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gh-143939: Fix assignment to _PyThreadStateImpl.generator_return_kind #143951

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gh-143939: Fix assignment to _PyThreadStateImpl.generator_return_kind #143951

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16 changes: 16 additions & 0 deletions Lib/test/test_coroutines.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2265,6 +2265,22 @@ def c():
# before fixing, visible stack from throw would be shorter than from send.
self.assertEqual(len_send, len_throw)

def test_call_generator_in_frame_clear(self):
# gh-143939: Running a generator while clearing the coroutine's frame
# should not be misinterpreted as a yield.
class CallGeneratorOnDealloc:
def __del__(self):
def gen():
yield 1
next(gen())

async def coro():
obj = CallGeneratorOnDealloc()
return 42
Comment on lines +2271 to +2279
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@johnslavik johnslavik Jan 17, 2026

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A little bit smaller in size:

Suggested change
class CallGeneratorOnDealloc:
def __del__(self):
def gen():
yield 1
next(gen())
async def coro():
obj = CallGeneratorOnDealloc()
return 42
class CallGeneratorOnDealloc:
def __del__(self):
next(x for x in [42])
async def coro():
obj = CallGeneratorOnDealloc()


yielded, result = run_async(coro())
self.assertEqual(yielded, [])
self.assertEqual(result, 42)

@unittest.skipIf(
support.is_emscripten or support.is_wasi,
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-01-16-23-19-38.gh-issue-143939.w9TWch.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix erroneous "cannot reuse already awaited coroutine" error that could
occur when a generator was run during the process of clearing a coroutine's
frame.
3 changes: 3 additions & 0 deletions Objects/genobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,9 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult, int exc)

if (return_kind == GENERATOR_YIELD) {
assert(result != NULL && !_PyErr_Occurred(tstate));
#ifndef Py_GIL_DISABLED
assert(FRAME_STATE_SUSPENDED(gen->gi_frame_state));
#endif
*presult = result;
return PYGEN_NEXT;
}
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4 changes: 3 additions & 1 deletion Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1914,14 +1914,16 @@ 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;
assert(frame->frame_obj == NULL || frame->frame_obj->f_frame == frame);
frame->previous = NULL;
_PyFrame_ClearExceptCode(frame);
_PyErr_ClearExcState(&gen->gi_exc_state);
// gh-143939: There must not be any escaping calls between setting
// the generator return kind and returning from _PyEval_EvalFrame.
((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_RETURN;
}

void
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