640 lines
20 KiB
Python
640 lines
20 KiB
Python
import unittest
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from test.test_support import verbose, run_unittest
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import sys
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import gc
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import weakref
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### Support code
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###############################################################################
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# Bug 1055820 has several tests of longstanding bugs involving weakrefs and
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# cyclic gc.
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# An instance of C1055820 has a self-loop, so becomes cyclic trash when
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# unreachable.
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class C1055820(object):
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def __init__(self, i):
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self.i = i
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self.loop = self
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class GC_Detector(object):
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# Create an instance I. Then gc hasn't happened again so long as
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# I.gc_happened is false.
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def __init__(self):
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self.gc_happened = False
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def it_happened(ignored):
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self.gc_happened = True
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# Create a piece of cyclic trash that triggers it_happened when
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# gc collects it.
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self.wr = weakref.ref(C1055820(666), it_happened)
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### Tests
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###############################################################################
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class GCTests(unittest.TestCase):
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def test_list(self):
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l = []
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l.append(l)
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gc.collect()
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del l
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self.assertEqual(gc.collect(), 1)
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def test_dict(self):
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d = {}
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d[1] = d
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gc.collect()
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del d
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self.assertEqual(gc.collect(), 1)
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def test_tuple(self):
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# since tuples are immutable we close the loop with a list
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l = []
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t = (l,)
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l.append(t)
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gc.collect()
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del t
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del l
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self.assertEqual(gc.collect(), 2)
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def test_class(self):
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class A:
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pass
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A.a = A
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gc.collect()
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del A
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self.assertNotEqual(gc.collect(), 0)
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def test_newstyleclass(self):
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class A(object):
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pass
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gc.collect()
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del A
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self.assertNotEqual(gc.collect(), 0)
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def test_instance(self):
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class A:
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pass
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a = A()
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a.a = a
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gc.collect()
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del a
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self.assertNotEqual(gc.collect(), 0)
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def test_newinstance(self):
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class A(object):
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pass
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a = A()
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a.a = a
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gc.collect()
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del a
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self.assertNotEqual(gc.collect(), 0)
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class B(list):
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pass
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class C(B, A):
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pass
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a = C()
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a.a = a
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gc.collect()
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del a
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self.assertNotEqual(gc.collect(), 0)
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del B, C
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self.assertNotEqual(gc.collect(), 0)
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A.a = A()
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del A
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self.assertNotEqual(gc.collect(), 0)
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self.assertEqual(gc.collect(), 0)
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def test_method(self):
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# Tricky: self.__init__ is a bound method, it references the instance.
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class A:
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def __init__(self):
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self.init = self.__init__
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a = A()
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gc.collect()
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del a
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self.assertNotEqual(gc.collect(), 0)
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def test_finalizer(self):
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# A() is uncollectable if it is part of a cycle, make sure it shows up
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# in gc.garbage.
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class A:
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def __del__(self): pass
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class B:
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pass
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a = A()
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a.a = a
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id_a = id(a)
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b = B()
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b.b = b
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gc.collect()
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del a
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del b
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self.assertNotEqual(gc.collect(), 0)
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for obj in gc.garbage:
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if id(obj) == id_a:
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del obj.a
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break
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else:
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self.fail("didn't find obj in garbage (finalizer)")
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gc.garbage.remove(obj)
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def test_finalizer_newclass(self):
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# A() is uncollectable if it is part of a cycle, make sure it shows up
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# in gc.garbage.
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class A(object):
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def __del__(self): pass
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class B(object):
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pass
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a = A()
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a.a = a
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id_a = id(a)
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b = B()
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b.b = b
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gc.collect()
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del a
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del b
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self.assertNotEqual(gc.collect(), 0)
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for obj in gc.garbage:
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if id(obj) == id_a:
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del obj.a
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break
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else:
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self.fail("didn't find obj in garbage (finalizer)")
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gc.garbage.remove(obj)
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def test_function(self):
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# Tricky: f -> d -> f, code should call d.clear() after the exec to
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# break the cycle.
