Pathological regular expression

[Steven D'Aprano]

On Thu, 09 Apr 2009 02:56:00 -0700, David Liang wrote:

> Hi all,
> I'm having a weird problem with a regular expression (tested in 2.6 and
> 3.0):
> 
> Basically, any of these:
> _re_comments = re.compile(r'^(([^\\]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
> _re_comments = re.compile(r'^(([^#]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
> _re_comments = re.compile(r'^(([^"]+|\\.|"([^"\\]+|\\.)*")*)#.*$')
> 
> followed by for example,
> line = r'~/.[m]ozilla/firefox/*.default/chrome'
> print(_re_comments.sub(r'\1', line))
> 
> ...hangs the interpreter.


I can confirm the first one hangs the interpreter in Python 2.5 as well. 
I haven't tested the other two.

To my mind, this is a bug in the RE engine. Is there any reason to not 
treat it as a bug?


-- 
Steven