Add create() and destroy().

python · ericsnowcurrently · Dec 14, 2016 · Dec 29, 2016 · Jan 1, 2017 · Dec 29, 2016
commit 84920ad6558c7fad4ba84b9f6eb7c330f95f8560
diff --git a/Doc/library/_interpreters.rst b/Doc/library/_interpreters.rst
@@ -28,7 +28,18 @@ support multiple interpreters.
 It defines the following functions:
 
 
-.. XXX TBD
+.. function:: create()
+
+   Initialize a new Python interpreter and return its identifier.  The
+   interpreter will be created in the current thread and will remain
+   idle until something is run in it.
+
+
+.. function:: destroy(id)
+
+   Finalize and destroy the identified interpreter.
+
+.. XXX must not be running?
 
 
 **Caveats:**

diff --git a/Lib/test/test__interpreters.py b/Lib/test/test__interpreters.py
@@ -1,10 +1,165 @@
+import threading
 import unittest
+
 from test import support
 interpreters = support.import_module('_interpreters')
 
 
 class InterpretersTests(unittest.TestCase):
-    pass
+
+    def setUp(self):
+        self.ids = []
+        self.lock = threading.Lock()
+
+    def tearDown(self):
+        for id in self.ids:
+            try:
+                interpreters.destroy(id)
+            except RuntimeError:
+                pass  # already destroyed
+
+    def _create(self):
+        id = interpreters.create()
+        self.ids.append(id)
+        return id
+
+    def test_create_in_main(self):
+        id = interpreters.create()
+        self.ids.append(id)
+
+        self.assertIn(id, interpreters._enumerate())
+
+    def test_create_unique_id(self):
+        seen = set()
+        for _ in range(100):
+            id = self._create()
+            interpreters.destroy(id)
+            seen.add(id)
+
+        self.assertEqual(len(seen), 100)
+
+    def test_create_in_thread(self):
+        id = None
+        def f():
+            nonlocal id
+            id = interpreters.create()
+            self.ids.append(id)
+            self.lock.acquire()
+            self.lock.release()
+
+        t = threading.Thread(target=f)
+        with self.lock:
+            t.start()
+        t.join()
+        self.assertIn(id, interpreters._enumerate())
+
+    @unittest.skip('waiting for run_string()')
+    def test_create_in_subinterpreter(self):
+        raise NotImplementedError
+
+    @unittest.skip('waiting for run_string()')
+    def test_create_in_threaded_subinterpreter(self):
+        raise NotImplementedError
+
+    def test_create_after_destroy_all(self):
+        before = set(interpreters._enumerate())
+        # Create 3 subinterpreters.
+        ids = []
+        for _ in range(3):
+            id = interpreters.create()
+            ids.append(id)
+        # Now destroy them.
+        for id in ids:
+            interpreters.destroy(id)
+        # Finally, create another.
+        id = interpreters.create()
+        self.ids.append(id)
+        self.assertEqual(set(interpreters._enumerate()), before | {id})
+
+    def test_create_after_destroy_some(self):
+        before = set(interpreters._enumerate())
+        # Create 3 subinterpreters.
+        id1 = interpreters.create()
+        id2 = interpreters.create()
+        self.ids.append(id2)
+        id3 = interpreters.create()
+        # Now destroy 2 of them.
+        interpreters.destroy(id1)
+        interpreters.destroy(id3)
+        # Finally, create another.
+        id = interpreters.create()
+        self.ids.append(id)
+        self.assertEqual(set(interpreters._enumerate()), before | {id, id2})
+
+    def test_destroy_one(self):
+        id1 = self._create()
+        id2 = self._create()
+        id3 = self._create()
+        self.assertIn(id2, interpreters._enumerate())
+        interpreters.destroy(id2)
+        self.assertNotIn(id2, interpreters._enumerate())
+        self.assertIn(id1, interpreters._enumerate())
+        self.assertIn(id3, interpreters._enumerate())
+
+    def test_destroy_all(self):
+        before = set(interpreters._enumerate())
+        ids = set()
+        for _ in range(3):
+            id = self._create()
+            ids.add(id)
+        self.assertEqual(set(interpreters._enumerate()), before | ids)
+        for id in ids:
+            interpreters.destroy(id)
+        self.assertEqual(set(interpreters._enumerate()), before)
+
+    def test_destroy_main(self):
+        main, = interpreters._enumerate()
+        with self.assertRaises(RuntimeError):
+            interpreters.destroy(main)
+
+        def f():
+            with self.assertRaises(RuntimeError):
+                interpreters.destroy(main)
+
+        t = threading.Thread(target=f)
+        t.start()
+        t.join()
+
+    def test_destroy_already_destroyed(self):
+        id = interpreters.create()
+        interpreters.destroy(id)
+        with self.assertRaises(RuntimeError):
+            interpreters.destroy(id)
+
+    def test_destroy_does_not_exist(self):
+        with self.assertRaises(RuntimeError):
+            interpreters.destroy(1_000_000)
+
+    def test_destroy_bad_id(self):
+        with self.assertRaises(RuntimeError):
+            interpreters.destroy(-1)
+
+    @unittest.skip('waiting for run_string()')
+    def test_destroy_from_current(self):
+        raise NotImplementedError
+
+    @unittest.skip('waiting for run_string()')
+    def test_destroy_from_sibling(self):
+        raise NotImplementedError
+
+    def test_destroy_from_other_thread(self):
+        id = interpreters.create()
+        self.ids.append(id)
+        def f():
+            interpreters.destroy(id)
+
+        t = threading.Thread(target=f)
+        t.start()
+        t.join()
+
+    @unittest.skip('waiting for run_string()')
+    def test_destroy_still_running(self):
+        raise NotImplementedError
 
 
 if __name__ == "__main__":

diff --git a/Modules/_interpretersmodule.c b/Modules/_interpretersmodule.c
@@ -5,8 +5,173 @@
 #include "Python.h"
 
