two version of R2R are here HEAD master

1 files changed, 1324 insertions, 0 deletions

diff --git a/.venv/lib/python3.12/site-packages/greenlet/tests/test_greenlet.py b/.venv/lib/python3.12/site-packages/greenlet/tests/test_greenlet.py
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+++ b/.venv/lib/python3.12/site-packages/greenlet/tests/test_greenlet.py
@@ -0,0 +1,1324 @@
+import gc
+import sys
+import time
+import threading
+import unittest
+
+from abc import ABCMeta
+from abc import abstractmethod
+
+import greenlet
+from greenlet import greenlet as RawGreenlet
+from . import TestCase
+from . import RUNNING_ON_MANYLINUX
+from . import PY313
+from .leakcheck import fails_leakcheck
+
+
+# We manually manage locks in many tests
+# pylint:disable=consider-using-with
+# pylint:disable=too-many-public-methods
+# This module is quite large.
+# TODO: Refactor into separate test files. For example,
+# put all the regression tests that used to produce
+# crashes in test_greenlet_no_crash; put tests that DO deliberately crash
+# the interpreter into test_greenlet_crash.
+# pylint:disable=too-many-lines
+
+class SomeError(Exception):
+    pass
+
+
+def fmain(seen):
+    try:
+        greenlet.getcurrent().parent.switch()
+    except:
+        seen.append(sys.exc_info()[0])
+        raise
+    raise SomeError
+
+
+def send_exception(g, exc):
+    # note: send_exception(g, exc)  can be now done with  g.throw(exc).
+    # the purpose of this test is to explicitly check the propagation rules.
+    def crasher(exc):
+        raise exc
+    g1 = RawGreenlet(crasher, parent=g)
+    g1.switch(exc)
+
+
+class TestGreenlet(TestCase):
+
+    def _do_simple_test(self):
+        lst = []
+
+        def f():
+            lst.append(1)
+            greenlet.getcurrent().parent.switch()
+            lst.append(3)
+        g = RawGreenlet(f)
+        lst.append(0)
+        g.switch()
+        lst.append(2)
+        g.switch()
+        lst.append(4)
+        self.assertEqual(lst, list(range(5)))
+
+    def test_simple(self):
+        self._do_simple_test()
+
+    def test_switch_no_run_raises_AttributeError(self):
+        g = RawGreenlet()
+        with self.assertRaises(AttributeError) as exc:
+            g.switch()
+
+        self.assertIn("run", str(exc.exception))
+
+    def test_throw_no_run_raises_AttributeError(self):
+        g = RawGreenlet()
+        with self.assertRaises(AttributeError) as exc:
+            g.throw(SomeError)
+
+        self.assertIn("run", str(exc.exception))
+
+    def test_parent_equals_None(self):
+        g = RawGreenlet(parent=None)
+        self.assertIsNotNone(g)
+        self.assertIs(g.parent, greenlet.getcurrent())
+
+    def test_run_equals_None(self):
+        g = RawGreenlet(run=None)
+        self.assertIsNotNone(g)
+        self.assertIsNone(g.run)
+
+    def test_two_children(self):
+        lst = []
+
+        def f():
+            lst.append(1)
+            greenlet.getcurrent().parent.switch()
+            lst.extend([1, 1])
+        g = RawGreenlet(f)
+        h = RawGreenlet(f)
+        g.switch()
+        self.assertEqual(len(lst), 1)
+        h.switch()
+        self.assertEqual(len(lst), 2)
+        h.switch()
+        self.assertEqual(len(lst), 4)
+        self.assertEqual(h.dead, True)
+        g.switch()
+        self.assertEqual(len(lst), 6)
+        self.assertEqual(g.dead, True)
+
+    def test_two_recursive_children(self):
+        lst = []
+
+        def f():
+            lst.append('b')
+            greenlet.getcurrent().parent.switch()
+
+        def g():
+            lst.append('a')
+            g = RawGreenlet(f)
+            g.switch()
+            lst.append('c')
+
+        g = RawGreenlet(g)
+        self.assertEqual(sys.getrefcount(g), 2)
+        g.switch()
+        self.assertEqual(lst, ['a', 'b', 'c'])
+        # Just the one in this frame, plus the one on the stack we pass to the function
+        self.assertEqual(sys.getrefcount(g), 2)
+
+    def test_threads(self):
+        success = []
+
+        def f():
+            self._do_simple_test()
+            success.append(True)
+        ths = [threading.Thread(target=f) for i in range(10)]
+        for th in ths:
+            th.start()
+        for th in ths:
+            th.join(10)
+        self.assertEqual(len(success), len(ths))
+
+    def test_exception(self):
+        seen = []
+        g1 = RawGreenlet(fmain)
+        g2 = RawGreenlet(fmain)
+        g1.switch(seen)
+        g2.switch(seen)
+        g2.parent = g1
+
+        self.assertEqual(seen, [])
+        #with self.assertRaises(SomeError):
+        #    p("***Switching back")
+        #    g2.switch()
+        # Creating this as a bound method can reveal bugs that
+        # are hidden on newer versions of Python that avoid creating
+        # bound methods for direct expressions; IOW, don't use the `with`
+        # form!
