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Issue #18112: PEP 442 implementation (safe object finalization).

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Antoine Pitrou 2013-07-30 19:59:21 +02:00
parent c5d95b17ac
commit 796564c27b
25 changed files with 1254 additions and 321 deletions
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49
Doc/c-api/typeobj.rst
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@ -465,6 +465,14 @@ type objects) *must* have the :attr:`ob_size` field.
:const:`Py_TPFLAGS_HAVE_VERSION_TAG`.
.. data:: Py_TPFLAGS_HAVE_FINALIZE
This bit is set when the :attr:`tp_finalize` slot is present in the
type structure.
.. versionadded:: 3.4
.. c:member:: char* PyTypeObject.tp_doc
An optional pointer to a NUL-terminated C string giving the docstring for this
@ -968,6 +976,47 @@ type objects) *must* have the :attr:`ob_size` field.
This field is not inherited; it is calculated fresh by :c:func:`PyType_Ready`.
.. c:member:: destructor PyTypeObject.tp_finalize
An optional pointer to an instance finalization function. Its signature is
:c:type:`destructor`::
void tp_finalize(PyObject *)
If :attr:`tp_finalize` is set, the interpreter calls it once when
finalizing an instance. It is called either from the garbage
collector (if the instance is part of an isolated reference cycle) or
just before the object is deallocated. Either way, it is guaranteed
to be called before attempting to break reference cycles, ensuring
that it finds the object in a sane state.
:attr:`tp_finalize` should not mutate the current exception status;
therefore, a recommended way to write a non-trivial finalizer is::
static void
local_finalize(PyObject *self)
{
PyObject *error_type, *error_value, *error_traceback;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
/* ... */
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
}
For this field to be taken into account (even through inheritance),
you must also set the :const:`Py_TPFLAGS_HAVE_FINALIZE` flags bit.
This field is inherited by subtypes.
.. versionadded:: 3.4
.. seealso:: "Safe object finalization" (:pep:`442`)
.. c:member:: PyObject* PyTypeObject.tp_cache
Unused. Not inherited. Internal use only.

24
Doc/extending/newtypes.rst
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@ -157,7 +157,8 @@ to :const:`Py_TPFLAGS_DEFAULT`. ::
Py_TPFLAGS_DEFAULT, /* tp_flags */
All types should include this constant in their flags. It enables all of the
members defined by the current version of Python.
members defined until at least Python 3.3. If you need further members,
you will need to OR the corresponding flags.
We provide a doc string for the type in :attr:`tp_doc`. ::
@ -928,8 +929,9 @@ Finalization and De-allocation
This function is called when the reference count of the instance of your type is
reduced to zero and the Python interpreter wants to reclaim it. If your type
has memory to free or other clean-up to perform, put it here. The object itself
needs to be freed here as well. Here is an example of this function::
has memory to free or other clean-up to perform, you can put it here. The
object itself needs to be freed here as well. Here is an example of this
function::
static void
newdatatype_dealloc(newdatatypeobject * obj)
@ -981,6 +983,22 @@ done. This can be done using the :c:func:`PyErr_Fetch` and
Py_TYPE(obj)->tp_free((PyObject*)self);
}
.. note::
There are limitations to what you can safely do in a deallocator function.
First, if your type supports garbage collection (using :attr:`tp_traverse`
and/or :attr:`tp_clear`), some of the object's members can have been
cleared or finalized by the time :attr:`tp_dealloc` is called. Second, in
:attr:`tp_dealloc`, your object is in an unstable state: its reference
count is equal to zero. Any call to a non-trivial object or API (as in the
example above) might end up calling :attr:`tp_dealloc` again, causing a
double free and a crash.
Starting with Python 3.4, it is recommended not to put any complex
finalization code in :attr:`tp_dealloc`, and instead use the new
:c:member:`~PyTypeObject.tp_finalize` type method.
.. seealso::
:pep:`442` explains the new finalization scheme.
.. index::
single: string; object representation

7
Doc/includes/typestruct.h
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@ -70,4 +70,11 @@ typedef struct _typeobject {
PyObject *tp_subclasses;
PyObject *tp_weaklist;
destructor tp_del;
/* Type attribute cache version tag. Added in version 2.6 */
unsigned int tp_version_tag;
destructor tp_finalize;
} PyTypeObject;

27
Doc/library/gc.rst
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@ -176,24 +176,13 @@ values but should not rebind them):
.. data:: garbage
A list of objects which the collector found to be unreachable but could not be
freed (uncollectable objects). By default, this list contains only objects with
:meth:`__del__` methods. Objects that have :meth:`__del__` methods and are
part of a reference cycle cause the entire reference cycle to be uncollectable,
including objects not necessarily in the cycle but reachable only from it.
Python doesn't collect such cycles automatically because, in general, it isn't
possible for Python to guess a safe order in which to run the :meth:`__del__`
methods. If you know a safe order, you can force the issue by examining the
*garbage* list, and explicitly breaking cycles due to your objects within the
list. Note that these objects are kept alive even so by virtue of being in the
*garbage* list, so they should be removed from *garbage* too. For example,
after breaking cycles, do ``del gc.garbage[:]`` to empty the list. It's
generally better to avoid the issue by not creating cycles containing objects
with :meth:`__del__` methods, and *garbage* can be examined in that case to
verify that no such cycles are being created.
A list of objects which the collector found to be unreachable but could
not be freed (uncollectable objects). Starting with Python 3.4, this
list should be empty most of the time, except when using instances of
C extension types with a non-NULL ``tp_del`` slot.
If :const:`DEBUG_SAVEALL` is set, then all unreachable objects will be added
to this list rather than freed.
If :const:`DEBUG_SAVEALL` is set, then all unreachable objects will be
added to this list rather than freed.
.. versionchanged:: 3.2
If this list is non-empty at interpreter shutdown, a
@ -201,6 +190,10 @@ values but should not rebind them):
:const:`DEBUG_UNCOLLECTABLE` is set, in addition all uncollectable objects
are printed.
.. versionchanged:: 3.4
Following :pep:`442`, objects with a :meth:`__del__` method don't end
up in :attr:`gc.garbage` anymore.
.. data:: callbacks
A list of callbacks that will be invoked by the garbage collector before and

21
Doc/library/weakref.rst
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@ -529,22 +529,13 @@ follows::
def __del__(self):
self.remove()
This solution has a couple of serious problems:
This solution has a serious problem: 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.
* 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::
Using finalizers we can avoid this problem::
class TempDir:
def __init__(self):

10
Doc/reference/datamodel.rst
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@ -1120,12 +1120,10 @@ Basic customization
``sys.last_traceback`` keeps the stack frame alive). The first situation
can only be remedied by explicitly breaking the cycles; the latter two
situations can be resolved by storing ``None`` in ``sys.last_traceback``.
Circular references which are garbage are detected when the option cycle
detector is enabled (it's on by default), but can only be cleaned up if
there are no Python- level :meth:`__del__` methods involved. Refer to the
documentation for the :mod:`gc` module for more information about how
:meth:`__del__` methods are handled by the cycle detector, particularly
the description of the ``garbage`` value.
Circular references which are garbage are detected and cleaned up when
the cyclic garbage collector is enabled (it's on by default). Refer to the
documentation for the :mod:`gc` module for more information about this
topic.
.. warning::

15
Doc/whatsnew/3.4.rst
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@ -119,6 +119,21 @@ The :pep:`445` adds new Application Programming Interfaces (API) to customize
Python memory allocators.
.. _pep-442:
PEP 442: Safe object finalization
=================================
This PEP removes the current limitations and quirks of object finalization.
With it, objects with :meth:`__del__` methods, as well as generators
with :keyword:`finally` clauses, can be finalized when they are part of a
reference cycle.
.. seealso::
:pep:`442` - Safe object finalization
PEP written and implemented by Antoine Pitrou
Other Language Changes
======================

10
Include/object.h
View file

@ -408,6 +408,8 @@ typedef struct _typeobject {
/* Type attribute cache version tag. Added in version 2.6 */
unsigned int tp_version_tag;
destructor tp_finalize;
#ifdef COUNT_ALLOCS
/* these must be last and never explicitly initialized */
Py_ssize_t tp_allocs;
@ -529,6 +531,8 @@ PyAPI_FUNC(int) PyObject_Not(PyObject *);
PyAPI_FUNC(int) PyCallable_Check(PyObject *);
PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
PyAPI_FUNC(void) PyObject_CallFinalizer(PyObject *);
PyAPI_FUNC(int) PyObject_CallFinalizerFromDealloc(PyObject *);
/* Same as PyObject_Generic{Get,Set}Attr, but passing the attributes
dict as the last parameter. */
@ -646,6 +650,12 @@ given type object has a specified feature.
Py_TPFLAGS_HAVE_VERSION_TAG | \
0)
/* NOTE: The following flags reuse lower bits (removed as part of the
* Python 3.0 transition). */
/* Type structure has tp_finalize member (3.4) */
#define Py_TPFLAGS_HAVE_FINALIZE (1UL << 0)
#ifdef Py_LIMITED_API
#define PyType_HasFeature(t,f) ((PyType_GetFlags(t) & (f)) != 0)
#else

