BUG: Segmentation fault when misusing `VariableWindowIndexer.get_window_bounds`

[BergLucas]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

from pandas.core.indexers.objects import VariableWindowIndexer

variable_window_indexer = VariableWindowIndexer()
variable_window_indexer.get_window_bounds(1)

Issue Description

Hi,

For a research paper, we carried out a large-scale benchmark of Pynguin, an Automatic Unit Test Generation Tool for Python, to test its new feature that can find Python interpreter crashes. In this benchmark, we found a potential bug in pandas, and we are making this issue to report it.

Expected Behavior

In our opinion, pandas should not produce a segmentation fault when calling a public function. However, we don't know whether this function is part of pandas' public API so we just wanted to at least warn you that this behaviour exists, so that you can take the action that suits you best.

Installed Versions

commit : 0ab10aa
python : 3.10.16
python-bits : 64
OS : Linux
OS-release : 6.14.11-300.fc42.x86_64
Version : #1 SMP PREEMPT_DYNAMIC Tue Jun 10 16:24:16 UTC 2025
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 3.0.0.dev0+2192.g0ab10aa141
numpy : 2.2.6
dateutil : 2.9.0.post0
pip : 23.0.1
Cython : None
sphinx : None
IPython : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
bottleneck : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : None
lxml.etree : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
psycopg2 : None
pymysql : None
pyarrow : None
pyiceberg : None
pyreadstat : None
pytest : 8.4.1
python-calamine : None
pytz : 2025.2
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : N/A
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2025.2
qtpy : None
pyqt5 : None

[jbrockmendel]

@mroeschke i suspect this is a non-issue, but maybe an underscore is appropriate somewhere?

[mroeschke]

Yeah this is a private API (.core) that we call correctly internally. get_window_bounds is probably rightfully public since users have access to its subclass BaseIndexer.

Thanks for the issue but going to close since we call this without segfaulting internally