[Python-checkins] cpython (2.7): Issue #13454: Fix a crash when deleting an iterator created by itertools.tee()

[serhiy.storchaka]

http://hg.python.org/cpython/rev/62f2d3f6015e
changeset:   81703:62f2d3f6015e
branch:      2.7
parent:      81694:fc21f8e83062
user:        Serhiy Storchaka <storchaka at gmail.com>
date:        Fri Jan 25 13:31:05 2013 +0200
summary:
  Issue #13454: Fix a crash when deleting an iterator created by itertools.tee()
if all other iterators were very advanced before.

files:
  Lib/test/test_itertools.py |   8 ++++++++
  Misc/NEWS                  |   3 +++
  Modules/itertoolsmodule.c  |  21 ++++++++++++++++++++-
  3 files changed, 31 insertions(+), 1 deletions(-)


diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -906,6 +906,14 @@
         del a
         self.assertRaises(ReferenceError, getattr, p, '__class__')
 
+    # Issue 13454: Crash when deleting backward iterator from tee()
+    def test_tee_del_backward(self):
+        forward, backward = tee(xrange(20000000))
+        for i in forward:
+            pass
+
+        del backward
+
     def test_StopIteration(self):
         self.assertRaises(StopIteration, izip().next)
 
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -189,6 +189,9 @@
 Library
 -------
 
+- Issue #13454: Fix a crash when deleting an iterator created by itertools.tee()
+  if all other iterators were very advanced before.
+
 - Issue #1159051: GzipFile now raises EOFError when reading a corrupted file
   with truncated header or footer.
 
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -401,14 +401,31 @@
     return 0;
 }
 
+static void
+teedataobject_safe_decref(PyObject *obj)
+{
+    while (obj && Py_TYPE(obj) == &teedataobject_type &&
+           Py_REFCNT(obj) == 1) {
+        PyObject *nextlink = ((teedataobject *)obj)->nextlink;
+        ((teedataobject *)obj)->nextlink = NULL;
+        Py_DECREF(obj);
+        obj = nextlink;
+    }
+    Py_XDECREF(obj);
+}
+
 static int
 teedataobject_clear(teedataobject *tdo)
 {
     int i;
+    PyObject *tmp;
+
     Py_CLEAR(tdo->it);
     for (i=0 ; i<tdo->numread ; i++)
         Py_CLEAR(tdo->values[i]);
-    Py_CLEAR(tdo->nextlink);
+    tmp = tdo->nextlink;
+    tdo->nextlink = NULL;
+    teedataobject_safe_decref(tmp);
     return 0;
 }
 
@@ -475,6 +492,8 @@
 
     if (to->index >= LINKCELLS) {
         link = teedataobject_jumplink(to->dataobj);
+        if (link == NULL)
+            return NULL;
         Py_DECREF(to->dataobj);
         to->dataobj = (teedataobject *)link;
         to->index = 0;

-- 
Repository URL: http://hg.python.org/cpython