Bug report

Bug description:

The re.Scanner class crashes with a segmentation fault (memory corruption) when any pattern in the lexicon contains named capturing groups.

import re

lexicon = [
    ('(?P<group1>a)(?P<group2>b)', None),  # Named capturing groups
]

scanner = re.Scanner(lexicon)
result, leftover = scanner.scan("ab")  # Segmentation fault occurs here

zsh: segmentation fault  python3 test.py

Scanner should process the input normally and return scan results without crashing, but Python interpreter crashes with segmentation fault, indicating memory corruption.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• gh-140797: Forbid capturing groups in re.Scanner lexicon patterns #140944
• [3.14] gh-140797: Forbid capturing groups in re.Scanner lexicon patterns (GH-140944) #140982
• [3.13] gh-140797: Forbid capturing groups in re.Scanner lexicon patterns (GH-140944) #140983
• gh-140979: Fix off-by-one error in the RE code validator #140984
• [3.13] Revert "[3.13] gh-140797: Forbid capturing groups in re.Scanner lexicon patterns (GH-140944) (GH-140983)" #142231
• [3.14] Revert "gh-140797: Forbid capturing groups in re.Scanner lexicon patterns (GH-140944) (GH-140982)" #142309