 
+static PyObject *
+_get_id(PyInterpreterState *interp)
+{
+    unsigned long id = PyInterpreterState_GetID(interp);
+    if (id == 0 && PyErr_Occurred() != NULL)
+        return NULL;
+    return PyLong_FromUnsignedLong(id);
+}
+
+static PyInterpreterState *
+_look_up(PyObject *requested_id)
+{
+    PyObject * id;
+    PyInterpreterState *interp;
+
+    interp = PyInterpreterState_Head();
+    while (interp != NULL) {
+        id = _get_id(interp);
+        if (id == NULL)
+            return NULL;
+        if (requested_id == id)
+            return interp;
+        interp = PyInterpreterState_Next(interp);
+    }
+
+    PyErr_Format(PyExc_RuntimeError,
+                 "unrecognized interpreter ID %R", requested_id);
+    return NULL;
+}
+
+static PyObject *
+_get_current(void)
+{
+    PyThreadState *tstate;
+    PyInterpreterState *interp;
+
+    tstate = PyThreadState_Get();
+    if (tstate == NULL)
+        return NULL;
+    interp = tstate->interp;
+
+    // get ID
+    return _get_id(interp);
+}
+
+
+/* module level code ********************************************************/
+
+// XXX track count?
+
+static PyObject *
+interp_create(PyObject *self, PyObject *args)
+{
+    if (!PyArg_UnpackTuple(args, "create", 0, 0))
+        return NULL;
+
+    // Create and initialize the new interpreter.
+    PyThreadState *tstate, *save_tstate;
+    save_tstate = PyThreadState_Swap(NULL);
+    tstate = Py_NewInterpreter();
+    PyThreadState_Swap(save_tstate);
+    if (tstate == NULL) {
+        /* Since no new thread state was created, there is no exception to
+           propagate; raise a fresh one after swapping in the old thread
+           state. */
+        PyErr_SetString(PyExc_RuntimeError, "interpreter creation failed");
+        return NULL;
+    }
+    return _get_id(tstate->interp);
+}
+
+PyDoc_STRVAR(create_doc,
+"create() -> ID\n\
+\n\
+Create a new interpreter and return a unique generated ID.");
+
+
+static PyObject *
+interp_destroy(PyObject *self, PyObject *args)
+{
+    PyObject *id;
+    if (!PyArg_UnpackTuple(args, "destroy", 1, 1, &id))
+        return NULL;
+    if (!PyLong_Check(id)) {
+        PyErr_SetString(PyExc_TypeError, "ID must be an int");
+        return NULL;
+    }
+
+    // Ensure the ID is not the current interpreter.
+    PyObject *current = _get_current();
+    if (current == NULL)
+        return NULL;
+    if (PyObject_RichCompareBool(id, current, Py_EQ) != 0) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "cannot destroy the current interpreter");
+        return NULL;
+    }
+
+    // Look up the interpreter.
+    PyInterpreterState *interp = _look_up(id);
+    if (interp == NULL)
+        return NULL;
+
+    // Destroy the interpreter.
+    //PyInterpreterState_Delete(interp);
+    PyThreadState *tstate, *save_tstate;
+    tstate = PyInterpreterState_ThreadHead(interp);  // XXX Is this the right one?
+    save_tstate = PyThreadState_Swap(tstate);
+    // XXX Stop current execution?
+    Py_EndInterpreter(tstate);  // XXX Handle possible errors?
+    PyThreadState_Swap(save_tstate);
+
+    Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(destroy_doc,
+"destroy(ID)\n\
+\n\
+Destroy the identified interpreter.\n\
+\n\
+Attempting to destroy the current interpreter results in a RuntimeError.\n\
+So does an unrecognized ID.");
+
+
+static PyObject *
+interp_enumerate(PyObject *self)
+{
+    PyObject *ids, *id;
+    PyInterpreterState *interp;
+
+    // XXX Handle multiple main interpreters.
+
+    ids = PyList_New(0);
+    if (ids == NULL)
+        return NULL;
+
+    interp = PyInterpreterState_Head();
+    while (interp != NULL) {
+        id = _get_id(interp);
+        if (id == NULL)
+            return NULL;
+        // insert at front of list
+        if (PyList_Insert(ids, 0, id) < 0)
+            return NULL;
+
+        interp = PyInterpreterState_Next(interp);
+    }
+
+    return ids;
+}
+
+PyDoc_STRVAR(enumerate_doc,
+"enumerate() -> [ID]\n\
+\n\
+Return a list containing the ID of every existing interpreter.");
+
+
 static PyMethodDef module_functions[] = {
-    {NULL, NULL}           /* sentinel */
+    {"create",      (PyCFunction)interp_create,
+     METH_VARARGS, create_doc},
+    {"destroy",     (PyCFunction)interp_destroy,
+     METH_VARARGS, destroy_doc},
+
+    {"_enumerate",   (PyCFunction)interp_enumerate,
+     METH_NOARGS, enumerate_doc},
+
+    {NULL,          NULL}           /* sentinel */
 };