script that reports a fairly safe recursionlimit for a specific platform

1 files changed, 88 insertions, 0 deletions

diff --git a/Misc/find_recursionlimit.py b/Misc/find_recursionlimit.py
new file mode 100644
index 0000000..f16c29f
--- /dev/null
+++ b/Misc/find_recursionlimit.py
@@ -0,0 +1,88 @@
+#! /usr/bin/env python
+"""Find the maximum recursion limit that prevents core dumps
+
+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.
+
+It ends when Python causes a segmentation fault because the limit is
+too high.  On platforms like Mac and Windows, it should exit with a
+MemoryError.
+
+NB: A program that does not use __methods__ can set a higher limit.
+"""
+
+import sys
+
+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 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()
+    except RuntimeError:
+        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")
+    print "Limit of %d is fine" % limit
+    limit = limit + 100
+