Comment 1 for bug 1217194

Just want to provide more data here, as it may not be clear how dangerous processing raw regular expressions can be:

clint@clint-HP:~/src$ cat /tmp/test.py
import re
import sys

n = int(sys.argv[1])

x = re.compile(('a?' * n) + ('a' * n))
print bool(x.match('a' * n))
clint@clint-HP:~/src$ time python /tmp/test.py 20
True

real 0m0.085s
user 0m0.080s
sys 0m0.004s
clint@clint-HP:~/src$ time python /tmp/test.py 25
True

real 0m2.062s
user 0m2.048s
sys 0m0.012s
clint@clint-HP:~/src$ time python /tmp/test.py 30
^CTraceback (most recent call last):
  File "/tmp/test.py", line 7, in <module>
    print bool(x.match('a' * n))
KeyboardInterrupt

real 0m22.336s
user 0m22.284s
sys 0m0.008s
clint@clint-HP:~/src$ time python /tmp/test.py 26
True

real 0m4.165s
user 0m4.148s
sys 0m0.008s
clint@clint-HP:~/src$ time python /tmp/test.py 27
True

real 0m8.501s
user 0m8.456s
sys 0m0.028s

Note that with every added character, the CPU time doubles.