+        self.assertRaises(SomeError, g2.switch)
+        self.assertEqual(seen, [SomeError])
+
+        value = g2.switch()
+        self.assertEqual(value, ())
+        self.assertEqual(seen, [SomeError])
+
+        value = g2.switch(25)
+        self.assertEqual(value, 25)
+        self.assertEqual(seen, [SomeError])
+
+
+    def test_send_exception(self):
+        seen = []
+        g1 = RawGreenlet(fmain)
+        g1.switch(seen)
+        self.assertRaises(KeyError, send_exception, g1, KeyError)
+        self.assertEqual(seen, [KeyError])
+
+    def test_dealloc(self):
+        seen = []
+        g1 = RawGreenlet(fmain)
+        g2 = RawGreenlet(fmain)
+        g1.switch(seen)
+        g2.switch(seen)
+        self.assertEqual(seen, [])
+        del g1
+        gc.collect()
+        self.assertEqual(seen, [greenlet.GreenletExit])
+        del g2
+        gc.collect()
+        self.assertEqual(seen, [greenlet.GreenletExit, greenlet.GreenletExit])
+
+    def test_dealloc_catches_GreenletExit_throws_other(self):
+        def run():
+            try:
+                greenlet.getcurrent().parent.switch()
+            except greenlet.GreenletExit:
+                raise SomeError from None
+
+        g = RawGreenlet(run)
+        g.switch()
+        # Destroying the only reference to the greenlet causes it
+        # to get GreenletExit; when it in turn raises, even though we're the parent
+        # we don't get the exception, it just gets printed.
+        # When we run on 3.8 only, we can use sys.unraisablehook
+        oldstderr = sys.stderr
+        from io import StringIO
+        stderr = sys.stderr = StringIO()
+        try:
+            del g
+        finally:
+            sys.stderr = oldstderr
+
+        v = stderr.getvalue()
+        self.assertIn("Exception", v)
+        self.assertIn('ignored', v)
+        self.assertIn("SomeError", v)
+
+
+    @unittest.skipIf(
+        PY313 and RUNNING_ON_MANYLINUX,
+        "Sometimes flaky (getting one GreenletExit in the second list)"
+        # Probably due to funky timing interactions?
+        # TODO: FIXME Make that work.
+    )
+
+    def test_dealloc_other_thread(self):
+        seen = []
+        someref = []
+
+        bg_glet_created_running_and_no_longer_ref_in_bg = threading.Event()
+        fg_ref_released = threading.Event()
+        bg_should_be_clear = threading.Event()
+        ok_to_exit_bg_thread = threading.Event()
+
+        def f():
+            g1 = RawGreenlet(fmain)
+            g1.switch(seen)
+            someref.append(g1)
+            del g1
+            gc.collect()
+
+            bg_glet_created_running_and_no_longer_ref_in_bg.set()
+            fg_ref_released.wait(3)
+
+            RawGreenlet()   # trigger release
+            bg_should_be_clear.set()
+            ok_to_exit_bg_thread.wait(3)
+            RawGreenlet() # One more time
+
+        t = threading.Thread(target=f)
+        t.start()
+        bg_glet_created_running_and_no_longer_ref_in_bg.wait(10)
+
+        self.assertEqual(seen, [])
+        self.assertEqual(len(someref), 1)
+        del someref[:]
+        gc.collect()
+        # g1 is not released immediately because it's from another thread
+        self.assertEqual(seen, [])
+        fg_ref_released.set()
+        bg_should_be_clear.wait(3)
+        try:
+            self.assertEqual(seen, [greenlet.GreenletExit])
+        finally:
+            ok_to_exit_bg_thread.set()
+            t.join(10)
+            del seen[:]
+            del someref[:]
+
+    def test_frame(self):
+        def f1():
+            f = sys._getframe(0) # pylint:disable=protected-access
+            self.assertEqual(f.f_back, None)
+            greenlet.getcurrent().parent.switch(f)
+            return "meaning of life"
+        g = RawGreenlet(f1)
+        frame = g.switch()
+        self.assertTrue(frame is g.gr_frame)
+        self.assertTrue(g)
+
+        from_g = g.switch()
+        self.assertFalse(g)
+        self.assertEqual(from_g, 'meaning of life')
+        self.assertEqual(g.gr_frame, None)
+
+    def test_thread_bug(self):
+        def runner(x):
+            g = RawGreenlet(lambda: time.sleep(x))
+            g.switch()
+        t1 = threading.Thread(target=runner, args=(0.2,))
+        t2 = threading.Thread(target=runner, args=(0.3,))
+        t1.start()
+        t2.start()
+        t1.join(10)
+        t2.join(10)
+
+    def test_switch_kwargs(self):
+        def run(a, b):
+            self.assertEqual(a, 4)
+            self.assertEqual(b, 2)
+            return 42
+        x = RawGreenlet(run).switch(a=4, b=2)
+        self.assertEqual(x, 42)
+
+    def test_switch_kwargs_to_parent(self):
+        def run(x):
+            greenlet.getcurrent().parent.switch(x=x)
+            greenlet.getcurrent().parent.switch(2, x=3)
+            return x, x ** 2
+        g = RawGreenlet(run)
+        self.assertEqual({'x': 3}, g.switch(3))
+        self.assertEqual(((2,), {'x': 3}), g.switch())
+        self.assertEqual((3, 9), g.switch())
+
+    def test_switch_to_another_thread(self):
+        data = {}
+        created_event = threading.Event()
+        done_event = threading.Event()
+
+        def run():
+            data['g'] = RawGreenlet(lambda: None)
+            created_event.set()
+            done_event.wait(10)
+        thread = threading.Thread(target=run)
+        thread.start()
+        created_event.wait(10)
+        with self.assertRaises(greenlet.error):
+            data['g'].switch()
+        done_event.set()
+        thread.join(10)
+        # XXX: Should handle this automatically
+        data.clear()
+
+    def test_exc_state(self):
+        def f():
+            try:
+                raise ValueError('fun')
+            except: # pylint:disable=bare-except
+                exc_info = sys.exc_info()
+                RawGreenlet(h).switch()
+                self.assertEqual(exc_info, sys.exc_info())
+
+        def h():
+            self.assertEqual(sys.exc_info(), (None, None, None))
+
+        RawGreenlet(f).switch()
+
+    def test_instance_dict(self):
+        def f():
+            greenlet.getcurrent().test = 42
+        def deldict(g):
+            del g.__dict__
+        def setdict(g, value):
+            g.__dict__ = value
+        g = RawGreenlet(f)
+        self.assertEqual(g.__dict__, {})
+        g.switch()
+        self.assertEqual(g.test, 42)
+        self.assertEqual(g.__dict__, {'test': 42})
+        g.__dict__ = g.__dict__
+        self.assertEqual(g.__dict__, {'test': 42})
+        self.assertRaises(TypeError, deldict, g)
+        self.assertRaises(TypeError, setdict, g, 42)
+
+    def test_running_greenlet_has_no_run(self):
+        has_run = []
+        def func():
+            has_run.append(
+                hasattr(greenlet.getcurrent(), 'run')
+            )
+
+        g = RawGreenlet(func)
+        g.switch()
+        self.assertEqual(has_run, [False])
+
+    def test_deepcopy(self):
+        import copy
+        self.assertRaises(TypeError, copy.copy, RawGreenlet())
+        self.assertRaises(TypeError, copy.deepcopy, RawGreenlet())
+
+    def test_parent_restored_on_kill(self):
+        hub = RawGreenlet(lambda: None)
+        main = greenlet.getcurrent()
+        result = []
+        def worker():
+            try:
+                # Wait to be killed by going back to the test.
