Backout 2e446e87ac5b; it breaks the unix buildbots.

4 files changed, 7 insertions, 500 deletions

diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst
index 5b5e460..ec50107 100644
--- a/Doc/library/weakref.rst
+++ b/Doc/library/weakref.rst
@@ -51,15 +51,10 @@ garbage collection.  :class:`WeakSet` implements the :class:`set` interface,
 but keeps weak references to its elements, just like a
 :class:`WeakKeyDictionary` does.
 
-:class:`finalize` provides a straight forward way to register a
-cleanup function to be called when an object is garbage collected.
-This is simpler to use than setting up a callback function on a raw
-weak reference.
-
-Most programs should find that using one of these weak container types
-or :class:`finalize` is all they need -- it's not usually necessary to
-create your own weak references directly.  The low-level machinery is
-exposed by the :mod:`weakref` module for the benefit of advanced uses.
+Most programs should find that using one of these weak container types is all
+they need -- it's not usually necessary to create your own weak references
+directly.  The low-level machinery used by the weak dictionary implementations
+is exposed by the :mod:`weakref` module for the benefit of advanced uses.
 
 Not all objects can be weakly referenced; those objects which can include class
 instances, functions written in Python (but not in C), instance methods, sets,
@@ -122,16 +117,7 @@ Extension types can easily be made to support weak references; see
       weakref.  If there is no callback or if the referent of the weakref is
       no longer alive then this attribute will have value ``None``.
 
-   .. note::
-
-      Like :meth:`__del__` methods, weak reference callbacks can be
-      called during interpreter shutdown when module globals have been
-      overwritten with :const:`None`.  This can make writing robust
-      weak reference callbacks a challenge.  Callbacks registered
-      using :class:`finalize` do not have to worry about this issue
-      because they will not be run after module teardown has begun.
-
-   .. versionchanged:: 3.4
+   .. versionadded:: 3.4
       Added the :attr:`__callback__` attribute.
 
 
@@ -243,66 +229,6 @@ These method have the same issues as the and :meth:`keyrefs` method of
 
    .. versionadded:: 3.4
 
-.. class:: finalize(obj, func, *args, **kwargs)
-
-   Return a callable finalizer object which will be called when *obj*
-   is garbage collected.  A finalizer is *alive* until it is called
-   (either explicitly or at garbage collection), and after that it is
-   *dead*.  Calling a live finalizer returns the result of evaluating
-   ``func(*arg, **kwargs)``, whereas calling a dead finalizer returns
-   :const:`None`.
-
-   Exceptions raised by finalizer callbacks during garbage collection
-   will be shown on the standard error output, but cannot be
-   propagated.  They are handled in the same way as exceptions raised
-   from an object's :meth:`__del__` method or a weak reference's
-   callback.
-
-   When the program exits, each remaining live finalizer is called
-   unless its :attr:`atexit` attribute has been set to false.  They
-   are called in reverse order of creation.
-
-   A finalizer will never invoke its callback during the later part of
-   the interpreter shutdown when module globals are liable to have
-   been replaced by :const:`None`.
-
-   .. method:: __call__()
-
-      If *self* is alive then mark it as dead and return the result of
-      calling ``func(*args, **kwargs)``.  If *self* is dead then return
-      :const:`None`.
-
-   .. method:: detach()
-
-      If *self* is alive then mark it as dead and return the tuple
-      ``(obj, func, args, kwargs)``.  If *self* is dead then return
-      :const:`None`.
-
-   .. method:: peek()
-
-      If *self* is alive then return the tuple ``(obj, func, args,
-      kwargs)``.  If *self* is dead then return :const:`None`.
-
-   .. attribute:: alive
-
-      Property which is true if the finalizer is alive, false otherwise.
-
-   .. attribute:: atexit
-
-      A writable boolean property which by default is true.  When the
-      program exits, it calls all remaining live finalizers for which
-      :attr:`.atexit` is true.  They are called in reverse order of
-      creation.
-
-   .. note::
-
-      It is important to ensure that *func*, *args* and *kwargs* do
-      not own any references to *obj*, either directly or indirectly,
-      since otherwise *obj* will never be garbage collected.  In
-      particular, *func* should not be a bound method of *obj*.
-
-   .. versionadded:: 3.4
-
 
