sre bug: lastmark_save/restore

[arigo]

BPO	9134
Nosy	@ezio-melotti, @serhiy-storchaka, @animalize, @tirkarthi
Files	x.py: Bug case

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2022-03-29.15:30:16.865>
created_at = <Date 2010-06-30.21:18:56.596>
labels = ['extension-modules', 'expert-regex', 'type-bug', '3.11']
title = 'sre bug: lastmark_save/restore'
updated_at = <Date 2022-03-29.15:30:16.864>
user = 'https://github.com/arigo'

bugs.python.org fields:

activity = <Date 2022-03-29.15:30:16.864>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2022-03-29.15:30:16.865>
closer = 'serhiy.storchaka'
components = ['Extension Modules', 'Regular Expressions']
creation = <Date 2010-06-30.21:18:56.596>
creator = 'arigo'
dependencies = []
files = ['17822']
hgrepos = []
issue_num = 9134
keywords = []
message_count = 5.0
messages = ['109019', '109034', '224499', '224502', '416267']
nosy_count = 5.0
nosy_names = ['ezio.melotti', 'abacabadabacaba', 'serhiy.storchaka', 'malin', 'xtreak']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue9134'
versions = ['Python 3.11']

[arigo]

The re module is buggy is rare cases; see attached example script.

The bug is caused by the macros LASTMARK_SAVE and LASTMARK_RESTORE which are sometimes used without the extra code that does if (state->repeat) {mark_save()/mark_restore()}.

The bug appears by mis-reporting the position of groups within a repeated match (with * or +), notably the position of some groups that matched in older repetitions but (after some backtracking) not in newer ones.

[arigo]

It's pretty trivial to turn my x.py into a unit test, of course.

[serhiy-storchaka]

It looks as the nature of this bug is clear to you, Armin. Do you want to write a patch?

[arigo]

It was clear to me four years ago. Now I'd have to dig again as much as you do.

[serhiy-storchaka]

Fixed in bpo-35859 together with other bugs, but the fix was only applied to 3.11, because that bug is old and the old behavior matches the behavior in some other engines (Perl and Java).