+                main.switch()
+            except greenlet.GreenletExit:
+                # Resurrect and switch to parent
+                result.append(greenlet.getcurrent().parent)
+                result.append(greenlet.getcurrent())
+                hub.switch()
+        g = RawGreenlet(worker, parent=hub)
+        g.switch()
+        # delete the only reference, thereby raising GreenletExit
+        del g
+        self.assertTrue(result)
+        self.assertIs(result[0], main)
+        self.assertIs(result[1].parent, hub)
+        # Delete them, thereby breaking the cycle between the greenlet
+        # and the frame, which otherwise would never be collectable
+        # XXX: We should be able to automatically fix this.
+        del result[:]
+        hub = None
+        main = None
+
+    def test_parent_return_failure(self):
+        # No run causes AttributeError on switch
+        g1 = RawGreenlet()
+        # Greenlet that implicitly switches to parent
+        g2 = RawGreenlet(lambda: None, parent=g1)
+        # AttributeError should propagate to us, no fatal errors
+        with self.assertRaises(AttributeError):
+            g2.switch()
+
+    def test_throw_exception_not_lost(self):
+        class mygreenlet(RawGreenlet):
+            def __getattribute__(self, name):
+                try:
+                    raise Exception # pylint:disable=broad-exception-raised
+                except: # pylint:disable=bare-except
+                    pass
+                return RawGreenlet.__getattribute__(self, name)
+        g = mygreenlet(lambda: None)
+        self.assertRaises(SomeError, g.throw, SomeError())
+
+    @fails_leakcheck
+    def _do_test_throw_to_dead_thread_doesnt_crash(self, wait_for_cleanup=False):
+        result = []
+        def worker():
+            greenlet.getcurrent().parent.switch()
+
+        def creator():
+            g = RawGreenlet(worker)
+            g.switch()
+            result.append(g)
+            if wait_for_cleanup:
+                # Let this greenlet eventually be cleaned up.
+                g.switch()
+                greenlet.getcurrent()
+        t = threading.Thread(target=creator)
+        t.start()
+        t.join(10)
+        del t
+        # But, depending on the operating system, the thread
+        # deallocator may not actually have run yet! So we can't be
+        # sure about the error message unless we wait.
+        if wait_for_cleanup:
+            self.wait_for_pending_cleanups()
+        with self.assertRaises(greenlet.error) as exc:
+            result[0].throw(SomeError)
+
+        if not wait_for_cleanup:
+            s = str(exc.exception)
+            self.assertTrue(
+                s == "cannot switch to a different thread (which happens to have exited)"
+                or 'Cannot switch' in s
+            )
+        else:
+            self.assertEqual(
+                str(exc.exception),
+                "cannot switch to a different thread (which happens to have exited)",
+            )
+
+        if hasattr(result[0].gr_frame, 'clear'):
+            # The frame is actually executing (it thinks), we can't clear it.
+            with self.assertRaises(RuntimeError):
+                result[0].gr_frame.clear()
+        # Unfortunately, this doesn't actually clear the references, they're in the
+        # fast local array.
+        if not wait_for_cleanup:
+            # f_locals has no clear method in Python 3.13
+            if hasattr(result[0].gr_frame.f_locals, 'clear'):
+                result[0].gr_frame.f_locals.clear()
+        else:
+            self.assertIsNone(result[0].gr_frame)
+
+        del creator
+        worker = None
+        del result[:]
+        # XXX: we ought to be able to automatically fix this.
