Misc/find_recursionlimit.py

   1 #! /usr/bin/env python
   2 """Find the maximum recursion limit that prevents core dumps
   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,
   7 call sys.setrecursionlimit.
   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
  14 After each round of tests, it prints a message
  15 Limit of NNNN is fine.
  16
  17 It ends when Python causes a segmentation fault because the limit is
  18 too high.  On platforms like Mac and Windows, it should exit with a
  19 MemoryError.
  20
  21 NB: A program that does not use __methods__ can set a higher limit.
  22 """
  23
  24 import sys
  25
  26 class RecursiveBlowup1:
  27     def __init__(self):
  28         self.__init__()
  29
  30 def test_init():
  31     return RecursiveBlowup1()
  32
  33 class RecursiveBlowup2:
  34     def __repr__(self):
  35         return repr(self)
  36
  37 def test_repr():
  38     return repr(RecursiveBlowup2())
  39
  40 class RecursiveBlowup4:
  41     def __add__(self, x):
  42         return x + self
  43
  44 def test_add():
  45     return RecursiveBlowup4() + RecursiveBlowup4()
  46
  47 class RecursiveBlowup5:
  48     def __getattr__(self, attr):
  49         return getattr(self, attr)
  50
  51 def test_getattr():
  52     return RecursiveBlowup5().attr
  53
  54 class RecursiveBlowup6:
  55     def __getitem__(self, item):
  56         return self[item - 2] + self[item - 1]
  57
  58 def test_getitem():
  59     return RecursiveBlowup6()[5]
  60
  61 def test_recurse():
  62     return test_recurse()
  63
  64 def check_limit(n, test_func_name):
  65     sys.setrecursionlimit(n)
  66     if test_func_name.startswith("test_"):
  67         print test_func_name[5:]
  68     else:
  69         print test_func_name
  70     test_func = globals()[test_func_name]
  71     try:
  72         test_func()
  73     except RuntimeError:
  74         pass
  75     else:
  76         print "Yikes!"
  77
  78 limit = 1000
  79 while 1:
  80     check_limit(limit, "test_recurse")
  81     check_limit(limit, "test_add")
  82     check_limit(limit, "test_repr")
  83     check_limit(limit, "test_init")
  84     check_limit(limit, "test_getattr")
  85     check_limit(limit, "test_getitem")
  86     print "Limit of %d is fine" % limit
  87     limit = limit + 100