 .. data:: ReferenceType
 
@@ -439,134 +365,3 @@ objects can still be retrieved by ID if they do.
    def id2obj(oid):
        return _id2obj_dict[oid]
 
-
-.. _finalize-examples:
-
-Finalizer Objects
------------------
-
-Often one uses :class:`finalize` to register a callback without
-bothering to keep the returned finalizer object.  For instance
-
-    >>> import weakref
-    >>> class Object:
-    ...     pass
-    ...
-    >>> kenny = Object()
-    >>> weakref.finalize(kenny, print, "You killed Kenny!")  #doctest:+ELLIPSIS
-    <finalize object at ...; for 'Object' at ...>
-    >>> del kenny
-    You killed Kenny!
-
-The finalizer can be called directly as well.  However the finalizer
-will invoke the callback at most once.
-
-    >>> def callback(x, y, z):
-    ...     print("CALLBACK")
-    ...     return x + y + z
-    ...
-    >>> obj = Object()
-    >>> f = weakref.finalize(obj, callback, 1, 2, z=3)
-    >>> assert f.alive
-    >>> assert f() == 6
-    CALLBACK
-    >>> assert not f.alive
-    >>> f()                     # callback not called because finalizer dead
-    >>> del obj                 # callback not called because finalizer dead
-
-You can unregister a finalizer using its :meth:`~finalize.detach`
-method.  This kills the finalizer and returns the arguments passed to
-the constructor when it was created.
-
-    >>> obj = Object()
-    >>> f = weakref.finalize(obj, callback, 1, 2, z=3)
-    >>> f.detach()                                           #doctest:+ELLIPSIS
-    (<__main__.Object object ...>, <function callback ...>, (1, 2), {'z': 3})
-    >>> newobj, func, args, kwargs = _
-    >>> assert not f.alive
-    >>> assert newobj is obj
-    >>> assert func(*args, **kwargs) == 6
-    CALLBACK
-
-Unless you set the :attr:`~finalize.atexit` attribute to
-:const:`False`, a finalizer will be called when the program exit if it
-is still alive.  For instance
-
-    >>> obj = Object()
-    >>> weakref.finalize(obj, print, "obj dead or exiting")  #doctest:+ELLIPSIS
-    <finalize object at ...; for 'Object' at ...>
-    >>> exit()                                               #doctest:+SKIP
-    obj dead or exiting
-
-
-Comparing finalizers with :meth:`__del__` methods
--------------------------------------------------
-
-Suppose we want to create a class whose instances represent temporary
-directories.  The directories should be deleted with their contents
-when the first of the following events occurs:
-
-* the object is garbage collected,
-* the object's :meth:`remove` method is called, or
-* the program exits.
-
-We might try to implement the class using a :meth:`__del__` method as
-follows::
-
-    class TempDir:
-        def __init__(self):
-            self.name = tempfile.mkdtemp()
-
-        def remove(self):
-            if self.name is not None:
-                shutil.rmtree(self.name)
-                self.name = None
-
-        @property
-        def removed(self):
-            return self.name is None
-
-        def __del__(self):
-            self.remove()
-
-This solution has a couple of serious problems:
-
-* There is no guarantee that the object will be garbage collected
-  before the program exists, so the directory might be left.  This is
-  because reference cycles containing an object with a :meth:`__del__`
-  method can never be collected.  And even if the :class:`TempDir`
-  object is not itself part of a reference cycle, it may still be kept
-  alive by some unkown uncollectable reference cycle.
-
-* The :meth:`__del__` method may be called at shutdown after the
-  :mod:`shutil` module has been cleaned up, in which case
-  :attr:`shutil.rmtree` will have been replaced by :const:`None`.
-  This will cause the :meth:`__del__` method to fail and the directory
-  will not be removed.
-
-Using finalizers we can avoid these problems::
-
-    class TempDir:
-        def __init__(self):
-            self.name = tempfile.mkdtemp()
-            self._finalizer = weakref.finalize(self, shutil.rmtree, self.name)
-
-        def remove(self):
-            self._finalizer()
-
-        @property
-        def removed(self):
-            return not self._finalizer.alive
-
-Defined like this, even if a :class:`TempDir` object is part of a
-reference cycle, that reference cycle can still be garbage collected.
-If the object never gets garbage collected the finalizer will still be
-called at exit.
-
-.. note::
-
-   If you create a finalizer object in a daemonic thread just as the
-   the program exits then there is the possibility that the finalizer
-   does not get called at exit.  However, in a daemonic thread
-   :func:`atexit.register`, ``try: ... finally: ...`` and ``with: ...``
-   do not guarantee that cleanup occurs either.
diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index 551d95c..e32e248 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -7,15 +7,11 @@ import operator
 import contextlib
 import copy
 
