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pythongh-156371: Fix missing PyRefTracer_DESTROY events for trashcan objects (pythongh-156372)
(cherry picked from commit 3dfa574) Co-authored-by: Donghee Na <donghee.na@python.org>
1 parent 63fab14 commit 2844af0

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‎Lib/test/test_capi/test_object.py‎

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Original file line numberDiff line numberDiff line change
@@ -342,5 +342,20 @@ def test_pyobject_dump(self):
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self.assertRegex(output, r'<object at .* is freed>')
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class RefTracerTest(unittest.TestCase):
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@support.requires_resource('cpu')
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@support.skip_emscripten_stack_overflow()
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@support.skip_wasi_stack_overflow()
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def test_destroy_traced_for_trashcan_deferred_objects(self):
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depth = 200_000
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chain = None
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for _ in range(depth):
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chain = [chain]
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_testcapi.start_counting_list_destroys()
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del chain
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destroys = _testcapi.stop_counting_list_destroys()
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self.assertEqual(destroys, depth)
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if __name__ == "__main__":
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unittest.main()

‎Misc/NEWS.d/next/Core_and_Builtins/2026-08-26-01-08-38.gh-issue-156371.USpwKG.rst‎

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@@ -0,0 +1,2 @@
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Fix missing ``PyRefTracer_DESTROY`` events for trashcan deferred objects.
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Patch by Donghee Na.

‎Modules/_testcapimodule.c‎

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@@ -39,6 +39,7 @@ static struct PyModuleDef _testcapimodule;
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// Module state
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typedef struct {
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PyObject *error; // _testcapi.error object
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Py_ssize_t list_destroys;
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} testcapistate_t;
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static testcapistate_t*
@@ -2418,6 +2419,36 @@ test_reftracer(PyObject *ob, PyObject *Py_UNUSED(ignored))
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return NULL;
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}
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static int
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_listdestroytracer(PyObject *obj, PyRefTracerEvent event, void *data)
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{
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if (event == PyRefTracer_DESTROY && PyList_CheckExact(obj)) {
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_Py_atomic_add_ssize((Py_ssize_t *)data, 1);
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}
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return 0;
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}
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static PyObject *
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start_counting_list_destroys(PyObject *self, PyObject *Py_UNUSED(ignored))
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{
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testcapistate_t *state = get_testcapi_state(self);
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_Py_atomic_store_ssize(&state->list_destroys, 0);
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if (PyRefTracer_SetTracer(_listdestroytracer, &state->list_destroys) != 0) {
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return NULL;
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}
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Py_RETURN_NONE;
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}
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static PyObject *
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stop_counting_list_destroys(PyObject *self, PyObject *Py_UNUSED(ignored))
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{
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if (PyRefTracer_SetTracer(NULL, NULL) != 0) {
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return NULL;
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}
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return PyLong_FromSsize_t(
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_Py_atomic_load_ssize(&get_testcapi_state(self)->list_destroys));
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}
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static PyObject *
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function_set_warning(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
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{
@@ -3022,6 +3053,8 @@ static PyMethodDef TestMethods[] = {
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{"test_buildvalue_N", test_buildvalue_N, METH_NOARGS},
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{"test_buildvalue_p", test_buildvalue_p, METH_NOARGS},
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{"test_reftracer", test_reftracer, METH_NOARGS},
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{"start_counting_list_destroys", start_counting_list_destroys, METH_NOARGS},
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{"stop_counting_list_destroys", stop_counting_list_destroys, METH_NOARGS},
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{"_test_thread_state", test_thread_state, METH_VARARGS},
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{"gilstate_ensure_release", gilstate_ensure_release, METH_NOARGS},
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#ifndef MS_WINDOWS

‎Objects/object.c‎

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Original file line numberDiff line numberDiff line change
@@ -3224,6 +3224,10 @@ _PyTrash_thread_destroy_chain(PyThreadState *tstate)
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* up distorting allocation statistics.
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*/
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_PyObject_ASSERT(op, Py_REFCNT(op) == 0);
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#ifdef Py_TRACE_REFS
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_Py_ForgetReference(op);
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#endif
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_PyReftracerTrack(op, PyRefTracer_DESTROY);
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(*dealloc)(op);
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}
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}

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