GH-100964: Break cycles involving exception state when returning from generator (GH-107563)

1 files changed, 4 insertions, 5 deletions

diff --git a/Objects/genobject.c b/Objects/genobject.c
index a630f84..65782be 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -149,14 +149,16 @@ gen_dealloc(PyGenObject *gen)
         gen->gi_frame_state = FRAME_CLEARED;
         frame->previous = NULL;
         _PyFrame_ClearExceptCode(frame);
+        _PyErr_ClearExcState(&gen->gi_exc_state);
     }
+    assert(gen->gi_exc_state.exc_value == NULL);
     if (_PyGen_GetCode(gen)->co_flags & CO_COROUTINE) {
         Py_CLEAR(((PyCoroObject *)gen)->cr_origin_or_finalizer);
     }
     Py_DECREF(_PyGen_GetCode(gen));
     Py_CLEAR(gen->gi_name);
     Py_CLEAR(gen->gi_qualname);
-    _PyErr_ClearExcState(&gen->gi_exc_state);
+
     PyObject_GC_Del(gen);
 }
 
@@ -252,10 +254,7 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
             !PyErr_ExceptionMatches(PyExc_StopAsyncIteration));
     }
 
-    /* generator can't be rerun, so release the frame */
-    /* first clean reference cycle through stored exception traceback */
-    _PyErr_ClearExcState(&gen->gi_exc_state);
-
+    assert(gen->gi_exc_state.exc_value == NULL);
     assert(gen->gi_frame_state == FRAME_CLEARED);
     *presult = result;
     return result ? PYGEN_RETURN : PYGEN_ERROR;