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

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Merged
markshannon merged 1 commit into from
Aug 2, 2023
Merged

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

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-07-30-18-05-11.gh-issue-100964.HluhBJ.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Clear generators' exception state after ``return`` to break reference
cycles.
9 changes: 4 additions & 5 deletions Objects/genobject.c
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Expand Up @@ -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);
}

Expand Down Expand Up @@ -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;
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1 change: 1 addition & 0 deletions Python/ceval.c
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Expand Up @@ -1466,6 +1466,7 @@ clear_gen_frame(PyThreadState *tstate, _PyInterpreterFrame * frame)
tstate->c_recursion_remaining--;
assert(frame->frame_obj == NULL || frame->frame_obj->f_frame == frame);
_PyFrame_ClearExceptCode(frame);
_PyErr_ClearExcState(&gen->gi_exc_state);
tstate->c_recursion_remaining++;
frame->previous = NULL;
}
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