clear BufferedRWPair weakrefs on deallocation (closes #22517)

Lib/test/test_io.py

@@ -1524,6 +1524,12 @@ class BufferedRWPairTest(unittest.TestCase):
         pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(True))
         self.assertTrue(pair.isatty())
 
+    def test_weakref_clearing(self):
+        brw = self.tp(self.MockRawIO(), self.MockRawIO())
+        ref = weakref.ref(brw)
+        brw = None
+        ref = None # Shouldn't segfault.
+
 class CBufferedRWPairTest(BufferedRWPairTest):
     tp = io.BufferedRWPair
 

Misc/NEWS

@@ -17,6 +17,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22517: When a io.BufferedRWPair object is deallocated, clear its
+  weakrefs.
+
 - Issue #22419: Limit the length of incoming HTTP request in wsgiref server to
   65536 bytes and send a 414 error code for higher lengths. Patch contributed
   by Devin Cook.

Modules/_io/bufferedio.c

@@ -2254,6 +2254,8 @@ static void
 bufferedrwpair_dealloc(rwpair *self)
 {
     _PyObject_GC_UNTRACK(self);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
     Py_CLEAR(self->reader);
     Py_CLEAR(self->writer);
     Py_CLEAR(self->dict);