summaryrefslogtreecommitdiffstats
path: root/Lib/test/test_exceptions.py
blob: 76f4249490f9105ed6fb752c5c42912e313e9127 (plain)
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
# Python test set -- part 5, built-in exceptions

import os
import sys
import unittest
import pickle
import weakref

from test.support import (TESTFN, unlink, run_unittest, captured_output,
                          gc_collect, cpython_only)

# XXX This is not really enough, each *operation* should be tested!

class ExceptionTests(unittest.TestCase):

    def raise_catch(self, exc, excname):
        try:
            raise exc("spam")
        except exc as err:
            buf1 = str(err)
        try:
            raise exc("spam")
        except exc as err:
            buf2 = str(err)
        self.assertEqual(buf1, buf2)
        self.assertEqual(exc.__name__, excname)

    def testRaising(self):
        self.raise_catch(AttributeError, "AttributeError")
        self.assertRaises(AttributeError, getattr, sys, "undefined_attribute")

        self.raise_catch(EOFError, "EOFError")
        fp = open(TESTFN, 'w')
        fp.close()
        fp = open(TESTFN, 'r')
        savestdin = sys.stdin
        try:
            try:
                import marshal
                marshal.loads('')
            except EOFError:
                pass
        finally:
            sys.stdin = savestdin
            fp.close()
            unlink(TESTFN)

        self.raise_catch(IOError, "IOError")
        self.assertRaises(IOError, open, 'this file does not exist', 'r')

        self.raise_catch(ImportError, "ImportError")
        self.assertRaises(ImportError, __import__, "undefined_module")

        self.raise_catch(IndexError, "IndexError")
        x = []
        self.assertRaises(IndexError, x.__getitem__, 10)

        self.raise_catch(KeyError, "KeyError")
        x = {}
        self.assertRaises(KeyError, x.__getitem__, 'key')

        self.raise_catch(KeyboardInterrupt, "KeyboardInterrupt")

        self.raise_catch(MemoryError, "MemoryError")

        self.raise_catch(NameError, "NameError")
        try: x = undefined_variable
        except NameError: pass

        self.raise_catch(OverflowError, "OverflowError")
        x = 1
        for dummy in range(128):
            x += x  # this simply shouldn't blow up

        self.raise_catch(RuntimeError, "RuntimeError")

        self.raise_catch(SyntaxError, "SyntaxError")
        try: exec('/\n')
        except SyntaxError: pass

        self.raise_catch(IndentationError, "IndentationError")

        self.raise_catch(TabError, "TabError")
        try: compile("try:\n\t1/0\n    \t1/0\nfinally:\n pass\n",
                     '<string>', 'exec')
        except TabError: pass
        else: self.fail("TabError not raised")

        self.raise_catch(SystemError, "SystemError")

        self.raise_catch(SystemExit, "SystemExit")
        self.assertRaises(SystemExit, sys.exit, 0)

        self.raise_catch(TypeError, "TypeError")
        try: [] + ()
        except TypeError: pass

        self.raise_catch(ValueError, "ValueError")
        self.assertRaises(ValueError, chr, 17<<16)

        self.raise_catch(ZeroDivisionError, "ZeroDivisionError")
        try: x = 1/0
        except ZeroDivisionError: pass

        self.raise_catch(Exception, "Exception")
        try: x = 1/0
        except Exception as e: pass

    def testSyntaxErrorMessage(self):
        # make sure the right exception message is raised for each of
        # these code fragments

        def ckmsg(src, msg):
            try:
                compile(src, '<fragment>', 'exec')
            except SyntaxError as e:
                if e.msg != msg:
                    self.fail("expected %s, got %s" % (msg, e.msg))
            else:
                self.fail("failed to get expected SyntaxError")

        s = '''while 1:
            try:
                pass
            finally:
                continue'''

        if not sys.platform.startswith('java'):
            ckmsg(s, "'continue' not supported inside 'finally' clause")

        s = '''if 1:
        try:
            continue
        except:
            pass'''

        ckmsg(s, "'continue' not properly in loop")
        ckmsg("continue\n", "'continue' not properly in loop")

