict;
-    char *buf;
+    PyObject *state;
+    const char *buf;
 
-    if (_PyObject_LookupAttr((PyObject *)self, &_Py_ID(__dict__), &dict) < 0) {
+    state = _PyObject_GetState((PyObject *)self);
+    if (state == NULL) {
         return NULL;
     }
-    if (dict == NULL) {
-        dict = Py_None;
-        Py_INCREF(dict);
-    }
 
+    if (!Py_SIZE(self)) {
+        return Py_BuildValue("(O()N)", Py_TYPE(self), state);
+    }
     buf = PyByteArray_AS_STRING(self);
     if (proto < 3) {
         /* use str based reduction for backwards compatibility with Python 2.x */
-        PyObject *latin1;
-        if (Py_SIZE(self))
-            latin1 = PyUnicode_DecodeLatin1(buf, Py_SIZE(self), NULL);
-        else
-            latin1 = PyUnicode_FromString("");
-        return Py_BuildValue("(O(Ns)N)", Py_TYPE(self), latin1, "latin-1", dict);
+        PyObject *latin1 = PyUnicode_DecodeLatin1(buf, Py_SIZE(self), NULL);
+        return Py_BuildValue("(O(Ns)N)", Py_TYPE(self), latin1, "latin-1", state);
     }
     else {
         /* use more efficient byte based reduction */
-        if (Py_SIZE(self)) {
-            return Py_BuildValue("(O(y#)N)", Py_TYPE(self), buf, Py_SIZE(self), dict);
-        }
-        else {
-            return Py_BuildValue("(O()N)", Py_TYPE(self), dict);
-        }
+        return Py_BuildValue("(O(y#)N)", Py_TYPE(self), buf, Py_SIZE(self), state);
     }
 }
 

Objects/clinic/typeobject.c.h

@@ -130,6 +130,24 @@ type___sizeof__(PyTypeObject *self, PyObject *Py_UNUSED(ignored))
     return type___sizeof___impl(self);
 }
 
+PyDoc_STRVAR(object___getstate____doc__,
+"__getstate__($self, /)\n"
+"--\n"
+"\n"
+"Helper for pickle.");
+
+#define OBJECT___GETSTATE___METHODDEF    \
+    {"__getstate__", (PyCFunction)object___getstate__, METH_NOARGS, object___getstate____doc__},
+
+static PyObject *
+object___getstate___impl(PyObject *self);
+
+static PyObject *
+object___getstate__(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    return object___getstate___impl(self);
+}
+
 PyDoc_STRVAR(object___reduce____doc__,
 "__reduce__($self, /)\n"
 "--\n"
@@ -243,4 +261,4 @@ object___dir__(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     return object___dir___impl(self);
 }
-/*[clinic end generated code: output=b4fb62939b08baf9 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=a30090032b8e6195 input=a9049054013a1b77]*/

Objects/odictobject.c

@@ -947,23 +947,13 @@ PyDoc_STRVAR(odict_reduce__doc__, "Return state information for pickling");
 static PyObject *
 odict_reduce(register PyODictObject *od, PyObject *Py_UNUSED(ignored))
 {
-    PyObject *dict = NULL, *result = NULL;
+    PyObject *state, *result = NULL;
     PyObject *items_iter, *items, *args = NULL;
 
     /* capture any instance state */
-    dict = PyObject_GetAttr((PyObject *)od, &_Py_ID(__dict__));
-    if (dict == NULL)
+    state = _PyObject_GetState((PyObject *)od);
+    if (state == NULL)
         goto Done;
-    else {
-        /* od.__dict__ isn't necessarily a dict... */
-        Py_ssize_t dict_len = PyObject_Length(dict);
-        if (dict_len == -1)
-            goto Done;
-        if (!dict_len) {
-            /* nothing to pickle in od.__dict__ */
-            Py_CLEAR(dict);
-        }
-    }
 
     /* build the result */
     args = PyTuple_New(0);
@@ -979,11 +969,11 @@ odict_reduce(register PyODictObject *od, PyObject *Py_UNUSED(ignored))
     if (items_iter == NULL)
         goto Done;
 
