pythongh-104645: fix error handling in marshal tests (python#104646)

Modules/_testcapimodule.c

@@ -1808,10 +1808,9 @@ pymarshal_write_long_to_file(PyObject* self, PyObject *args)
  }
 
  PyMarshal_WriteLongToFile(value, fp, version);
+ assert(!PyErr_Occurred());
 
  fclose(fp);
- if (PyErr_Occurred())
- return NULL;
  Py_RETURN_NONE;
 }
 
@@ -1834,10 +1833,9 @@ pymarshal_write_object_to_file(PyObject* self, PyObject *args)
  }
 
  PyMarshal_WriteObjectToFile(obj, fp, version);
+ assert(!PyErr_Occurred());
 
  fclose(fp);
- if (PyErr_Occurred())
- return NULL;
  Py_RETURN_NONE;
 }
 
@@ -1895,48 +1893,46 @@ pymarshal_read_long_from_file(PyObject* self, PyObject *args)
 static PyObject*
 pymarshal_read_last_object_from_file(PyObject* self, PyObject *args)
 {
- PyObject *obj;
- long pos;
  PyObject *filename;
- FILE *fp;
-
  if (!PyArg_ParseTuple(args, "O:pymarshal_read_last_object_from_file", &filename))
  return NULL;
 
- fp = _Py_fopen_obj(filename, "rb");
+ FILE *fp = _Py_fopen_obj(filename, "rb");
  if (fp == NULL) {
  PyErr_SetFromErrno(PyExc_OSError);
  return NULL;
  }
 
- obj = PyMarshal_ReadLastObjectFromFile(fp);
- pos = ftell(fp);
+ PyObject *obj = PyMarshal_ReadLastObjectFromFile(fp);
+ long pos = ftell(fp);
 
  fclose(fp);
+ if (obj == NULL) {
+ return NULL;
+ }
  return Py_BuildValue("Nl", obj, pos);
 }
 
 static PyObject*
 pymarshal_read_object_from_file(PyObject* self, PyObject *args)
 {
- PyObject *obj;
- long pos;
  PyObject *filename;
- FILE *fp;
-
  if (!PyArg_ParseTuple(args, "O:pymarshal_read_object_from_file", &filename))
  return NULL;
 
- fp = _Py_fopen_obj(filename, "rb");
+ FILE *fp = _Py_fopen_obj(filename, "rb");
  if (fp == NULL) {
  PyErr_SetFromErrno(PyExc_OSError);
  return NULL;
  }
 
- obj = PyMarshal_ReadObjectFromFile(fp);
- pos = ftell(fp);
+ PyObject *obj = PyMarshal_ReadObjectFromFile(fp);
+ long pos = ftell(fp);
 
  fclose(fp);
+ if (obj == NULL) {
+ return NULL;
+ }
  return Py_BuildValue("Nl", obj, pos);
 }