    @cpython_only
    def testSettingException(self):
        # test that setting an exception at the C level works even if the
        # exception object can't be constructed.

        class BadException(Exception):
            def __init__(self_):
                raise RuntimeError("can't instantiate BadException")

        class InvalidException:
            pass

        def test_capi1():
            import _testcapi
            try:
                _testcapi.raise_exception(BadException, 1)
            except TypeError as err:
                exc, err, tb = sys.exc_info()
                co = tb.tb_frame.f_code
                self.assertEqual(co.co_name, "test_capi1")
                self.assertTrue(co.co_filename.endswith('test_exceptions.py'))
            else:
                self.fail("Expected exception")

        def test_capi2():
            import _testcapi
            try:
                _testcapi.raise_exception(BadException, 0)
            except RuntimeError as err:
                exc, err, tb = sys.exc_info()
                co = tb.tb_frame.f_code
                self.assertEqual(co.co_name, "__init__")
                self.assertTrue(co.co_filename.endswith('test_exceptions.py'))
                co2 = tb.tb_frame.f_back.f_code
                self.assertEqual(co2.co_name, "test_capi2")
            else:
                self.fail("Expected exception")

        def test_capi3():
            import _testcapi
            self.assertRaises(SystemError, _testcapi.raise_exception,
                              InvalidException, 1)

        if not sys.platform.startswith('java'):
            test_capi1()
            test_capi2()
            test_capi3()

    def test_WindowsError(self):
        try:
            WindowsError
        except NameError:
            pass
        else:
            self.assertEqual(str(WindowsError(1001)), "1001")
            self.assertEqual(str(WindowsError(1001, "message")),
                             "[Error 1001] message")
            self.assertEqual(WindowsError(1001, "message").errno, 22)
            self.assertEqual(WindowsError(1001, "message").winerror, 1001)

    def testAttributes(self):
        # test that exception attributes are happy

        exceptionList = [
            (BaseException, (), {'args' : ()}),
            (BaseException, (1, ), {'args' : (1,)}),
            (BaseException, ('foo',),
                {'args' : ('foo',)}),
            (BaseException, ('foo', 1),
                {'args' : ('foo', 1)}),
            (SystemExit, ('foo',),
                {'args' : ('foo',), 'code' : 'foo'}),
            (IOError, ('foo',),
                {'args' : ('foo',), 'filename' : None,
                 'errno' : None, 'strerror' : None}),
            (IOError, ('foo', 'bar'),
                {'args' : ('foo', 'bar'), 'filename' : None,
                 'errno' : 'foo', 'strerror' : 'bar'}),
            (IOError, ('foo', 'bar', 'baz'),
                {'args' : ('foo', 'bar'), 'filename' : 'baz',
                 'errno' : 'foo', 'strerror' : 'bar'}),
            (IOError, ('foo', 'bar', 'baz', 'quux'),
                {'args' : ('foo', 'bar', 'baz', 'quux')}),
            (EnvironmentError, ('errnoStr', 'strErrorStr', 'filenameStr'),
                {'args' : ('errnoStr', 'strErrorStr'),
                 'strerror' : 'strErrorStr', 'errno' : 'errnoStr',
                 'filename' : 'filenameStr'}),
            (EnvironmentError, (1, 'strErrorStr', 'filenameStr'),
                {'args' : (1, 'strErrorStr'), 'errno' : 1,
                 'strerror' : 'strErrorStr', 'filename' : 'filenameStr'}),
            (SyntaxError, (), {'msg' : None, 'text' : None,
                'filename' : None, 'lineno' : None, 'offset' : None,
                'print_file_and_line' : None}),
            (SyntaxError, ('msgStr',),
                {'args' : ('msgStr',), 'text' : None,
                 'print_file_and_line' : None, 'msg' : 'msgStr',
                 'filename' : None, 'lineno' : None, 'offset' : None}),
            (SyntaxError, ('msgStr', ('filenameStr', 'linenoStr', 'offsetStr',
                           'textStr')),
                {'offset' : 'offsetStr', 'text' : 'textStr',
                 'args' : ('msgStr', ('filenameStr', 'linenoStr',
                                      'offsetStr', 'textStr')),
                 'print_file_and_line' : None, 'msg' : 'msgStr',
                 'filename' : 'filenameStr', 'lineno' : 'linenoStr'}),
            (SyntaxError, ('msgStr', 'filenameStr', 'linenoStr', 'offsetStr',
                           'textStr', 'print_file_and_lineStr'),
                {'text' : None,
                 'args' : ('msgStr', 'filenameStr', 'linenoStr', 'offsetStr',
                           'textStr', 'print_file_and_lineStr'),
                 'print_file_and_line' : None, 'msg' : 'msgStr',
                 'filename' : None, 'lineno' : None, 'offset' : None}),
            (UnicodeError, (), {'args' : (),}),
            (UnicodeEncodeError, ('ascii', 'a', 0, 1,
                                  'ordinal not in range'),
                {'args' : ('ascii', 'a', 0, 1,
                                           'ordinal not in range'),
                 'encoding' : 'ascii', 'object' : 'a',
                 'start' : 0, 'reason' : 'ordinal not in range'}),
            (UnicodeDecodeError, ('ascii', bytearray(b'\xff'), 0, 1,
                                  'ordinal not in range'),
                {'args' : ('ascii', bytearray(b'\xff'), 0, 1,
                                           'ordinal not in range'),
                 'encoding' : 'ascii', 'object' : b'\xff',
                 'start' : 0, 'reason' : 'ordinal not in range'}),
            (UnicodeDecodeError, ('ascii', b'\xff', 0, 1,
                                  'ordinal not in range'),
                {'args' : ('ascii', b'\xff', 0, 1,
                                           'ordinal not in range'),
                 'encoding' : 'ascii', 'object' : b'\xff',
                 'start' : 0, 'reason' : 'ordinal not in range'}),
            (UnicodeTranslateError, ("\u3042", 0, 1, "ouch"),
                {'args' : ('\u3042', 0, 1, 'ouch'),
                 'object' : '\u3042', 'reason' : 'ouch',
                 'start' : 0, 'end' : 1}),
        ]
        try:
            exceptionList.append(
                (WindowsError, (1, 'strErrorStr', 'filenameStr'),
                    {'args' : (1, 'strErrorStr'),
                     'strerror' : 'strErrorStr', 'winerror' : 1,
                     'errno' : 22, 'filename' : 'filenameStr'})
            )
        except NameError:
            pass