-    result = PyTuple_Pack(5, Py_TYPE(od), args, dict ? dict : Py_None, Py_None, items_iter);
+    result = PyTuple_Pack(5, Py_TYPE(od), args, state, Py_None, items_iter);
     Py_DECREF(items_iter);
 
 Done:
-    Py_XDECREF(dict);
+    Py_XDECREF(state);
     Py_XDECREF(args);
 
     return result;

Objects/setobject.c

@@ -1947,7 +1947,7 @@ an exception when an element is missing from the set.");
 static PyObject *
 set_reduce(PySetObject *so, PyObject *Py_UNUSED(ignored))
 {
-    PyObject *keys=NULL, *args=NULL, *result=NULL, *dict=NULL;
+    PyObject *keys=NULL, *args=NULL, *result=NULL, *state=NULL;
 
     keys = PySequence_List((PyObject *)so);
     if (keys == NULL)
@@ -1955,18 +1955,14 @@ set_reduce(PySetObject *so, PyObject *Py_UNUSED(ignored))
     args = PyTuple_Pack(1, keys);
     if (args == NULL)
         goto done;
-    if (_PyObject_LookupAttr((PyObject *)so, &_Py_ID(__dict__), &dict) < 0) {
+    state = _PyObject_GetState((PyObject *)so);
+    if (state == NULL)
         goto done;
-    }
-    if (dict == NULL) {
-        dict = Py_None;
-        Py_INCREF(dict);
-    }
-    result = PyTuple_Pack(3, Py_TYPE(so), args, dict);
+    result = PyTuple_Pack(3, Py_TYPE(so), args, state);
 done:
     Py_XDECREF(args);
     Py_XDECREF(keys);
-    Py_XDECREF(dict);
+    Py_XDECREF(state);
     return result;
 }
 

Objects/typeobject.c

@@ -4960,143 +4960,175 @@ _PyType_GetSlotNames(PyTypeObject *cls)
 }
 
 static PyObject *
-_PyObject_GetState(PyObject *obj, int required)
+object_getstate_default(PyObject *obj, int required)
 {
     PyObject *state;
-    PyObject *getstate;
+    PyObject *slotnames;
 
-    if (_PyObject_LookupAttr(obj, &_Py_ID(__getstate__), &getstate) < 0) {
+    if (required && Py_TYPE(obj)->tp_itemsize) {
+        PyErr_Format(PyExc_TypeError,
+                     "cannot pickle %.200s objects",
+                     Py_TYPE(obj)->tp_name);
         return NULL;
     }
-    if (getstate == NULL) {
-        PyObject *slotnames;
 
-        if (required && Py_TYPE(obj)->tp_itemsize) {
+    if (_PyObject_IsInstanceDictEmpty(obj)) {
+        state = Py_None;
+        Py_INCREF(state);
+    }
+    else {
+        state = PyObject_GenericGetDict(obj, NULL);
+        if (state == NULL) {
+            return NULL;
+        }
+    }
+
+    slotnames = _PyType_GetSlotNames(Py_TYPE(obj));
+    if (slotnames == NULL) {
+        Py_DECREF(state);
+        return NULL;
+    }
+
+    assert(slotnames == Py_None || PyList_Check(slotnames));
+    if (required) {
+        Py_ssize_t basicsize = PyBaseObject_Type.tp_basicsize;
+        if (Py_TYPE(obj)->tp_dictoffset &&
+            (Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0)
+        {
+            basicsize += sizeof(PyObject *);
+        }
+        if (Py_TYPE(obj)->tp_weaklistoffset) {
+            basicsize += sizeof(PyObject *);
+        }
+        if (slotnames != Py_None) {
+            basicsize += sizeof(PyObject *) * PyList_GET_SIZE(slotnames);
+        }
+        if (Py_TYPE(obj)->tp_basicsize > basicsize) {
+            Py_DECREF(slotnames);
+            Py_DECREF(state);
             PyErr_Format(PyExc_TypeError,
                          "cannot pickle '%.200s' object",
                          Py_TYPE(obj)->tp_name);
             return NULL;
         }
-        if (_PyObject_IsInstanceDictEmpty(obj)) {
-            state = Py_None;
-            Py_INCREF(state);
-        }
-        else {
-            state = PyObject_GenericGetDict(obj, NULL);
-            if (state == NULL) {
-                return NULL;
-            }
-        }
+    }
 
