[New-bugs-announce] [issue35932] Interpreter gets stuck while applying a compiled regex pattern

[Sateesh Kumar]

New submission from Sateesh Kumar <sateeshkumarb at gmail.com>:

The python interpreter gets stuck while applying a compiled regex pattern against a given string.

The regex matching doesn't get stuck if uncompiled regex pattern is used, or if the flag "re.IGNORECASE" is not used for regex match. 

Below code snippets gives more details.

* Variant-1
# Python process gets stuck

~/workbench$ cat match.py 
import re
pattern = "^[_a-z0-9-]+([\.'_a-z0-9-]+)*@[a-z0-9]+([\.a-z0-9-]+)*(\.[a-z]{2,4})$"
compiled_pattern = re.compile(pattern, re.IGNORECASE)
val = "Z230-B900_X-Suite_Migration_Shared_Volume"
re.match(compiled_pattern, val)

~/workbench$ python match.py 
^^^ The interpreter gets stuck.

* Variant-2 (Using uncompiled pattern) 
# python interpreter doesn't get stuck

~/workbench$ cat match.py
import re
pattern = "^[_a-z0-9-]+([\.'_a-z0-9-]+)*@[a-z0-9]+([\.a-z0-9-]+)*(\.[a-z]{2,4})$"
compiled_pattern = re.compile(pattern, re.IGNORECASE)
val = "Z230-B900_X-Suite_Migration_Shared_Volume"
re.match(pattern, val)

* Variant-3 (Using compiled pattern, but without flag re.IGNORECASE)
# Python interpreter doesn't get stuck

~/workbench$ cat match.py
import re
pattern = "^[_a-z0-9-]+([\.'_a-z0-9-]+)*@[a-z0-9]+([\.a-z0-9-]+)*(\.[a-z]{2,4})$"
compiled_pattern = re.compile(pattern)
val = "Z230-B900_X-Suite_Migration_Shared_Volume"
re.match(compiled_pattern, val)

# Platform details
~/workbench$ python -V
Python 2.7.12

~/workbench$ uname -a
Linux ubuntu16-template 4.4.0-59-generic #80-Ubuntu SMP Fri Jan 6 17:47:47 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Though above details are from Python/2.7 I see similar beahviour with Python/3.5.2 too.

----------
files: gdb_trace
messages: 335029
nosy: Sateesh Kumar
priority: normal
severity: normal
status: open
title: Interpreter gets stuck while applying a compiled regex pattern
type: crash
versions: Python 2.7
Added file: https://bugs.python.org/file48110/gdb_trace

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35932>
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