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
  22 import sys
  23
  24 class RecursiveBlowup1:
  25     def __init__(self):
  26         self.__init__()
  27
  28 def test_init():
  29     return RecursiveBlowup1()
  30
  31 class RecursiveBlowup2:
  32     def __repr__(self):
  33         return repr(self)
  34
  35 def test_repr():
  36     return repr(RecursiveBlowup2())
  37
  38 class RecursiveBlowup4:
  39     def __add__(self, x):
  40         return x + self
  41
  42 def test_add():
  43     return RecursiveBlowup4() + RecursiveBlowup4()
  44
  45 class RecursiveBlowup5:
  46     def __getattr__(self, attr):
  47         return getattr(self, attr)
  48
  49 def test_getattr():
  50     return RecursiveBlowup5().attr
  51
  52 class RecursiveBlowup6:
  53     def __getitem__(self, item):
  54         return self[item - 2] + self[item - 1]
  55
  56 def test_getitem():
  57     return RecursiveBlowup6()[5]
  58
  59 def test_recurse():
  60     return test_recurse()
  61
  62 def check_limit(n, test_func_name):
  63     sys.setrecursionlimit(n)
  64     if test_func_name.startswith("test_"):
  65         print(test_func_name[5:])
  66     else:
  67         print(test_func_name)
  68     test_func = globals()[test_func_name]
  69     try:
  70         test_func()
  71     except RuntimeError:
  72         pass
  73     else:
  74         print("Yikes!")
  75
  76 limit = 1000
  77 while 1:
  78     check_limit(limit, "test_recurse")
  79     check_limit(limit, "test_add")
  80     check_limit(limit, "test_repr")
  81     check_limit(limit, "test_init")
  82     check_limit(limit, "test_getattr")
  83     check_limit(limit, "test_getitem")
  84     print("Limit of %d is fine" % limit)
  85     limit = limit + 100