Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 1 | #! /usr/bin/env python |
Benjamin Peterson | 5478b47 | 2008-09-17 22:25:09 +0000 | [diff] [blame] | 2 | """Find the maximum recursion limit that prevents interpreter termination. |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 3 | |
| 4 | This script finds the maximum safe recursion limit on a particular |
| 5 | platform. If you need to change the recursion limit on your system, |
| 6 | this script will tell you a safe upper bound. To use the new limit, |
Benjamin Peterson | 5478b47 | 2008-09-17 22:25:09 +0000 | [diff] [blame] | 7 | call sys.setrecursionlimit(). |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 8 | |
| 9 | This module implements several ways to create infinite recursion in |
| 10 | Python. Different implementations end up pushing different numbers of |
| 11 | C stack frames, depending on how many calls through Python's abstract |
| 12 | C API occur. |
| 13 | |
Benjamin Peterson | 5478b47 | 2008-09-17 22:25:09 +0000 | [diff] [blame] | 14 | After each round of tests, it prints a message: |
| 15 | "Limit of NNNN is fine". |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 16 | |
Benjamin Peterson | 5478b47 | 2008-09-17 22:25:09 +0000 | [diff] [blame] | 17 | The highest printed value of "NNNN" is therefore the highest potentially |
| 18 | safe limit for your system (which depends on the OS, architecture, but also |
| 19 | the compilation flags). Please note that it is practically impossible to |
| 20 | test all possible recursion paths in the interpreter, so the results of |
| 21 | this test should not be trusted blindly -- although they give a good hint |
| 22 | of which values are reasonable. |
| 23 | |
| 24 | NOTE: When the C stack space allocated by your system is exceeded due |
| 25 | to excessive recursion, exact behaviour depends on the platform, although |
| 26 | the interpreter will always fail in a likely brutal way: either a |
| 27 | segmentation fault, a MemoryError, or just a silent abort. |
| 28 | |
| 29 | NB: A program that does not use __methods__ can set a higher limit. |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 30 | """ |
| 31 | |
| 32 | import sys |
Amaury Forgeot d'Arc | fb1a5eb | 2008-09-11 21:03:37 +0000 | [diff] [blame] | 33 | import itertools |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 34 | |
| 35 | class RecursiveBlowup1: |
| 36 | def __init__(self): |
| 37 | self.__init__() |
| 38 | |
| 39 | def test_init(): |
| 40 | return RecursiveBlowup1() |
| 41 | |
| 42 | class RecursiveBlowup2: |
| 43 | def __repr__(self): |
| 44 | return repr(self) |
| 45 | |
| 46 | def test_repr(): |
| 47 | return repr(RecursiveBlowup2()) |
| 48 | |
| 49 | class RecursiveBlowup4: |
| 50 | def __add__(self, x): |
| 51 | return x + self |
| 52 | |
| 53 | def test_add(): |
| 54 | return RecursiveBlowup4() + RecursiveBlowup4() |
| 55 | |
| 56 | class RecursiveBlowup5: |
| 57 | def __getattr__(self, attr): |
| 58 | return getattr(self, attr) |
| 59 | |
| 60 | def test_getattr(): |
| 61 | return RecursiveBlowup5().attr |
| 62 | |
| 63 | class RecursiveBlowup6: |
| 64 | def __getitem__(self, item): |
| 65 | return self[item - 2] + self[item - 1] |
| 66 | |
| 67 | def test_getitem(): |
| 68 | return RecursiveBlowup6()[5] |
Tim Peters | 182b5ac | 2004-07-18 06:16:08 +0000 | [diff] [blame] | 69 | |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 70 | def test_recurse(): |
| 71 | return test_recurse() |
| 72 | |
Amaury Forgeot d'Arc | fb1a5eb | 2008-09-11 21:03:37 +0000 | [diff] [blame] | 73 | def test_cpickle(_cache={}): |
| 74 | import io |
| 75 | try: |
| 76 | import _pickle |
| 77 | except ImportError: |
| 78 | print("cannot import _pickle, skipped!") |
| 79 | return |
| 80 | l = None |
| 81 | for n in itertools.count(): |
| 82 | try: |
| 83 | l = _cache[n] |
| 84 | continue # Already tried and it works, let's save some time |
| 85 | except KeyError: |
| 86 | for i in range(100): |
| 87 | l = [l] |
| 88 | _pickle.Pickler(io.BytesIO(), protocol=-1).dump(l) |
| 89 | _cache[n] = l |
| 90 | |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 91 | def check_limit(n, test_func_name): |
| 92 | sys.setrecursionlimit(n) |
| 93 | if test_func_name.startswith("test_"): |
Collin Winter | e7bf59f | 2007-08-30 18:39:28 +0000 | [diff] [blame] | 94 | print(test_func_name[5:]) |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 95 | else: |
Collin Winter | e7bf59f | 2007-08-30 18:39:28 +0000 | [diff] [blame] | 96 | print(test_func_name) |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 97 | test_func = globals()[test_func_name] |
| 98 | try: |
| 99 | test_func() |
Benjamin Peterson | 5478b47 | 2008-09-17 22:25:09 +0000 | [diff] [blame] | 100 | # AttributeError can be raised because of the way e.g. PyDict_GetItem() |
| 101 | # silences all exceptions and returns NULL, which is usually interpreted |
| 102 | # as "missing attribute". |
| 103 | except (RuntimeError, AttributeError): |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 104 | pass |
| 105 | else: |
Collin Winter | e7bf59f | 2007-08-30 18:39:28 +0000 | [diff] [blame] | 106 | print("Yikes!") |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 107 | |
| 108 | limit = 1000 |
| 109 | while 1: |
| 110 | check_limit(limit, "test_recurse") |
| 111 | check_limit(limit, "test_add") |
| 112 | check_limit(limit, "test_repr") |
| 113 | check_limit(limit, "test_init") |
| 114 | check_limit(limit, "test_getattr") |
| 115 | check_limit(limit, "test_getitem") |
Amaury Forgeot d'Arc | fb1a5eb | 2008-09-11 21:03:37 +0000 | [diff] [blame] | 116 | check_limit(limit, "test_cpickle") |
Collin Winter | e7bf59f | 2007-08-30 18:39:28 +0000 | [diff] [blame] | 117 | print("Limit of %d is fine" % limit) |
Jeremy Hylton | c18b7d9 | 2000-08-31 19:24:17 +0000 | [diff] [blame] | 118 | limit = limit + 100 |