gh-116946: fully implement GC protocol for _curses_panel.panel

Modules/_curses_panel.c

@@ -410,8 +410,11 @@ static PyObject *
 PyCursesPanel_New(_curses_panel_state *state, PANEL *pan,
  PyCursesWindowObject *wo)
 {
- PyCursesPanelObject *po = PyObject_New(PyCursesPanelObject,
- state->PyCursesPanel_Type);
+ assert(state != NULL);
+ PyTypeObject *type = state->PyCursesPanel_Type;
+ assert(type != NULL);
+ assert(type->tp_alloc != NULL);
+ PyCursesPanelObject *po = (PyCursesPanelObject *)type->tp_alloc(type, 0);
  if (po == NULL){
  return NULL;
  }
@@ -426,20 +429,31 @@ PyCursesPanel_New(_curses_panel_state *state, PANEL *pan,
  return (PyObject *)po;
 }
 
+static int
+PyCursesPanel_Clear(PyObject *op)
+{
+ PyCursesPanelObject *self = _PyCursesPanelObject_CAST(op);
+ PyObject *extra = (PyObject *)panel_userptr(self->pan);
+ if (extra != NULL){
+ Py_DECREF(extra);
+ if (set_panel_userptr(self->pan, NULL) == ERR){
+ curses_panel_panel_set_error(self, "set_panel_userptr", NULL);
+ return -1;
+ }
+ }
+ // self->wo should not be cleared because an associated WINDOW may exist
+ return 0;
+}
+
 static void
 PyCursesPanel_Dealloc(PyObject *self)
 {
-PyObject *tp, *obj;
-PyCursesPanelObject *po = _PyCursesPanelObject_CAST(self);
+PyTypeObject *tp = Py_TYPE(self);
+PyObject_GC_UnTrack(self);
 
- tp = (PyObject *) Py_TYPE(po);
- obj = (PyObject *) panel_userptr(po->pan);
- if (obj){
- Py_DECREF(obj);
- if (set_panel_userptr(po->pan, NULL) == ERR){
- curses_panel_panel_set_error(po, "set_panel_userptr", "__del__");
- PyErr_FormatUnraisable("Exception ignored in PyCursesPanel_Dealloc()");
- }
+ PyCursesPanelObject *po = _PyCursesPanelObject_CAST(self);
+ if (PyCursesPanel_Clear(self) < 0){
+ PyErr_FormatUnraisable("Exception ignored in PyCursesPanel_Dealloc()");
  }
  if (del_panel(po->pan) == ERR && !PyErr_Occurred()){
  curses_panel_panel_set_error(po, "del_panel", "__del__");
@@ -452,10 +466,20 @@ PyCursesPanel_Dealloc(PyObject *self)
  PyErr_FormatUnraisable("Exception ignored in PyCursesPanel_Dealloc()");
  }
  }
-PyObject_Free(po);
+tp->tp_free(po);
  Py_DECREF(tp);
 }
 
+static int
+PyCursesPanel_Traverse(PyObject *op, visitproc visit, void *arg)
+{
+ PyCursesPanelObject *self = _PyCursesPanelObject_CAST(op);
+ Py_VISIT(Py_TYPE(op));
+ Py_VISIT(panel_userptr(self->pan));
+ Py_VISIT(self->wo);
+ return 0;
+}
+
 /* panel_above(NULL) returns the bottom panel in the stack. To get
  this behaviour we use curses.panel.bottom_panel(). */
 /*[clinic input]
@@ -647,15 +671,21 @@ static PyMethodDef PyCursesPanel_Methods[] ={
 /* -------------------------------------------------------*/
 
 static PyType_Slot PyCursesPanel_Type_slots[] ={
+{Py_tp_clear, PyCursesPanel_Clear},
 {Py_tp_dealloc, PyCursesPanel_Dealloc},
+{Py_tp_traverse, PyCursesPanel_Traverse},
 {Py_tp_methods, PyCursesPanel_Methods},
 {0, 0},
 };
 
 static PyType_Spec PyCursesPanel_Type_spec ={
  .name = "_curses_panel.panel",
  .basicsize = sizeof(PyCursesPanelObject),
- .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
+ .flags = (
+ Py_TPFLAGS_DEFAULT
+ | Py_TPFLAGS_DISALLOW_INSTANTIATION
+ | Py_TPFLAGS_HAVE_GC
+ ),
  .slots = PyCursesPanel_Type_slots
 };