34
Include/objimpl.h
View file

@ -256,6 +256,30 @@ extern PyGC_Head *_PyGC_generation0;
#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
/* Bit 0 is set when tp_finalize is called */
#define _PyGC_REFS_MASK_FINALIZED (1 << 0)
/* The (N-1) most significant bits contain the gc state / refcount */
#define _PyGC_REFS_SHIFT (1)
#define _PyGC_REFS_MASK (((size_t) -1) << _PyGC_REFS_SHIFT)
#define _PyGCHead_REFS(g) ((g)->gc.gc_refs >> _PyGC_REFS_SHIFT)
#define _PyGCHead_SET_REFS(g, v) do { \
(g)->gc.gc_refs = ((g)->gc.gc_refs & ~_PyGC_REFS_MASK) \
| (v << _PyGC_REFS_SHIFT); \
} while (0)
#define _PyGCHead_DECREF(g) ((g)->gc.gc_refs -= 1 << _PyGC_REFS_SHIFT)
#define _PyGCHead_FINALIZED(g) (((g)->gc.gc_refs & _PyGC_REFS_MASK_FINALIZED) != 0)
#define _PyGCHead_SET_FINALIZED(g, v) do { \
(g)->gc.gc_refs = ((g)->gc.gc_refs & ~_PyGC_REFS_MASK_FINALIZED) \
| (v != 0); \
} while (0)
#define _PyGC_FINALIZED(o) _PyGCHead_FINALIZED(_Py_AS_GC(o))
#define _PyGC_SET_FINALIZED(o, v) _PyGCHead_SET_FINALIZED(_Py_AS_GC(o), v)
#define _PyGC_REFS(o) _PyGCHead_REFS(_Py_AS_GC(o))
#define _PyGC_REFS_UNTRACKED (-2)
#define _PyGC_REFS_REACHABLE (-3)
#define _PyGC_REFS_TENTATIVELY_UNREACHABLE (-4)
@ -264,9 +288,9 @@ extern PyGC_Head *_PyGC_generation0;
* collector it must be safe to call the ob_traverse method. */
#define _PyObject_GC_TRACK(o) do { \
PyGC_Head *g = _Py_AS_GC(o); \
if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \
if (_PyGCHead_REFS(g) != _PyGC_REFS_UNTRACKED) \
Py_FatalError("GC object already tracked"); \
g->gc.gc_refs = _PyGC_REFS_REACHABLE; \
_PyGCHead_SET_REFS(g, _PyGC_REFS_REACHABLE); \
g->gc.gc_next = _PyGC_generation0; \
g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \
g->gc.gc_prev->gc.gc_next = g; \
@ -279,8 +303,8 @@ extern PyGC_Head *_PyGC_generation0;
*/
#define _PyObject_GC_UNTRACK(o) do { \
PyGC_Head *g = _Py_AS_GC(o); \
assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \
g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \
assert(_PyGCHead_REFS(g) != _PyGC_REFS_UNTRACKED); \
_PyGCHead_SET_REFS(g, _PyGC_REFS_UNTRACKED); \
g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
g->gc.gc_next = NULL; \
@ -288,7 +312,7 @@ extern PyGC_Head *_PyGC_generation0;
/* True if the object is currently tracked by the GC. */
#define _PyObject_GC_IS_TRACKED(o) \
((_Py_AS_GC(o))->gc.gc_refs != _PyGC_REFS_UNTRACKED)
(_PyGC_REFS(o) != _PyGC_REFS_UNTRACKED)
/* True if the object may be tracked by the GC in the future, or already is.
This can be useful to implement some optimizations. */

10
Lib/test/test_descr.py
View file

@ -3736,18 +3736,8 @@ def __del__(self):
# bug).
del c
# If that didn't blow up, it's also interesting to see whether clearing
# the last container slot works: that will attempt to delete c again,
# which will cause c to get appended back to the container again
# "during" the del. (On non-CPython implementations, however, __del__
# is typically not called again.)
support.gc_collect()
self.assertEqual(len(C.container), 1)
del C.container[-1]
if support.check_impl_detail():
support.gc_collect()
self.assertEqual(len(C.container), 1)
self.assertEqual(C.container[-1].attr, 42)
# Make c mortal again, so that the test framework with -l doesn't report
# it as a leak.