-        slotnames = _PyType_GetSlotNames(Py_TYPE(obj));
-        if (slotnames == NULL) {
+    if (slotnames != Py_None && PyList_GET_SIZE(slotnames) > 0) {
+        PyObject *slots;
+        Py_ssize_t slotnames_size, i;
+
+        slots = PyDict_New();
+        if (slots == NULL) {
+            Py_DECREF(slotnames);
             Py_DECREF(state);
             return NULL;
         }
 
-        assert(slotnames == Py_None || PyList_Check(slotnames));
-        if (required) {
-            Py_ssize_t basicsize = PyBaseObject_Type.tp_basicsize;
-            if (Py_TYPE(obj)->tp_dictoffset &&
-                (Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0)
-            {
-                basicsize += sizeof(PyObject *);
+        slotnames_size = PyList_GET_SIZE(slotnames);
+        for (i = 0; i < slotnames_size; i++) {
+            PyObject *name, *value;
+
+            name = PyList_GET_ITEM(slotnames, i);
+            Py_INCREF(name);
+            value = PyObject_GetAttr(obj, name);
+            if (_PyObject_LookupAttr(obj, name, &value) < 0) {
+                Py_DECREF(name);
+                goto error;
             }
-            if (Py_TYPE(obj)->tp_weaklistoffset) {
-                basicsize += sizeof(PyObject *);
+            if (value == NULL) {
+                Py_DECREF(name);
+                /* It is not an error if the attribute is not present. */
             }
-            if (slotnames != Py_None) {
-                basicsize += sizeof(PyObject *) * PyList_GET_SIZE(slotnames);
+            else {
+                int err = PyDict_SetItem(slots, name, value);
+                Py_DECREF(name);
+                Py_DECREF(value);
+                if (err) {
+                    goto error;
+                }
             }
-            if (Py_TYPE(obj)->tp_basicsize > basicsize) {
+
+            /* The list is stored on the class so it may mutate while we
+               iterate over it */
+            if (slotnames_size != PyList_GET_SIZE(slotnames)) {
+                PyErr_Format(PyExc_RuntimeError,
+                             "__slotsname__ changed size during iteration");
+                goto error;
+            }
+
+            /* We handle errors within the loop here. */
+            if (0) {
+              error:
                 Py_DECREF(slotnames);
+                Py_DECREF(slots);
                 Py_DECREF(state);
-                PyErr_Format(PyExc_TypeError,
-                             "cannot pickle '%.200s' object",
-                             Py_TYPE(obj)->tp_name);
                 return NULL;
             }
         }
 
-        if (slotnames != Py_None && PyList_GET_SIZE(slotnames) > 0) {
-            PyObject *slots;
-            Py_ssize_t slotnames_size, i;
+        /* If we found some slot attributes, pack them in a tuple along
+           the original attribute dictionary. */
+        if (PyDict_GET_SIZE(slots) > 0) {
+            PyObject *state2;
 