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d = {}
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exec("def f(): pass\n") in d
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gc.collect()
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del d
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self.assertEqual(gc.collect(), 2)
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def test_frame(self):
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def f():
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frame = sys._getframe()
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gc.collect()
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f()
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self.assertEqual(gc.collect(), 1)
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def test_saveall(self):
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# Verify that cyclic garbage like lists show up in gc.garbage if the
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# SAVEALL option is enabled.
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# First make sure we don't save away other stuff that just happens to
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# be waiting for collection.
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gc.collect()
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# if this fails, someone else created immortal trash
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self.assertEqual(gc.garbage, [])
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L = []
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L.append(L)
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id_L = id(L)
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debug = gc.get_debug()
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gc.set_debug(debug | gc.DEBUG_SAVEALL)
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del L
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gc.collect()
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gc.set_debug(debug)
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self.assertEqual(len(gc.garbage), 1)
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obj = gc.garbage.pop()
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self.assertEqual(id(obj), id_L)
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def test_del(self):
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# __del__ methods can trigger collection, make this to happen
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thresholds = gc.get_threshold()
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gc.enable()
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gc.set_threshold(1)
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class A:
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def __del__(self):
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dir(self)
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a = A()
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del a
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gc.disable()
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gc.set_threshold(*thresholds)
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def test_del_newclass(self):
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# __del__ methods can trigger collection, make this to happen
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thresholds = gc.get_threshold()
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gc.enable()
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gc.set_threshold(1)
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class A(object):
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def __del__(self):
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dir(self)
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a = A()
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del a
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gc.disable()
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gc.set_threshold(*thresholds)
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# The following two tests are fragile:
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# They precisely count the number of allocations,
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# which is highly implementation-dependent.
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# For example:
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# - disposed tuples are not freed, but reused
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# - the call to assertEqual somehow avoids building its args tuple
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def test_get_count(self):
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# Avoid future allocation of method object
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assertEqual = self._baseAssertEqual
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gc.collect()
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assertEqual(gc.get_count(), (0, 0, 0))
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a = dict()
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# since gc.collect(), we created two objects:
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# the dict, and the tuple returned by get_count()
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assertEqual(gc.get_count(), (2, 0, 0))
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def test_collect_generations(self):
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# Avoid future allocation of method object
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assertEqual = self.assertEqual
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gc.collect()
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a = dict()
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gc.collect(0)
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assertEqual(gc.get_count(), (0, 1, 0))
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gc.collect(1)
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assertEqual(gc.get_count(), (0, 0, 1))
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gc.collect(2)
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assertEqual(gc.get_count(), (0, 0, 0))
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def test_trashcan(self):
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class Ouch:
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n = 0
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def __del__(self):
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Ouch.n = Ouch.n + 1
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if Ouch.n % 17 == 0:
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gc.collect()
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# "trashcan" is a hack to prevent stack overflow when deallocating
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# very deeply nested tuples etc. It works in part by abusing the
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# type pointer and refcount fields, and that can yield horrible
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# problems when gc tries to traverse the structures.
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# If this test fails (as it does in 2.0, 2.1 and 2.2), it will
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# most likely die via segfault.
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# Note: In 2.3 the possibility for compiling without cyclic gc was
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# removed, and that in turn allows the trashcan mechanism to work
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# via much simpler means (e.g., it never abuses the type pointer or
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# refcount fields anymore). Since it's much less likely to cause a
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# problem now, the various constants in this expensive (we force a lot
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# of full collections) test are cut back from the 2.2 version.
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gc.enable()
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N = 150
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for count in range(2):
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t = []
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for i in range(N):
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t = [t, Ouch()]
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u = []
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for i in range(N):
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u = [u, Ouch()]
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v = {}
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for i in range(N):
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v = {1: v, 2: Ouch()}
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gc.disable()
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def test_boom(self):
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class Boom:
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def __getattr__(self, someattribute):
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del self.attr
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raise AttributeError
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a = Boom()
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b = Boom()
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a.attr = b
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b.attr = a
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gc.collect()
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garbagelen = len(gc.garbage)
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del a, b
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# a<->b are in a trash cycle now. Collection will invoke
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# Boom.__getattr__ (to see whether a and b have __del__ methods), and
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# __getattr__ deletes the internal "attr" attributes as a side effect.
