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classification
Title: Prevent recursion limit when using ".*?xxx"
Type: Stage:
Components: Extension Modules Versions:
process
Status: closed Resolution:
Dependencies: Superseder:
Assigned To: effbot Nosy List: dgallion, effbot, tim.peters
Priority: normal Keywords: patch

Created on 2000-09-23 04:06 by dgallion, last changed 2022-04-10 16:02 by admin. This issue is now closed.

Files
File name Uploaded Description Edit
None dgallion, 2000-09-23 04:06 None
Messages (4)
msg34410 - (view) Author: Darrell Gallion (dgallion) Date: 2000-09-23 04:06
 
msg34411 - (view) Author: Tim Peters (tim.peters) * (Python committer) Date: 2000-09-23 04:23
Assigned to Fredrik.

dgallion, please resubmit a context diff.  Straight diffs aren't accepted (they're too brittle).
msg34412 - (view) Author: Fredrik Lundh (effbot) * (Python committer) Date: 2001-01-14 23:20
I've adapted a variant of this patch.

Not 100% sure this approach works in all cases, but it has survived all tests I've thrown at it.
msg34413 - (view) Author: Darrell Gallion (dgallion) Date: 2000-09-23 04:12
This pattern fails with sre:
>>> re.match("(?s){.*?}","{"+' '*17000+"}")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "E:\pythonWinCVS\python\dist\src\lib\sre.py", line 44, in match
    return _compile(pattern, flags).match(string)
RuntimeError: maximum recursion limit exceeded

The same pattern with even a much larger search buffer works fine on 1.52

This patch optimizes the case ".*?"  and avoids the recursion limit.

After the patch:
>>> import re
>>> re.findall('ab.*?bc', 'abababbc')
['abababbc']
>>> re.findall('ab??bc', 'abababbc')
['abbc']
>>> re.sub("(?s){.*?}","","{"+' '*19047+"}")
''
>>> re.match("(?s){.*?}","{"+' '*16048+"}")
<SRE_Match object at 007E4490>
>>> import test.test_re
Running tests on re.search and re.match
Running tests on re.sub
Running tests on symbolic references
Running tests on re.subn
Running tests on re.split
Running tests on re.findall
Running tests on re.match
Running tests on re.escape
Pickling a RegexObject instance
Test engine limitations
maximum recursion limit exceeded
Running re_tests test suite
>>>


History
Date User Action Args
2022-04-10 16:02:25adminsetgithub: 33182
2000-09-23 04:06:02dgallioncreate