+        # See issue 252
+        self.expect_greenlet_leak = True # direct us not to wait for it to go away
+
+    @fails_leakcheck
+    def test_throw_to_dead_thread_doesnt_crash(self):
+        self._do_test_throw_to_dead_thread_doesnt_crash()
+
+    def test_throw_to_dead_thread_doesnt_crash_wait(self):
+        self._do_test_throw_to_dead_thread_doesnt_crash(True)
+
+    @fails_leakcheck
+    def test_recursive_startup(self):
+        class convoluted(RawGreenlet):
+            def __init__(self):
+                RawGreenlet.__init__(self)
+                self.count = 0
+            def __getattribute__(self, name):
+                if name == 'run' and self.count == 0:
+                    self.count = 1
+                    self.switch(43)
+                return RawGreenlet.__getattribute__(self, name)
+            def run(self, value):
+                while True:
+                    self.parent.switch(value)
+        g = convoluted()
+        self.assertEqual(g.switch(42), 43)
+        # Exits the running greenlet, otherwise it leaks
+        # XXX: We should be able to automatically fix this
+        #g.throw(greenlet.GreenletExit)
+        #del g
+        self.expect_greenlet_leak = True
+
+    def test_threaded_updatecurrent(self):
+        # released when main thread should execute
+        lock1 = threading.Lock()
+        lock1.acquire()
+        # released when another thread should execute
+        lock2 = threading.Lock()
+        lock2.acquire()
+        class finalized(object):
+            def __del__(self):
+                # happens while in green_updatecurrent() in main greenlet
+                # should be very careful not to accidentally call it again
+                # at the same time we must make sure another thread executes
+                lock2.release()
+                lock1.acquire()
+                # now ts_current belongs to another thread
+        def deallocator():
+            greenlet.getcurrent().parent.switch()
+        def fthread():
+            lock2.acquire()
+            greenlet.getcurrent()
+            del g[0]
+            lock1.release()
+            lock2.acquire()
+            greenlet.getcurrent()
+            lock1.release()
+        main = greenlet.getcurrent()
+        g = [RawGreenlet(deallocator)]
+        g[0].bomb = finalized()
+        g[0].switch()
+        t = threading.Thread(target=fthread)
+        t.start()
+        # let another thread grab ts_current and deallocate g[0]
+        lock2.release()
+        lock1.acquire()
+        # this is the corner stone
+        # getcurrent() will notice that ts_current belongs to another thread
+        # and start the update process, which would notice that g[0] should
+        # be deallocated, and that will execute an object's finalizer. Now,
+        # that object will let another thread run so it can grab ts_current
+        # again, which would likely crash the interpreter if there's no
+        # check for this case at the end of green_updatecurrent(). This test
+        # passes if getcurrent() returns correct result, but it's likely
+        # to randomly crash if it's not anyway.
+        self.assertEqual(greenlet.getcurrent(), main)
+        # wait for another thread to complete, just in case
+        t.join(10)
+
+    def test_dealloc_switch_args_not_lost(self):
+        seen = []
+        def worker():
+            # wait for the value
+            value = greenlet.getcurrent().parent.switch()
+            # delete all references to ourself
+            del worker[0]
+            initiator.parent = greenlet.getcurrent().parent
+            # switch to main with the value, but because
+            # ts_current is the last reference to us we
+            # return here immediately, where we resurrect ourself.
+            try:
+                greenlet.getcurrent().parent.switch(value)
+            finally:
+                seen.append(greenlet.getcurrent())
+        def initiator():
+            return 42 # implicitly falls thru to parent
+
+        worker = [RawGreenlet(worker)]
+
+        worker[0].switch() # prime worker
+        initiator = RawGreenlet(initiator, worker[0])
+        value = initiator.switch()
+        self.assertTrue(seen)
+        self.assertEqual(value, 42)
+
+    def test_tuple_subclass(self):
+        # The point of this test is to see what happens when a custom
+        # tuple subclass is used as an object passed directly to the C
+        # function ``green_switch``; part of ``green_switch`` checks
+        # the ``len()`` of the ``args`` tuple, and that can call back
+        # into Python. Here, when it calls back into Python, we
+        # recursively enter ``green_switch`` again.
+
+        # This test is really only relevant on Python 2. The builtin
+        # `apply` function directly passes the given args tuple object
+        # to the underlying function, whereas the Python 3 version
+        # unpacks and repacks into an actual tuple. This could still
+        # happen using the C API on Python 3 though. We should write a
+        # builtin version of apply() ourself.
+        def _apply(func, a, k):
+            func(*a, **k)
+
+        class mytuple(tuple):
+            def __len__(self):
+                greenlet.getcurrent().switch()
+                return tuple.__len__(self)
+        args = mytuple()
+        kwargs = dict(a=42)
+        def switchapply():
+            _apply(greenlet.getcurrent().parent.switch, args, kwargs)
+        g = RawGreenlet(switchapply)
+        self.assertEqual(g.switch(), kwargs)
+
+    def test_abstract_subclasses(self):
+        AbstractSubclass = ABCMeta(
+            'AbstractSubclass',
+            (RawGreenlet,),
+            {'run': abstractmethod(lambda self: None)})
+
+        class BadSubclass(AbstractSubclass):
+            pass
+
+        class GoodSubclass(AbstractSubclass):
+            def run(self):
+                pass
+
+        GoodSubclass() # should not raise
+        self.assertRaises(TypeError, BadSubclass)
+
+    def test_implicit_parent_with_threads(self):
+        if not gc.isenabled():
+            return # cannot test with disabled gc
+        N = gc.get_threshold()[0]
+        if N < 50:
+            return # cannot test with such a small N
+        def attempt():
+            lock1 = threading.Lock()
+            lock1.acquire()
+            lock2 = threading.Lock()
+            lock2.acquire()
+            recycled = [False]
+            def another_thread():
+                lock1.acquire() # wait for gc
+                greenlet.getcurrent() # update ts_current
+                lock2.release() # release gc
+            t = threading.Thread(target=another_thread)
+            t.start()
+            class gc_callback(object):
+                def __del__(self):
+                    lock1.release()
+                    lock2.acquire()
+                    recycled[0] = True
+            class garbage(object):
+                def __init__(self):
+                    self.cycle = self
+                    self.callback = gc_callback()
+            l = []
+            x = range(N*2)
+            current = greenlet.getcurrent()
+            g = garbage()
+            for _ in x:
+                g = None # lose reference to garbage
+                if recycled[0]:
+                    # gc callback called prematurely
+                    t.join(10)
+                    return False
+                last = RawGreenlet()
+                if recycled[0]:
+                    break # yes! gc called in green_new
+                l.append(last) # increase allocation counter
+            else:
+                # gc callback not called when expected
+                gc.collect()
+                if recycled[0]:
+                    t.join(10)
+                return False
+            self.assertEqual(last.parent, current)
+            for g in l:
+                self.assertEqual(g.parent, current)
+            return True
+        for _ in range(5):
+            if attempt():
+                break
+
+    def test_issue_245_reference_counting_subclass_no_threads(self):
+        # https://github.com/python-greenlet/greenlet/issues/245
+        # Before the fix, this crashed pretty reliably on
+        # Python 3.10, at least on macOS; but much less reliably on other
+        # interpreters (memory layout must have changed).
