GH-118074: Executors in the COLD_EXITS array are not GC'able (#118117)

Author: gvanrossum

Misc/NEWS.d/next/Core and Builtins/2024-04-22-08-34-28.gh-issue-118074.5_JnIa.rst

@@ -0,0 +1,2 @@
+Make sure that the Executor objects in the COLD_EXITS array aren't assumed
+to be GC-able (which would access bytes outside the object).

Python/optimizer.c

@@ -394,6 +394,15 @@ executor_traverse(PyObject *o, visitproc visit, void *arg)
     return 0;
 }
 
+static int
+executor_is_gc(PyObject *o)
+{
+    if ((PyObject *)&COLD_EXITS[0] <= o && o < (PyObject *)&COLD_EXITS[COLD_EXIT_COUNT]) {
+        return 0;
+    }
+    return 1;
+}
+
 PyTypeObject _PyUOpExecutor_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     .tp_name = "uop_executor",
@@ -405,6 +414,7 @@ PyTypeObject _PyUOpExecutor_Type = {
     .tp_methods = executor_methods,
     .tp_traverse = executor_traverse,
     .tp_clear = executor_clear,
+    .tp_is_gc = executor_is_gc,
 };
 
 /* TO DO -- Generate these tables */