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configparser: quadratic time in ParsingError.combine() when many lines fail to parse #148370
Description
Bug report
Bug description:
Found by OSS Fuzz in #501627726.
A simplified reproducer:
import time
import configparser
for N in (5000, 10000, 20000, 40000):
s = '[*]\n' + '=\n' * N
p = configparser.ConfigParser(strict=False)
t0 = time.perf_counter()
try:
p.read_string(s)
except configparser.ParsingError:
pass
print(f'{N}: {time.perf_counter() - t0}s')produces:
5000: 0.5495022920076735s
10000: 2.0415573030040832s
20000: 7.589155077002943s
40000: 30.856201829999918s
CPython versions tested on:
CPython main branch
Operating systems tested on:
No response
Activity
adityakrmishra commentedon Apr 12, 2026
picnixz commentedon Apr 12, 2026
picnixz commentedon Apr 12, 2026
pythongh-148370: prevent quadratic behavior in `configparser.ParsingE…
gh-148370: prevent quadratic behavior in `configparser.ParsingError.c…
pythongh-148370: prevent quadratic behavior in `configparser.ParsingE…
pythongh-148370: prevent quadratic behavior in `configparser.ParsingE…
[3.14] gh-148370: prevent quadratic behavior in `configparser.Parsing…
[3.13] gh-148370: prevent quadratic behavior in `configparser.Parsing…
pythongh-148370: prevent quadratic behavior in `configparser.ParsingE…