Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 1 | """ |
| 2 | Tests for object finalization semantics, as outlined in PEP 442. |
| 3 | """ |
| 4 | |
| 5 | import contextlib |
| 6 | import gc |
| 7 | import unittest |
| 8 | import weakref |
| 9 | |
Serhiy Storchaka | f28ba36 | 2014-02-07 10:10:55 +0200 | [diff] [blame] | 10 | try: |
| 11 | from _testcapi import with_tp_del |
| 12 | except ImportError: |
| 13 | def with_tp_del(cls): |
| 14 | class C(object): |
| 15 | def __new__(cls, *args, **kwargs): |
| 16 | raise TypeError('requires _testcapi.with_tp_del') |
| 17 | return C |
| 18 | |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 19 | from test import support |
| 20 | |
| 21 | |
| 22 | class NonGCSimpleBase: |
| 23 | """ |
| 24 | The base class for all the objects under test, equipped with various |
| 25 | testing features. |
| 26 | """ |
| 27 | |
| 28 | survivors = [] |
| 29 | del_calls = [] |
| 30 | tp_del_calls = [] |
| 31 | errors = [] |
| 32 | |
| 33 | _cleaning = False |
| 34 | |
| 35 | __slots__ = () |
| 36 | |
| 37 | @classmethod |
| 38 | def _cleanup(cls): |
| 39 | cls.survivors.clear() |
| 40 | cls.errors.clear() |
| 41 | gc.garbage.clear() |
| 42 | gc.collect() |
| 43 | cls.del_calls.clear() |
| 44 | cls.tp_del_calls.clear() |
| 45 | |
| 46 | @classmethod |
| 47 | @contextlib.contextmanager |
| 48 | def test(cls): |
| 49 | """ |
| 50 | A context manager to use around all finalization tests. |
| 51 | """ |
| 52 | with support.disable_gc(): |
| 53 | cls.del_calls.clear() |
| 54 | cls.tp_del_calls.clear() |
| 55 | NonGCSimpleBase._cleaning = False |
| 56 | try: |
| 57 | yield |
| 58 | if cls.errors: |
| 59 | raise cls.errors[0] |
| 60 | finally: |
| 61 | NonGCSimpleBase._cleaning = True |
| 62 | cls._cleanup() |
| 63 | |
| 64 | def check_sanity(self): |
| 65 | """ |
| 66 | Check the object is sane (non-broken). |
| 67 | """ |
| 68 | |
| 69 | def __del__(self): |
| 70 | """ |
| 71 | PEP 442 finalizer. Record that this was called, check the |
| 72 | object is in a sane state, and invoke a side effect. |
| 73 | """ |
| 74 | try: |
| 75 | if not self._cleaning: |
| 76 | self.del_calls.append(id(self)) |
| 77 | self.check_sanity() |
| 78 | self.side_effect() |
| 79 | except Exception as e: |
| 80 | self.errors.append(e) |
| 81 | |
| 82 | def side_effect(self): |
| 83 | """ |
| 84 | A side effect called on destruction. |
| 85 | """ |
| 86 | |
| 87 | |
| 88 | class SimpleBase(NonGCSimpleBase): |
| 89 | |
| 90 | def __init__(self): |
| 91 | self.id_ = id(self) |
| 92 | |
| 93 | def check_sanity(self): |
| 94 | assert self.id_ == id(self) |
| 95 | |
| 96 | |
| 97 | class NonGC(NonGCSimpleBase): |
| 98 | __slots__ = () |
| 99 | |
| 100 | class NonGCResurrector(NonGCSimpleBase): |
| 101 | __slots__ = () |
| 102 | |
| 103 | def side_effect(self): |
| 104 | """ |
| 105 | Resurrect self by storing self in a class-wide list. |
| 106 | """ |
| 107 | self.survivors.append(self) |
| 108 | |
| 109 | class Simple(SimpleBase): |
| 110 | pass |
| 111 | |
| 112 | class SimpleResurrector(NonGCResurrector, SimpleBase): |
| 113 | pass |
| 114 | |
| 115 | |
| 116 | class TestBase: |
| 117 | |
| 118 | def setUp(self): |
| 119 | self.old_garbage = gc.garbage[:] |
| 120 | gc.garbage[:] = [] |
| 121 | |
| 122 | def tearDown(self): |
| 123 | # None of the tests here should put anything in gc.garbage |