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# That causes the trash cycle to get reclaimed via refcounts falling to
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# 0, thus mutating the trash graph as a side effect of merely asking
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# whether __del__ exists. This used to (before 2.3b1) crash Python.
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# Now __getattr__ isn't called.
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self.assertEqual(gc.collect(), 4)
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self.assertEqual(len(gc.garbage), garbagelen)
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def test_boom2(self):
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class Boom2:
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def __init__(self):
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self.x = 0
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def __getattr__(self, someattribute):
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self.x += 1
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if self.x > 1:
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del self.attr
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raise AttributeError
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a = Boom2()
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b = Boom2()
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a.attr = b
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b.attr = a
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gc.collect()
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garbagelen = len(gc.garbage)
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del a, b
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# Much like test_boom(), except that __getattr__ doesn't break the
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# cycle until the second time gc checks for __del__. As of 2.3b1,
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# there isn't a second time, so this simply cleans up the trash cycle.
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# We expect a, b, a.__dict__ and b.__dict__ (4 objects) to get
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# reclaimed this way.
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self.assertEqual(gc.collect(), 4)
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self.assertEqual(len(gc.garbage), garbagelen)
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def test_boom_new(self):
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# boom__new and boom2_new are exactly like boom and boom2, except use
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# new-style classes.
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class Boom_New(object):
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def __getattr__(self, someattribute):
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del self.attr
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raise AttributeError
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a = Boom_New()
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b = Boom_New()
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a.attr = b
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b.attr = a
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gc.collect()
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garbagelen = len(gc.garbage)
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del a, b
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self.assertEqual(gc.collect(), 4)
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self.assertEqual(len(gc.garbage), garbagelen)
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def test_boom2_new(self):
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class Boom2_New(object):
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def __init__(self):
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self.x = 0
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def __getattr__(self, someattribute):
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self.x += 1
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if self.x > 1:
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del self.attr
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raise AttributeError
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a = Boom2_New()
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b = Boom2_New()
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a.attr = b
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b.attr = a
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gc.collect()
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garbagelen = len(gc.garbage)
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del a, b
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self.assertEqual(gc.collect(), 4)
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self.assertEqual(len(gc.garbage), garbagelen)
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def test_get_referents(self):
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alist = [1, 3, 5]
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got = gc.get_referents(alist)
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got.sort()
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self.assertEqual(got, alist)
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atuple = tuple(alist)
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got = gc.get_referents(atuple)
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got.sort()
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self.assertEqual(got, alist)
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adict = {1: 3, 5: 7}
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expected = [1, 3, 5, 7]
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got = gc.get_referents(adict)
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got.sort()
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self.assertEqual(got, expected)
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got = gc.get_referents([1, 2], {3: 4}, (0, 0, 0))
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got.sort()
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self.assertEqual(got, [0, 0] + range(5))
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self.assertEqual(gc.get_referents(1, 'a', 4j), [])
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def test_is_tracked(self):
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# Atomic built-in types are not tracked, user-defined objects and
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# mutable containers are.
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# NOTE: types with special optimizations (e.g. tuple) have tests
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# in their own test files instead.
