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