Fix array overflow bug in bdiff
I ran into a bug while importing a large repository into mercurial.
The diff algorithm does not allocate a big enough array of hunks
for some test cases. This results in memory corruption, and possibly,
as in my case, a seg fault.
You should be able to reproduce this problem with any case of more
than a few lines that follows this pattern:
a b
= =
1 1
2
2 3
4
3 5
.
4 .
.
5
.
.
.
I.e., "a" has blank lines on every other line that have been removed in
"b". In this case, the number of matching hunks is equal to the number
of lines in "b". This is more than ((an + bn)/4 + 2). I'm not sure what
motivates this formula, but when I changed it to the smaller of an or
bn (+ 1), it works.
[comment added by mpm]
# Copyright (C) 2005 by Intevation GmbH
# Author(s):
# Thomas Arendsen Hein <thomas@intevation.de>
#
# This program is free software under the GNU GPL (>=v2)
# Read the file COPYING coming with the software for details.
"""
Mercurial version
"""
import os
import os.path
import re
import time
import util
unknown_version = 'unknown'
remembered_version = False
def get_version():
"""Return version information if available."""
try:
from mercurial.__version__ import version
except ImportError:
version = unknown_version
return version
def write_version(version):
"""Overwrite version file."""
filename = os.path.join(os.path.dirname(__file__), '__version__.py')
f = open(filename, 'w')
f.write("# This file is auto-generated.\n")
f.write("version = %r\n" % version)
f.close()
def remember_version(version=None):
"""Store version information."""
global remembered_version
if not version and os.path.isdir(".hg"):
f = os.popen("hg identify 2> %s" % util.nulldev) # use real hg installation
ident = f.read()[:-1]
if not f.close() and ident:
ids = ident.split(' ', 1)
version = ids.pop(0)
if version[-1] == '+':
version = version[:-1]
modified = True
else:
modified = False
if version.isalnum() and ids:
for tag in ids[0].split('/'):
# is a tag is suitable as a version number?
if re.match(r'^(\d+\.)+[\w.-]+$', tag):
version = tag
break
if modified:
version += time.strftime('+%Y%m%d')
if version:
remembered_version = True
write_version(version)
def forget_version():
"""Remove version information."""
if remembered_version:
write_version(unknown_version)