Test that GC frame is not cleared

Author: sergey-miryanov

Lib/test/test_gc.py

@@ -1289,6 +1289,24 @@ def test_heap_size(self):
         del l
         self.assertEqual(count, _testinternalcapi.get_tracked_heap_size())
 
+    @unittest.skipIf(_testinternalcapi is None, "requires _testinternalcapi")
+    def test_clear_frame_on_early_return(self):
+        # __del__ methods can trigger collection, make this to happen
+        thresholds = gc.get_threshold()
+        gc.enable()
+        gc.set_threshold(1)
+
+        class A:
+            def __del__(self):
+                dir(self)
+
+        x = [A() for _ in range(10)]
+        del x
+        self.assertTrue(_testinternalcapi.is_gc_frame_clear())
+
+        gc.disable()
+        gc.set_threshold(*thresholds)
+
 
 class GCCallbackTests(unittest.TestCase):
     def setUp(self):

Modules/_testinternalcapi.c

@@ -3206,6 +3206,19 @@ test_thread_state_ensure_from_view_interp_switch(PyObject *self, PyObject *unuse
     Py_RETURN_NONE;
 }
 
+static PyObject *
+is_gc_frame_clear(PyObject *self, PyObject *unused)
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    assert(interp != NULL);
+
+    if (!interp->gc.frame) {
+        Py_RETURN_TRUE;
+    }
+
+    Py_RETURN_FALSE;
+}
+
 /* Self interrupting context manager */
 
 typedef struct {
@@ -3393,6 +3406,7 @@ static PyMethodDef module_functions[] = {
     {"test_interp_guard_countdown", test_interp_guard_countdown, METH_NOARGS},
     {"test_interp_view_countdown", test_interp_view_countdown, METH_NOARGS},
     {"test_thread_state_ensure_from_view_interp_switch", test_thread_state_ensure_from_view_interp_switch, METH_NOARGS},
+    {"is_gc_frame_clear", is_gc_frame_clear, METH_NOARGS},
     {NULL, NULL} /* sentinel */
 };