Stackless issue python#241: add precondition test to tasklet.__setstate__

Add a check to tasklet.__setstate__() to raise RuntimeError, if the
tasklet is already alive.

(cherry picked from commit 58613bc)

Author: Anselm Kruis

Stackless/changelog.txt

@@ -4,6 +4,16 @@ Stackless-Python News
 This file documents user visible changes to the Stackless extension of C-Python.
 For other changes see Misc/NEWS.
 
+What's New in Stackless 3.X.X?
+==============================
+
+*Release date: 20XX-XX-XX*
+
+- https://github.com/stackless-dev/stackless/issues/241
+  Prevent a crash, if you call tasklet.__setstate__() on a tasklet, that is
+  alive.
+
+
 What's New in Stackless 3.6.9, 3.6.10, 3.6.11, 3.6.12 and 3.6.13?
 =================================================================
 

Stackless/module/taskletobject.c

@@ -535,6 +535,11 @@ tasklet_setstate(PyObject *self, PyObject *args)
     Py_ssize_t i, nframes;
     int j;
 
+    assert(t && PyTasklet_Check(t));
+
+    if (PyTasklet_Alive(t))
+        RUNTIME_ERROR("tasklet is alive", NULL);
+
     if (!PyArg_ParseTuple(args, "iOiO!:tasklet",
                           &flags,
                           &tempval,

Stackless/unittests/test_defects.py

@@ -646,6 +646,23 @@ def func():
         self.assertEqual(r, 4711)
 
 
+class TestTaskletSetstate(StacklessTestCase):
+    # a test case for https://github.com/stackless-dev/stackless/issues/241
+
+    def test_setstate_not_alive(self):
+        state = stackless.tasklet().__reduce__()[2]
+        t = stackless.tasklet()
+        self.assertFalse(t.alive)
+        self.assertIs(t.__setstate__(state), t)
+        t.bind()  # unbind t
+
+    def test_setstate_alive(self):
+        state = stackless.tasklet().__reduce__()[2]
+        t = stackless.tasklet(lambda: None,())
+        self.assertTrue(t.alive)
+        self.assertRaisesRegex(RuntimeError, "tasklet is alive", t.__setstate__, state)
+
+
 if __name__ == '__main__':
     if not sys.argv[1:]:
         sys.argv.append('-v')