Repository navigation
Regex with the backreference to a non-greedy group fails unexpectedly #127291
Description
Bug report
Bug description:
Hello,
There is a problem in the regex module. The regular expression with the backreference to a non-greedy group fails (matches nothing) on some inputs unexpectedly.
For example:
import re
r1 = re.compile('(a+)+\\1')
print(r1.search('a' * 28))
# OK, matches the whole string
r2 = re.compile('(a+)+?\\1')
print(r2.search('a' * 28))
# runs very slowly and eventually returns NoneThis problem seems to exist even in Python 2.7, which has been fixed in a version of Python 3.11. Since version 3.9 is still under maintenance, would this problem be fixed in the following release? (or is the pull request about this problem accepted?)
Thank You!
CPython versions tested on:
3.9
Operating systems tested on:
Linux, Windows
Activity
hugovk commentedon Nov 26, 2024
I can reproduce on macOS with Python 3.9 and 3.10, but 3.11-3.14 match the whole string quickly.
3.9-3.11 are only receiving security updates, whereas 3.12+ get bug fixes:
https://devguide.python.org/versions/
I don't think this is a security issue? I recommend upgrading to a newer Python version.
wjssz commentedon Nov 26, 2024
I tested. It was fixed in PR #12427, the change for
JUMP_REPEAT_ONE_2.You can use
regexmodule, it has no known bug. Just:ericvsmith commentedon Nov 26, 2024
I don't think this is a security issue, and we can close this.