        for exc, args, expected in exceptionList:
            try:
                e = exc(*args)
            except:
                print("\nexc=%r, args=%r" % (exc, args), file=sys.stderr)
                raise
            else:
                # Verify module name
                self.assertEqual(type(e).__module__, 'builtins')
                # Verify no ref leaks in Exc_str()
                s = str(e)
                for checkArgName in expected:
                    value = getattr(e, checkArgName)
                    self.assertEqual(repr(value),
                                     repr(expected[checkArgName]),
                                     '%r.%s == %r, expected %r' % (
                                     e, checkArgName,
                                     value, expected[checkArgName]))

                # test for pickling support
                for p in [pickle]:
                    for protocol in range(p.HIGHEST_PROTOCOL + 1):
                        s = p.dumps(e, protocol)
                        new = p.loads(s)
                        for checkArgName in expected:
                            got = repr(getattr(new, checkArgName))
                            want = repr(expected[checkArgName])
                            self.assertEqual(got, want,
                                             'pickled "%r", attribute "%s' %
                                             (e, checkArgName))

    def testWithTraceback(self):
        try:
            raise IndexError(4)
        except:
            tb = sys.exc_info()[2]

        e = BaseException().with_traceback(tb)
        self.assertIsInstance(e, BaseException)
        self.assertEqual(e.__traceback__, tb)

        e = IndexError(5).with_traceback(tb)
        self.assertIsInstance(e, IndexError)
        self.assertEqual(e.__traceback__, tb)

        class MyException(Exception):
            pass

        e = MyException().with_traceback(tb)
        self.assertIsInstance(e, MyException)
        self.assertEqual(e.__traceback__, tb)

    def testInvalidTraceback(self):
        try:
            Exception().__traceback__ = 5
        except TypeError as e:
            self.assertIn("__traceback__ must be a traceback", str(e))
        else:
            self.fail("No exception raised")

