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)

3 files changed, 26 insertions, 0 deletions

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index faee6bc..8a05653 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -3861,6 +3861,11 @@ dictiter_iternextitem(dictiterobject *di)
         Py_INCREF(result);
         Py_DECREF(oldkey);
         Py_DECREF(oldvalue);
+        // 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(2);
@@ -3976,6 +3981,11 @@ dictreviter_iternext(dictiterobject *di)
             Py_INCREF(result);
             Py_DECREF(oldkey);
             Py_DECREF(oldvalue);
+            // 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(2);
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index 4a83bb4..bdd0ea5 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -1,6 +1,7 @@
 /* enumerate object */
 
 #include "Python.h"
+#include "pycore_object.h"        // _PyObject_GC_TRACK()
 
 #include "clinic/enumobject.c.h"
 
@@ -130,6 +131,11 @@ enum_next_long(enumobject *en, PyObject* next_item)
         PyTuple_SET_ITEM(result, 1, next_item);
         Py_DECREF(old_index);
         Py_DECREF(old_item);
+        // 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);
+        }
         return result;
     }
     result = PyTuple_New(2);
@@ -175,6 +181,11 @@ enum_next(enumobject *en)
         PyTuple_SET_ITEM(result, 1, next_item);
         Py_DECREF(old_index);
         Py_DECREF(old_item);
+        // 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);
+        }
         return result;
     }
     result = PyTuple_New(2);
diff --git a/Objects/odictobject.c b/Objects/odictobject.c
index d5bf499..b9f2169 100644
--- a/Objects/odictobject.c
+++ b/Objects/odictobject.c
@@ -1817,6 +1817,11 @@ odictiter_iternext(odictiterobject *di)
         Py_INCREF(result);
         Py_DECREF(PyTuple_GET_ITEM(result, 0));  /* borrowed */
         Py_DECREF(PyTuple_GET_ITEM(result, 1));  /* borrowed */
+        // 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(2);