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self.assertFalse(gc.is_tracked(None))
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self.assertFalse(gc.is_tracked(1))
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self.assertFalse(gc.is_tracked(1.0))
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self.assertFalse(gc.is_tracked(1.0 + 5.0j))
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self.assertFalse(gc.is_tracked(True))
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self.assertFalse(gc.is_tracked(False))
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self.assertFalse(gc.is_tracked("a"))
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self.assertFalse(gc.is_tracked(u"a"))
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self.assertFalse(gc.is_tracked(bytearray("a")))
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self.assertFalse(gc.is_tracked(type))
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self.assertFalse(gc.is_tracked(int))
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self.assertFalse(gc.is_tracked(object))
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self.assertFalse(gc.is_tracked(object()))
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class OldStyle:
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pass
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class NewStyle(object):
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pass
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self.assertTrue(gc.is_tracked(gc))
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self.assertTrue(gc.is_tracked(OldStyle))
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self.assertTrue(gc.is_tracked(OldStyle()))
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self.assertTrue(gc.is_tracked(NewStyle))
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self.assertTrue(gc.is_tracked(NewStyle()))
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self.assertTrue(gc.is_tracked([]))
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self.assertTrue(gc.is_tracked(set()))
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def test_bug1055820b(self):
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# Corresponds to temp2b.py in the bug report.
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ouch = []
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def callback(ignored):
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ouch[:] = [wr() for wr in WRs]
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Cs = [C1055820(i) for i in range(2)]
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WRs = [weakref.ref(c, callback) for c in Cs]
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c = None
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gc.collect()
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self.assertEqual(len(ouch), 0)
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# Make the two instances trash, and collect again. The bug was that
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# the callback materialized a strong reference to an instance, but gc
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# cleared the instance's dict anyway.
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Cs = None
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gc.collect()
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self.assertEqual(len(ouch), 2) # else the callbacks didn't run
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for x in ouch:
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# If the callback resurrected one of these guys, the instance
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# would be damaged, with an empty __dict__.
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self.assertEqual(x, None)
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class GCTogglingTests(unittest.TestCase):
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def setUp(self):
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gc.enable()
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def tearDown(self):
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gc.disable()
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def test_bug1055820c(self):
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# Corresponds to temp2c.py in the bug report. This is pretty
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# elaborate.
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c0 = C1055820(0)
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# Move c0 into generation 2.
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gc.collect()
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c1 = C1055820(1)
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c1.keep_c0_alive = c0
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del c0.loop # now only c1 keeps c0 alive
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c2 = C1055820(2)
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c2wr = weakref.ref(c2) # no callback!
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ouch = []
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def callback(ignored):
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ouch[:] = [c2wr()]
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# The callback gets associated with a wr on an object in generation 2.
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c0wr = weakref.ref(c0, callback)
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c0 = c1 = c2 = None
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# What we've set up: c0, c1, and c2 are all trash now. c0 is in
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# generation 2. The only thing keeping it alive is that c1 points to
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# it. c1 and c2 are in generation 0, and are in self-loops. There's a
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# global weakref to c2 (c2wr), but that weakref has no callback.
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# There's also a global weakref to c0 (c0wr), and that does have a
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# callback, and that callback references c2 via c2wr().
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#
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# c0 has a wr with callback, which references c2wr
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# ^
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# |
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# | Generation 2 above dots
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#. . . . . . . .|. . . . . . . . . . . . . . . . . . . . . . . .
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# | Generation 0 below dots
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# |
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# |
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# ^->c1 ^->c2 has a wr but no callback
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# | | | |
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# <--v <--v
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#
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# So this is the nightmare: when generation 0 gets collected, we see
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# that c2 has a callback-free weakref, and c1 doesn't even have a
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# weakref. Collecting generation 0 doesn't see c0 at all, and c0 is
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# the only object that has a weakref with a callback. gc clears c1
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# and c2. Clearing c1 has the side effect of dropping the refcount on
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# c0 to 0, so c0 goes away (despite that it's in an older generation)
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# and c0's wr callback triggers. That in turn materializes a reference
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# to c2 via c2wr(), but c2 gets cleared anyway by gc.
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# We want to let gc happen "naturally", to preserve the distinction
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# between generations.