-            slots = PyDict_New();
-            if (slots == NULL) {
+            state2 = PyTuple_Pack(2, state, slots);
+            Py_DECREF(state);
+            if (state2 == NULL) {
                 Py_DECREF(slotnames);
-                Py_DECREF(state);
+                Py_DECREF(slots);
                 return NULL;
             }
-
-            slotnames_size = PyList_GET_SIZE(slotnames);
-            for (i = 0; i < slotnames_size; i++) {
-                PyObject *name, *value;
-
-                name = PyList_GET_ITEM(slotnames, i);
-                Py_INCREF(name);
-                if (_PyObject_LookupAttr(obj, name, &value) < 0) {
-                    goto error;
-                }
-                if (value == NULL) {
-                    Py_DECREF(name);
-                    /* It is not an error if the attribute is not present. */
-                }
-                else {
-                    int err = PyDict_SetItem(slots, name, value);
-                    Py_DECREF(name);
-                    Py_DECREF(value);
-                    if (err) {
-                        goto error;
-                    }
-                }
-
-                /* The list is stored on the class so it may mutate while we
-                   iterate over it */
-                if (slotnames_size != PyList_GET_SIZE(slotnames)) {
-                    PyErr_Format(PyExc_RuntimeError,
-                                 "__slotsname__ changed size during iteration");
-                    goto error;
-                }
-
-                /* We handle errors within the loop here. */
-                if (0) {
-                  error:
-                    Py_DECREF(slotnames);
-                    Py_DECREF(slots);
-                    Py_DECREF(state);
-                    return NULL;
-                }
-            }
-
-            /* If we found some slot attributes, pack them in a tuple along
-               the original attribute dictionary. */
-            if (PyDict_GET_SIZE(slots) > 0) {
-                PyObject *state2;
-
-                state2 = PyTuple_Pack(2, state, slots);
-                Py_DECREF(state);
-                if (state2 == NULL) {
-                    Py_DECREF(slotnames);
-                    Py_DECREF(slots);
-                    return NULL;
-                }
-                state = state2;
-            }
-            Py_DECREF(slots);
+            state = state2;
         }
-        Py_DECREF(slotnames);
-    }
-    else { /* getstate != NULL */
-        state = _PyObject_CallNoArgs(getstate);
-        Py_DECREF(getstate);
-        if (state == NULL)
-            return NULL;
+        Py_DECREF(slots);
     }
+    Py_DECREF(slotnames);
 
     return state;
 }
 
+static PyObject *
+object_getstate(PyObject *obj, int required)
+{
+    PyObject *getstate, *state;
+
+    getstate = PyObject_GetAttr(obj, &_Py_ID(__getstate__));
+    if (getstate == NULL) {
+        return NULL;
+    }
+    if (PyCFunction_Check(getstate) &&
+        PyCFunction_GET_SELF(getstate) == obj &&
+        PyCFunction_GET_FUNCTION(getstate) == object___getstate__)
+    {
+        /* If __getstate__ is not overriden pass the required argument. */
+        state = object_getstate_default(obj, required);
+    }
+    else {
+        state = _PyObject_CallNoArgs(getstate);
+    }
+    Py_DECREF(getstate);
+    return state;
+}
+
+PyObject *
+_PyObject_GetState(PyObject *obj)
+{
+    return object_getstate(obj, 0);
+}
+
+/*[clinic input]
+object.__getstate__
+
+Helper for pickle.
+[clinic start generated code]*/
+
+static PyObject *
+object___getstate___impl(PyObject *self)
+/*[clinic end generated code: output=5a2500dcb6217e9e input=692314d8fbe194ee]*/
+{
+    return object_getstate_default(self, 0);
+}
+
 static int
 _PyObject_GetNewArguments(PyObject *obj, PyObject **args, PyObject **kwargs)
 {
@@ -5309,8 +5341,7 @@ reduce_newobj(PyObject *obj)
         return NULL;
     }
 
-    state = _PyObject_GetState(obj,
-                !hasargs && !PyList_Check(obj) && !PyDict_Check(obj));
+    state = object_getstate(obj, !(hasargs || PyList_Check(obj) || PyDict_Check(obj)));
     if (state == NULL) {
         Py_DECREF(newobj);
         Py_DECREF(newargs);
@@ -5558,6 +5589,7 @@ error:
 static PyMethodDef object_methods[] = {
     OBJECT___REDUCE_EX___METHODDEF
     OBJECT___REDUCE___METHODDEF
+    OBJECT___GETSTATE___METHODDEF
     {"__subclasshook__", object_subclasshook, METH_CLASS | METH_VARARGS,
      object_subclasshook_doc},
     {"__init_subclass__", object_init_subclass, METH_CLASS | METH_NOARGS,