[Python-bugs-list] [ python-Bugs-753711 ] Infinite Loop in RE

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Bugs item #753711, was opened at 2003-06-12 20:27
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=753711&group_id=5470

Category: Regular Expressions
Group: Python 2.2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: Matthew Bogosian (mbogosian)
Assigned to: Fredrik Lundh (effbot)
Summary: Infinite Loop in RE

Initial Comment:
This *may* be similar to
<http://sourceforge.net/tracker/?group_id=5470&atid=105470&func=detail&aid=439997>,
but I don't think the current behavior (infinite
loop/unbound execution) is correct.

Here's the python version:

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#!/usr/bin/python

import re

pattern =
'^UPDATE\s+\w+\s+SET\s+locked_until\s*=\s*(\S+\s*)+,'

# This won't match (missing ',' at end
str = 'UPDATE arena_teams SET locked_until =
CAST(EXTRACT(EPOCH FROM CURRENT_TIMESTAMP)'

re.search(pattern, str, re.I)

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When run, this script just pegs the CPU and hangs (I'm
running RedHat 8.0). Note: if I change the pattern
slightly it still doesn't work:

pattern = '^UPDATE\s+\w+\s+SET\s+locked_until\s*=\s*([^
=,]+\s*)+,'

It's not until the pattern actually matches that things
get better (with both the original and modified patterns):

# Pattern now matches (added a ',' at the end)
str = 'UPDATE arena_teams SET locked_until =
CAST(EXTRACT(EPOCH FROM CURRENT_TIMESTAMP),'

I tried doing the same thing in Perl:

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#!/usr/bin/perl

'UPDATE arena_teams SET locked_until =
CAST(EXTRACT(EPOCH FROM CURRENT_TIMESTAMP)' =~
'/UPDATE\s+\w+\s+SET\s+locked_until\s*=\s*(\S+\s*)+,/i';

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This of course runs just fine. Any ideas?

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=753711&group_id=5470