513
Lib/test/test_finalization.py Normal file
View file

@ -0,0 +1,513 @@
"""
Tests for object finalization semantics, as outlined in PEP 442.
"""
import contextlib
import gc
import unittest
import weakref
import _testcapi
from test import support
class NonGCSimpleBase:
"""
The base class for all the objects under test, equipped with various
testing features.
"""
survivors = []
del_calls = []
tp_del_calls = []
errors = []
_cleaning = False
__slots__ = ()
@classmethod
def _cleanup(cls):
cls.survivors.clear()
cls.errors.clear()
gc.garbage.clear()
gc.collect()
cls.del_calls.clear()
cls.tp_del_calls.clear()
@classmethod
@contextlib.contextmanager
def test(cls):
"""
A context manager to use around all finalization tests.
"""
with support.disable_gc():
cls.del_calls.clear()
cls.tp_del_calls.clear()
NonGCSimpleBase._cleaning = False
try:
yield
if cls.errors:
raise cls.errors[0]
finally:
NonGCSimpleBase._cleaning = True
cls._cleanup()
def check_sanity(self):
"""
Check the object is sane (non-broken).
"""
def __del__(self):
"""
PEP 442 finalizer. Record that this was called, check the
object is in a sane state, and invoke a side effect.
"""
try:
if not self._cleaning:
self.del_calls.append(id(self))
self.check_sanity()
self.side_effect()
except Exception as e:
self.errors.append(e)
def side_effect(self):
"""
A side effect called on destruction.
"""
class SimpleBase(NonGCSimpleBase):
def __init__(self):
self.id_ = id(self)
def check_sanity(self):
assert self.id_ == id(self)
class NonGC(NonGCSimpleBase):
__slots__ = ()
class NonGCResurrector(NonGCSimpleBase):
__slots__ = ()
def side_effect(self):
"""
Resurrect self by storing self in a class-wide list.
"""
self.survivors.append(self)
class Simple(SimpleBase):
pass
class SimpleResurrector(NonGCResurrector, SimpleBase):
pass
class TestBase:
def setUp(self):
self.old_garbage = gc.garbage[:]
gc.garbage[:] = []
def tearDown(self):
# None of the tests here should put anything in gc.garbage
try:
self.assertEqual(gc.garbage, [])
finally:
del self.old_garbage
gc.collect()
def assert_del_calls(self, ids):
self.assertEqual(sorted(SimpleBase.del_calls), sorted(ids))
def assert_tp_del_calls(self, ids):
self.assertEqual(sorted(SimpleBase.tp_del_calls), sorted(ids))
def assert_survivors(self, ids):
self.assertEqual(sorted(id(x) for x in SimpleBase.survivors), sorted(ids))
def assert_garbage(self, ids):
self.assertEqual(sorted(id(x) for x in gc.garbage), sorted(ids))
def clear_survivors(self):
SimpleBase.survivors.clear()
class SimpleFinalizationTest(TestBase, unittest.TestCase):
"""
Test finalization without refcycles.
"""
def test_simple(self):
with SimpleBase.test():
s = Simple()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
def test_simple_resurrect(self):
with SimpleBase.test():
s = SimpleResurrector()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors(ids)
self.assertIsNot(wr(), None)
self.clear_survivors()
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
def test_non_gc(self):
with SimpleBase.test():
s = NonGC()
self.assertFalse(gc.is_tracked(s))
ids = [id(s)]
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
def test_non_gc_resurrect(self):
with SimpleBase.test():
s = NonGCResurrector()
self.assertFalse(gc.is_tracked(s))
ids = [id(s)]
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors(ids)
self.clear_survivors()
gc.collect()
self.assert_del_calls(ids * 2)
self.assert_survivors(ids)
class SelfCycleBase:
def __init__(self):
super().__init__()
self.ref = self
def check_sanity(self):
super().check_sanity()
assert self.ref is self
class SimpleSelfCycle(SelfCycleBase, Simple):
pass
class SelfCycleResurrector(SelfCycleBase, SimpleResurrector):
pass
class SuicidalSelfCycle(SelfCycleBase, Simple):
def side_effect(self):
"""
Explicitly break the reference cycle.
"""
self.ref = None
class SelfCycleFinalizationTest(TestBase, unittest.TestCase):
"""
Test finalization of an object having a single cyclic reference to
itself.
"""
def test_simple(self):
with SimpleBase.test():
s = SimpleSelfCycle()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
def test_simple_resurrect(self):
# Test that __del__ can resurrect the object being finalized.
with SimpleBase.test():
s = SelfCycleResurrector()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors(ids)
# XXX is this desirable?
self.assertIs(wr(), None)
# When trying to destroy the object a second time, __del__
# isn't called anymore (and the object isn't resurrected).
self.clear_survivors()
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
def test_simple_suicide(self):
# Test the GC is able to deal with an object that kills its last
# reference during __del__.
with SimpleBase.test():
s = SuicidalSelfCycle()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
class ChainedBase:
def chain(self, left):
self.suicided = False
self.left = left
left.right = self
def check_sanity(self):
super().check_sanity()
if self.suicided:
assert self.left is None
assert self.right is None
else:
left = self.left
if left.suicided:
assert left.right is None
else:
assert left.right is self
right = self.right
if right.suicided:
assert right.left is None
else:
assert right.left is self
class SimpleChained(ChainedBase, Simple):
pass
class ChainedResurrector(ChainedBase, SimpleResurrector):
pass
class SuicidalChained(ChainedBase, Simple):
def side_effect(self):
"""
Explicitly break the reference cycle.
"""
self.suicided = True
self.left = None
self.right = None
class CycleChainFinalizationTest(TestBase, unittest.TestCase):
"""
Test finalization of a cyclic chain. These tests are similar in
spirit to the self-cycle tests above, but the collectable object
graph isn't trivial anymore.
"""
def build_chain(self, classes):
nodes = [cls() for cls in classes]
for i in range(len(nodes)):
nodes[i].chain(nodes[i-1])
return nodes
def check_non_resurrecting_chain(self, classes):
N = len(classes)
with SimpleBase.test():
nodes = self.build_chain(classes)
ids = [id(s) for s in nodes]
wrs = [weakref.ref(s) for s in nodes]
del nodes
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
self.assertEqual([wr() for wr in wrs], [None] * N)
gc.collect()
self.assert_del_calls(ids)
def check_resurrecting_chain(self, classes):
N = len(classes)
with SimpleBase.test():
nodes = self.build_chain(classes)
N = len(nodes)
ids = [id(s) for s in nodes]
survivor_ids = [id(s) for s in nodes if isinstance(s, SimpleResurrector)]
wrs = [weakref.ref(s) for s in nodes]
del nodes
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors(survivor_ids)
# XXX desirable?
self.assertEqual([wr() for wr in wrs], [None] * N)
self.clear_survivors()
gc.collect()
self.assert_del_calls(ids)
self.assert_survivors([])
def test_homogenous(self):
self.check_non_resurrecting_chain([SimpleChained] * 3)
def test_homogenous_resurrect(self):
self.check_resurrecting_chain([ChainedResurrector] * 3)
def test_homogenous_suicidal(self):
self.check_non_resurrecting_chain([SuicidalChained] * 3)
def test_heterogenous_suicidal_one(self):
self.check_non_resurrecting_chain([SuicidalChained, SimpleChained] * 2)
def test_heterogenous_suicidal_two(self):
self.check_non_resurrecting_chain(
[SuicidalChained] * 2 + [SimpleChained] * 2)
def test_heterogenous_resurrect_one(self):
self.check_resurrecting_chain([ChainedResurrector, SimpleChained] * 2)
def test_heterogenous_resurrect_two(self):
self.check_resurrecting_chain(
[ChainedResurrector, SimpleChained, SuicidalChained] * 2)
def test_heterogenous_resurrect_three(self):
self.check_resurrecting_chain(
[ChainedResurrector] * 2 + [SimpleChained] * 2 + [SuicidalChained] * 2)
# NOTE: the tp_del slot isn't automatically inherited, so we have to call
# with_tp_del() for each instantiated class.
class LegacyBase(SimpleBase):
def __del__(self):
try:
# Do not invoke side_effect here, since we are now exercising
# the tp_del slot.
if not self._cleaning:
self.del_calls.append(id(self))
self.check_sanity()
except Exception as e:
self.errors.append(e)
def __tp_del__(self):
"""
Legacy (pre-PEP 442) finalizer, mapped to a tp_del slot.
"""
try:
if not self._cleaning:
self.tp_del_calls.append(id(self))
self.check_sanity()
self.side_effect()
except Exception as e:
self.errors.append(e)
@_testcapi.with_tp_del
class Legacy(LegacyBase):
pass
@_testcapi.with_tp_del
class LegacyResurrector(LegacyBase):
def side_effect(self):
"""
Resurrect self by storing self in a class-wide list.
"""
self.survivors.append(self)
@_testcapi.with_tp_del
class LegacySelfCycle(SelfCycleBase, LegacyBase):
pass
class LegacyFinalizationTest(TestBase, unittest.TestCase):
"""
Test finalization of objects with a tp_del.
"""
def tearDown(self):
# These tests need to clean up a bit more, since they create
# uncollectable objects.
gc.garbage.clear()
gc.collect()
super().tearDown()
def test_legacy(self):
with SimpleBase.test():
s = Legacy()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_tp_del_calls(ids)
self.assert_survivors([])
self.assertIs(wr(), None)
gc.collect()
self.assert_del_calls(ids)
self.assert_tp_del_calls(ids)
def test_legacy_resurrect(self):
with SimpleBase.test():
s = LegacyResurrector()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls(ids)
self.assert_tp_del_calls(ids)
self.assert_survivors(ids)
# weakrefs are cleared before tp_del is called.
self.assertIs(wr(), None)
self.clear_survivors()
gc.collect()
self.assert_del_calls(ids)
self.assert_tp_del_calls(ids * 2)
self.assert_survivors(ids)
self.assertIs(wr(), None)
def test_legacy_self_cycle(self):
# Self-cycles with legacy finalizers end up in gc.garbage.
with SimpleBase.test():
s = LegacySelfCycle()
ids = [id(s)]
wr = weakref.ref(s)
del s
gc.collect()
self.assert_del_calls([])
self.assert_tp_del_calls([])
self.assert_survivors([])
self.assert_garbage(ids)
self.assertIsNot(wr(), None)
# Break the cycle to allow collection
gc.garbage[0].ref = None
self.assert_garbage([])
self.assertIs(wr(), None)
def test_main():
support.run_unittest(__name__)
if __name__ == "__main__":
test_main()

18
Lib/test/test_gc.py
View file

@ -1,3 +1,4 @@
import _testcapi
import unittest
from test.support import (verbose, refcount_test, run_unittest,
strip_python_stderr)
@ -40,6 +41,7 @@ def it_happened(ignored):
# gc collects it.
self.wr = weakref.ref(C1055820(666), it_happened)
@_testcapi.with_tp_del
class Uncollectable(object):
"""Create a reference cycle with multiple __del__ methods.
@ -52,7 +54,7 @@ def __init__(self, partner=None):
self.partner = Uncollectable(partner=self)
else:
self.partner = partner
def __del__(self):
def __tp_del__(self):
pass
### Tests
@ -141,11 +143,12 @@ def __init__(self):
del a
self.assertNotEqual(gc.collect(), 0)
def test_finalizer(self):
def test_legacy_finalizer(self):
# A() is uncollectable if it is part of a cycle, make sure it shows up
# in gc.garbage.
@_testcapi.with_tp_del
class A:
def __del__(self): pass
def __tp_del__(self): pass
class B:
pass
a = A()
@ -165,11 +168,12 @@ class B:
self.fail("didn't find obj in garbage (finalizer)")
gc.garbage.remove(obj)
def test_finalizer_newclass(self):
def test_legacy_finalizer_newclass(self):
# A() is uncollectable if it is part of a cycle, make sure it shows up
# in gc.garbage.
@_testcapi.with_tp_del
class A(object):
def __del__(self): pass
def __tp_del__(self): pass
class B(object):
pass
a = A()
@ -570,12 +574,14 @@ def test_garbage_at_shutdown(self):
import subprocess
code = """if 1:
import gc
import _testcapi
@_testcapi.with_tp_del
class X:
def __init__(self, name):
self.name = name
def __repr__(self):
return "<X %%r>" %% self.name
def __del__(self):
def __tp_del__(self):
pass
x = X('first')

53
Lib/test/test_generators.py
View file

@ -1,3 +1,55 @@
import gc
import sys
import unittest
import weakref
from test import support
class FinalizationTest(unittest.TestCase):
def test_frame_resurrect(self):
# A generator frame can be resurrected by a generator's finalization.
def gen():
nonlocal frame
try:
yield
finally:
frame = sys._getframe()
g = gen()
wr = weakref.ref(g)
next(g)
del g
support.gc_collect()
self.assertIs(wr(), None)
self.assertTrue(frame)
del frame
support.gc_collect()
def test_refcycle(self):
# A generator caught in a refcycle gets finalized anyway.
old_garbage = gc.garbage[:]
finalized = False
def gen():
nonlocal finalized
try:
g = yield
yield 1
finally:
finalized = True
g = gen()
next(g)
g.send(g)
self.assertGreater(sys.getrefcount(g), 2)
self.assertFalse(finalized)
del g
support.gc_collect()
self.assertTrue(finalized)
self.assertEqual(gc.garbage, old_garbage)
tutorial_tests = """
Let's try a simple generator:
@ -1880,6 +1932,7 @@ def printsolution(self, x):
# so this works as expected in both ways of running regrtest.
def test_main(verbose=None):
from test import support, test_generators
support.run_unittest(__name__)
support.run_doctest(test_generators, verbose)
# This part isn't needed for regrtest, but for running the test directly.

