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cpython/Lib/test/test_gc.py
Benjamin Peterson 7fe73a17c5 Merged revisions 70837,70864,70878,71004,71032,71043 via svnmerge from 
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r70837 | gregory.p.smith | 2009-03-31 11:54:10 -0500 (Tue, 31 Mar 2009) | 9 lines

  The unittest.TestCase.assertEqual() now displays the differences in lists,
  tuples, dicts and sets on failure.

  Many new handy type and comparison specific assert* methods have been added
  that fail with error messages actually useful for debugging.  Contributed in
  by Google and completed with help from mfoord and GvR at PyCon 2009 sprints.

  Discussion lives in http://bugs.python.org/issue2578.
........
  r70864 | gregory.p.smith | 2009-03-31 14:03:28 -0500 (Tue, 31 Mar 2009) | 10 lines

  Rename the actual method definitions to the official assertFoo names.

  Adds unittests to make sure the old fail* names continue to work now
  and adds a comment that they are pending deprecation.

  Also adds a test to confirm that the plural Equals method variants
  continue to exist even though we're unlikely to deprecate those.

  http://bugs.python.org/issue2578
........
  r70878 | gregory.p.smith | 2009-03-31 14:59:14 -0500 (Tue, 31 Mar 2009) | 3 lines

  Issue an actual PendingDeprecationWarning for the TestCase.fail* methods.
  Document the deprecation.
........
  r71004 | benjamin.peterson | 2009-04-01 18:15:49 -0500 (Wed, 01 Apr 2009) | 1 line

  remove double underscores
........
  r71032 | michael.foord | 2009-04-01 22:20:38 -0500 (Wed, 01 Apr 2009) | 13 lines

  Better exception messages for unittest assert methods.

  - unittest.assertNotEqual() now uses the inequality operator (!=) instead
    of the equality operator.

  - Default assertTrue and assertFalse messages are now useful.

  - TestCase has a longMessage attribute. This defaults to False, but if set to True
    useful error messages are shown in addition to explicit messages passed to assert methods.

  Issue #5663
........
  r71043 | michael.foord | 2009-04-02 00:51:54 -0500 (Thu, 02 Apr 2009) | 7 lines

  Store the functions in the _type_equality_funcs as wrapped objects that are deep copyable.

  This allows for the deep copying of TestCase instances.

  Issue 5660
........
2009-04-04 16:35:46 +00:00

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