python · Mariatta · May 27, 2017 · Apr 22, 2017 · May 27, 2017
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
@@ -348,6 +348,7 @@ def test_setstate_first_arg(self):
        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
@@ -361,6 +362,10 @@ def test_setstate_middle_arg(self):
            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
@@ -1090,6 +1090,7 @@ 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
@@ -56,6 +56,9 @@ Extension Modules
 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
@@ -313,6 +313,7 @@ random_setstate(RandomObject *self, PyObject *state)
    int i;
    unsigned long element;
    long index;
+    PY_UINT32_T new_state[N];

    if (!PyTuple_Check(state)) {
        PyErr_SetString(PyExc_TypeError,
@@ -329,7 +330,7 @@ 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] = (PY_UINT32_T)element;
+        new_state[i] = (PY_UINT32_T)element;
    }

    index = PyLong_AsLong(PyTuple_GET_ITEM(state, i));
@@ -340,6 +341,8 @@ 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;