[3.6] bpo-29960 _random.Random corrupted on exception in setstate(). … (#1287)

(cherry picked from commit 9616a82e7802241a4b74cf7ae38d43c37bf66e48)

4 files changed, 13 insertions, 1 deletions

diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 5b6a4f0..03adc0a 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -427,6 +427,7 @@ class MersenneTwister_TestBasicOps(TestBasicOps, unittest.TestCase):
         self.assertRaises(ValueError, self.gen.setstate, (1, None, None))
 
     def test_setstate_middle_arg(self):
+        start_state = self.gen.getstate()
         # Wrong type, s/b tuple
         self.assertRaises(TypeError, self.gen.setstate, (2, None, None))
         # Wrong length, s/b 625
@@ -440,6 +441,10 @@ class MersenneTwister_TestBasicOps(TestBasicOps, unittest.TestCase):
             self.gen.setstate((2, (1,)*624+(625,), None))
         with self.assertRaises((ValueError, OverflowError)):
             self.gen.setstate((2, (1,)*624+(-1,), None))
+        # Failed calls to setstate() should not have changed the state.
+        bits100 = self.gen.getrandbits(100)
+        self.gen.setstate(start_state)
+        self.assertEqual(self.gen.getrandbits(100), bits100)
 
         # Little trick to make "tuple(x % (2**32) for x in internalstate)"
         # raise ValueError. I cannot think of a simple way to achieve this, so
diff --git a/Misc/ACKS b/Misc/ACKS
index b8bac24..d03fe47 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1109,6 +1109,7 @@ Milan Oberkirch
 Pascal Oberndoerfer
 Jeffrey Ollie
 Adam Olsen
+Bryan Olson
 Grant Olson
 Koray Oner
 Piet van Oostrum
diff --git a/Misc/NEWS b/Misc/NEWS
index bdaf7aa..600da2d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -45,6 +45,9 @@ Core and Builtins
 Library
 -------
 
+- bpo-29960: Preserve generator state when _random.Random.setstate()
+  raises an exception.  Patch by Bryan Olson.
+
 - bpo-30414: multiprocessing.Queue._feed background running
   thread do not break from main loop on exception.
 
diff --git a/Modules/_randommodule.c b/Modules/_randommodule.c
index e5dd2c9..d006aeb 100644
--- a/Modules/_randommodule.c
+++ b/Modules/_randommodule.c
@@ -348,6 +348,7 @@ random_setstate(RandomObject *self, PyObject *state)
     int i;
     unsigned long element;
     long index;
+    uint32_t new_state[N];
 
     if (!PyTuple_Check(state)) {
         PyErr_SetString(PyExc_TypeError,
@@ -364,7 +365,7 @@ random_setstate(RandomObject *self, PyObject *state)
         element = PyLong_AsUnsignedLong(PyTuple_GET_ITEM(state, i));
         if (element == (unsigned long)-1 && PyErr_Occurred())
             return NULL;
-        self->state[i] = (uint32_t)element;
+        new_state[i] = (uint32_t)element;
     }
 
     index = PyLong_AsLong(PyTuple_GET_ITEM(state, i));
@@ -375,6 +376,8 @@ random_setstate(RandomObject *self, PyObject *state)
         return NULL;
     }
     self->index = (int)index;
+    for (i = 0; i < N; i++)
+        self->state[i] = new_state[i];
 
     Py_INCREF(Py_None);
     return Py_None;