bpo-35983: skip trashcan for subclasses (GH-11841)

Add new trashcan macros to deal with a double deallocation that could occur when the `tp_dealloc` of a subclass calls the `tp_dealloc` of a base class and that base class uses the trashcan mechanism.

Patch by Jeroen Demeyer.

1 files changed, 2 insertions, 13 deletions

diff --git a/Objects/odictobject.c b/Objects/odictobject.c
index 6c75a42..773827d 100644
--- a/Objects/odictobject.c
+++ b/Objects/odictobject.c
@@ -1356,28 +1356,17 @@ static PyGetSetDef odict_getset[] = {
 static void
 odict_dealloc(PyODictObject *self)
 {
-    PyThreadState *tstate = _PyThreadState_GET();
-
     PyObject_GC_UnTrack(self);
-    Py_TRASHCAN_SAFE_BEGIN(self)
+    Py_TRASHCAN_BEGIN(self, odict_dealloc)
 
     Py_XDECREF(self->od_inst_dict);
     if (self->od_weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *)self);
 
     _odict_clear_nodes(self);
-
-    /* Call the base tp_dealloc().  Since it too uses the trashcan mechanism,
-     * temporarily decrement trash_delete_nesting to prevent triggering it
-     * and putting the partially deallocated object on the trashcan's
-     * to-be-deleted-later list.
-     */
-    --tstate->trash_delete_nesting;
-    assert(_tstate->trash_delete_nesting < PyTrash_UNWIND_LEVEL);
     PyDict_Type.tp_dealloc((PyObject *)self);
-    ++tstate->trash_delete_nesting;
 
-    Py_TRASHCAN_SAFE_END(self)
+    Py_TRASHCAN_END
 }
 
 /* tp_repr */