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import gc
import weakref
import greenlet
from . import TestCase
from .leakcheck import fails_leakcheck
# These only work with greenlet gc support
# which is no longer optional.
assert greenlet.GREENLET_USE_GC
class GCTests(TestCase):
def test_dead_circular_ref(self):
o = weakref.ref(greenlet.greenlet(greenlet.getcurrent).switch())
gc.collect()
if o() is not None:
import sys
print("O IS NOT NONE.", sys.getrefcount(o()))
self.assertIsNone(o())
self.assertFalse(gc.garbage, gc.garbage)
def test_circular_greenlet(self):
class circular_greenlet(greenlet.greenlet):
self = None
o = circular_greenlet()
o.self = o
o = weakref.ref(o)
gc.collect()
self.assertIsNone(o())
self.assertFalse(gc.garbage, gc.garbage)
def test_inactive_ref(self):
class inactive_greenlet(greenlet.greenlet):
def __init__(self):
greenlet.greenlet.__init__(self, run=self.run)
def run(self):
pass
o = inactive_greenlet()
o = weakref.ref(o)
gc.collect()
self.assertIsNone(o())
self.assertFalse(gc.garbage, gc.garbage)
@fails_leakcheck
def test_finalizer_crash(self):
# This test is designed to crash when active greenlets
# are made garbage collectable, until the underlying
# problem is resolved. How does it work:
# - order of object creation is important
# - array is created first, so it is moved to unreachable first
# - we create a cycle between a greenlet and this array
# - we create an object that participates in gc, is only
# referenced by a greenlet, and would corrupt gc lists
# on destruction, the easiest is to use an object with
# a finalizer
# - because array is the first object in unreachable it is
# cleared first, which causes all references to greenlet
# to disappear and causes greenlet to be destroyed, but since
# it is still live it causes a switch during gc, which causes
# an object with finalizer to be destroyed, which causes stack
# corruption and then a crash
class object_with_finalizer(object):
def __del__(self):
pass
array = []
parent = greenlet.getcurrent()
def greenlet_body():
greenlet.getcurrent().object = object_with_finalizer()
try:
parent.switch()
except greenlet.GreenletExit:
print("Got greenlet exit!")
finally:
del greenlet.getcurrent().object
g = greenlet.greenlet(greenlet_body)
g.array = array
array.append(g)
g.switch()
del array
del g
greenlet.getcurrent()
gc.collect()
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