commit f64de53ff01e734d48d1d42195443d7d1646f220
author Serhiy Storchaka <storchaka@gmail.com> Tue Jul 06 01:19:35 2021 +0300
committer GitHub <noreply@github.com> Mon Jul 05 23:19:35 2021 +0100
tree 7be6dfc9d95a79a432c6302b7260ec2f86b7b5de
parent 17f94e28882e1e2b331ace93f42e8615383dee59

bpo-44563: Fix error handling in tee.fromiterable() (GH-27020)

In debug build failed tee.fromiterable() corrupted the linked list of all GC objects.

Modules/itertoolsmodule.c

diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 293735a..643f47b 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -863,7 +863,7 @@
 tee_fromiterable(PyObject *iterable)
 {
     teeobject *to;
-    PyObject *it = NULL;
+    PyObject *it;
 
     it = PyObject_GetIter(iterable);
     if (it == NULL)
@@ -873,21 +873,22 @@
         goto done;
     }
 
-    to = PyObject_GC_New(teeobject, &tee_type);
-    if (to == NULL)
-        goto done;
-    to->dataobj = (teedataobject *)teedataobject_newinternal(it);
-    if (!to->dataobj) {
-        PyObject_GC_Del(to);
+    PyObject *dataobj = teedataobject_newinternal(it);
+    if (!dataobj) {
         to = NULL;
         goto done;
     }
-
+    to = PyObject_GC_New(teeobject, &tee_type);
+    if (to == NULL) {
+        Py_DECREF(dataobj);
+        goto done;
+    }
+    to->dataobj = (teedataobject *)dataobj;
     to->index = 0;
     to->weakreflist = NULL;
     PyObject_GC_Track(to);
 done:
-    Py_XDECREF(it);
+    Py_DECREF(it);
     return (PyObject *)to;
 }