Merged revisions 75370-75372 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

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  r75370 | georg.brandl | 2009-10-11 23:10:07 +0200 (So, 11 Okt 2009) | 1 line

  Move find_recursionlimit.py to Tools/scripts; it is out of place in Misc.
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  r75371 | georg.brandl | 2009-10-11 23:14:37 +0200 (So, 11 Okt 2009) | 1 line

  Add find_recursionlimit.py to README.
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  r75372 | georg.brandl | 2009-10-11 23:17:14 +0200 (So, 11 Okt 2009) | 1 line

  Update Misc/README.
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2 files changed, 124 insertions, 5 deletions

diff --git a/Tools/scripts/README b/Tools/scripts/README
index 64fc2bd..b1c167e 100644
--- a/Tools/scripts/README
+++ b/Tools/scripts/README
@@ -19,7 +19,8 @@ db2pickle.py		Dump a database file to a pickle
 diff.py			Print file diffs in context, unified, or ndiff formats
 dutree.py		Format du(1) output as a tree sorted by size
 eptags.py		Create Emacs TAGS file for Python modules
-finddiv.py		A grep-like tool that looks for division operators.
+find_recursionlimit.py  Find the maximum recursion limit on this machine 
+finddiv.py		A grep-like tool that looks for division operators
 findlinksto.py		Recursively find symbolic links to a given path prefix
 findnocoding.py		Find source files which need an encoding declaration
 fixcid.py		Massive identifier substitution on C source files
@@ -28,8 +29,8 @@ fixheader.py		Add some cpp magic to a C include file
 fixnotice.py		Fix the copyright notice in source files
 fixps.py		Fix Python scripts' first line (if #!)
 ftpmirror.py		FTP mirror script
-google.py		Open a webbrowser with Google.
-gprof2html.py		Transform gprof(1) output into useful HTML.
+google.py		Open a webbrowser with Google
+gprof2html.py		Transform gprof(1) output into useful HTML
 h2py.py			Translate #define's into Python assignments
 idle			Main program to start IDLE
 ifdef.py		Remove #if(n)def groups from C sources
@@ -55,9 +56,9 @@ pysource.py		Find Python source files
 redemo.py		Basic regular expression demonstration facility
 reindent.py		Change .py files to use 4-space indents.
 rgrep.py		Reverse grep through a file (useful for big logfiles)
-setup.py		Install all scripts listed here.
+setup.py		Install all scripts listed here
 suff.py			Sort a list of files by suffix
-svneol.py		Sets svn:eol-style on all files in directory.
+svneol.py		Sets svn:eol-style on all files in directory
 texcheck.py             Validate Python LaTeX formatting (Raymond Hettinger)
 texi2html.py		Convert GNU texinfo files into HTML
 treesync.py		Synchronize source trees (very ideosyncratic)
diff --git a/Tools/scripts/find_recursionlimit.py b/Tools/scripts/find_recursionlimit.py
new file mode 100644
index 0000000..2e202be
--- /dev/null
+++ b/Tools/scripts/find_recursionlimit.py
@@ -0,0 +1,118 @@
+#! /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={}):
+    import io
+    try:
+        import _pickle
+    except ImportError:
+        print("cannot import _pickle, 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]
+        _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