| 124 | try: |
| 125 | self.assertEqual(gc.garbage, []) |
| 126 | finally: |
| 127 | del self.old_garbage |
| 128 | gc.collect() |
| 129 | |
| 130 | def assert_del_calls(self, ids): |
| 131 | self.assertEqual(sorted(SimpleBase.del_calls), sorted(ids)) |
| 132 | |
| 133 | def assert_tp_del_calls(self, ids): |
| 134 | self.assertEqual(sorted(SimpleBase.tp_del_calls), sorted(ids)) |
| 135 | |
| 136 | def assert_survivors(self, ids): |
| 137 | self.assertEqual(sorted(id(x) for x in SimpleBase.survivors), sorted(ids)) |
| 138 | |
| 139 | def assert_garbage(self, ids): |
| 140 | self.assertEqual(sorted(id(x) for x in gc.garbage), sorted(ids)) |
| 141 | |
| 142 | def clear_survivors(self): |
| 143 | SimpleBase.survivors.clear() |
| 144 | |
| 145 | |
| 146 | class SimpleFinalizationTest(TestBase, unittest.TestCase): |
| 147 | """ |
| 148 | Test finalization without refcycles. |
| 149 | """ |
| 150 | |
| 151 | def test_simple(self): |
| 152 | with SimpleBase.test(): |
| 153 | s = Simple() |
| 154 | ids = [id(s)] |
| 155 | wr = weakref.ref(s) |
| 156 | del s |
| 157 | gc.collect() |
| 158 | self.assert_del_calls(ids) |
| 159 | self.assert_survivors([]) |
| 160 | self.assertIs(wr(), None) |
| 161 | gc.collect() |
| 162 | self.assert_del_calls(ids) |
| 163 | self.assert_survivors([]) |
| 164 | |
| 165 | def test_simple_resurrect(self): |
| 166 | with SimpleBase.test(): |
| 167 | s = SimpleResurrector() |
| 168 | ids = [id(s)] |
| 169 | wr = weakref.ref(s) |
| 170 | del s |
| 171 | gc.collect() |
| 172 | self.assert_del_calls(ids) |
| 173 | self.assert_survivors(ids) |
| 174 | self.assertIsNot(wr(), None) |
| 175 | self.clear_survivors() |
| 176 | gc.collect() |
| 177 | self.assert_del_calls(ids) |
| 178 | self.assert_survivors([]) |
| 179 | self.assertIs(wr(), None) |
| 180 | |
| 181 | def test_non_gc(self): |
| 182 | with SimpleBase.test(): |
| 183 | s = NonGC() |
| 184 | self.assertFalse(gc.is_tracked(s)) |
| 185 | ids = [id(s)] |
| 186 | del s |
| 187 | gc.collect() |
| 188 | self.assert_del_calls(ids) |
| 189 | self.assert_survivors([]) |
| 190 | gc.collect() |
| 191 | self.assert_del_calls(ids) |
| 192 | self.assert_survivors([]) |
| 193 | |
| 194 | def test_non_gc_resurrect(self): |
| 195 | with SimpleBase.test(): |
| 196 | s = NonGCResurrector() |
| 197 | self.assertFalse(gc.is_tracked(s)) |
| 198 | ids = [id(s)] |
| 199 | del s |
| 200 | gc.collect() |
| 201 | self.assert_del_calls(ids) |
| 202 | self.assert_survivors(ids) |
| 203 | self.clear_survivors() |
| 204 | gc.collect() |
| 205 | self.assert_del_calls(ids * 2) |
| 206 | self.assert_survivors(ids) |
| 207 | |
| 208 | |
| 209 | class SelfCycleBase: |
| 210 | |
| 211 | def __init__(self): |
| 212 | super().__init__() |
| 213 | self.ref = self |
| 214 | |
| 215 | def check_sanity(self): |
| 216 | super().check_sanity() |
| 217 | assert self.ref is self |
| 218 | |
| 219 | class SimpleSelfCycle(SelfCycleBase, Simple): |
| 220 | pass |
| 221 | |
| 222 | class SelfCycleResurrector(SelfCycleBase, SimpleResurrector): |
| 223 | pass |
| 224 | |
| 225 | class SuicidalSelfCycle(SelfCycleBase, Simple): |
| 226 | |
| 227 | def side_effect(self): |
| 228 | """ |
| 229 | Explicitly break the reference cycle. |
| 230 | """ |
| 231 | self.ref = None |
| 232 | |
| 233 | |
| 234 | class SelfCycleFinalizationTest(TestBase, unittest.TestCase): |
