Set generator_return_kind in clear_gen_frame

Generator calls may be nested so it's not sufficient to set the field
before the call to PyEval_Frame.

Author: colesbury

Objects/genobject.c

@@ -235,21 +235,19 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult, int exc)
         _PyErr_ChainStackItem();
     }
 
-    // The generator_return_kind field is used to distinguish between a
-    // yield and a return from within _PyEval_EvalFrame(). Earlier versions
-    // of CPython (prior to 3.15) used gi_frame_state for this purpose, but
-    // that requires the GIL for thread-safety.
-    ((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_RETURN;
-
     EVAL_CALL_STAT_INC(EVAL_CALL_GENERATOR);
-    PyObject *result = _PyEval_EvalFrame(tstate, frame, exc);
+    PyObject *result = PyEval_EvalFrame(tstate, frame, exc);
     assert(tstate->exc_info == prev_exc_info);
 #ifndef Py_GIL_DISABLED
     assert(gen->gi_exc_state.previous_item == NULL);
     assert(frame->previous == NULL);
     assert(gen->gi_frame_state != FRAME_EXECUTING);
 #endif
 
+    // The generator_return_kind field is used to distinguish between a
+    // yield and a return from within PyEval_EvalFrame(). Earlier versions
+    // of CPython (prior to 3.15) used gi_frame_state for this purpose, but
+    // that requires the GIL for thread-safety.
     int return_kind = ((_PyThreadStateImpl *)tstate)->generator_return_kind;
 
     if (return_kind == GENERATOR_YIELD) {

Python/ceval.c

@@ -2305,6 +2305,7 @@ clear_gen_frame(PyThreadState *tstate, _PyInterpreterFrame * frame)
     assert(frame->owner == FRAME_OWNED_BY_GENERATOR);
     PyGenObject *gen = _PyGen_GetGeneratorFromFrame(frame);
     FT_ATOMIC_STORE_INT8_RELEASE(gen->gi_frame_state, FRAME_CLEARED);
+    ((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_RETURN;
     assert(tstate->exc_info == &gen->gi_exc_state);
     tstate->exc_info = gen->gi_exc_state.previous_item;
     gen->gi_exc_state.previous_item = NULL;