+        # The threaded test crashed more reliably on more interpreters.
+        from greenlet import getcurrent
+        from greenlet import GreenletExit
+
+        class Greenlet(RawGreenlet):
+            pass
+
+        initial_refs = sys.getrefcount(Greenlet)
+        # This has to be an instance variable because
+        # Python 2 raises a SyntaxError if we delete a local
+        # variable referenced in an inner scope.
+        self.glets = [] # pylint:disable=attribute-defined-outside-init
+
+        def greenlet_main():
+            try:
+                getcurrent().parent.switch()
+            except GreenletExit:
+                self.glets.append(getcurrent())
+
+        # Before the
+        for _ in range(10):
+            Greenlet(greenlet_main).switch()
+
+        del self.glets
+        self.assertEqual(sys.getrefcount(Greenlet), initial_refs)
+
+    @unittest.skipIf(
+        PY313 and RUNNING_ON_MANYLINUX,
+        "The manylinux images appear to hang on this test on 3.13rc2"
+        # Or perhaps I just got tired of waiting for the 450s timeout.
+        # Still, it shouldn't take anywhere near that long. Does not reproduce in
+        # Ubuntu images, on macOS or Windows.
+    )
+    def test_issue_245_reference_counting_subclass_threads(self):
+        # https://github.com/python-greenlet/greenlet/issues/245
+        from threading import Thread
+        from threading import Event
+
+        from greenlet import getcurrent
+
+        class MyGreenlet(RawGreenlet):
+            pass
+
+        glets = []
+        ref_cleared = Event()
+
+        def greenlet_main():
+            getcurrent().parent.switch()
+
+        def thread_main(greenlet_running_event):
+            mine = MyGreenlet(greenlet_main)
+            glets.append(mine)
+            # The greenlets being deleted must be active
+            mine.switch()
+            # Don't keep any reference to it in this thread
+            del mine
+            # Let main know we published our greenlet.
+            greenlet_running_event.set()
+            # Wait for main to let us know the references are
+            # gone and the greenlet objects no longer reachable
+            ref_cleared.wait(10)
+            # The creating thread must call getcurrent() (or a few other
+            # greenlet APIs) because that's when the thread-local list of dead
+            # greenlets gets cleared.
+            getcurrent()
+
+        # We start with 3 references to the subclass:
+        # - This module
+        # - Its __mro__
+        # - The __subclassess__ attribute of greenlet
+        # - (If we call gc.get_referents(), we find four entries, including
+        #   some other tuple ``(greenlet)`` that I'm not sure about but must be part
+        #   of the machinery.)
+        #
+        # On Python 3.10 it's often enough to just run 3 threads; on Python 2.7,
+        # more threads are needed, and the results are still
+        # non-deterministic. Presumably the memory layouts are different
+        initial_refs = sys.getrefcount(MyGreenlet)
+        thread_ready_events = []
+        for _ in range(
+                initial_refs + 45
+        ):
+            event = Event()
+            thread = Thread(target=thread_main, args=(event,))
+            thread_ready_events.append(event)
+            thread.start()
+
+
+        for done_event in thread_ready_events:
+            done_event.wait(10)
+
+
+        del glets[:]
+        ref_cleared.set()
+        # Let any other thread run; it will crash the interpreter
+        # if not fixed (or silently corrupt memory and we possibly crash
+        # later).
+        self.wait_for_pending_cleanups()
+        self.assertEqual(sys.getrefcount(MyGreenlet), initial_refs)
+
+    def test_falling_off_end_switches_to_unstarted_parent_raises_error(self):
+        def no_args():
+            return 13
+
+        parent_never_started = RawGreenlet(no_args)
+
+        def leaf():
+            return 42
+
+        child = RawGreenlet(leaf, parent_never_started)
+
+        # Because the run function takes to arguments
+        with self.assertRaises(TypeError):
+            child.switch()
+
+    def test_falling_off_end_switches_to_unstarted_parent_works(self):
+        def one_arg(x):
+            return (x, 24)
+
+        parent_never_started = RawGreenlet(one_arg)
+
+        def leaf():
+            return 42
+
+        child = RawGreenlet(leaf, parent_never_started)
+
+        result = child.switch()
+        self.assertEqual(result, (42, 24))
+
+    def test_switch_to_dead_greenlet_with_unstarted_perverse_parent(self):
+        class Parent(RawGreenlet):
+            def __getattribute__(self, name):
+                if name == 'run':
+                    raise SomeError
+
+
+        parent_never_started = Parent()
+        seen = []
+        child = RawGreenlet(lambda: seen.append(42), parent_never_started)
+        # Because we automatically start the parent when the child is
+        # finished
+        with self.assertRaises(SomeError):
+            child.switch()
+
+        self.assertEqual(seen, [42])
+
+        with self.assertRaises(SomeError):
+            child.switch()
+        self.assertEqual(seen, [42])
+
+    def test_switch_to_dead_greenlet_reparent(self):
+        seen = []
+        parent_never_started = RawGreenlet(lambda: seen.append(24))
+        child = RawGreenlet(lambda: seen.append(42))
+
+        child.switch()
+        self.assertEqual(seen, [42])
+
+        child.parent = parent_never_started
+        # This actually is the same as switching to the parent.
