[3.13] GH-100964: Fix reference cycle in exhausted generator frames (G… (#142904)

* [3.13] GH-100964: Fix reference cycle in exhausted generator frames (GH-141112)
(cherry picked from commit 92243dc)

Co-authored-by: Savannah Ostrowski <[email protected]>

Author: savannahostrowski

Lib/test/test_generators.py

@@ -112,6 +112,18 @@ def g3(): return (yield from f())
                 gen.send(2)
             self.assertEqual(cm.exception.value, 2)
 
+    def test_exhausted_generator_frame_cycle(self):
+        def g():
+            yield
+
+        generator = g()
+        frame = generator.gi_frame
+        self.assertIsNone(frame.f_back)
+        next(generator)
+        self.assertIsNone(frame.f_back)
+        next(generator, None)
+        self.assertIsNone(frame.f_back)
+
 
 class GeneratorTest(unittest.TestCase):
 

Misc/NEWS.d/next/Core and Builtins/2025-11-06-05-21-25.gh-issue-100964.TxPf1b.rst

@@ -0,0 +1 @@
+Fix reference cycle in exhausted generator frames. Patch by Savannah Ostrowski.

Python/ceval.c

@@ -1696,10 +1696,10 @@ clear_gen_frame(PyThreadState *tstate, _PyInterpreterFrame * frame)
     gen->gi_exc_state.previous_item = NULL;
     tstate->c_recursion_remaining--;
     assert(frame->frame_obj == NULL || frame->frame_obj->f_frame == frame);
+    frame->previous = NULL;
     _PyFrame_ClearExceptCode(frame);
     _PyErr_ClearExcState(&gen->gi_exc_state);
     tstate->c_recursion_remaining++;
-    frame->previous = NULL;
 }
 
 void