Move find_recursionlimit.py to Tools/scripts; it is out of place in Misc.

1 files changed, 117 insertions, 0 deletions

diff --git a/Tools/scripts/find_recursionlimit.py b/Tools/scripts/find_recursionlimit.py
new file mode 100644
index 0000000..88e9bb5
--- /dev/null
+++ b/Tools/scripts/find_recursionlimit.py
@@ -0,0 +1,117 @@
+#! /usr/bin/env python
+"""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={}):
+    try:
+        import cPickle
+    except ImportError:
+        print "cannot import cPickle, skipped!"
+        return
+    l = 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 = [l]
+        cPickle.dumps(l, protocol=-1)
+        _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