+        result = child.switch()
+        self.assertIsNone(result)
+        self.assertEqual(seen, [42, 24])
+
+    def test_can_access_f_back_of_suspended_greenlet(self):
+        # This tests our frame rewriting to work around Python 3.12+ having
+        # some interpreter frames on the C stack. It will crash in the absence
+        # of that logic.
+        main = greenlet.getcurrent()
+
+        def outer():
+            inner()
+
+        def inner():
+            main.switch(sys._getframe(0))
+
+        hub = RawGreenlet(outer)
+        # start it
+        hub.switch()
+
+        # start another greenlet to make sure we aren't relying on
+        # anything in `hub` still being on the C stack
+        unrelated = RawGreenlet(lambda: None)
+        unrelated.switch()
+
+        # now it is suspended
+        self.assertIsNotNone(hub.gr_frame)
+        self.assertEqual(hub.gr_frame.f_code.co_name, "inner")
+        self.assertIsNotNone(hub.gr_frame.f_back)
+        self.assertEqual(hub.gr_frame.f_back.f_code.co_name, "outer")
+        # The next line is what would crash
+        self.assertIsNone(hub.gr_frame.f_back.f_back)
+
+    def test_get_stack_with_nested_c_calls(self):
+        from functools import partial
+        from . import _test_extension_cpp
+
+        def recurse(v):
+            if v > 0:
+                return v * _test_extension_cpp.test_call(partial(recurse, v - 1))
+            return greenlet.getcurrent().parent.switch()
+
+        gr = RawGreenlet(recurse)
+        gr.switch(5)
+        frame = gr.gr_frame
+        for i in range(5):
+            self.assertEqual(frame.f_locals["v"], i)
+            frame = frame.f_back
+        self.assertEqual(frame.f_locals["v"], 5)
+        self.assertIsNone(frame.f_back)
+        self.assertEqual(gr.switch(10), 1200)  # 1200 = 5! * 10
+
+    def test_frames_always_exposed(self):
+        # On Python 3.12 this will crash if we don't set the
+        # gr_frames_always_exposed attribute. More background:
+        # https://github.com/python-greenlet/greenlet/issues/388
+        main = greenlet.getcurrent()
+
+        def outer():
+            inner(sys._getframe(0))
+
+        def inner(frame):
+            main.switch(frame)
+
+        gr = RawGreenlet(outer)
+        frame = gr.switch()
+
+        # Do something else to clobber the part of the C stack used by `gr`,
+        # so we can't skate by on "it just happened to still be there"
+        unrelated = RawGreenlet(lambda: None)
+        unrelated.switch()
+
+        self.assertEqual(frame.f_code.co_name, "outer")
+        # The next line crashes on 3.12 if we haven't exposed the frames.
+        self.assertIsNone(frame.f_back)
+
+
+class TestGreenletSetParentErrors(TestCase):
+    def test_threaded_reparent(self):
+        data = {}
+        created_event = threading.Event()
+        done_event = threading.Event()
+
+        def run():
+            data['g'] = RawGreenlet(lambda: None)
+            created_event.set()
+            done_event.wait(10)
+
+        def blank():
+            greenlet.getcurrent().parent.switch()
+
+        thread = threading.Thread(target=run)
+        thread.start()
+        created_event.wait(10)
+        g = RawGreenlet(blank)
+        g.switch()
+        with self.assertRaises(ValueError) as exc:
+            g.parent = data['g']
+        done_event.set()
+        thread.join(10)
+
+        self.assertEqual(str(exc.exception), "parent cannot be on a different thread")
+
+    def test_unexpected_reparenting(self):
+        another = []
+        def worker():
+            g = RawGreenlet(lambda: None)
+            another.append(g)
+            g.switch()
+        t = threading.Thread(target=worker)
+        t.start()
+        t.join(10)
+        # The first time we switch (running g_initialstub(), which is
+        # when we look up the run attribute) we attempt to change the
+        # parent to one from another thread (which also happens to be
+        # dead). ``g_initialstub()`` should detect this and raise a
+        # greenlet error.
+        #
+        # EXCEPT: With the fix for #252, this is actually detected
+        # sooner, when setting the parent itself. Prior to that fix,
+        # the main greenlet from the background thread kept a valid
+        # value for ``run_info``, and appeared to be a valid parent
+        # until we actually started the greenlet. But now that it's
+        # cleared, this test is catching whether ``green_setparent``
+        # can detect the dead thread.
+        #
+        # Further refactoring once again changes this back to a greenlet.error
+        #
+        # We need to wait for the cleanup to happen, but we're
+        # deliberately leaking a main greenlet here.
+        self.wait_for_pending_cleanups(initial_main_greenlets=self.main_greenlets_before_test + 1)
+
+        class convoluted(RawGreenlet):
+            def __getattribute__(self, name):
+                if name == 'run':
+                    self.parent = another[0] # pylint:disable=attribute-defined-outside-init
+                return RawGreenlet.__getattribute__(self, name)
+        g = convoluted(lambda: None)
+        with self.assertRaises(greenlet.error) as exc:
+            g.switch()
+        self.assertEqual(str(exc.exception),
+                         "cannot switch to a different thread (which happens to have exited)")
+        del another[:]
+
+    def test_unexpected_reparenting_thread_running(self):
+        # Like ``test_unexpected_reparenting``, except the background thread is
+        # actually still alive.
