1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
|
import unittest
from test.support import (verbose, refcount_test, run_unittest,
strip_python_stderr, cpython_only, start_threads,
temp_dir, requires_type_collecting, TESTFN, unlink,
import_module)
from test.support.script_helper import assert_python_ok, make_script
import gc
import sys
import sysconfig
import textwrap
import threading
import time
import weakref
try:
from _testcapi import with_tp_del
except ImportError:
def with_tp_del(cls):
class C(object):
def __new__(cls, *args, **kwargs):
raise TypeError('requires _testcapi.with_tp_del')
return C
### 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)
@with_tp_del
class Uncollectable(object):
"""Create a reference cycle with multiple __del__ methods.
An object in a reference cycle will never have zero references,
and so must be garbage collected. If one or more objects in the
cycle have __del__ methods, the gc refuses to guess an order,
and leaves the cycle uncollected."""
def __init__(self, partner=None):
if partner is None:
self.partner = Uncollectable(partner=self)
else:
self.partner = partner
def __tp_del__(self):
pass
if sysconfig.get_config_vars().get('PY_CFLAGS', ''):
BUILD_WITH_NDEBUG = ('-DNDEBUG' in sysconfig.get_config_vars()['PY_CFLAGS'])
else:
# Usually, sys.gettotalrefcount() is only present if Python has been
# compiled in debug mode. If it's missing, expect that Python has
# been released in release mode: with NDEBUG defined.
BUILD_WITH_NDEBUG = (not hasattr(sys, 'gettotalrefcount'))
### 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)
@requires_type_collecting
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)
@cpython_only
def test_legacy_finalizer(self):
# A() is uncollectable if it is part of a cycle, make sure it shows up
# in gc.garbage.
@with_tp_del
class A:
def __tp_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)
@cpython_only
def test_legacy_finalizer_newclass(self):
# A() is uncollectable if it is part of a cycle, make sure it shows up
# in gc.garbage.
@with_tp_del
class A(object):
def __tp_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)
@refcount_test
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.
# To minimize variations, though, we first store the get_count() results
# and check them at the end.
@refcount_test
def test_get_count(self):
gc.collect()
a, b, c = gc.get_count()
x = []
d, e, f = gc.get_count()
self.assertEqual((b, c), (0, 0))
self.assertEqual((e, f), (0, 0))
# This is less fragile than asserting that a equals 0.
self.assertLess(a, 5)
# Between the two calls to get_count(), at least one object was
# created (the list).
self.assertGreater(d, a)
@refcount_test
def test_collect_generations(self):
gc.collect()
# This object will "trickle" into generation N + 1 after
# each call to collect(N)
x = []
gc.collect(0)
# x is now in gen 1
a, b, c = gc.get_count()
gc.collect(1)
# x is now in gen 2
d, e, f = gc.get_count()
gc.collect(2)
# x is now in gen 3
g, h, i = gc.get_count()
# We don't check a, d, g since their exact values depends on
# internal implementation details of the interpreter.
self.assertEqual((b, c), (1, 0))
self.assertEqual((e, f), (0, 1))
self.assertEqual((h, i), (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_trashcan_threads(self):
# Issue #13992: trashcan mechanism should be thread-safe
NESTING = 60
N_THREADS = 2
def sleeper_gen():
"""A generator that releases the GIL when closed or dealloc'ed."""
try:
yield
finally:
time.sleep(0.000001)
class C(list):
# Appending to a list is atomic, which avoids the use of a lock.
inits = []
dels = []
def __init__(self, alist):
self[:] = alist
C.inits.append(None)
def __del__(self):
# This __del__ is called by subtype_dealloc().
C.dels.append(None)
# `g` will release the GIL when garbage-collected. This
# helps assert subtype_dealloc's behaviour when threads
# switch in the middle of it.
g = sleeper_gen()
next(g)
# Now that __del__ is finished, subtype_dealloc will proceed
# to call list_dealloc, which also uses the trashcan mechanism.
def make_nested():
"""Create a sufficiently nested container object so that the
trashcan mechanism is invoked when deallocating it."""
x = C([])
for i in range(NESTING):
x = [C([x])]
del x
def run_thread():
"""Exercise make_nested() in a loop."""
