Crash report

What happened?

Calling itertools.count(sys.maxsize) aborts with the following message:

python -c "from sys import maxsize; from itertools import count; count(maxsize)"
python: ./Modules/itertoolsmodule.c:3325: itertools_count_impl: Assertion `(cnt != PY_SSIZE_T_MAX && long_cnt == NULL && fast_mode) || (cnt == PY_SSIZE_T_MAX && long_cnt != NULL && !fast_mode)' failed.
Aborted (core dumped)

Found using fusil by @vstinner.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux, Windows

Output from running 'python -VV' on the command line:

Python 3.14.0a1+ (heads/main:4ea214ea982, Nov 6 2024, 00:52:15) [MSC v.1941 64 bit (AMD64)]

Linked PRs

• gh-126595: fix a crash when calling itertools.count(sys.maxsize) #126617
• [3.13] gh-126595: fix a crash when calling itertools.count(sys.maxsize) (GH-126617) #126739
• [3.12] gh-126595: fix a crash when calling itertools.count(sys.maxsize) (GH-126617) #126740