re: undocumented exception is raised

[fuzzah]

Bug report

Bug description:

The re module's documentation says it only raises the re.error exception, but the regex "\x00(?<!\x00{2147483648})" causes RuntimeError:

Python 3.11.5 (main, Sep 20 2023, 10:46:56) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import re
>>> re.compile("\x00(?<!\x00{2147483647})")
re.compile('\x00(?<!\x00{2147483647})')
>>>
>>>
>>> re.compile("\x00(?<!\x00{2147483648})")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.11/re/__init__.py", line 227, in compile
    return _compile(pattern, flags)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/re/__init__.py", line 294, in _compile
    p = _compiler.compile(pattern, flags)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/re/_compiler.py", line 759, in compile
    return _sre.compile(
           ^^^^^^^^^^^^^
RuntimeError: invalid SRE code

Other re methods, such as match or split show the same result.

For brevity:
"\x00(?<!\x00{2147483648})" -> RuntimeError
"\x00(?<!\x00{2147483647})" -> no errors

I have found this with libFuzzer by testing the fuzz_sre_compile binary.

CPython versions tested on:

3.11

Operating systems tested on:

Linux

Linked PRs

• gh-109747: Improve errors for unsupported look-behind patterns #109859
• [3.12] gh-109747: Improve errors for unsupported look-behind patterns (GH-109859) #110859
• [3.11] gh-109747: Improve errors for unsupported look-behind patterns (GH-109859) #110860

[AA-Turner]

cc: @serhiy-storchaka @ezio-melotti

[AA-Turner]

@fuzzah are you able to reproduce the error with 3.12.0rc3 or 3.13.0a0?

A

[fuzzah]

@AA-Turner , for both versions the answer is yes.

My checked out commit of 3.13.0a0 is this:

commit 7c553991724d8d537f8444db73f016008753d77a (grafted, HEAD -> main, origin/main, origin/HEAD)
Author: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>
Date:   Fri Sep 22 17:59:35 2023 +0100

    gh-109719: Fix missing jump target labels when compiler reorders cold/warm blocks (#109734)

[fuzzah]

Might be related: #91700, #98740

[serhiy-storchaka]

Confirm the bug. The RE engine has limitation on the width of look-behind pattern. But there were no checks for this or they did not work. I will see how it can be fixed.

[serhiy-storchaka]

Now you will get better error message. Also, the limit is increased.