diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index 9503f4086b1cb9..b3893a15566fa6 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -14,6 +14,8 @@
import unittest
import unittest.mock
import os
+import weakref
+import gc
from weakref import proxy
import contextlib
@@ -1938,6 +1940,35 @@ def f():
return 1
self.assertEqual(f.cache_parameters(), {'maxsize': 1000, "typed": True})
+ def test_lru_cache_weakrefable(self):
+ @self.module.lru_cache
+ def test_function(x):
+ return x
+
+ class A:
+ @self.module.lru_cache
+ def test_method(self, x):
+ return (self, x)
+
+ @staticmethod
+ @self.module.lru_cache
+ def test_staticmethod(x):
+ return (self, x)
+
+ refs = [weakref.ref(test_function),
+ weakref.ref(A.test_method),
+ weakref.ref(A.test_staticmethod)]
+
+ for ref in refs:
+ self.assertIsNotNone(ref())
+
+ del A
+ del test_function
+ gc.collect()
+
+ for ref in refs:
+ self.assertIsNone(ref())
+
@py_functools.lru_cache()
def py_cached_func(x, y):
diff --git a/Misc/NEWS.d/next/Library/2020-05-05-17-12-47.bpo-40504.EX6wPn.rst b/Misc/NEWS.d/next/Library/2020-05-05-17-12-47.bpo-40504.EX6wPn.rst
new file mode 100644
index 00000000000000..261a49e4329280
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-05-05-17-12-47.bpo-40504.EX6wPn.rst
@@ -0,0 +1 @@
+:func:`functools.lru_cache` objects can now be the targets of weakrefs.
\ No newline at end of file
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index fd4b4c268cc979..d158d3bae157b2 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -783,6 +783,7 @@ typedef struct lru_cache_object {
Py_ssize_t misses;
PyObject *cache_info_type;
PyObject *dict;
+ PyObject *weakreflist;
} lru_cache_object;
static PyTypeObject lru_cache_type;
@@ -1196,6 +1197,7 @@ lru_cache_new(PyTypeObject *type, PyObject *args, PyObject *kw)
Py_INCREF(cache_info_type);
obj->cache_info_type = cache_info_type;
obj->dict = NULL;
+ obj->weakreflist = NULL;
return (PyObject *)obj;
}
@@ -1227,6 +1229,8 @@ lru_cache_dealloc(lru_cache_object *obj)
lru_list_elem *list;
/* bpo-31095: UnTrack is needed before calling any callbacks */
PyObject_GC_UnTrack(obj);
+ if (obj->weakreflist != NULL)
+ PyObject_ClearWeakRefs((PyObject*)obj);
list = lru_cache_unlink_list(obj);
Py_XDECREF(obj->cache);
@@ -1384,7 +1388,8 @@ static PyTypeObject lru_cache_type = {
(traverseproc)lru_cache_tp_traverse,/* tp_traverse */
(inquiry)lru_cache_tp_clear, /* tp_clear */
0, /* tp_richcompare */
- 0, /* tp_weaklistoffset */
+ offsetof(lru_cache_object, weakreflist),
+ /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
lru_cache_methods, /* tp_methods */
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