make select.poll immutable instead of supporting full GC

picnixz · picnixz · commit 55c88e43c833 · 2025-09-02T10:32:27.000+02:00
diff --git a/Misc/NEWS.d/next/Library/2025-09-02-10-27-21.gh-issue-116946.VxXNGD.rst b/Misc/NEWS.d/next/Library/2025-09-02-10-27-21.gh-issue-116946.VxXNGD.rst
@@ -1,2 +1,2 @@
-The C type of :func:`select.epoll` objects is now immutable. Patch by
-Bénédikt Tran.
+The C types of :func:`select.poll` and :func:`select.epoll` objects are now
+immutable. Patch by Bénédikt Tran.
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
@@ -433,7 +433,7 @@ select_select_impl(PyObject *module, PyObject *rlist, PyObject *wlist,
 
 typedef struct {
     PyObject_HEAD
-    PyObject *dict;
+    PyObject *dict;     // cannot create cycles as it only contains exact ints
     int ufd_uptodate;
     int ufd_len;
     struct pollfd *ufds;
@@ -791,15 +791,6 @@ poll_dealloc(PyObject *op)
     Py_DECREF(type);
 }
 
-static int
-poll_traverse(PyObject *op, visitproc visit, void *arg)
-{
-    pollObject *self = pollObject_CAST(op);
-    Py_VISIT(Py_TYPE(op));
-    Py_VISIT(self->dict);
-    return 0;
-}
-
 #ifdef HAVE_SYS_DEVPOLL_H
 static PyMethodDef devpoll_methods[];
 
@@ -2489,7 +2480,6 @@ static PyMethodDef poll_methods[] = {
 
 static PyType_Slot poll_Type_slots[] = {
     {Py_tp_dealloc, poll_dealloc},
-    {Py_tp_traverse, poll_traverse},
     {Py_tp_methods, poll_methods},
     {0, 0},
 };
@@ -2500,7 +2490,7 @@ static PyType_Spec poll_Type_spec = {
     .flags = (
         Py_TPFLAGS_DEFAULT
         | Py_TPFLAGS_DISALLOW_INSTANTIATION
-        | Py_TPFLAGS_HAVE_GC
+        | Py_TPFLAGS_IMMUTABLETYPE
     ),
     .slots = poll_Type_slots,
 };
