bpo-42536: GC track recycled tuples (GH-23623) (GH-23651)

Several built-in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector:

- collections.OrderedDict.items
- dict.items
- enumerate
- functools.reduce
- itertools.combinations
- itertools.combinations_with_replacement
- itertools.permutations
- itertools.product
- itertools.zip_longest
- zip

Previously, they could have become untracked by a prior garbage collection.
(cherry picked from commit 226a012d1cd61f42ecd3056c554922f359a1a35d)

1 files changed, 5 insertions, 0 deletions

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 199b09c..614012d 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2619,6 +2619,11 @@ zip_next(zipobject *lz)
             PyTuple_SET_ITEM(result, i, item);
             Py_DECREF(olditem);
         }
+        // bpo-42536: The GC may have untracked this result tuple. Since we're
+        // recycling it, make sure it's tracked again:
+        if (!_PyObject_GC_IS_TRACKED(result)) {
+            _PyObject_GC_TRACK(result);
+        }
     } else {
         result = PyTuple_New(tuplesize);
         if (result == NULL)