45
Lib/test/test_io.py
View file

@ -1072,12 +1072,13 @@ def test_misbehaved_io_read(self):
def test_garbage_collection(self):
# C BufferedReader objects are collected.
# The Python version has __del__, so it ends into gc.garbage instead
rawio = self.FileIO(support.TESTFN, "w+b")
f = self.tp(rawio)
f.f = f
wr = weakref.ref(f)
del f
support.gc_collect()
with support.check_warnings(('', ResourceWarning)):
rawio = self.FileIO(support.TESTFN, "w+b")
f = self.tp(rawio)
f.f = f
wr = weakref.ref(f)
del f
support.gc_collect()
self.assertTrue(wr() is None, wr)
def test_args_error(self):
@ -1366,13 +1367,14 @@ def test_garbage_collection(self):
# C BufferedWriter objects are collected, and collecting them flushes
# all data to disk.
# The Python version has __del__, so it ends into gc.garbage instead
rawio = self.FileIO(support.TESTFN, "w+b")
f = self.tp(rawio)
f.write(b"123xxx")
f.x = f
wr = weakref.ref(f)
del f
support.gc_collect()
with support.check_warnings(('', ResourceWarning)):
rawio = self.FileIO(support.TESTFN, "w+b")
f = self.tp(rawio)
f.write(b"123xxx")
f.x = f
wr = weakref.ref(f)
del f
support.gc_collect()
self.assertTrue(wr() is None, wr)
with self.open(support.TESTFN, "rb") as f:
self.assertEqual(f.read(), b"123xxx")
@ -2607,14 +2609,15 @@ def test_garbage_collection(self):
# C TextIOWrapper objects are collected, and collecting them flushes
# all data to disk.
# The Python version has __del__, so it ends in gc.garbage instead.
rawio = io.FileIO(support.TESTFN, "wb")
b = self.BufferedWriter(rawio)
t = self.TextIOWrapper(b, encoding="ascii")
t.write("456def")
t.x = t
wr = weakref.ref(t)
del t
support.gc_collect()
with support.check_warnings(('', ResourceWarning)):
rawio = io.FileIO(support.TESTFN, "wb")
b = self.BufferedWriter(rawio)
t = self.TextIOWrapper(b, encoding="ascii")
t.write("456def")
t.x = t
wr = weakref.ref(t)
del t
support.gc_collect()
self.assertTrue(wr() is None, wr)
with self.open(support.TESTFN, "rb") as f:
self.assertEqual(f.read(), b"456def")

4
Lib/test/test_sys.py
View file

@ -864,11 +864,11 @@ def delx(self): del self.__x
check((1,2,3), vsize('') + 3*self.P)
# type
# static type: PyTypeObject
s = vsize('P2n15Pl4Pn9Pn11PI')
s = vsize('P2n15Pl4Pn9Pn11PIP')
check(int, s)
# (PyTypeObject + PyNumberMethods + PyMappingMethods +
# PySequenceMethods + PyBufferProcs + 4P)
s = vsize('P2n15Pl4Pn9Pn11PI') + struct.calcsize('34P 3P 10P 2P 4P')
s = vsize('P2n15Pl4Pn9Pn11PIP') + struct.calcsize('34P 3P 10P 2P 4P')
# Separate block for PyDictKeysObject with 4 entries
s += struct.calcsize("2nPn") + 4*struct.calcsize("n2P")
# class

2
Misc/NEWS
View file

@ -10,6 +10,8 @@ What's New in Python 3.4.0 Alpha 1?
Core and Builtins
-----------------
- Issue #18112: PEP 442 implementation (safe object finalization).
- Issue #18552: Check return value of PyArena_AddPyObject() in
obj2ast_object().

74
Modules/_io/bufferedio.c
View file

@ -190,7 +190,8 @@ PyTypeObject PyBufferedIOBase_Type = {
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
bufferediobase_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
@ -209,6 +210,16 @@ PyTypeObject PyBufferedIOBase_Type = {
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};
@ -220,7 +231,7 @@ typedef struct {
int detached;
int readable;
int writable;
int deallocating;
char finalizing;
/* True if this is a vanilla Buffered object (rather than a user derived
class) *and* the raw stream is a vanilla FileIO object. */
@ -384,8 +395,8 @@ _enter_buffered_busy(buffered *self)
static void
buffered_dealloc(buffered *self)
{
self->deallocating = 1;
if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
self->finalizing = 1;
if (_PyIOBase_finalize((PyObject *) self) < 0)
return;
_PyObject_GC_UNTRACK(self);
self->ok = 0;
@ -428,8 +439,6 @@ buffered_traverse(buffered *self, visitproc visit, void *arg)
static int
buffered_clear(buffered *self)
{
if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
return -1;
self->ok = 0;
Py_CLEAR(self->raw);
Py_CLEAR(self->dict);
@ -508,7 +517,7 @@ buffered_close(buffered *self, PyObject *args)
goto end;
}
if (self->deallocating) {
if (self->finalizing) {
PyObject *r = buffered_dealloc_warn(self, (PyObject *) self);
if (r)
Py_DECREF(r);
@ -1749,6 +1758,7 @@ static PyMethodDef bufferedreader_methods[] = {
static PyMemberDef bufferedreader_members[] = {
{"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
{"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
{NULL}
};
@ -1781,7 +1791,7 @@ PyTypeObject PyBufferedReader_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
bufferedreader_doc, /* tp_doc */
(traverseproc)buffered_traverse, /* tp_traverse */
(inquiry)buffered_clear, /* tp_clear */
@ -1800,6 +1810,16 @@ PyTypeObject PyBufferedReader_Type = {
(initproc)bufferedreader_init, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};
@ -2130,6 +2150,7 @@ static PyMethodDef bufferedwriter_methods[] = {
static PyMemberDef bufferedwriter_members[] = {
{"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
{"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
{NULL}
};
@ -2162,7 +2183,7 @@ PyTypeObject PyBufferedWriter_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
bufferedwriter_doc, /* tp_doc */
(traverseproc)buffered_traverse, /* tp_traverse */
(inquiry)buffered_clear, /* tp_clear */
@ -2181,6 +2202,16 @@ PyTypeObject PyBufferedWriter_Type = {
(initproc)bufferedwriter_init, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};
@ -2416,7 +2447,7 @@ PyTypeObject PyBufferedRWPair_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /* tp_flags */
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
bufferedrwpair_doc, /* tp_doc */
(traverseproc)bufferedrwpair_traverse, /* tp_traverse */
(inquiry)bufferedrwpair_clear, /* tp_clear */
@ -2435,6 +2466,16 @@ PyTypeObject PyBufferedRWPair_Type = {
(initproc)bufferedrwpair_init, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};
@ -2522,6 +2563,7 @@ static PyMethodDef bufferedrandom_methods[] = {
static PyMemberDef bufferedrandom_members[] = {
{"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
{"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
{NULL}
};
@ -2554,7 +2596,7 @@ PyTypeObject PyBufferedRandom_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
bufferedrandom_doc, /* tp_doc */
(traverseproc)buffered_traverse, /* tp_traverse */
(inquiry)buffered_clear, /* tp_clear */
@ -2573,4 +2615,14 @@ PyTypeObject PyBufferedRandom_Type = {
(initproc)bufferedrandom_init, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};