+        another = []
+        switched_to_greenlet = threading.Event()
+        keep_main_alive = threading.Event()
+        def worker():
+            g = RawGreenlet(lambda: None)
+            another.append(g)
+            g.switch()
+            switched_to_greenlet.set()
+            keep_main_alive.wait(10)
+        class convoluted(RawGreenlet):
+            def __getattribute__(self, name):
+                if name == 'run':
+                    self.parent = another[0] # pylint:disable=attribute-defined-outside-init
+                return RawGreenlet.__getattribute__(self, name)
+
+        t = threading.Thread(target=worker)
+        t.start()
+
+        switched_to_greenlet.wait(10)
+        try:
+            g = convoluted(lambda: None)
+
+            with self.assertRaises(greenlet.error) as exc:
+                g.switch()
+            self.assertIn("Cannot switch to a different thread", str(exc.exception))
+            self.assertIn("Expected", str(exc.exception))
+            self.assertIn("Current", str(exc.exception))
+        finally:
+            keep_main_alive.set()
+            t.join(10)
+            # XXX: Should handle this automatically.
+            del another[:]
+
+    def test_cannot_delete_parent(self):
+        worker = RawGreenlet(lambda: None)
+        self.assertIs(worker.parent, greenlet.getcurrent())
+
+        with self.assertRaises(AttributeError) as exc:
+            del worker.parent
+        self.assertEqual(str(exc.exception), "can't delete attribute")
+
+    def test_cannot_delete_parent_of_main(self):
+        with self.assertRaises(AttributeError) as exc:
+            del greenlet.getcurrent().parent
+        self.assertEqual(str(exc.exception), "can't delete attribute")
+
+
+    def test_main_greenlet_parent_is_none(self):
+        # assuming we're in a main greenlet here.
+        self.assertIsNone(greenlet.getcurrent().parent)
+
+    def test_set_parent_wrong_types(self):
+        def bg():
+            # Go back to main.
+            greenlet.getcurrent().parent.switch()
+
+        def check(glet):
+            for p in None, 1, self, "42":
+                with self.assertRaises(TypeError) as exc:
+                    glet.parent = p
+
+                self.assertEqual(
+                    str(exc.exception),
+                    "GreenletChecker: Expected any type of greenlet, not " + type(p).__name__)
+
+        # First, not running
+        g = RawGreenlet(bg)
+        self.assertFalse(g)
+        check(g)
+
+        # Then when running.
+        g.switch()
+        self.assertTrue(g)
+        check(g)
+
+        # Let it finish
+        g.switch()
+
+
+    def test_trivial_cycle(self):
+        glet = RawGreenlet(lambda: None)
+        with self.assertRaises(ValueError) as exc:
+            glet.parent = glet
+        self.assertEqual(str(exc.exception), "cyclic parent chain")
+
+    def test_trivial_cycle_main(self):
+        # This used to produce a ValueError, but we catch it earlier than that now.
+        with self.assertRaises(AttributeError) as exc:
+            greenlet.getcurrent().parent = greenlet.getcurrent()
+        self.assertEqual(str(exc.exception), "cannot set the parent of a main greenlet")
+
+    def test_deeper_cycle(self):
+        g1 = RawGreenlet(lambda: None)
+        g2 = RawGreenlet(lambda: None)
+        g3 = RawGreenlet(lambda: None)
+
+        g1.parent = g2
+        g2.parent = g3
+        with self.assertRaises(ValueError) as exc:
+            g3.parent = g1
+        self.assertEqual(str(exc.exception), "cyclic parent chain")
+
+
+class TestRepr(TestCase):
+
+    def assertEndsWith(self, got, suffix):
+        self.assertTrue(got.endswith(suffix), (got, suffix))
+
+    def test_main_while_running(self):
+        r = repr(greenlet.getcurrent())
+        self.assertEndsWith(r, " current active started main>")
+
+    def test_main_in_background(self):
+        main = greenlet.getcurrent()
+        def run():
+            return repr(main)
+
+        g = RawGreenlet(run)
+        r = g.switch()
+        self.assertEndsWith(r, ' suspended active started main>')
+
+    def test_initial(self):
+        r = repr(RawGreenlet())
+        self.assertEndsWith(r, ' pending>')
+
+    def test_main_from_other_thread(self):
+        main = greenlet.getcurrent()
+
+        class T(threading.Thread):
+            original_main = thread_main = None
+            main_glet = None
+            def run(self):
+                self.original_main = repr(main)
+                self.main_glet = greenlet.getcurrent()
+                self.thread_main = repr(self.main_glet)
+
+        t = T()
+        t.start()
+        t.join(10)
+
+        self.assertEndsWith(t.original_main, ' suspended active started main>')
+        self.assertEndsWith(t.thread_main, ' current active started main>')
+        # give the machinery time to notice the death of the thread,
+        # and clean it up. Note that we don't use
+        # ``expect_greenlet_leak`` or wait_for_pending_cleanups,
+        # because at this point we know we have an extra greenlet
+        # still reachable.
+        for _ in range(3):
+            time.sleep(0.001)
+
+        # In the past, main greenlets, even from dead threads, never
+        # really appear dead. We have fixed that, and we also report
+        # that the thread is dead in the repr. (Do this multiple times
+        # to make sure that we don't self-modify and forget our state
+        # in the C++ code).
+        for _ in range(3):
+            self.assertTrue(t.main_glet.dead)
+            r = repr(t.main_glet)
+            self.assertEndsWith(r, ' (thread exited) dead>')
+
+    def test_dead(self):
+        g = RawGreenlet(lambda: None)
+        g.switch()
+        self.assertEndsWith(repr(g), ' dead>')
+        self.assertNotIn('suspended', repr(g))
+        self.assertNotIn('started', repr(g))
+        self.assertNotIn('active', repr(g))
+
+    def test_formatting_produces_native_str(self):
+        # https://github.com/python-greenlet/greenlet/issues/218
+        # %s formatting on Python 2 was producing unicode, not str.
