bpo-40521: Empty frozenset is no longer a singleton (GH-21085)

* Revert "bpo-40521: Make the empty frozenset per interpreter (GH-21068)"

This reverts commit 261cfedf76.

* bpo-40521: Empty frozensets are no longer singletons

* Complete the removal of the frozenset singleton
This commit is contained in:
Raymond Hettinger 2020-06-23 08:42:55 -07:00 committed by GitHub
parent 522691c46e
commit f9bd05e83e
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GPG Key ID: 4AEE18F83AFDEB23
8 changed files with 8 additions and 54 deletions

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@ -244,8 +244,6 @@ struct _is {
/* Using a cache is very effective since typically only a single slice is
created and then deleted again. */
PySliceObject *slice_cache;
// The empty frozenset is a singleton.
PyObject *empty_frozenset;
struct _Py_tuple_state tuple;
struct _Py_list_state list;

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@ -62,7 +62,6 @@ extern void _PyFrame_Fini(PyThreadState *tstate);
extern void _PyDict_Fini(PyThreadState *tstate);
extern void _PyTuple_Fini(PyThreadState *tstate);
extern void _PyList_Fini(PyThreadState *tstate);
extern void _PySet_Fini(PyThreadState *tstate);
extern void _PyBytes_Fini(PyThreadState *tstate);
extern void _PyFloat_Fini(PyThreadState *tstate);
extern void _PySlice_Fini(PyThreadState *tstate);

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@ -158,13 +158,6 @@ class ContainerTestCase(unittest.TestCase, HelperMixin):
for constructor in (set, frozenset):
self.helper(constructor(self.d.keys()))
@support.cpython_only
def test_empty_frozenset_singleton(self):
# marshal.loads() must reuse the empty frozenset singleton
obj = frozenset()
obj2 = marshal.loads(marshal.dumps(obj))
self.assertIs(obj2, obj)
class BufferTestCase(unittest.TestCase, HelperMixin):

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@ -661,15 +661,6 @@ class TestFrozenSet(TestJointOps, unittest.TestCase):
s.__init__(self.otherword)
self.assertEqual(s, set(self.word))
def test_singleton_empty_frozenset(self):
f = frozenset()
efs = [frozenset(), frozenset([]), frozenset(()), frozenset(''),
frozenset(), frozenset([]), frozenset(()), frozenset(''),
frozenset(range(0)), frozenset(frozenset()),
frozenset(f), f]
# All of the empty frozensets should have just one id()
self.assertEqual(len(set(map(id, efs))), 1)
def test_constructor_identity(self):
s = self.thetype(range(3))
t = self.thetype(s)

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@ -2,8 +2,9 @@ Each interpreter now its has own free lists, singletons and caches:
* Free lists: float, tuple, list, dict, frame, context,
asynchronous generator.
* Singletons: empty tuple, empty frozenset, empty bytes string,
* Singletons: empty tuple, empty bytes string,
single byte character.
* Slice cache.
They are no longer shared by all interpreters.

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@ -0,0 +1 @@
Empty frozensets are no longer singletons.

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@ -978,38 +978,16 @@ make_new_set_basetype(PyTypeObject *type, PyObject *iterable)
static PyObject *
make_new_frozenset(PyTypeObject *type, PyObject *iterable)
{
PyObject *res;
if (type != &PyFrozenSet_Type) {
return make_new_set(type, iterable);
}
if (iterable != NULL) {
if (PyFrozenSet_CheckExact(iterable)) {
/* frozenset(f) is idempotent */
Py_INCREF(iterable);
return iterable;
}
res = make_new_set((PyTypeObject *)type, iterable);
if (res == NULL || PySet_GET_SIZE(res) != 0) {
return res;
}
/* If the created frozenset is empty, return the empty frozenset singleton instead */
Py_DECREF(res);
if (iterable != NULL && PyFrozenSet_CheckExact(iterable)) {
/* frozenset(f) is idempotent */
Py_INCREF(iterable);
return iterable;
}
// The empty frozenset is a singleton
PyInterpreterState *interp = _PyInterpreterState_GET();
res = interp->empty_frozenset;
if (res == NULL) {
interp->empty_frozenset = make_new_set((PyTypeObject *)type, NULL);
res = interp->empty_frozenset;
if (res == NULL) {
return NULL;
}
}
Py_INCREF(res);
return res;
return make_new_set((PyTypeObject *)type, iterable);
}
static PyObject *
@ -2304,12 +2282,6 @@ PySet_Add(PyObject *anyset, PyObject *key)
return set_add_key((PySetObject *)anyset, key);
}
void
_PySet_Fini(PyThreadState *tstate)
{
Py_CLEAR(tstate->interp->empty_frozenset);
}
int
_PySet_NextEntry(PyObject *set, Py_ssize_t *pos, PyObject **key, Py_hash_t *hash)
{

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@ -1253,7 +1253,6 @@ finalize_interp_types(PyThreadState *tstate, int is_main_interp)
_PyAsyncGen_Fini(tstate);
_PyContext_Fini(tstate);
_PySet_Fini(tstate);
_PyDict_Fini(tstate);
_PyList_Fini(tstate);
_PyTuple_Fini(tstate);