pythongh-101819: Prepare _io._IOBase for module state

- Add PyIOBase_Type to _io module state
- Pass defining class to _io._IOBase.fileno

Modules/_io/_iomodule.c

@@ -582,6 +582,7 @@ iomodule_traverse(PyObject *mod, visitproc visit, void *arg) {
         return 0;
     Py_VISIT(state->unsupported_operation);
 
+    Py_VISIT(state->PyIOBase_Type);
     Py_VISIT(state->PyIncrementalNewlineDecoder_Type);
     Py_VISIT(state->PyRawIOBase_Type);
     Py_VISIT(state->PyBufferedIOBase_Type);
@@ -609,6 +610,7 @@ iomodule_clear(PyObject *mod) {
         return 0;
     Py_CLEAR(state->unsupported_operation);
 
+    Py_CLEAR(state->PyIOBase_Type);
     Py_CLEAR(state->PyIncrementalNewlineDecoder_Type);
     Py_CLEAR(state->PyRawIOBase_Type);
     Py_CLEAR(state->PyBufferedIOBase_Type);
@@ -751,6 +753,7 @@ PyInit__io(void)
     }
 
     // Base classes
+    state->PyIOBase_Type = (PyTypeObject *)Py_NewRef(&PyIOBase_Type);
     ADD_TYPE(m, state->PyIncrementalNewlineDecoder_Type, &nldecoder_spec, NULL);
     ADD_TYPE(m, state->PyBytesIOBuffer_Type, &bytesiobuf_spec, NULL);
 

Modules/_io/_iomodule.h

@@ -149,6 +149,7 @@ struct _io_state {
     PyObject *unsupported_operation;
 
     /* Types */
+    PyTypeObject *PyIOBase_Type;
     PyTypeObject *PyIncrementalNewlineDecoder_Type;
     PyTypeObject *PyRawIOBase_Type;
     PyTypeObject *PyBufferedIOBase_Type;

Modules/_io/iobase.c

@@ -511,15 +511,17 @@ iobase_exit(PyObject *self, PyObject *args)
 
 /*[clinic input]
 _io._IOBase.fileno
+    cls: defining_class
+    /
 
-Returns underlying file descriptor if one exists.
+Return underlying file descriptor if one exists.
 
-OSError is raised if the IO object does not use a file descriptor.
+Raise OSError if the IO object does not use a file descriptor.
 [clinic start generated code]*/
 
 static PyObject *
-_io__IOBase_fileno_impl(PyObject *self)
-/*[clinic end generated code: output=7cc0973f0f5f3b73 input=4e37028947dc1cc8]*/
+_io__IOBase_fileno_impl(PyObject *self, PyTypeObject *cls)
+/*[clinic end generated code: output=7caaa32a6f4ada3d input=1927c8bea5c85099]*/
 {
     _PyIO_State *state = IO_STATE();
     return iobase_unsupported(state, "fileno");