while not exit:
make_nested()
old_switchinterval = sys.getswitchinterval()
sys.setswitchinterval(1e-5)
try:
exit = []
threads = []
for i in range(N_THREADS):
t = threading.Thread(target=run_thread)
threads.append(t)
with start_threads(threads, lambda: exit.append(1)):
time.sleep(1.0)
finally:
sys.setswitchinterval(old_switchinterval)
gc.collect()
self.assertEqual(len(C.inits), len(C.dels))
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
class UserInt(int):
pass
# Base class is object; no extra fields.
class UserClassSlots:
__slots__ = ()
# Base class is fixed size larger than object; no extra fields.
class UserFloatSlots(float):
__slots__ = ()
# Base class is variable size; no extra fields.
class UserIntSlots(int):
__slots__ = ()
self.assertTrue(gc.is_tracked(gc))
self.assertTrue(gc.is_tracked(UserClass))
self.assertTrue(gc.is_tracked(UserClass()))
self.assertTrue(gc.is_tracked(UserInt()))
self.assertTrue(gc.is_tracked([]))
self.assertTrue(gc.is_tracked(set()))
self.assertFalse(gc.is_tracked(UserClassSlots()))
self.assertFalse(gc.is_tracked(UserFloatSlots()))
self.assertFalse(gc.is_tracked(UserIntSlots()))
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)
def test_bug21435(self):
# This is a poor test - its only virtue is that it happened to
# segfault on Tim's Windows box before the patch for 21435 was
# applied. That's a nasty bug relying on specific pieces of cyclic
# trash appearing in exactly the right order in finalize_garbage()'s
# input list.
# But there's no reliable way to force that order from Python code,
# so over time chances are good this test won't really be testing much
# of anything anymore. Still, if it blows up, there's _some_
# problem ;-)
gc.collect()
class A:
pass
class B:
def __init__(self, x):
self.x = x
def __del__(self):
self.attr = None
def do_work():
a = A()
b = B(A())
a.attr = b
b.attr = a
do_work()
gc.collect() # this blows up (bad C pointer) when it fails
@cpython_only
def test_garbage_at_shutdown(self):
import subprocess
code = """if 1:
import gc
import _testcapi
@_testcapi.with_tp_del
class X:
def __init__(self, name):
self.name = name
def __repr__(self):
return "<X %%r>" %% self.name
def __tp_del__(self):
pass
x = X('first')
x.x = x
x.y = X('second')
del x
gc.set_debug(%s)
"""
def run_command(code):
p = subprocess.Popen([sys.executable, "-Wd", "-c", code],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
stdout, stderr = p.communicate()
p.stdout.close()
p.stderr.close()
self.assertEqual(p.returncode, 0)
self.assertEqual(stdout.strip(), b"")
return strip_python_stderr(stderr)
stderr = run_command(code % "0")
self.assertIn(b"ResourceWarning: gc: 2 uncollectable objects at "
b"shutdown; use", stderr)
self.assertNotIn(b"<X 'first'>", stderr)
# With DEBUG_UNCOLLECTABLE, the garbage list gets printed
stderr = run_command(code % "gc.DEBUG_UNCOLLECTABLE")
self.assertIn(b"ResourceWarning: gc: 2 uncollectable objects at "
b"shutdown", stderr)
self.assertTrue(
(b"[<X 'first'>, <X 'second'>]" in stderr) or
(b"[<X 'second'>, <X 'first'>]" in stderr), stderr)
# With DEBUG_SAVEALL, no additional message should get printed
# (because gc.garbage also contains normally reclaimable cyclic
# references, and its elements get printed at runtime anyway).
stderr = run_command(code % "gc.DEBUG_SAVEALL")
self.assertNotIn(b"uncollectable objects at shutdown", stderr)
@requires_type_collecting
def test_gc_main_module_at_shutdown(self):
# Create a reference cycle through the __main__ module and check
# it gets collected at interpreter shutdown.
code = """if 1:
class C:
def __del__(self):
print('__del__ called')
l = [C()]
l.append(l)
"""
rc, out, err = assert_python_ok('-c', code)
self.assertEqual(out.strip(), b'__del__ called')
@requires_type_collecting
def test_gc_ordinary_module_at_shutdown(self):
