bpo-44531: Add _PyType_AllocNoTrack() function (GH-26947)

Add an internal _PyType_AllocNoTrack() function to allocate an object
without tracking it in the GC.

Modify dict_new() to use _PyType_AllocNoTrack(): dict subclasses are
now only tracked once all PyDictObject members are initialized.
Calling _PyObject_GC_UNTRACK() is no longer needed for the dict type.

Similar change in tuple_subtype_new() for tuple subclasses.

Replace tuple_gc_track() with _PyObject_GC_TRACK().

1 files changed, 11 insertions, 1 deletions

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 8ee4e81..116ac14 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1164,7 +1164,7 @@ type_call(PyTypeObject *type, PyObject *args, PyObject *kwds)
 }
 
 PyObject *
-PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
+_PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems)
 {
     PyObject *obj;
     const size_t size = _PyObject_VAR_SIZE(type, nitems+1);
@@ -1189,6 +1189,16 @@ PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
     else {
         _PyObject_InitVar((PyVarObject *)obj, type, nitems);
     }
+    return obj;
+}
+
+PyObject *
+PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
+{
+    PyObject *obj = _PyType_AllocNoTrack(type, nitems);
+    if (obj == NULL) {
+        return NULL;
+    }
 
     if (_PyType_IS_GC(type)) {
         _PyObject_GC_TRACK(obj);