    def testInvalidAttrs(self):
        self.assertRaises(TypeError, setattr, Exception(), '__cause__', 1)
        self.assertRaises(TypeError, delattr, Exception(), '__cause__')
        self.assertRaises(TypeError, setattr, Exception(), '__context__', 1)
        self.assertRaises(TypeError, delattr, Exception(), '__context__')

    def testNoneClearsTracebackAttr(self):
        try:
            raise IndexError(4)
        except:
            tb = sys.exc_info()[2]

        e = Exception()
        e.__traceback__ = tb
        e.__traceback__ = None
        self.assertEqual(e.__traceback__, None)

    def testChainingAttrs(self):
        e = Exception()
        self.assertEqual(e.__context__, None)
        self.assertEqual(e.__cause__, None)

        e = TypeError()
        self.assertEqual(e.__context__, None)
        self.assertEqual(e.__cause__, None)

        class MyException(EnvironmentError):
            pass

        e = MyException()
        self.assertEqual(e.__context__, None)
        self.assertEqual(e.__cause__, None)

    def testKeywordArgs(self):
        # test that builtin exception don't take keyword args,
        # but user-defined subclasses can if they want
        self.assertRaises(TypeError, BaseException, a=1)

        class DerivedException(BaseException):
            def __init__(self, fancy_arg):
                BaseException.__init__(self)
                self.fancy_arg = fancy_arg

        x = DerivedException(fancy_arg=42)
        self.assertEqual(x.fancy_arg, 42)

    def testInfiniteRecursion(self):
        def f():
            return f()
        self.assertRaises(RuntimeError, f)

        def g():
            try:
                return g()
            except ValueError:
                return -1
        self.assertRaises(RuntimeError, g)

    def test_str(self):
        # Make sure both instances and classes have a str representation.
        self.assertTrue(str(Exception))
        self.assertTrue(str(Exception('a')))
        self.assertTrue(str(Exception('a', 'b')))

    def testExceptionCleanupNames(self):
        # Make sure the local variable bound to the exception instance by
        # an "except" statement is only visible inside the except block.
        try:
            raise Exception()
        except Exception as e:
            self.assertTrue(e)
            del e
        self.assertNotIn('e', locals())

    def testExceptionCleanupState(self):
        # Make sure exception state is cleaned up as soon as the except
        # block is left. See #2507

        class MyException(Exception):
            def __init__(self, obj):
                self.obj = obj
        class MyObj:
            pass

        def inner_raising_func():
            # Create some references in exception value and traceback
            local_ref = obj
            raise MyException(obj)

        # Qualified "except" with "as"
        obj = MyObj()
        wr = weakref.ref(obj)
        try:
            inner_raising_func()
        except MyException as e:
            pass
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

        # Qualified "except" without "as"
        obj = MyObj()
        wr = weakref.ref(obj)
        try:
            inner_raising_func()
        except MyException:
            pass
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

        # Bare "except"
        obj = MyObj()
        wr = weakref.ref(obj)
        try:
            inner_raising_func()
        except:
            pass
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

        # "except" with premature block leave
        obj = MyObj()
        wr = weakref.ref(obj)
        for i in [0]:
            try:
                inner_raising_func()
            except:
                break
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

        # "except" block raising another exception
        obj = MyObj()
        wr = weakref.ref(obj)
        try:
            try:
                inner_raising_func()
            except:
                raise KeyError
        except KeyError as e:
            # We want to test that the except block above got rid of
            # the exception raised in inner_raising_func(), but it
            # also ends up in the __context__ of the KeyError, so we
            # must clear the latter manually for our test to succeed.
            e.__context__ = None
            obj = None
            obj = wr()
            self.assertTrue(obj is None, "%s" % obj)

        # Some complicated construct
        obj = MyObj()
        wr = weakref.ref(obj)
        try:
            inner_raising_func()
        except MyException:
            try:
                try:
                    raise
                finally:
                    raise
            except MyException:
                pass
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