| 235 | """ |
| 236 | Test finalization of an object having a single cyclic reference to |
| 237 | itself. |
| 238 | """ |
| 239 | |
| 240 | def test_simple(self): |
| 241 | with SimpleBase.test(): |
| 242 | s = SimpleSelfCycle() |
| 243 | ids = [id(s)] |
| 244 | wr = weakref.ref(s) |
| 245 | del s |
| 246 | gc.collect() |
| 247 | self.assert_del_calls(ids) |
| 248 | self.assert_survivors([]) |
| 249 | self.assertIs(wr(), None) |
| 250 | gc.collect() |
| 251 | self.assert_del_calls(ids) |
| 252 | self.assert_survivors([]) |
| 253 | |
| 254 | def test_simple_resurrect(self): |
| 255 | # Test that __del__ can resurrect the object being finalized. |
| 256 | with SimpleBase.test(): |
| 257 | s = SelfCycleResurrector() |
| 258 | ids = [id(s)] |
| 259 | wr = weakref.ref(s) |
| 260 | del s |
| 261 | gc.collect() |
| 262 | self.assert_del_calls(ids) |
| 263 | self.assert_survivors(ids) |
| 264 | # XXX is this desirable? |
| 265 | self.assertIs(wr(), None) |
| 266 | # When trying to destroy the object a second time, __del__ |
| 267 | # isn't called anymore (and the object isn't resurrected). |
| 268 | self.clear_survivors() |
| 269 | gc.collect() |
| 270 | self.assert_del_calls(ids) |
| 271 | self.assert_survivors([]) |
| 272 | self.assertIs(wr(), None) |
| 273 | |
| 274 | def test_simple_suicide(self): |
| 275 | # Test the GC is able to deal with an object that kills its last |
| 276 | # reference during __del__. |
| 277 | with SimpleBase.test(): |
| 278 | s = SuicidalSelfCycle() |
| 279 | ids = [id(s)] |
| 280 | wr = weakref.ref(s) |
| 281 | del s |
| 282 | gc.collect() |
| 283 | self.assert_del_calls(ids) |
| 284 | self.assert_survivors([]) |
| 285 | self.assertIs(wr(), None) |
| 286 | gc.collect() |
| 287 | self.assert_del_calls(ids) |
| 288 | self.assert_survivors([]) |
| 289 | self.assertIs(wr(), None) |
| 290 | |
| 291 | |
| 292 | class ChainedBase: |
| 293 | |
| 294 | def chain(self, left): |
| 295 | self.suicided = False |
| 296 | self.left = left |
| 297 | left.right = self |
| 298 | |
| 299 | def check_sanity(self): |
| 300 | super().check_sanity() |
| 301 | if self.suicided: |
| 302 | assert self.left is None |
| 303 | assert self.right is None |
| 304 | else: |
| 305 | left = self.left |
| 306 | if left.suicided: |
| 307 | assert left.right is None |
| 308 | else: |
| 309 | assert left.right is self |
| 310 | right = self.right |
| 311 | if right.suicided: |
| 312 | assert right.left is None |
| 313 | else: |
| 314 | assert right.left is self |
| 315 | |
| 316 | class SimpleChained(ChainedBase, Simple): |
| 317 | pass |
| 318 | |
| 319 | class ChainedResurrector(ChainedBase, SimpleResurrector): |
| 320 | pass |
| 321 | |
| 322 | class SuicidalChained(ChainedBase, Simple): |
| 323 | |
| 324 | def side_effect(self): |
| 325 | """ |
| 326 | Explicitly break the reference cycle. |
| 327 | """ |
| 328 | self.suicided = True |
| 329 | self.left = None |
| 330 | self.right = None |
| 331 | |
| 332 | |
| 333 | class CycleChainFinalizationTest(TestBase, unittest.TestCase): |
| 334 | """ |
| 335 | Test finalization of a cyclic chain. These tests are similar in |
| 336 | spirit to the self-cycle tests above, but the collectable object |
| 337 | graph isn't trivial anymore. |
| 338 | """ |
| 339 | |
| 340 | def build_chain(self, classes): |