-from test import support, script_helper
+from test import support
 
 # Used in ReferencesTestCase.test_ref_created_during_del() .
 ref_from_del = None
 
-# Used by FinalizeTestCase as a global that may be replaced by None
-# when the interpreter shuts down.
-_global_var = 'foobar'
-
 class C:
     def method(self):
         pass
@@ -1555,151 +1551,6 @@ class WeakKeyDictionaryTestCase(mapping_tests.BasicTestMappingProtocol):
     def _reference(self):
         return self.__ref.copy()
 
-
-class FinalizeTestCase(unittest.TestCase):
-
-    class A:
-        pass
-
-    def _collect_if_necessary(self):
-        # we create no ref-cycles so in CPython no gc should be needed
-        if sys.implementation.name != 'cpython':
-            support.gc_collect()
-
-    def test_finalize(self):
-        def add(x,y,z):
-            res.append(x + y + z)
-            return x + y + z
-
-        a = self.A()
-
-        res = []
-        f = weakref.finalize(a, add, 67, 43, z=89)
-        self.assertEqual(f.alive, True)
-        self.assertEqual(f.peek(), (a, add, (67,43), {'z':89}))
-        self.assertEqual(f(), 199)
-        self.assertEqual(f(), None)
-        self.assertEqual(f(), None)
-        self.assertEqual(f.peek(), None)
-        self.assertEqual(f.detach(), None)
-        self.assertEqual(f.alive, False)
-        self.assertEqual(res, [199])
-
-        res = []
-        f = weakref.finalize(a, add, 67, 43, 89)
-        self.assertEqual(f.peek(), (a, add, (67,43,89), {}))
-        self.assertEqual(f.detach(), (a, add, (67,43,89), {}))
-        self.assertEqual(f(), None)
-        self.assertEqual(f(), None)
-        self.assertEqual(f.peek(), None)
-        self.assertEqual(f.detach(), None)
-        self.assertEqual(f.alive, False)
-        self.assertEqual(res, [])
-
-        res = []
-        f = weakref.finalize(a, add, x=67, y=43, z=89)
-        del a
-        self._collect_if_necessary()
-        self.assertEqual(f(), None)
-        self.assertEqual(f(), None)
-        self.assertEqual(f.peek(), None)
-        self.assertEqual(f.detach(), None)
-        self.assertEqual(f.alive, False)
-        self.assertEqual(res, [199])
-
-    def test_order(self):
-        a = self.A()
-        res = []
-
-        f1 = weakref.finalize(a, res.append, 'f1')
-        f2 = weakref.finalize(a, res.append, 'f2')
-        f3 = weakref.finalize(a, res.append, 'f3')
-        f4 = weakref.finalize(a, res.append, 'f4')
-        f5 = weakref.finalize(a, res.append, 'f5')
-
-        # make sure finalizers can keep themselves alive
-        del f1, f4
-
-        self.assertTrue(f2.alive)
-        self.assertTrue(f3.alive)
-        self.assertTrue(f5.alive)
-
-        self.assertTrue(f5.detach())
-        self.assertFalse(f5.alive)
-
-        f5()                       # nothing because previously unregistered
-        res.append('A')
-        f3()                       # => res.append('f3')
-        self.assertFalse(f3.alive)
-        res.append('B')
-        f3()                       # nothing because previously called
-        res.append('C')
-        del a
-        self._collect_if_necessary()
-                                   # => res.append('f4')
-                                   # => res.append('f2')
-                                   # => res.append('f1')
-        self.assertFalse(f2.alive)
-        res.append('D')
-        f2()                       # nothing because previously called by gc
-
-        expected = ['A', 'f3', 'B', 'C', 'f4', 'f2', 'f1', 'D']
-        self.assertEqual(res, expected)
-
-    def test_all_freed(self):
-        # we want a weakrefable subclass of weakref.finalize
-        class MyFinalizer(weakref.finalize):
-            pass
-
-        a = self.A()
-        res = []
-        def callback():
-            res.append(123)
-        f = MyFinalizer(a, callback)
-
-        wr_callback = weakref.ref(callback)
-        wr_f = weakref.ref(f)
-        del callback, f
-
-        self.assertIsNotNone(wr_callback())
-        self.assertIsNotNone(wr_f())
-
-        del a
-        self._collect_if_necessary()
-
-        self.assertIsNone(wr_callback())
-        self.assertIsNone(wr_f())
-        self.assertEqual(res, [123])
-
-    @classmethod
-    def run_in_child(cls):
-        def error():
-            # Create an atexit finalizer from inside a finalizer called
-            # at exit.  This should be the next to be run.
-            g1 = weakref.finalize(cls, print, 'g1')
-            print('f3 error')
-            1/0
-
-        # cls should stay alive till atexit callbacks run
-        f1 = weakref.finalize(cls, print, 'f1', _global_var)
-        f2 = weakref.finalize(cls, print, 'f2', _global_var)
-        f3 = weakref.finalize(cls, error)
-        f4 = weakref.finalize(cls, print, 'f4', _global_var)
-
-        assert f1.atexit == True
-        f2.atexit = False
-        assert f3.atexit == True
-        assert f4.atexit == True
-
-    def test_atexit(self):
-        prog = ('from test.test_weakref import FinalizeTestCase;'+
-                'FinalizeTestCase.run_in_child()')
-        rc, out, err = script_helper.assert_python_ok('-c', prog)
-        out = out.decode('ascii').splitlines()
-        self.assertEqual(out, ['f4 foobar', 'f3 error', 'g1', 'f1 foobar'])
-        self.assertTrue(b'ZeroDivisionError' in err)
-
-
 libreftest = """ Doctest for examples in the library reference: weakref.rst
 
