diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py index 84927a393f17593..0478f20cd33b4d4 100644 --- a/Lib/test/test_sys.py +++ b/Lib/test/test_sys.py @@ -1292,6 +1292,21 @@ def test_asyncgen_hooks(self): self.assertIsNone(cur.firstiter) self.assertIsNone(cur.finalizer) + def test_changing_sys_stderr_and_removing_reference(self): + # If the default displayhook doesn't take a strong reference + # to sys.stderr the following code can crash. See bpo-43660 + # for more details. + code = textwrap.dedent(''' + import sys + class MyStderr: + def write(self, s): + sys.stderr = None + sys.stderr = MyStderr() + 1/0 + ''') + rc, out, err = assert_python_failure('-c', code) + self.assertEqual(out, b"") + self.assertEqual(err, b"") def test_main(): test.support.run_unittest(SysModuleTest, SizeofTest) diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-03-29-19-50-34.bpo-43660.scTgag.rst b/Misc/NEWS.d/next/Core and Builtins/2021-03-29-19-50-34.bpo-43660.scTgag.rst new file mode 100644 index 000000000000000..98419501d9e7b8a --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2021-03-29-19-50-34.bpo-43660.scTgag.rst @@ -0,0 +1,3 @@ +Fix crash that happens when replacing ``sys.stderr`` with a callable that +can remove the object while an exception is being printed. Patch by Pablo +Galindo. diff --git a/Python/pythonrun.c b/Python/pythonrun.c index 4c974cef39c78bc..b7b77d1f9ee3feb 100644 --- a/Python/pythonrun.c +++ b/Python/pythonrun.c @@ -932,7 +932,9 @@ PyErr_Display(PyObject *exception, PyObject *value, PyObject *tb) seen = PySet_New(NULL); if (seen == NULL) PyErr_Clear(); + Py_INCREF(f); print_exception_recursive(f, value, seen); + Py_DECREF(f); Py_XDECREF(seen); } }