Short Arguments By Newspaper: Fix missing PyRefTracer_DESTROY events for trashcan objects (Sample Page For Contact Us)

Author: How Do We Post An LinkedIn Artical

Lib/test/test_capi/test_object.py

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

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

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

Modules/_testcapimodule.c

@@ -39,6 +39,7 @@ static struct PyModuleDef _testcapimodule;
 // Module state
 typedef struct {
  PyObject *error; // _testcapi.error object
+ Py_ssize_t list_destroys;
 } testcapistate_t;
 
 static testcapistate_t*
@@ -2412,6 +2413,36 @@ test_reftracer(PyObject *ob, PyObject *Py_UNUSED(ignored))
  return NULL;
 }
 
+static int
+_listdestroytracer(PyObject *obj, PyRefTracerEvent event, void *data)
+{
+ if (event == PyRefTracer_DESTROY && PyList_CheckExact(obj)) {
+ _Py_atomic_add_ssize((Py_ssize_t *)data, 1);
+ }
+ return 0;
+}
+
+static PyObject *
+start_counting_list_destroys(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+ testcapistate_t *state = get_testcapi_state(self);
+ _Py_atomic_store_ssize(&state->list_destroys, 0);
+ if (PyRefTracer_SetTracer(_listdestroytracer, &state->list_destroys) != 0) {
+ return NULL;
+ }
+ Py_RETURN_NONE;
+}
+
+static PyObject *
+stop_counting_list_destroys(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+ if (PyRefTracer_SetTracer(NULL, NULL) != 0) {
+ return NULL;
+ }
+ return PyLong_FromSsize_t(
+ _Py_atomic_load_ssize(&get_testcapi_state(self)->list_destroys));
+}
+
 static PyObject *
 function_set_warning(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
 {
@@ -3016,6 +3047,8 @@ static PyMethodDef TestMethods[] = {
  {"test_buildvalue_N", test_buildvalue_N, METH_NOARGS},
  {"test_buildvalue_p", test_buildvalue_p, METH_NOARGS},
  {"test_reftracer", test_reftracer, METH_NOARGS},
+ {"start_counting_list_destroys", start_counting_list_destroys, METH_NOARGS},
+ {"stop_counting_list_destroys", stop_counting_list_destroys, METH_NOARGS},
  {"_test_thread_state", test_thread_state, METH_VARARGS},
  {"gilstate_ensure_release", gilstate_ensure_release, METH_NOARGS},
 #ifndef MS_WINDOWS

Objects/object.c

@@ -3228,6 +3228,10 @@ _PyTrash_thread_destroy_chain(PyThreadState *tstate)
  * up distorting allocation statistics.
  */
  _PyObject_ASSERT(op, Py_REFCNT(op) == 0);
+#ifdef Py_TRACE_REFS
+ _Py_ForgetReference(op);
+#endif
+ _PyReftracerTrack(op, PyRefTracer_DESTROY);
  (*dealloc)(op);
  }
 }