+
+        g_dead = RawGreenlet(lambda: None)
+        g_not_started = RawGreenlet(lambda: None)
+        g_cur = greenlet.getcurrent()
+
+        for g in g_dead, g_not_started, g_cur:
+
+            self.assertIsInstance(
+                '%s' % (g,),
+                str
+            )
+            self.assertIsInstance(
+                '%r' % (g,),
+                str,
+            )
+
+
+class TestMainGreenlet(TestCase):
+    # Tests some implementation details, and relies on some
+    # implementation details.
+
+    def _check_current_is_main(self):
+        # implementation detail
+        assert 'main' in repr(greenlet.getcurrent())
+
+        t = type(greenlet.getcurrent())
+        assert 'main' not in repr(t)
+        return t
+
+    def test_main_greenlet_type_can_be_subclassed(self):
+        main_type = self._check_current_is_main()
+        subclass = type('subclass', (main_type,), {})
+        self.assertIsNotNone(subclass)
+
+    def test_main_greenlet_is_greenlet(self):
+        self._check_current_is_main()
+        self.assertIsInstance(greenlet.getcurrent(), RawGreenlet)
+
+
+
+class TestBrokenGreenlets(TestCase):
+    # Tests for things that used to, or still do, terminate the interpreter.
+    # This often means doing unsavory things.
+
+    def test_failed_to_initialstub(self):
+        def func():
+            raise AssertionError("Never get here")
+
+
+        g = greenlet._greenlet.UnswitchableGreenlet(func)
+        g.force_switch_error = True
+
+        with self.assertRaisesRegex(SystemError,
+                                    "Failed to switch stacks into a greenlet for the first time."):
+            g.switch()
+
+    def test_failed_to_switch_into_running(self):
+        runs = []
+        def func():
+            runs.append(1)
+            greenlet.getcurrent().parent.switch()
+            runs.append(2)
+            greenlet.getcurrent().parent.switch()
+            runs.append(3) # pragma: no cover
+
+        g = greenlet._greenlet.UnswitchableGreenlet(func)
+        g.switch()
+        self.assertEqual(runs, [1])
+        g.switch()
+        self.assertEqual(runs, [1, 2])
+        g.force_switch_error = True
+
+        with self.assertRaisesRegex(SystemError,
+                                    "Failed to switch stacks into a running greenlet."):
+            g.switch()
+
+        # If we stopped here, we would fail the leakcheck, because we've left
+        # the ``inner_bootstrap()`` C frame and its descendents hanging around,
+        # which have a bunch of Python references. They'll never get cleaned up
+        # if we don't let the greenlet finish.
+        g.force_switch_error = False
+        g.switch()
+        self.assertEqual(runs, [1, 2, 3])
+
+    def test_failed_to_slp_switch_into_running(self):
+        ex = self.assertScriptRaises('fail_slp_switch.py')
+
+        self.assertIn('fail_slp_switch is running', ex.output)
+        self.assertIn(ex.returncode, self.get_expected_returncodes_for_aborted_process())
+
+    def test_reentrant_switch_two_greenlets(self):
+        # Before we started capturing the arguments in g_switch_finish, this could crash.
+        output = self.run_script('fail_switch_two_greenlets.py')
+        self.assertIn('In g1_run', output)
+        self.assertIn('TRACE', output)
+        self.assertIn('LEAVE TRACE', output)
+        self.assertIn('Falling off end of main', output)
+        self.assertIn('Falling off end of g1_run', output)
+        self.assertIn('Falling off end of g2', output)
+
+    def test_reentrant_switch_three_greenlets(self):
+        # On debug builds of greenlet, this used to crash with an assertion error;
+        # on non-debug versions, it ran fine (which it should not do!).
+        # Now it always crashes correctly with a TypeError
+        ex = self.assertScriptRaises('fail_switch_three_greenlets.py', exitcodes=(1,))
+
+        self.assertIn('TypeError', ex.output)
+        self.assertIn('positional arguments', ex.output)
+
+    def test_reentrant_switch_three_greenlets2(self):
+        # This actually passed on debug and non-debug builds. It
+        # should probably have been triggering some debug assertions
+        # but it didn't.
+        #
+        # I think the fixes for the above test also kicked in here.
+        output = self.run_script('fail_switch_three_greenlets2.py')
+        self.assertIn(
+            "RESULTS: [('trace', 'switch'), "
+            "('trace', 'switch'), ('g2 arg', 'g2 from tracefunc'), "
+            "('trace', 'switch'), ('main g1', 'from g2_run'), ('trace', 'switch'), "
+            "('g1 arg', 'g1 from main'), ('trace', 'switch'), ('main g2', 'from g1_run'), "
+            "('trace', 'switch'), ('g1 from parent', 'g1 from main 2'), ('trace', 'switch'), "
+            "('main g1.2', 'g1 done'), ('trace', 'switch'), ('g2 from parent', ()), "
+            "('trace', 'switch'), ('main g2.2', 'g2 done')]",
+            output
+        )
+
+    def test_reentrant_switch_GreenletAlreadyStartedInPython(self):
+        output = self.run_script('fail_initialstub_already_started.py')
+
+        self.assertIn(
+            "RESULTS: ['Begin C', 'Switch to b from B.__getattribute__ in C', "
+            "('Begin B', ()), '_B_run switching to main', ('main from c', 'From B'), "
+            "'B.__getattribute__ back from main in C', ('Begin A', (None,)), "
+            "('A dead?', True, 'B dead?', True, 'C dead?', False), "
+            "'C done', ('main from c.2', None)]",
+            output
+        )
+
+    def test_reentrant_switch_run_callable_has_del(self):
+        output = self.run_script('fail_clearing_run_switches.py')
+        self.assertIn(
+             "RESULTS ["
+            "('G.__getattribute__', 'run'), ('RunCallable', '__del__'), "
+            "('main: g.switch()', 'from RunCallable'), ('run_func', 'enter')"
+            "]",
+            output
+        )
+
+if __name__ == '__main__':
+    unittest.main()