 >>> import weakref
@@ -1793,7 +1644,6 @@ def test_main():
         WeakValueDictionaryTestCase,
         WeakKeyDictionaryTestCase,
         SubclassableWeakrefTestCase,
-        FinalizeTestCase,
         )
     support.run_doctest(sys.modules[__name__])
 
diff --git a/Lib/weakref.py b/Lib/weakref.py
index 7a17d17..8f9c107 100644
--- a/Lib/weakref.py
+++ b/Lib/weakref.py
@@ -21,16 +21,13 @@ from _weakref import (
 from _weakrefset import WeakSet, _IterationGuard
 
 import collections  # Import after _weakref to avoid circular import.
-import sys
-import atexit
-import itertools
 
 ProxyTypes = (ProxyType, CallableProxyType)
 
 __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
            "WeakKeyDictionary", "ReferenceType", "ProxyType",
            "CallableProxyType", "ProxyTypes", "WeakValueDictionary",
-           "WeakSet", "WeakMethod", "finalize"]
+           "WeakSet", "WeakMethod"]
 
 
 class WeakMethod(ref):
@@ -439,135 +436,3 @@ class WeakKeyDictionary(collections.MutableMapping):
                 d[ref(key, self._remove)] = value
         if len(kwargs):
             self.update(kwargs)
-
-
-class finalize:
-    """Class for finalization of weakrefable objects
-
-    finalize(obj, func, *args, **kwargs) returns a callable finalizer
-    object which will be called when obj is garbage collected. The
-    first time the finalizer is called it evaluates func(*arg, **kwargs)
-    and returns the result. After this the finalizer is dead, and
-    calling it just returns None.
-
-    When the program exits any remaining finalizers for which the
-    atexit attribute is true will be run in reverse order of creation.
-    By default atexit is true.
-    """
-
-    # Finalizer objects don't have any state of their own.  They are
-    # just used as keys to lookup _Info objects in the registry.  This
-    # ensures that they cannot be part of a ref-cycle.
-
-    __slots__ = ()
-    _registry = {}
-    _shutdown = False
-    _index_iter = itertools.count()
-    _dirty = False
-
-    class _Info:
-        __slots__ = ("weakref", "func", "args", "kwargs", "atexit", "index")
-
-    def __init__(self, obj, func, *args, **kwargs):
-        info = self._Info()
-        info.weakref = ref(obj, self)
-        info.func = func
-        info.args = args
-        info.kwargs = kwargs or None
-        info.atexit = True
-        info.index = next(self._index_iter)
-        self._registry[self] = info
-        finalize._dirty = True
-
-    def __call__(self, _=None):
-        """If alive then mark as dead and return func(*args, **kwargs);
-        otherwise return None"""
-        info = self._registry.pop(self, None)
-        if info and not self._shutdown:
-            return info.func(*info.args, **(info.kwargs or {}))
-
-    def detach(self):
-        """If alive then mark as dead and return (obj, func, args, kwargs);
-        otherwise return None"""
-        info = self._registry.get(self)
-        obj = info and info.weakref()
-        if obj is not None and self._registry.pop(self, None):
-            return (obj, info.func, info.args, info.kwargs or {})
-
-    def peek(self):