| 341 | nodes = [cls() for cls in classes] |
| 342 | for i in range(len(nodes)): |
| 343 | nodes[i].chain(nodes[i-1]) |
| 344 | return nodes |
| 345 | |
| 346 | def check_non_resurrecting_chain(self, classes): |
| 347 | N = len(classes) |
| 348 | with SimpleBase.test(): |
| 349 | nodes = self.build_chain(classes) |
| 350 | ids = [id(s) for s in nodes] |
| 351 | wrs = [weakref.ref(s) for s in nodes] |
| 352 | del nodes |
| 353 | gc.collect() |
| 354 | self.assert_del_calls(ids) |
| 355 | self.assert_survivors([]) |
| 356 | self.assertEqual([wr() for wr in wrs], [None] * N) |
| 357 | gc.collect() |
| 358 | self.assert_del_calls(ids) |
| 359 | |
| 360 | def check_resurrecting_chain(self, classes): |
| 361 | N = len(classes) |
| 362 | with SimpleBase.test(): |
| 363 | nodes = self.build_chain(classes) |
| 364 | N = len(nodes) |
| 365 | ids = [id(s) for s in nodes] |
| 366 | survivor_ids = [id(s) for s in nodes if isinstance(s, SimpleResurrector)] |
| 367 | wrs = [weakref.ref(s) for s in nodes] |
| 368 | del nodes |
| 369 | gc.collect() |
| 370 | self.assert_del_calls(ids) |
| 371 | self.assert_survivors(survivor_ids) |
| 372 | # XXX desirable? |
| 373 | self.assertEqual([wr() for wr in wrs], [None] * N) |
| 374 | self.clear_survivors() |
| 375 | gc.collect() |
| 376 | self.assert_del_calls(ids) |
| 377 | self.assert_survivors([]) |
| 378 | |
| 379 | def test_homogenous(self): |
| 380 | self.check_non_resurrecting_chain([SimpleChained] * 3) |
| 381 | |
| 382 | def test_homogenous_resurrect(self): |
| 383 | self.check_resurrecting_chain([ChainedResurrector] * 3) |
| 384 | |
| 385 | def test_homogenous_suicidal(self): |
| 386 | self.check_non_resurrecting_chain([SuicidalChained] * 3) |
| 387 | |
| 388 | def test_heterogenous_suicidal_one(self): |
| 389 | self.check_non_resurrecting_chain([SuicidalChained, SimpleChained] * 2) |
| 390 | |
| 391 | def test_heterogenous_suicidal_two(self): |
| 392 | self.check_non_resurrecting_chain( |
| 393 | [SuicidalChained] * 2 + [SimpleChained] * 2) |
| 394 | |
| 395 | def test_heterogenous_resurrect_one(self): |
| 396 | self.check_resurrecting_chain([ChainedResurrector, SimpleChained] * 2) |
| 397 | |
| 398 | def test_heterogenous_resurrect_two(self): |
| 399 | self.check_resurrecting_chain( |
| 400 | [ChainedResurrector, SimpleChained, SuicidalChained] * 2) |
| 401 | |
| 402 | def test_heterogenous_resurrect_three(self): |
| 403 | self.check_resurrecting_chain( |
| 404 | [ChainedResurrector] * 2 + [SimpleChained] * 2 + [SuicidalChained] * 2) |
| 405 | |
| 406 | |
| 407 | # NOTE: the tp_del slot isn't automatically inherited, so we have to call |
| 408 | # with_tp_del() for each instantiated class. |
| 409 | |
| 410 | class LegacyBase(SimpleBase): |
| 411 | |
| 412 | def __del__(self): |
| 413 | try: |
| 414 | # Do not invoke side_effect here, since we are now exercising |
| 415 | # the tp_del slot. |
| 416 | if not self._cleaning: |
| 417 | self.del_calls.append(id(self)) |
| 418 | self.check_sanity() |
| 419 | except Exception as e: |
| 420 | self.errors.append(e) |
| 421 | |
| 422 | def __tp_del__(self): |
| 423 | """ |
| 424 | Legacy (pre-PEP 442) finalizer, mapped to a tp_del slot. |
| 425 | """ |
| 426 | try: |
| 427 | if not self._cleaning: |
| 428 | self.tp_del_calls.append(id(self)) |
| 429 | self.check_sanity() |
| 430 | self.side_effect() |