24
Modules/_io/fileio.c
View file

@ -51,7 +51,7 @@ typedef struct {
unsigned int writable : 1;
signed int seekable : 2; /* -1 means unknown */
unsigned int closefd : 1;
unsigned int deallocating: 1;
char finalizing;
PyObject *weakreflist;
PyObject *dict;
} fileio;
@ -128,7 +128,7 @@ fileio_close(fileio *self)
self->fd = -1;
Py_RETURN_NONE;
}
if (self->deallocating) {
if (self->finalizing) {
PyObject *r = fileio_dealloc_warn(self, (PyObject *) self);
if (r)
Py_DECREF(r);
@ -447,7 +447,7 @@ fileio_clear(fileio *self)
static void
fileio_dealloc(fileio *self)
{
self->deallocating = 1;
self->finalizing = 1;
if (_PyIOBase_finalize((PyObject *) self) < 0)
return;
_PyObject_GC_UNTRACK(self);
@ -1182,6 +1182,11 @@ static PyGetSetDef fileio_getsetlist[] = {
{NULL},
};
static PyMemberDef fileio_members[] = {
{"_finalizing", T_BOOL, offsetof(fileio, finalizing), 0},
{NULL}
};
PyTypeObject PyFileIO_Type = {
PyVarObject_HEAD_INIT(NULL, 0)
"_io.FileIO",
@ -1203,7 +1208,7 @@ PyTypeObject PyFileIO_Type = {
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /* tp_flags */
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
fileio_doc, /* tp_doc */
(traverseproc)fileio_traverse, /* tp_traverse */
(inquiry)fileio_clear, /* tp_clear */
@ -1212,7 +1217,7 @@ PyTypeObject PyFileIO_Type = {
0, /* tp_iter */
0, /* tp_iternext */
fileio_methods, /* tp_methods */
0, /* tp_members */
fileio_members, /* tp_members */
fileio_getsetlist, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
@ -1223,4 +1228,13 @@ PyTypeObject PyFileIO_Type = {
PyType_GenericAlloc, /* tp_alloc */
fileio_new, /* tp_new */
PyObject_GC_Del, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};

92
Modules/_io/iobase.c
View file

@ -196,21 +196,17 @@ iobase_close(PyObject *self, PyObject *args)
/* Finalization and garbage collection support */
int
_PyIOBase_finalize(PyObject *self)
static void
iobase_finalize(PyObject *self)
{
PyObject *res;
PyObject *tp, *v, *tb;
int closed = 1;
int is_zombie;
PyObject *error_type, *error_value, *error_traceback;
int closed;
_Py_IDENTIFIER(_finalizing);
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
/* If _PyIOBase_finalize() is called from a destructor, we need to
resurrect the object as calling close() can invoke arbitrary code. */
is_zombie = (Py_REFCNT(self) == 0);
if (is_zombie) {
++Py_REFCNT(self);
}
PyErr_Fetch(&tp, &v, &tb);
/* If `closed` doesn't exist or can't be evaluated as bool, then the
object is probably in an unusable state, so ignore. */
res = PyObject_GetAttr(self, _PyIO_str_closed);
@ -223,6 +219,10 @@ _PyIOBase_finalize(PyObject *self)
PyErr_Clear();
}
if (closed == 0) {
/* Signal close() that it was called as part of the object
finalization process. */
if (_PyObject_SetAttrId(self, &PyId__finalizing, Py_True))
PyErr_Clear();
res = PyObject_CallMethodObjArgs((PyObject *) self, _PyIO_str_close,
NULL);
/* Silencing I/O errors is bad, but printing spurious tracebacks is
@ -233,31 +233,25 @@ _PyIOBase_finalize(PyObject *self)
else
Py_DECREF(res);
}
PyErr_Restore(tp, v, tb);
if (is_zombie) {
if (--Py_REFCNT(self) != 0) {
/* The object lives again. The following code is taken from
slot_tp_del in typeobject.c. */
Py_ssize_t refcnt = Py_REFCNT(self);
_Py_NewReference(self);
Py_REFCNT(self) = refcnt;
/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
* we need to undo that. */
_Py_DEC_REFTOTAL;
/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there.
* If COUNT_ALLOCS, the original decref bumped tp_frees, and
* _Py_NewReference bumped tp_allocs: both of those need to be
* undone.
*/
#ifdef COUNT_ALLOCS
--Py_TYPE(self)->tp_frees;
--Py_TYPE(self)->tp_allocs;
#endif
return -1;
}
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
}
int
_PyIOBase_finalize(PyObject *self)
{
int is_zombie;
/* If _PyIOBase_finalize() is called from a destructor, we need to
resurrect the object as calling close() can invoke arbitrary code. */
is_zombie = (Py_REFCNT(self) == 0);
if (is_zombie)
return PyObject_CallFinalizerFromDealloc(self);
else {
PyObject_CallFinalizer(self);
return 0;
}
return 0;
}
static int
@ -270,8 +264,6 @@ iobase_traverse(iobase *self, visitproc visit, void *arg)
static int
iobase_clear(iobase *self)
{
if (_PyIOBase_finalize((PyObject *) self) < 0)
return -1;
Py_CLEAR(self->dict);
return 0;
}
@ -741,7 +733,7 @@ PyTypeObject PyIOBase_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
iobase_doc, /* tp_doc */
(traverseproc)iobase_traverse, /* tp_traverse */
(inquiry)iobase_clear, /* tp_clear */
@ -760,6 +752,16 @@ PyTypeObject PyIOBase_Type = {
0, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
(destructor)iobase_finalize, /* tp_finalize */
};
@ -905,7 +907,7 @@ PyTypeObject PyRawIOBase_Type = {
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
rawiobase_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
@ -924,4 +926,14 @@ PyTypeObject PyRawIOBase_Type = {
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};

37
Modules/_io/textio.c
View file

@ -173,7 +173,8 @@ PyTypeObject PyTextIOBase_Type = {
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
textiobase_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
@ -192,6 +193,16 @@ PyTypeObject PyTextIOBase_Type = {
0, /* tp_init */
0, /* tp_alloc */
0, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};
@ -691,7 +702,7 @@ typedef struct
char seekable;
char has_read1;
char telling;
char deallocating;
char finalizing;
/* Specialized encoding func (see below) */
encodefunc_t encodefunc;
/* Whether or not it's the start of the stream */
@ -1112,8 +1123,6 @@ textiowrapper_init(textio *self, PyObject *args, PyObject *kwds)
static int
_textiowrapper_clear(textio *self)
{
if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
return -1;
self->ok = 0;
Py_CLEAR(self->buffer);
Py_CLEAR(self->encoding);
@ -1131,9 +1140,10 @@ _textiowrapper_clear(textio *self)
static void
textiowrapper_dealloc(textio *self)
{
self->deallocating = 1;
if (_textiowrapper_clear(self) < 0)
self->finalizing = 1;
if (_PyIOBase_finalize((PyObject *) self) < 0)
return;
_textiowrapper_clear(self);
_PyObject_GC_UNTRACK(self);
if (self->weakreflist != NULL)
PyObject_ClearWeakRefs((PyObject *)self);
@ -2573,7 +2583,7 @@ textiowrapper_close(textio *self, PyObject *args)
}
else {
PyObject *exc = NULL, *val, *tb;
if (self->deallocating) {
if (self->finalizing) {
res = _PyObject_CallMethodId(self->buffer, &PyId__dealloc_warn, "O", self);
if (res)
Py_DECREF(res);
@ -2734,6 +2744,7 @@ static PyMemberDef textiowrapper_members[] = {
{"encoding", T_OBJECT, offsetof(textio, encoding), READONLY},
{"buffer", T_OBJECT, offsetof(textio, buffer), READONLY},
{"line_buffering", T_BOOL, offsetof(textio, line_buffering), READONLY},
{"_finalizing", T_BOOL, offsetof(textio, finalizing), 0},
{NULL}
};
@ -2770,7 +2781,7 @@ PyTypeObject PyTextIOWrapper_Type = {
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
textiowrapper_doc, /* tp_doc */
(traverseproc)textiowrapper_traverse, /* tp_traverse */
(inquiry)textiowrapper_clear, /* tp_clear */
@ -2789,4 +2800,14 @@ PyTypeObject PyTextIOWrapper_Type = {
(initproc)textiowrapper_init, /* tp_init */
0, /* tp_alloc */
PyType_GenericNew, /* tp_new */
0, /* tp_free */
0, /* tp_is_gc */
0, /* tp_bases */
0, /* tp_mro */
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
0, /* tp_del */
0, /* tp_version_tag */
0, /* tp_finalize */
};

