From 2b2b75374e7215e622b95f89ce93259c05002f24 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Sat, 5 Sep 2015 17:05:52 -0700
Subject: Prevent reentrant badness by deferring the decrefs as long as
 possible.

---
 Modules/_collectionsmodule.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 3856d83..f450f25 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -419,9 +419,11 @@ deque_extend(dequeobject *deque, PyObject *iterable)
         deque->rightblock->data[deque->rightindex] = item;
         deque_trim_left(deque);
     }
-    Py_DECREF(it);
-    if (PyErr_Occurred())
+    if (PyErr_Occurred()) {
+        Py_DECREF(it);
         return NULL;
+    }
+    Py_DECREF(it);
     Py_RETURN_NONE;
 }
 
@@ -480,9 +482,11 @@ deque_extendleft(dequeobject *deque, PyObject *iterable)
         deque->leftblock->data[deque->leftindex] = item;
         deque_trim_right(deque);
     }
-    Py_DECREF(it);
-    if (PyErr_Occurred())
+    if (PyErr_Occurred()) {
+        Py_DECREF(it);
         return NULL;
+    }
+    Py_DECREF(it);
     Py_RETURN_NONE;
 }
 
@@ -497,8 +501,8 @@ deque_inplace_concat(dequeobject *deque, PyObject *other)
     result = deque_extend(deque, other);
     if (result == NULL)
         return result;
-    Py_DECREF(result);
     Py_INCREF(deque);
+    Py_DECREF(result);
     return (PyObject *)deque;
 }
 
@@ -1260,8 +1264,8 @@ deque_repr(PyObject *deque)
                                       aslist, ((dequeobject *)deque)->maxlen);
     else
         result = PyUnicode_FromFormat("deque(%R)", aslist);
-    Py_DECREF(aslist);
     Py_ReprLeave(deque);
+    Py_DECREF(aslist);
     return result;
 }
 
-- 
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