        # Inside an exception-silencing "with" block
        class Context:
            def __enter__(self):
                return self
            def __exit__ (self, exc_type, exc_value, exc_tb):
                return True
        obj = MyObj()
        wr = weakref.ref(obj)
        with Context():
            inner_raising_func()
        obj = None
        obj = wr()
        self.assertTrue(obj is None, "%s" % obj)

    def test_exception_target_in_nested_scope(self):
        # issue 4617: This used to raise a SyntaxError
        # "can not delete variable 'e' referenced in nested scope"
        def print_error():
            e
        try:
            something
        except Exception as e:
            print_error()
            # implicit "del e" here

    def test_generator_leaking(self):
        # Test that generator exception state doesn't leak into the calling
        # frame
        def yield_raise():
            try:
                raise KeyError("caught")
            except KeyError:
                yield sys.exc_info()[0]
                yield sys.exc_info()[0]
            yield sys.exc_info()[0]
        g = yield_raise()
        self.assertEqual(next(g), KeyError)
        self.assertEqual(sys.exc_info()[0], None)
        self.assertEqual(next(g), KeyError)
        self.assertEqual(sys.exc_info()[0], None)
        self.assertEqual(next(g), None)

        # Same test, but inside an exception handler
        try:
            raise TypeError("foo")
        except TypeError:
            g = yield_raise()
            self.assertEqual(next(g), KeyError)
            self.assertEqual(sys.exc_info()[0], TypeError)
            self.assertEqual(next(g), KeyError)
            self.assertEqual(sys.exc_info()[0], TypeError)
            self.assertEqual(next(g), TypeError)
            del g
            self.assertEqual(sys.exc_info()[0], TypeError)

    def test_generator_finalizing_and_exc_info(self):
        # See #7173
        def simple_gen():
            yield 1
        def run_gen():
            gen = simple_gen()
            try:
                raise RuntimeError
            except RuntimeError:
                return next(gen)
        run_gen()
        gc_collect()
        self.assertEqual(sys.exc_info(), (None, None, None))

    def test_3114(self):
        # Bug #3114: in its destructor, MyObject retrieves a pointer to
        # obsolete and/or deallocated objects.
        class MyObject:
            def __del__(self):
                nonlocal e
                e = sys.exc_info()
        e = ()
        try:
            raise Exception(MyObject())
        except:
            pass
        self.assertEqual(e, (None, None, None))

    def testUnicodeChangeAttributes(self):
        # See issue 7309. This was a crasher.

        u = UnicodeEncodeError('baz', 'xxxxx', 1, 5, 'foo')
        self.assertEqual(str(u), "'baz' codec can't encode characters in position 1-4: foo")
        u.end = 2
        self.assertEqual(str(u), "'baz' codec can't encode character '\\x78' in position 1: foo")
        u.end = 5
        u.reason = 0x345345345345345345
        self.assertEqual(str(u), "'baz' codec can't encode characters in position 1-4: 965230951443685724997")
        u.encoding = 4000
        self.assertEqual(str(u), "'4000' codec can't encode characters in position 1-4: 965230951443685724997")
        u.start = 1000
        self.assertEqual(str(u), "'4000' codec can't encode characters in position 1000-4: 965230951443685724997")

        u = UnicodeDecodeError('baz', b'xxxxx', 1, 5, 'foo')
        self.assertEqual(str(u), "'baz' codec can't decode bytes in position 1-4: foo")
        u.end = 2
        self.assertEqual(str(u), "'baz' codec can't decode byte 0x78 in position 1: foo")
        u.end = 5
        u.reason = 0x345345345345345345
        self.assertEqual(str(u), "'baz' codec can't decode bytes in position 1-4: 965230951443685724997")
        u.encoding = 4000
        self.assertEqual(str(u), "'4000' codec can't decode bytes in position 1-4: 965230951443685724997")
        u.start = 1000
        self.assertEqual(str(u), "'4000' codec can't decode bytes in position 1000-4: 965230951443685724997")

        u = UnicodeTranslateError('xxxx', 1, 5, 'foo')
        self.assertEqual(str(u), "can't translate characters in position 1-4: foo")
        u.end = 2
        self.assertEqual(str(u), "can't translate character '\\x78' in position 1: foo")
        u.end = 5
        u.reason = 0x345345345345345345
        self.assertEqual(str(u), "can't translate characters in position 1-4: 965230951443685724997")
        u.start = 1000
        self.assertEqual(str(u), "can't translate characters in position 1000-4: 965230951443685724997")