# Same as above, but with a non-__main__ module.
with temp_dir() as script_dir:
module = """if 1:
class C:
def __del__(self):
print('__del__ called')
l = [C()]
l.append(l)
"""
code = """if 1:
import sys
sys.path.insert(0, %r)
import gctest
""" % (script_dir,)
make_script(script_dir, 'gctest', module)
rc, out, err = assert_python_ok('-c', code)
self.assertEqual(out.strip(), b'__del__ called')
@requires_type_collecting
def test_global_del_SystemExit(self):
code = """if 1:
class ClassWithDel:
def __del__(self):
print('__del__ called')
a = ClassWithDel()
a.link = a
raise SystemExit(0)"""
self.addCleanup(unlink, TESTFN)
with open(TESTFN, 'w') as script:
script.write(code)
rc, out, err = assert_python_ok(TESTFN)
self.assertEqual(out.strip(), b'__del__ called')
def test_get_stats(self):
stats = gc.get_stats()
self.assertEqual(len(stats), 3)
for st in stats:
self.assertIsInstance(st, dict)
self.assertEqual(set(st),
{"collected", "collections", "uncollectable"})
self.assertGreaterEqual(st["collected"], 0)
self.assertGreaterEqual(st["collections"], 0)
self.assertGreaterEqual(st["uncollectable"], 0)
# Check that collection counts are incremented correctly
if gc.isenabled():
self.addCleanup(gc.enable)
gc.disable()
old = gc.get_stats()
gc.collect(0)
new = gc.get_stats()
self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
self.assertEqual(new[1]["collections"], old[1]["collections"])
self.assertEqual(new[2]["collections"], old[2]["collections"])
gc.collect(2)
new = gc.get_stats()
self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
self.assertEqual(new[1]["collections"], old[1]["collections"])
self.assertEqual(new[2]["collections"], old[2]["collections"] + 1)
def test_freeze(self):
gc.freeze()
self.assertGreater(gc.get_freeze_count(), 0)
gc.unfreeze()
self.assertEqual(gc.get_freeze_count(), 0)
def test_get_objects(self):
gc.collect()
l = []
l.append(l)
self.assertTrue(
any(l is element for element in gc.get_objects(generation=0))
)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=1))
)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=2))
)
gc.collect(generation=0)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=0))
)
self.assertTrue(
any(l is element for element in gc.get_objects(generation=1))
)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=2))
)
gc.collect(generation=1)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=0))
)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=1))
)
self.assertTrue(
any(l is element for element in gc.get_objects(generation=2))
)
gc.collect(generation=2)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=0))
)
self.assertFalse(
any(l is element for element in gc.get_objects(generation=1))
)
self.assertTrue(
any(l is element for element in gc.get_objects(generation=2))
)
del l
gc.collect()
def test_get_objects_arguments(self):
gc.collect()
self.assertEqual(len(gc.get_objects()),
len(gc.get_objects(generation=None)))
self.assertRaises(ValueError, gc.get_objects, 1000)
self.assertRaises(ValueError, gc.get_objects, -1000)
self.assertRaises(TypeError, gc.get_objects, "1")
self.assertRaises(TypeError, gc.get_objects, 1.234)
class GCCallbackTests(unittest.TestCase):
def setUp(self):
# Save gc state and disable it.
self.enabled = gc.isenabled()
gc.disable()
self.debug = gc.get_debug()
gc.set_debug(0)
gc.callbacks.append(self.cb1)
gc.callbacks.append(self.cb2)
self.othergarbage = []
def tearDown(self):
# Restore gc state
del self.visit
gc.callbacks.remove(self.cb1)
gc.callbacks.remove(self.cb2)
gc.set_debug(self.debug)
if self.enabled:
gc.enable()
# destroy any uncollectables
gc.collect()
for obj in gc.garbage:
if isinstance(obj, Uncollectable):
obj.partner = None
del gc.garbage[:]
del self.othergarbage
gc.collect()
def preclean(self):