-        """If alive then return (obj, func, args, kwargs);
-        otherwise return None"""
-        info = self._registry.get(self)
-        obj = info and info.weakref()
-        if obj is not None:
-            return (obj, info.func, info.args, info.kwargs or {})
-
-    @property
-    def alive(self):
-        """Whether finalizer is alive"""
-        return self in self._registry
-
-    @property
-    def atexit(self):
-        """Whether finalizer should be called at exit"""
-        info = self._registry.get(self)
-        return bool(info) and info.atexit
-
-    @atexit.setter
-    def atexit(self, value):
-        info = self._registry.get(self)
-        if info:
-            info.atexit = bool(value)
-
-    def __repr__(self):
-        info = self._registry.get(self)
-        obj = info and info.weakref()
-        if obj is None:
-            return '<%s object at %#x; dead>' % (type(self).__name__, id(self))
-        else:
-            return '<%s object at %#x; for %r at %#x>' % \
-                (type(self).__name__, id(self), type(obj).__name__, id(obj))
-
-    @classmethod
-    def _select_for_exit(cls):
-        # Return live finalizers marked for exit, oldest first
-        L = [(f,i) for (f,i) in cls._registry.items() if i.atexit]
-        L.sort(key=lambda item:item[1].index)
-        return [f for (f,i) in L]
-
-    @classmethod
-    def _exitfunc(cls):
-        # At shutdown invoke finalizers for which atexit is true.
-        # This is called once all other non-daemonic threads have been
-        # joined.
-        reenable_gc = False
-        try:
-            if cls._registry:
-                import gc
-                if gc.isenabled():
-                    reenable_gc = True
-                    gc.disable()
-                pending = None
-                while True:
-                    if pending is None or finalize._dirty:
-                        pending = cls._select_for_exit()
-                        finalize._dirty = False
-                    if not pending:
-                        break
-                    f = pending.pop()
-                    try:
-                        # gc is disabled, so (assuming no daemonic
-                        # threads) the following is the only line in
-                        # this function which might trigger creation
-                        # of a new finalizer
-                        f()
-                    except Exception:
-                        sys.excepthook(*sys.exc_info())
-                    assert f not in cls._registry
-        finally:
-            # prevent any more finalizers from executing during shutdown
-            finalize._shutdown = True
-            if reenable_gc:
-                gc.enable()
-
-atexit.register(finalize._exitfunc)
diff --git a/Misc/NEWS b/Misc/NEWS
index 42bd382..70e8f21 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -69,9 +69,6 @@ Core and Builtins
 Library
 -------
 
-- Issue #15528: Add weakref.finalize to support finalization using
-  weakref callbacks.
-
 - Issue #14173: Avoid crashing when reading a signal handler during
   interpreter shutdown.