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128 lines
3.9 KiB
Python
Executable file
128 lines
3.9 KiB
Python
Executable file
#! /usr/bin/env python3
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"""Find the maximum recursion limit that prevents interpreter termination.
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This script finds the maximum safe recursion limit on a particular
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platform. If you need to change the recursion limit on your system,
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this script will tell you a safe upper bound. To use the new limit,
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call sys.setrecursionlimit().
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This module implements several ways to create infinite recursion in
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Python. Different implementations end up pushing different numbers of
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C stack frames, depending on how many calls through Python's abstract
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C API occur.
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After each round of tests, it prints a message:
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"Limit of NNNN is fine".
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The highest printed value of "NNNN" is therefore the highest potentially
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safe limit for your system (which depends on the OS, architecture, but also
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the compilation flags). Please note that it is practically impossible to
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test all possible recursion paths in the interpreter, so the results of
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this test should not be trusted blindly -- although they give a good hint
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of which values are reasonable.
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NOTE: When the C stack space allocated by your system is exceeded due
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to excessive recursion, exact behaviour depends on the platform, although
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the interpreter will always fail in a likely brutal way: either a
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segmentation fault, a MemoryError, or just a silent abort.
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NB: A program that does not use __methods__ can set a higher limit.
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"""
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import sys
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import itertools
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class RecursiveBlowup1:
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def __init__(self):
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self.__init__()
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def test_init():
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return RecursiveBlowup1()
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class RecursiveBlowup2:
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def __repr__(self):
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return repr(self)
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def test_repr():
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return repr(RecursiveBlowup2())
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class RecursiveBlowup4:
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def __add__(self, x):
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return x + self
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def test_add():
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return RecursiveBlowup4() + RecursiveBlowup4()
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class RecursiveBlowup5:
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def __getattr__(self, attr):
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return getattr(self, attr)
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def test_getattr():
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return RecursiveBlowup5().attr
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class RecursiveBlowup6:
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def __getitem__(self, item):
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return self[item - 2] + self[item - 1]
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def test_getitem():
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return RecursiveBlowup6()[5]
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def test_recurse():
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return test_recurse()
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def test_cpickle(_cache={}):
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import io
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try:
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import _pickle
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except ImportError:
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print("cannot import _pickle, skipped!")
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return
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k, l = None, None
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for n in itertools.count():
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try:
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l = _cache[n]
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continue # Already tried and it works, let's save some time
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except KeyError:
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for i in range(100):
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l = [k, l]
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k = {i: l}
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_pickle.Pickler(io.BytesIO(), protocol=-1).dump(l)
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_cache[n] = l
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def test_compiler_recursion():
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# The compiler uses a scaling factor to support additional levels
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# of recursion. This is a sanity check of that scaling to ensure
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# it still raises RecursionError even at higher recursion limits
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compile("()" * (10 * sys.getrecursionlimit()), "<single>", "single")
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def check_limit(n, test_func_name):
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sys.setrecursionlimit(n)
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if test_func_name.startswith("test_"):
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print(test_func_name[5:])
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else:
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print(test_func_name)
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test_func = globals()[test_func_name]
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try:
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test_func()
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# AttributeError can be raised because of the way e.g. PyDict_GetItem()
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# silences all exceptions and returns NULL, which is usually interpreted
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# as "missing attribute".
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except (RecursionError, AttributeError):
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pass
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else:
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print("Yikes!")
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if __name__ == '__main__':
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limit = 1000
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while 1:
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check_limit(limit, "test_recurse")
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check_limit(limit, "test_add")
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check_limit(limit, "test_repr")
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check_limit(limit, "test_init")
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check_limit(limit, "test_getattr")
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check_limit(limit, "test_getitem")
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check_limit(limit, "test_cpickle")
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check_limit(limit, "test_compiler_recursion")
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print("Limit of %d is fine" % limit)
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limit = limit + 100
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