80
Modules/_testcapimodule.c
View file

@ -2491,6 +2491,85 @@ test_pytime_object_to_timespec(PyObject *self, PyObject *args)
return Py_BuildValue("Nl", _PyLong_FromTime_t(sec), nsec);
}
static void
slot_tp_del(PyObject *self)
{
_Py_IDENTIFIER(__tp_del__);
PyObject *del, *res;
PyObject *error_type, *error_value, *error_traceback;
/* Temporarily resurrect the object. */
assert(self->ob_refcnt == 0);
self->ob_refcnt = 1;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
/* Execute __del__ method, if any. */
del = _PyObject_LookupSpecial(self, &PyId___tp_del__);
if (del != NULL) {
res = PyEval_CallObject(del, NULL);
if (res == NULL)
PyErr_WriteUnraisable(del);
else
Py_DECREF(res);
Py_DECREF(del);
}
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return; /* this is the normal path out */
/* __del__ resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
Py_ssize_t refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(!PyType_IS_GC(Py_TYPE(self)) ||
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
* we need to undo that. */
_Py_DEC_REFTOTAL;
/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there.
* If COUNT_ALLOCS, the original decref bumped tp_frees, and
* _Py_NewReference bumped tp_allocs: both of those need to be
* undone.
*/
#ifdef COUNT_ALLOCS
--Py_TYPE(self)->tp_frees;
--Py_TYPE(self)->tp_allocs;
#endif
}
static PyObject *
with_tp_del(PyObject *self, PyObject *args)
{
PyObject *obj;
PyTypeObject *tp;
if (!PyArg_ParseTuple(args, "O:with_tp_del", &obj))
return NULL;
tp = (PyTypeObject *) obj;
if (!PyType_Check(obj) || !PyType_HasFeature(tp, Py_TPFLAGS_HEAPTYPE)) {
PyErr_Format(PyExc_TypeError,
"heap type expected, got %R", obj);
return NULL;
}
tp->tp_del = slot_tp_del;
Py_INCREF(obj);
return obj;
}
static PyObject *
_test_incref(PyObject *ob)
{
@ -2789,6 +2868,7 @@ static PyMethodDef TestMethods[] = {
{"pytime_object_to_time_t", test_pytime_object_to_time_t, METH_VARARGS},
{"pytime_object_to_timeval", test_pytime_object_to_timeval, METH_VARARGS},
{"pytime_object_to_timespec", test_pytime_object_to_timespec, METH_VARARGS},
{"with_tp_del", with_tp_del, METH_VARARGS},
{"test_pymem",
(PyCFunction)test_pymem_alloc0, METH_NOARGS},
{"test_pymem_alloc0",

156
Modules/gcmodule.c
View file

@ -223,10 +223,10 @@ GC_TENTATIVELY_UNREACHABLE
#define GC_REACHABLE _PyGC_REFS_REACHABLE
#define GC_TENTATIVELY_UNREACHABLE _PyGC_REFS_TENTATIVELY_UNREACHABLE
#define IS_TRACKED(o) ((AS_GC(o))->gc.gc_refs != GC_UNTRACKED)
#define IS_REACHABLE(o) ((AS_GC(o))->gc.gc_refs == GC_REACHABLE)
#define IS_TRACKED(o) (_PyGC_REFS(o) != GC_UNTRACKED)
#define IS_REACHABLE(o) (_PyGC_REFS(o) == GC_REACHABLE)
#define IS_TENTATIVELY_UNREACHABLE(o) ( \
(AS_GC(o))->gc.gc_refs == GC_TENTATIVELY_UNREACHABLE)
_PyGC_REFS(o) == GC_TENTATIVELY_UNREACHABLE)
/*** list functions ***/
@ -341,8 +341,8 @@ update_refs(PyGC_Head *containers)
{
PyGC_Head *gc = containers->gc.gc_next;
for (; gc != containers; gc = gc->gc.gc_next) {
assert(gc->gc.gc_refs == GC_REACHABLE);
gc->gc.gc_refs = Py_REFCNT(FROM_GC(gc));
assert(_PyGCHead_REFS(gc) == GC_REACHABLE);
_PyGCHead_SET_REFS(gc, Py_REFCNT(FROM_GC(gc)));
/* Python's cyclic gc should never see an incoming refcount
* of 0: if something decref'ed to 0, it should have been
* deallocated immediately at that time.
@ -361,7 +361,7 @@ update_refs(PyGC_Head *containers)
* so serious that maybe this should be a release-build
* check instead of an assert?
*/
assert(gc->gc.gc_refs != 0);
assert(_PyGCHead_REFS(gc) != 0);
}
}
@ -376,9 +376,9 @@ visit_decref(PyObject *op, void *data)
* generation being collected, which can be recognized
* because only they have positive gc_refs.
*/
assert(gc->gc.gc_refs != 0); /* else refcount was too small */
if (gc->gc.gc_refs > 0)
gc->gc.gc_refs--;
assert(_PyGCHead_REFS(gc) != 0); /* else refcount was too small */
if (_PyGCHead_REFS(gc) > 0)
_PyGCHead_DECREF(gc);
}
return 0;
}
@ -407,7 +407,7 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
{
if (PyObject_IS_GC(op)) {
PyGC_Head *gc = AS_GC(op);
const Py_ssize_t gc_refs = gc->gc.gc_refs;
const Py_ssize_t gc_refs = _PyGCHead_REFS(gc);
if (gc_refs == 0) {
/* This is in move_unreachable's 'young' list, but
@ -415,7 +415,7 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
* we need to do is tell move_unreachable that it's
* reachable.
*/
gc->gc.gc_refs = 1;
_PyGCHead_SET_REFS(gc, 1);
}
else if (gc_refs == GC_TENTATIVELY_UNREACHABLE) {
/* This had gc_refs = 0 when move_unreachable got
@ -425,7 +425,7 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
* again.
*/
gc_list_move(gc, reachable);
gc->gc.gc_refs = 1;
_PyGCHead_SET_REFS(gc, 1);
}
/* Else there's nothing to do.
* If gc_refs > 0, it must be in move_unreachable's 'young'
@ -469,7 +469,7 @@ move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
while (gc != young) {
PyGC_Head *next;
if (gc->gc.gc_refs) {
if (_PyGCHead_REFS(gc)) {
/* gc is definitely reachable from outside the
* original 'young'. Mark it as such, and traverse
* its pointers to find any other objects that may
@ -480,8 +480,8 @@ move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
*/
PyObject *op = FROM_GC(gc);
traverseproc traverse = Py_TYPE(op)->tp_traverse;
assert(gc->gc.gc_refs > 0);
gc->gc.gc_refs = GC_REACHABLE;
assert(_PyGCHead_REFS(gc) > 0);
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
(void) traverse(op,
(visitproc)visit_reachable,
(void *)young);
@ -500,7 +500,7 @@ move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
*/
next = gc->gc.gc_next;
gc_list_move(gc, unreachable);
gc->gc.gc_refs = GC_TENTATIVELY_UNREACHABLE;
_PyGCHead_SET_REFS(gc, GC_TENTATIVELY_UNREACHABLE);
}
gc = next;
}
@ -520,22 +520,19 @@ untrack_dicts(PyGC_Head *head)
}
}
/* Return true if object has a finalization method. */
/* Return true if object has a pre-PEP 442 finalization method. */
static int
has_finalizer(PyObject *op)
has_legacy_finalizer(PyObject *op)
{
if (PyGen_CheckExact(op))
return PyGen_NeedsFinalizing((PyGenObject *)op);
else
return op->ob_type->tp_del != NULL;
return op->ob_type->tp_del != NULL;
}
/* Move the objects in unreachable with __del__ methods into `finalizers`.
/* Move the objects in unreachable with tp_del slots into `finalizers`.
* Objects moved into `finalizers` have gc_refs set to GC_REACHABLE; the
* objects remaining in unreachable are left at GC_TENTATIVELY_UNREACHABLE.
*/
static void
move_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
move_legacy_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
{
PyGC_Head *gc;
PyGC_Head *next;
@ -549,14 +546,14 @@ move_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
assert(IS_TENTATIVELY_UNREACHABLE(op));
next = gc->gc.gc_next;
if (has_finalizer(op)) {
if (has_legacy_finalizer(op)) {
gc_list_move(gc, finalizers);
gc->gc.gc_refs = GC_REACHABLE;
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
}
}
}
/* A traversal callback for move_finalizer_reachable. */
/* A traversal callback for move_legacy_finalizer_reachable. */
static int
visit_move(PyObject *op, PyGC_Head *tolist)
{
@ -564,7 +561,7 @@ visit_move(PyObject *op, PyGC_Head *tolist)
if (IS_TENTATIVELY_UNREACHABLE(op)) {
PyGC_Head *gc = AS_GC(op);
gc_list_move(gc, tolist);
gc->gc.gc_refs = GC_REACHABLE;
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
}
}
return 0;
@ -574,7 +571,7 @@ visit_move(PyObject *op, PyGC_Head *tolist)
* into finalizers set.
*/
static void
move_finalizer_reachable(PyGC_Head *finalizers)
move_legacy_finalizer_reachable(PyGC_Head *finalizers)
{
traverseproc traverse;
PyGC_Head *gc = finalizers->gc.gc_next;
@ -747,7 +744,7 @@ debug_cycle(char *msg, PyObject *op)
msg, Py_TYPE(op)->tp_name, op);
}
/* Handle uncollectable garbage (cycles with finalizers, and stuff reachable
/* Handle uncollectable garbage (cycles with tp_del slots, and stuff reachable
* only from such cycles).
* If DEBUG_SAVEALL, all objects in finalizers are appended to the module
* garbage list (a Python list), else only the objects in finalizers with
@ -757,7 +754,7 @@ debug_cycle(char *msg, PyObject *op)
* The finalizers list is made empty on a successful return.
*/
static int
handle_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
handle_legacy_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
{
PyGC_Head *gc = finalizers->gc.gc_next;
@ -769,7 +766,7 @@ handle_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
for (; gc != finalizers; gc = gc->gc.gc_next) {
PyObject *op = FROM_GC(gc);
if ((debug & DEBUG_SAVEALL) || has_finalizer(op)) {
if ((debug & DEBUG_SAVEALL) || has_legacy_finalizer(op)) {
if (PyList_Append(garbage, op) < 0)
return -1;
}
@ -779,6 +776,62 @@ handle_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
return 0;
}
static void
finalize_garbage(PyGC_Head *collectable, PyGC_Head *old)
{
destructor finalize;
PyGC_Head *gc = collectable->gc.gc_next;
for (; gc != collectable; gc = gc->gc.gc_next) {
PyObject *op = FROM_GC(gc);
if (!_PyGCHead_FINALIZED(gc) &&
PyType_HasFeature(Py_TYPE(op), Py_TPFLAGS_HAVE_FINALIZE) &&
(finalize = Py_TYPE(op)->tp_finalize) != NULL) {
_PyGCHead_SET_FINALIZED(gc, 1);
Py_INCREF(op);
finalize(op);
if (Py_REFCNT(op) == 1) {
/* op will be destroyed */
gc = gc->gc.gc_prev;
}
Py_DECREF(op);
}
}
}
/* Walk the collectable list and check that they are really unreachable
from the outside (some objects could have been resurrected by a
finalizer). */
static int
check_garbage(PyGC_Head *collectable)
{
PyGC_Head *gc;
for (gc = collectable->gc.gc_next; gc != collectable;
gc = gc->gc.gc_next) {
_PyGCHead_SET_REFS(gc, Py_REFCNT(FROM_GC(gc)));
assert(_PyGCHead_REFS(gc) != 0);
}
subtract_refs(collectable);
for (gc = collectable->gc.gc_next; gc != collectable;
gc = gc->gc.gc_next) {
assert(_PyGCHead_REFS(gc) >= 0);
if (_PyGCHead_REFS(gc) != 0)
return -1;
}
return 0;
}
static void
revive_garbage(PyGC_Head *collectable)
{
PyGC_Head *gc;
for (gc = collectable->gc.gc_next; gc != collectable;
gc = gc->gc.gc_next) {
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
}
}
/* Break reference cycles by clearing the containers involved. This is
* tricky business as the lists can be changing and we don't know which
* objects may be freed. It is possible I screwed something up here.
@ -792,7 +845,6 @@ delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
PyGC_Head *gc = collectable->gc.gc_next;
PyObject *op = FROM_GC(gc);
assert(IS_TENTATIVELY_UNREACHABLE(op));
if (debug & DEBUG_SAVEALL) {
PyList_Append(garbage, op);
}
@ -806,7 +858,7 @@ delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
if (collectable->gc.gc_next == gc) {
/* object is still alive, move it, it may die later */
gc_list_move(gc, old);
gc->gc.gc_refs = GC_REACHABLE;
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
}
}
}
@ -929,19 +981,15 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
}
/* All objects in unreachable are trash, but objects reachable from
* finalizers can't safely be deleted. Python programmers should take
* care not to create such things. For Python, finalizers means
* instance objects with __del__ methods. Weakrefs with callbacks
* can also call arbitrary Python code but they will be dealt with by
* handle_weakrefs().
* legacy finalizers (e.g. tp_del) can't safely be deleted.
*/
gc_list_init(&finalizers);
move_finalizers(&unreachable, &finalizers);
/* finalizers contains the unreachable objects with a finalizer;
move_legacy_finalizers(&unreachable, &finalizers);
/* finalizers contains the unreachable objects with a legacy finalizer;
* unreachable objects reachable *from* those are also uncollectable,
* and we move those into the finalizers list too.
*/
move_finalizer_reachable(&finalizers);
move_legacy_finalizer_reachable(&finalizers);
/* Collect statistics on collectable objects found and print
* debugging information.
@ -957,11 +1005,20 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
/* Clear weakrefs and invoke callbacks as necessary. */
m += handle_weakrefs(&unreachable, old);
/* Call tp_clear on objects in the unreachable set. This will cause
* the reference cycles to be broken. It may also cause some objects
* in finalizers to be freed.
*/
delete_garbage(&unreachable, old);
/* Call tp_finalize on objects which have one. */
finalize_garbage(&unreachable, old);
if (check_garbage(&unreachable)) {
revive_garbage(&unreachable);
gc_list_merge(&unreachable, old);
}
else {
/* Call tp_clear on objects in the unreachable set. This will cause
* the reference cycles to be broken. It may also cause some objects
* in finalizers to be freed.
*/
delete_garbage(&unreachable, old);
}
/* Collect statistics on uncollectable objects found and print
* debugging information. */
@ -992,7 +1049,7 @@ collect(int generation, Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable,
* reachable list of garbage. The programmer has to deal with
* this if they insist on creating this type of structure.
*/
(void)handle_finalizers(&finalizers, old);
(void)handle_legacy_finalizers(&finalizers, old);
/* Clear free list only during the collection of the highest
* generation */
@ -1662,7 +1719,8 @@ _PyObject_GC_Malloc(size_t basicsize)
sizeof(PyGC_Head) + basicsize);
if (g == NULL)
return PyErr_NoMemory();
g->gc.gc_refs = GC_UNTRACKED;
g->gc.gc_refs = 0;
_PyGCHead_SET_REFS(g, GC_UNTRACKED);
generations[0].count++; /* number of allocated GC objects */
if (generations[0].count > generations[0].threshold &&
enabled &&