    def test_badisinstance(self):
        # Bug #2542: if issubclass(e, MyException) raises an exception,
        # it should be ignored
        class Meta(type):
            def __subclasscheck__(cls, subclass):
                raise ValueError()
        class MyException(Exception, metaclass=Meta):
            pass

        with captured_output("stderr") as stderr:
            try:
                raise KeyError()
            except MyException as e:
                self.fail("exception should not be a MyException")
            except KeyError:
                pass
            except:
                self.fail("Should have raised KeyError")
            else:
                self.fail("Should have raised KeyError")

        def g():
            try:
                return g()
            except RuntimeError:
                return sys.exc_info()
        e, v, tb = g()
        self.assertTrue(isinstance(v, RuntimeError), type(v))
        self.assertIn("maximum recursion depth exceeded", str(v))


    def test_MemoryError(self):
        # PyErr_NoMemory always raises the same exception instance.
        # Check that the traceback is not doubled.
        import traceback
        from _testcapi import raise_memoryerror
        def raiseMemError():
            try:
                raise_memoryerror()
            except MemoryError as e:
                tb = e.__traceback__
            else:
                self.fail("Should have raises a MemoryError")
            return traceback.format_tb(tb)

        tb1 = raiseMemError()
        tb2 = raiseMemError()
        self.assertEqual(tb1, tb2)

    @cpython_only
    def test_exception_with_doc(self):
        import _testcapi
        doc2 = "This is a test docstring."
        doc4 = "This is another test docstring."

        self.assertRaises(SystemError, _testcapi.make_exception_with_doc,
                          "error1")

        # test basic usage of PyErr_NewException
        error1 = _testcapi.make_exception_with_doc("_testcapi.error1")
        self.assertIs(type(error1), type)
        self.assertTrue(issubclass(error1, Exception))
        self.assertIsNone(error1.__doc__)

        # test with given docstring
        error2 = _testcapi.make_exception_with_doc("_testcapi.error2", doc2)
        self.assertEqual(error2.__doc__, doc2)

        # test with explicit base (without docstring)
        error3 = _testcapi.make_exception_with_doc("_testcapi.error3",
                                                   base=error2)
        self.assertTrue(issubclass(error3, error2))

        # test with explicit base tuple
        class C(object):
            pass
        error4 = _testcapi.make_exception_with_doc("_testcapi.error4", doc4,
                                                   (error3, C))
        self.assertTrue(issubclass(error4, error3))
        self.assertTrue(issubclass(error4, C))
        self.assertEqual(error4.__doc__, doc4)

        # test with explicit dictionary
        error5 = _testcapi.make_exception_with_doc("_testcapi.error5", "",
                                                   error4, {'a': 1})
        self.assertTrue(issubclass(error5, error4))
        self.assertEqual(error5.a, 1)
        self.assertEqual(error5.__doc__, "")

    def test_memory_error_cleanup(self):
        # Issue #5437: preallocated MemoryError instances should not keep
        # traceback objects alive.
        from _testcapi import raise_memoryerror
        class C:
            pass
        wr = None
        def inner():
            nonlocal wr
            c = C()
            wr = weakref.ref(c)
            raise_memoryerror()
        # We cannot use assertRaises since it manually deletes the traceback
        try:
            inner()
        except MemoryError as e:
            self.assertNotEqual(wr(), None)
        else:
            self.fail("MemoryError not raised")
        self.assertEqual(wr(), None)

    def test_recursion_error_cleanup(self):
        # Same test as above, but with "recursion exceeded" errors
        class C:
            pass
        wr = None
        def inner():
            nonlocal wr
            c = C()
            wr = weakref.ref(c)
            inner()
        # We cannot use assertRaises since it manually deletes the traceback
        try:
            inner()
        except RuntimeError as e:
            self.assertNotEqual(wr(), None)
        else:
            self.fail("RuntimeError not raised")
        self.assertEqual(wr(), None)

def test_main():
    run_unittest(ExceptionTests)

if __name__ == '__main__':
    unittest.main()