From e9a651476760fea6dfa12b9621ce57f015823b69 Mon Sep 17 00:00:00 2001
From: Collin Winter <collinw@gmail.com>
Date: Tue, 26 May 2009 05:37:22 +0000
Subject: [PATCH] Merged revisions 72930 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk

........
  r72930 | collin.winter | 2009-05-25 21:12:39 -0700 (Mon, 25 May 2009) | 1 line

  Issue 5794: fix cPickle's unpickling of recursive tuples.
........
---
 Lib/test/pickletester.py | 10 ++++++++++
 Lib/test/test_cpickle.py |  5 +++++
 Modules/cPickle.c        | 19 +++++++++----------
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index e34d55b85d1..f7099a1b300 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -428,6 +428,16 @@ class AbstractPickleTests(unittest.TestCase):
             self.assertEqual(len(x), 1)
             self.assert_(x is x[0])
 
+    def test_recursive_tuple(self):
+        t = ([],)
+        t[0].append(t)
+        for proto in protocols:
+            s = self.dumps(t, proto)
+            x = self.loads(s)
+            self.assertEqual(len(x), 1)
+            self.assertEqual(len(x[0]), 1)
+            self.assert_(x is x[0][0])
+
     def test_recursive_dict(self):
         d = {}
         d[1] = d
diff --git a/Lib/test/test_cpickle.py b/Lib/test/test_cpickle.py
index 0b02b624734..c874481cdd6 100644
--- a/Lib/test/test_cpickle.py
+++ b/Lib/test/test_cpickle.py
@@ -64,6 +64,11 @@ class cPickleFastPicklerTests(AbstractPickleTests):
                           AbstractPickleTests.test_recursive_list,
                           self)
 
+    def test_recursive_tuple(self):
+        self.assertRaises(ValueError,
+                          AbstractPickleTests.test_recursive_tuple,
+                          self)
+
     def test_recursive_inst(self):
         self.assertRaises(ValueError,
                           AbstractPickleTests.test_recursive_inst,
diff --git a/Modules/cPickle.c b/Modules/cPickle.c
index fb13ba18bc4..1cef5c1f704 100644
--- a/Modules/cPickle.c
+++ b/Modules/cPickle.c
@@ -4016,25 +4016,24 @@ load_binpersid(Unpicklerobject *self)
 static int
 load_pop(Unpicklerobject *self)
 {
-	int len;
-
-	if (!( (len=self->stack->length) > 0 ))  return stackUnderflow();
+	int len = self->stack->length;
 
 	/* Note that we split the (pickle.py) stack into two stacks,
 	   an object stack and a mark stack. We have to be clever and
 	   pop the right one. We do this by looking at the top of the
-	   mark stack.
+	   mark stack first, and only signalling a stack underflow if
+	   the object stack is empty and the mark stack doesn't match
+	   our expectations.
 	*/
-
-	if ((self->num_marks > 0) &&
-	    (self->marks[self->num_marks - 1] == len))
+	if (self->num_marks > 0 && self->marks[self->num_marks - 1] == len) {
 		self->num_marks--;
-	else {
+	} else if (len >= 0) {
 		len--;
 		Py_DECREF(self->stack->data[len]);
-		self->stack->length=len;
+		self->stack->length = len;
+	} else {
+		return stackUnderflow();
 	}
-
 	return 0;
 }