103
Objects/genobject.c
View file

@ -15,6 +15,31 @@ gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
return 0;
}
static void
gen_finalize(PyObject *self)
{
PyGenObject *gen = (PyGenObject *)self;
PyObject *res;
PyObject *error_type, *error_value, *error_traceback;
if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
/* Generator isn't paused, so no need to close */
return;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
res = gen_close(gen, NULL);
if (res == NULL)
PyErr_WriteUnraisable(self);
else
Py_DECREF(res);
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
}
static void
gen_dealloc(PyGenObject *gen)
{
@ -27,12 +52,8 @@ gen_dealloc(PyGenObject *gen)
_PyObject_GC_TRACK(self);
if (gen->gi_frame != NULL && gen->gi_frame->f_stacktop != NULL) {
/* Generator is paused, so we need to close */
Py_TYPE(gen)->tp_del(self);
if (self->ob_refcnt > 0)
return; /* resurrected. :( */
}
if (PyObject_CallFinalizerFromDealloc(self))
return; /* resurrected. :( */
_PyObject_GC_UNTRACK(self);
Py_CLEAR(gen->gi_frame);
@ -40,7 +61,6 @@ gen_dealloc(PyGenObject *gen)
PyObject_GC_Del(gen);
}
static PyObject *
gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
{
@ -222,68 +242,6 @@ gen_close(PyGenObject *gen, PyObject *args)
return NULL;
}
static void
gen_del(PyObject *self)
{
PyObject *res;
PyObject *error_type, *error_value, *error_traceback;
PyGenObject *gen = (PyGenObject *)self;
if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
/* Generator isn't paused, so no need to close */
return;
/* Temporarily resurrect the object. */
assert(self->ob_refcnt == 0);
self->ob_refcnt = 1;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
res = gen_close(gen, NULL);
if (res == NULL)
PyErr_WriteUnraisable(self);
else
Py_DECREF(res);
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return; /* this is the normal path out */
/* close() resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
Py_ssize_t refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(PyType_IS_GC(Py_TYPE(self)) &&
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
* we need to undo that. */
_Py_DEC_REFTOTAL;
/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there.
* If COUNT_ALLOCS, the original decref bumped tp_frees, and
* _Py_NewReference bumped tp_allocs: both of those need to be
* undone.
*/
#ifdef COUNT_ALLOCS
--(Py_TYPE(self)->tp_frees);
--(Py_TYPE(self)->tp_allocs);
#endif
}
PyDoc_STRVAR(throw_doc,
"throw(typ[,val[,tb]]) -> raise exception in generator,\n\
@ -517,7 +475,8 @@ PyTypeObject PyGen_Type = {
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
0, /* tp_doc */
(traverseproc)gen_traverse, /* tp_traverse */
0, /* tp_clear */
@ -544,7 +503,9 @@ PyTypeObject PyGen_Type = {
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
gen_del, /* tp_del */
0, /* tp_del */
0, /* tp_version_tag */
gen_finalize, /* tp_finalize */
};
PyObject *