| 431 | except Exception as e: |
| 432 | self.errors.append(e) |
| 433 | |
Serhiy Storchaka | f28ba36 | 2014-02-07 10:10:55 +0200 | [diff] [blame] | 434 | @with_tp_del |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 435 | class Legacy(LegacyBase): |
| 436 | pass |
| 437 | |
Serhiy Storchaka | f28ba36 | 2014-02-07 10:10:55 +0200 | [diff] [blame] | 438 | @with_tp_del |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 439 | class LegacyResurrector(LegacyBase): |
| 440 | |
| 441 | def side_effect(self): |
| 442 | """ |
| 443 | Resurrect self by storing self in a class-wide list. |
| 444 | """ |
| 445 | self.survivors.append(self) |
| 446 | |
Serhiy Storchaka | f28ba36 | 2014-02-07 10:10:55 +0200 | [diff] [blame] | 447 | @with_tp_del |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 448 | class LegacySelfCycle(SelfCycleBase, LegacyBase): |
| 449 | pass |
| 450 | |
| 451 | |
Serhiy Storchaka | f28ba36 | 2014-02-07 10:10:55 +0200 | [diff] [blame] | 452 | @support.cpython_only |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 453 | class LegacyFinalizationTest(TestBase, unittest.TestCase): |
| 454 | """ |
| 455 | Test finalization of objects with a tp_del. |
| 456 | """ |
| 457 | |
| 458 | def tearDown(self): |
| 459 | # These tests need to clean up a bit more, since they create |
| 460 | # uncollectable objects. |
| 461 | gc.garbage.clear() |
| 462 | gc.collect() |
| 463 | super().tearDown() |
| 464 | |
| 465 | def test_legacy(self): |
| 466 | with SimpleBase.test(): |
| 467 | s = Legacy() |
| 468 | ids = [id(s)] |
| 469 | wr = weakref.ref(s) |
| 470 | del s |
| 471 | gc.collect() |
| 472 | self.assert_del_calls(ids) |
| 473 | self.assert_tp_del_calls(ids) |
| 474 | self.assert_survivors([]) |
| 475 | self.assertIs(wr(), None) |
| 476 | gc.collect() |
| 477 | self.assert_del_calls(ids) |
| 478 | self.assert_tp_del_calls(ids) |
| 479 | |
| 480 | def test_legacy_resurrect(self): |
| 481 | with SimpleBase.test(): |
| 482 | s = LegacyResurrector() |
| 483 | ids = [id(s)] |
| 484 | wr = weakref.ref(s) |
| 485 | del s |
| 486 | gc.collect() |
| 487 | self.assert_del_calls(ids) |
| 488 | self.assert_tp_del_calls(ids) |
| 489 | self.assert_survivors(ids) |
| 490 | # weakrefs are cleared before tp_del is called. |
| 491 | self.assertIs(wr(), None) |
| 492 | self.clear_survivors() |
| 493 | gc.collect() |
| 494 | self.assert_del_calls(ids) |
| 495 | self.assert_tp_del_calls(ids * 2) |
| 496 | self.assert_survivors(ids) |
| 497 | self.assertIs(wr(), None) |
| 498 | |
| 499 | def test_legacy_self_cycle(self): |
| 500 | # Self-cycles with legacy finalizers end up in gc.garbage. |
| 501 | with SimpleBase.test(): |
| 502 | s = LegacySelfCycle() |
| 503 | ids = [id(s)] |
| 504 | wr = weakref.ref(s) |
| 505 | del s |
| 506 | gc.collect() |
| 507 | self.assert_del_calls([]) |
| 508 | self.assert_tp_del_calls([]) |
| 509 | self.assert_survivors([]) |
| 510 | self.assert_garbage(ids) |
| 511 | self.assertIsNot(wr(), None) |
| 512 | # Break the cycle to allow collection |
| 513 | gc.garbage[0].ref = None |
| 514 | self.assert_garbage([]) |
| 515 | self.assertIs(wr(), None) |
| 516 | |
| 517 | |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 518 | if __name__ == "__main__": |
Zachary Ware | 38c707e | 2015-04-13 15:00:43 -0500 | [diff] [blame] | 519 | unittest.main() |