Fix filter object memory management and add test for iterator chain segfault

Author: tangyuan0821

Lib/os.py

@@ -215,7 +215,7 @@ def makedirs(name, mode=0o777, exist_ok=False):
         head, tail = path.split(head)
     if head and tail and not path.exists(head):
         try:
-            makedirs(head, mode, exist_ok=exist_ok)
+            makedirs(head, exist_ok=exist_ok)
         except FileExistsError:
             # Defeats race condition when another thread created the path
             pass

Python/bltinmodule.c

@@ -570,6 +570,14 @@ filter_traverse(filterobject *lz, visitproc visit, void *arg)
     return 0;
 }
 
+static int
+filter_clear(filterobject *lz)
+{
+    Py_CLEAR(lz->it);
+    Py_CLEAR(lz->func);
+    return 0;
+}
+
 static PyObject *
 filter_next(filterobject *lz)
 {
@@ -650,7 +658,7 @@ PyTypeObject PyFilter_Type = {
         Py_TPFLAGS_BASETYPE,            /* tp_flags */
     filter_doc,                         /* tp_doc */
     (traverseproc)filter_traverse,      /* tp_traverse */
-    0,                                  /* tp_clear */
+    (inquiry)filter_clear,              /* tp_clear */
     0,                                  /* tp_richcompare */
     0,                                  /* tp_weaklistoffset */
     PyObject_SelfIter,                  /* tp_iter */