# Remove all fluff from the system. Invoke this function
# manually rather than through self.setUp() for maximum
# safety.
self.visit = []
gc.collect()
garbage, gc.garbage[:] = gc.garbage[:], []
self.othergarbage.append(garbage)
self.visit = []
def cb1(self, phase, info):
self.visit.append((1, phase, dict(info)))
def cb2(self, phase, info):
self.visit.append((2, phase, dict(info)))
if phase == "stop" and hasattr(self, "cleanup"):
# Clean Uncollectable from garbage
uc = [e for e in gc.garbage if isinstance(e, Uncollectable)]
gc.garbage[:] = [e for e in gc.garbage
if not isinstance(e, Uncollectable)]
for e in uc:
e.partner = None
def test_collect(self):
self.preclean()
gc.collect()
# Algorithmically verify the contents of self.visit
# because it is long and tortuous.
# Count the number of visits to each callback
n = [v[0] for v in self.visit]
n1 = [i for i in n if i == 1]
n2 = [i for i in n if i == 2]
self.assertEqual(n1, [1]*2)
self.assertEqual(n2, [2]*2)
# Count that we got the right number of start and stop callbacks.
n = [v[1] for v in self.visit]
n1 = [i for i in n if i == "start"]
n2 = [i for i in n if i == "stop"]
self.assertEqual(n1, ["start"]*2)
self.assertEqual(n2, ["stop"]*2)
# Check that we got the right info dict for all callbacks
for v in self.visit:
info = v[2]
self.assertTrue("generation" in info)
self.assertTrue("collected" in info)
self.assertTrue("uncollectable" in info)
def test_collect_generation(self):
self.preclean()
gc.collect(2)
for v in self.visit:
info = v[2]
self.assertEqual(info["generation"], 2)
@cpython_only
def test_collect_garbage(self):
self.preclean()
# Each of these cause four objects to be garbage: Two
# Uncolectables and their instance dicts.
Uncollectable()
Uncollectable()
C1055820(666)
gc.collect()
for v in self.visit:
if v[1] != "stop":
continue
info = v[2]
self.assertEqual(info["collected"], 2)
self.assertEqual(info["uncollectable"], 8)
# We should now have the Uncollectables in gc.garbage
self.assertEqual(len(gc.garbage), 4)
for e in gc.garbage:
self.assertIsInstance(e, Uncollectable)
# Now, let our callback handle the Uncollectable instances
self.cleanup=True
self.visit = []
gc.garbage[:] = []
gc.collect()
for v in self.visit:
if v[1] != "stop":
continue
info = v[2]
self.assertEqual(info["collected"], 0)
self.assertEqual(info["uncollectable"], 4)
# Uncollectables should be gone
self.assertEqual(len(gc.garbage), 0)
@unittest.skipIf(BUILD_WITH_NDEBUG,
'built with -NDEBUG')
def test_refcount_errors(self):
self.preclean()
# Verify the "handling" of objects with broken refcounts
# Skip the test if ctypes is not available
import_module("ctypes")
import subprocess
code = textwrap.dedent('''
from test.support import gc_collect, SuppressCrashReport
a = [1, 2, 3]
b = [a]
# Avoid coredump when Py_FatalError() calls abort()
SuppressCrashReport().__enter__()
# Simulate the refcount of "a" being too low (compared to the
# references held on it by live data), but keeping it above zero
# (to avoid deallocating it):
import ctypes
ctypes.pythonapi.Py_DecRef(ctypes.py_object(a))
# The garbage collector should now have a fatal error
# when it reaches the broken object
gc_collect()
''')
p = subprocess.Popen([sys.executable, "-c", code],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
stdout, stderr = p.communicate()
p.stdout.close()
p.stderr.close()
# Verify that stderr has a useful error message:
self.assertRegex(stderr,
br'gcmodule\.c:[0-9]+: gc_decref: Assertion "gc_get_refs\(g\) > 0" failed.')
self.assertRegex(stderr,
br'refcount is too small')
self.assertRegex(stderr,
br'object : \[1, 2, 3\]')
self.assertRegex(stderr,
br'type : list')
self.assertRegex(stderr,
br'refcount: 1')
# "address : 0x7fb5062efc18"
# "address : 7FB5062EFC18"
self.assertRegex(stderr,
br'address : [0-9a-fA-Fx]+')
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, GCCallbackTests)
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()
|