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junk = []
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i = 0
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detector = GC_Detector()
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while not detector.gc_happened:
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i += 1
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if i > 10000:
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self.fail("gc didn't happen after 10000 iterations")
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self.assertEqual(len(ouch), 0)
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|
junk.append([]) # this will eventually trigger gc
|
|
|
|
self.assertEqual(len(ouch), 1) # else the callback wasn't invoked
|
|
for x in ouch:
|
|
# If the callback resurrected c2, the instance would be damaged,
|
|
# with an empty __dict__.
|
|
self.assertEqual(x, None)
|
|
|
|
def test_bug1055820d(self):
|
|
# Corresponds to temp2d.py in the bug report. This is very much like
|
|
# test_bug1055820c, but uses a __del__ method instead of a weakref
|
|
# callback to sneak in a resurrection of cyclic trash.
|
|
|
|
ouch = []
|
|
class D(C1055820):
|
|
def __del__(self):
|
|
ouch[:] = [c2wr()]
|
|
|
|
d0 = D(0)
|
|
# Move all the above into generation 2.
|
|
gc.collect()
|
|
|
|
c1 = C1055820(1)
|
|
c1.keep_d0_alive = d0
|
|
del d0.loop # now only c1 keeps d0 alive
|
|
|
|
c2 = C1055820(2)
|
|
c2wr = weakref.ref(c2) # no callback!
|
|
|
|
d0 = c1 = c2 = None
|
|
|
|
# What we've set up: d0, c1, and c2 are all trash now. d0 is in
|
|
# generation 2. The only thing keeping it alive is that c1 points to
|
|
# it. c1 and c2 are in generation 0, and are in self-loops. There's
|
|
# a global weakref to c2 (c2wr), but that weakref has no callback.
|
|
# There are no other weakrefs.
|
|
#
|
|
# d0 has a __del__ method that references c2wr
|
|
# ^
|
|
# |
|
|
# | Generation 2 above dots
|
|
#. . . . . . . .|. . . . . . . . . . . . . . . . . . . . . . . .
|
|
# | Generation 0 below dots
|
|
# |
|
|
# |
|
|
# ^->c1 ^->c2 has a wr but no callback
|
|
# | | | |
|
|
# <--v <--v
|
|
#
|
|
# So this is the nightmare: when generation 0 gets collected, we see
|
|
# that c2 has a callback-free weakref, and c1 doesn't even have a
|
|
# weakref. Collecting generation 0 doesn't see d0 at all. gc clears
|
|
# c1 and c2. Clearing c1 has the side effect of dropping the refcount
|
|
# on d0 to 0, so d0 goes away (despite that it's in an older
|
|
# generation) and d0's __del__ triggers. That in turn materializes
|
|
# a reference to c2 via c2wr(), but c2 gets cleared anyway by gc.
|
|
|
|
# We want to let gc happen "naturally", to preserve the distinction
|
|
# between generations.
|
|
detector = GC_Detector()
|
|
junk = []
|
|
i = 0
|
|
while not detector.gc_happened:
|
|
i += 1
|
|
if i > 10000:
|
|
self.fail("gc didn't happen after 10000 iterations")
|
|
self.assertEqual(len(ouch), 0)
|
|
junk.append([]) # this will eventually trigger gc
|
|
|
|
self.assertEqual(len(ouch), 1) # else __del__ wasn't invoked
|
|
for x in ouch:
|
|
# If __del__ resurrected c2, the instance would be damaged, with an
|
|
# empty __dict__.
|
|
self.assertEqual(x, None)
|
|
|
|
def test_main():
|
|
enabled = gc.isenabled()
|
|
gc.disable()
|
|
assert not gc.isenabled()
|
|
debug = gc.get_debug()
|
|
gc.set_debug(debug & ~gc.DEBUG_LEAK) # this test is supposed to leak
|
|
|
|
try:
|
|
gc.collect() # Delete 2nd generation garbage
|
|
run_unittest(GCTests, GCTogglingTests)
|
|
finally:
|
|
gc.set_debug(debug)
|
|
# test gc.enable() even if GC is disabled by default
|
|
if verbose:
|
|
print "restoring automatic collection"
|
|
# make sure to always test gc.enable()
|
|
gc.enable()
|
|
assert gc.isenabled()
|
|
if not enabled:
|
|
gc.disable()
|
|
|
|
if __name__ == "__main__":
|
|
test_main()
|