[Python-checkins] bpo-18533: Avoid RecursionError from repr() of recursive dictview (#4823)

Fri Jan 26 10:46:04 EST 2018

https://github.com/python/cpython/commit/d7773d92bd11640a8c950d6c36a9cef1cee36f96
commit: d7773d92bd11640a8c950d6c36a9cef1cee36f96
branch: master
author: bennorth <ben at redfrontdoor.org>
committer: Senthil Kumaran <skumaran at gatech.edu>
date: 2018年01月26日T07:46:01-08:00
summary:
bpo-18533: Avoid RecursionError from repr() of recursive dictview (#4823)
dictview_repr(): Use a Py_ReprEnter() / Py_ReprLeave() pair to check
for recursion, and produce "..." if so.
test_recursive_repr(): Check for the string rather than a
RecursionError. (Test cannot be any tighter as contents are
implementation-dependent.)
test_deeply_nested_repr(): Add new test, replacing the original
test_recursive_repr(). It checks that a RecursionError is raised in
the case of a non-recursive but deeply nested structure. (Very
similar to what test_repr_deep() in test/test_dict.py does for a
normal dict.)
OrderedDictTests: Add new test case, to test behavior on OrderedDict
instances containing their own values() or items().
files:
A Misc/NEWS.d/next/Core and Builtins/2017-12-13-16-46-23.bpo-18533.Dlk8d7.rst
M Lib/test/test_dictviews.py
M Lib/test/test_ordered_dict.py
M Objects/dictobject.c

diff --git a/Lib/test/test_dictviews.py b/Lib/test/test_dictviews.py
index 51ad9b381c5..2763cbfb4bb 100644
--- a/Lib/test/test_dictviews.py
+++ b/Lib/test/test_dictviews.py
@@ -1,6 +1,7 @@
 import collections.abc
 import copy
 import pickle
+import sys
 import unittest
 
 class DictSetTest(unittest.TestCase):
@@ -202,6 +203,20 @@ def test_items_set_operations(self):
 def test_recursive_repr(self):
 d = {}
 d[42] = d.values()
+ r = repr(d)
+ # Cannot perform a stronger test, as the contents of the repr
+ # are implementation-dependent. All we can say is that we
+ # want a str result, not an exception of any sort.
+ self.assertIsInstance(r, str)
+ d[42] = d.items()
+ r = repr(d)
+ # Again.
+ self.assertIsInstance(r, str)
+
+ def test_deeply_nested_repr(self):
+ d = {}
+ for i in range(sys.getrecursionlimit() + 100):
+ d = {42: d.values()}
 self.assertRaises(RecursionError, repr, d)
 
 def test_copy(self):
diff --git a/Lib/test/test_ordered_dict.py b/Lib/test/test_ordered_dict.py
index 6bafb8be307..20efe3729de 100644
--- a/Lib/test/test_ordered_dict.py
+++ b/Lib/test/test_ordered_dict.py
@@ -355,6 +355,20 @@ def test_repr_recursive(self):
 self.assertEqual(repr(od),
 "OrderedDict([('a', None), ('b', None), ('c', None), ('x', ...)])")
 
+ def test_repr_recursive_values(self):
+ OrderedDict = self.OrderedDict
+ od = OrderedDict()
+ od[42] = od.values()
+ r = repr(od)
+ # Cannot perform a stronger test, as the contents of the repr
+ # are implementation-dependent. All we can say is that we
+ # want a str result, not an exception of any sort.
+ self.assertIsInstance(r, str)
+ od[42] = od.items()
+ r = repr(od)
+ # Again.
+ self.assertIsInstance(r, str)
+
 def test_setdefault(self):
 OrderedDict = self.OrderedDict
 pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]
diff --git a/Misc/NEWS.d/next/Core and Builtins/2017-12-13-16-46-23.bpo-18533.Dlk8d7.rst b/Misc/NEWS.d/next/Core and Builtins/2017-12-13-16-46-23.bpo-18533.Dlk8d7.rst
new file mode 100644
index 00000000000..a33eff5c705
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2017-12-13-16-46-23.bpo-18533.Dlk8d7.rst	
@@ -0,0 +1,3 @@
+``repr()`` on a dict containing its own ``values()`` or ``items()`` no
+longer raises ``RecursionError``; OrderedDict similarly. Instead, use
+``...``, as for other recursive structures. Patch by Ben North.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 0d25739f72c..bb4ea1f5f9c 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -3853,14 +3853,22 @@ static PyObject *
 dictview_repr(_PyDictViewObject *dv)
 {
 PyObject *seq;
- PyObject *result;
+ PyObject *result = NULL;
+ Py_ssize_t rc;
 
+ rc = Py_ReprEnter((PyObject *)dv);
+ if (rc != 0) {
+ return rc > 0 ? PyUnicode_FromString("...") : NULL;
+ }
 seq = PySequence_List((PyObject *)dv);
- if (seq == NULL)
- return NULL;
-
+ if (seq == NULL) {
+ goto Done;
+ }
 result = PyUnicode_FromFormat("%s(%R)", Py_TYPE(dv)->tp_name, seq);
 Py_DECREF(seq);
+
+Done:
+ Py_ReprLeave((PyObject *)dv);
 return result;
 }
 
