bpo-40504: Allow weakrefs to lru_cache objects (GH-19938)

1 files changed, 6 insertions, 1 deletions

diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index fd4b4c2..d158d3b 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 */