70
Objects/object.c
View file

@ -255,6 +255,72 @@ _PyObject_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
return PyObject_INIT_VAR(op, tp, nitems);
}
void
PyObject_CallFinalizer(PyObject *self)
{
PyTypeObject *tp = Py_TYPE(self);
/* The former could happen on heaptypes created from the C API, e.g.
PyType_FromSpec(). */
if (!PyType_HasFeature(tp, Py_TPFLAGS_HAVE_FINALIZE) ||
tp->tp_finalize == NULL)
return;
/* tp_finalize should only be called once. */
if (PyType_IS_GC(tp) && _PyGC_FINALIZED(self))
return;
tp->tp_finalize(self);
if (PyType_IS_GC(tp))
_PyGC_SET_FINALIZED(self, 1);
}
int
PyObject_CallFinalizerFromDealloc(PyObject *self)
{
Py_ssize_t refcnt;
/* Temporarily resurrect the object. */
if (self->ob_refcnt != 0) {
Py_FatalError("PyObject_CallFinalizerFromDealloc called on "
"object with a non-zero refcount");
}
self->ob_refcnt = 1;
PyObject_CallFinalizer(self);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return 0; /* this is the normal path out */
/* tp_finalize resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
if (PyType_IS_GC(Py_TYPE(self))) {
assert(_PyGC_REFS(self) != _PyGC_REFS_UNTRACKED);
}
/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
* we need to undo that. */
_Py_DEC_REFTOTAL;
/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there.
* If COUNT_ALLOCS, the original decref bumped tp_frees, and
* _Py_NewReference bumped tp_allocs: both of those need to be
* undone.
*/
#ifdef COUNT_ALLOCS
--Py_TYPE(self)->tp_frees;
--Py_TYPE(self)->tp_allocs;
#endif
return -1;
}
int
PyObject_Print(PyObject *op, FILE *fp, int flags)
{
@ -1981,7 +2047,7 @@ void
_PyTrash_deposit_object(PyObject *op)
{
assert(PyObject_IS_GC(op));
assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
assert(_PyGC_REFS(op) == _PyGC_REFS_UNTRACKED);
assert(op->ob_refcnt == 0);
_Py_AS_GC(op)->gc.gc_prev = (PyGC_Head *)_PyTrash_delete_later;
_PyTrash_delete_later = op;
@ -1993,7 +2059,7 @@ _PyTrash_thread_deposit_object(PyObject *op)
{
PyThreadState *tstate = PyThreadState_GET();
assert(PyObject_IS_GC(op));
assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
assert(_PyGC_REFS(op) == _PyGC_REFS_UNTRACKED);
assert(op->ob_refcnt == 0);
_Py_AS_GC(op)->gc.gc_prev = (PyGC_Head *) tstate->trash_delete_later;
tstate->trash_delete_later = op;

97
Objects/typeobject.c
View file

@ -921,6 +921,7 @@ subtype_dealloc(PyObject *self)
PyTypeObject *type, *base;
destructor basedealloc;
PyThreadState *tstate = PyThreadState_GET();
int has_finalizer;
/* Extract the type; we expect it to be a heap type */
type = Py_TYPE(self);
@ -936,6 +937,10 @@ subtype_dealloc(PyObject *self)
clear_slots(), or DECREF the dict, or clear weakrefs. */
/* Maybe call finalizer; exit early if resurrected */
if (type->tp_finalize) {
if (PyObject_CallFinalizerFromDealloc(self) < 0)
return;
}
if (type->tp_del) {
type->tp_del(self);
if (self->ob_refcnt > 0)
@ -987,25 +992,36 @@ subtype_dealloc(PyObject *self)
assert(base);
}
/* If we added a weaklist, we clear it. Do this *before* calling
the finalizer (__del__), clearing slots, or clearing the instance
dict. */
has_finalizer = type->tp_finalize || type->tp_del;
/* Maybe call finalizer; exit early if resurrected */
if (has_finalizer)
_PyObject_GC_TRACK(self);
if (type->tp_finalize) {
if (PyObject_CallFinalizerFromDealloc(self) < 0) {
/* Resurrected */
goto endlabel;
}
}
/* If we added a weaklist, we clear it. Do this *before* calling
tp_del, clearing slots, or clearing the instance dict. */
if (type->tp_weaklistoffset && !base->tp_weaklistoffset)
PyObject_ClearWeakRefs(self);
/* Maybe call finalizer; exit early if resurrected */
if (type->tp_del) {
_PyObject_GC_TRACK(self);
type->tp_del(self);
if (self->ob_refcnt > 0)
goto endlabel; /* resurrected */
else
_PyObject_GC_UNTRACK(self);
if (self->ob_refcnt > 0) {
/* Resurrected */
goto endlabel;
}
}
if (has_finalizer) {
_PyObject_GC_UNTRACK(self);
/* New weakrefs could be created during the finalizer call.
If this occurs, clear them out without calling their
finalizers since they might rely on part of the object
being finalized that has already been destroyed. */
If this occurs, clear them out without calling their
finalizers since they might rely on part of the object
being finalized that has already been destroyed. */
if (type->tp_weaklistoffset && !base->tp_weaklistoffset) {
/* Modeled after GET_WEAKREFS_LISTPTR() */
PyWeakReference **list = (PyWeakReference **) \
@ -2231,7 +2247,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
/* Initialize tp_flags */
type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HEAPTYPE |
Py_TPFLAGS_BASETYPE;
Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_FINALIZE;
if (base->tp_flags & Py_TPFLAGS_HAVE_GC)
type->tp_flags |= Py_TPFLAGS_HAVE_GC;
@ -4111,6 +4127,10 @@ inherit_slots(PyTypeObject *type, PyTypeObject *base)
COPYSLOT(tp_init);
COPYSLOT(tp_alloc);
COPYSLOT(tp_is_gc);
if ((type->tp_flags & Py_TPFLAGS_HAVE_FINALIZE) &&
(base->tp_flags & Py_TPFLAGS_HAVE_FINALIZE)) {
COPYSLOT(tp_finalize);
}
if ((type->tp_flags & Py_TPFLAGS_HAVE_GC) ==
(base->tp_flags & Py_TPFLAGS_HAVE_GC)) {
/* They agree about gc. */
@ -4736,6 +4756,18 @@ wrap_call(PyObject *self, PyObject *args, void *wrapped, PyObject *kwds)
return (*func)(self, args, kwds);
}
static PyObject *
wrap_del(PyObject *self, PyObject *args, void *wrapped)
{
destructor func = (destructor)wrapped;
if (!check_num_args(args, 0))
return NULL;
(*func)(self);
Py_RETURN_NONE;
}
static PyObject *
wrap_richcmpfunc(PyObject *self, PyObject *args, void *wrapped, int op)
{
@ -5617,16 +5649,12 @@ slot_tp_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
static void
slot_tp_del(PyObject *self)
slot_tp_finalize(PyObject *self)
{
_Py_IDENTIFIER(__del__);
PyObject *del, *res;
PyObject *error_type, *error_value, *error_traceback;
/* Temporarily resurrect the object. */
assert(self->ob_refcnt == 0);
self->ob_refcnt = 1;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
@ -5643,37 +5671,6 @@ slot_tp_del(PyObject *self)
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return; /* this is the normal path out */
/* __del__ resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
Py_ssize_t refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(!PyType_IS_GC(Py_TYPE(self)) ||
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
* we need to undo that. */
_Py_DEC_REFTOTAL;
/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there.
* If COUNT_ALLOCS, the original decref bumped tp_frees, and
* _Py_NewReference bumped tp_allocs: both of those need to be
* undone.
*/
#ifdef COUNT_ALLOCS
--Py_TYPE(self)->tp_frees;
--Py_TYPE(self)->tp_allocs;
#endif
}
@ -5782,7 +5779,7 @@ static slotdef slotdefs[] = {
"see help(type(x)) for signature",
PyWrapperFlag_KEYWORDS),
TPSLOT("__new__", tp_new, slot_tp_new, NULL, ""),
TPSLOT("__del__", tp_del, slot_tp_del, NULL, ""),
TPSLOT("__del__", tp_finalize, slot_tp_finalize, (wrapperfunc)wrap_del, ""),
BINSLOT("__add__", nb_add, slot_nb_add,
"+"),