Segmentation fault in Python 3.13 when chaining deep filter() iterators · Issue #137894 · python/cpython · GitHub

Crash report

What happened?

When creating a deeply nested chain of filter() iterators, Python 3.12 can handle it (although very slow), but Python 3.13 results in a segmentation fault instead of raising an exception.

This appears to be a regression in Python 3.13’s iterator implementation, as user code should never cause a segfault. Ideally, this should raise a RecursionError or another Python exception, not crash the interpreter.

if __name__ == '__main__':
    import sys
    import gc
    
    def main():
        i = filter(bool, range(1000000))
        for _ in range(100000):
            i = filter(bool, i)
        print(list(i))

    #sys.setrecursionlimit(1000000)
    main()

CPython versions tested on:

3.13

Operating systems tested on:

Linux

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

Python 3.13.2 crashes with:Segmentation fault (core dumped) Python 3.12.9 executes successfully (though very slow).

Linked PRs

pythongh-137894:Fix os.makedirs to properly pass mode parameter to re…

See other similar issues:

This is an exact duplicate of

Сrash when deleting deeply recursive iterator wrappers #61502

which was closed as a duplicate of #58218.

I'm going to close it as a duplicate as well and not planned as the original was considered not worth the fix (which I agree as it's not a straightforward one).

FTR, I have added _Py_EnterRecursiveCall to the filter_next (sergey-miryanov@d3b76ee) and have following microbenchmark's results:

Windows 11, x64, CPU 11th Gen Intel(R) Core(TM) i5-11600K @ 3.90GHz

+----------------+--------------+------------------------+
| Benchmark      | main-windows | filter-windows         |
+================+==============+========================+
| filter-1000    | 119 ms       | 114 ms: 1.04x faster   |
+----------------+--------------+------------------------+
| filter-2000    | 238 ms       | 230 ms: 1.03x faster   |
+----------------+--------------+------------------------+
| filter-4000    | 484 ms       | 469 ms: 1.03x faster   |
+----------------+--------------+------------------------+
| filter-8000    | 991 ms       | 959 ms: 1.03x faster   |
+----------------+--------------+------------------------+
| filter-16000   | 2.00 sec     | 1.93 sec: 1.03x faster |
+----------------+--------------+------------------------+
| Geometric mean | (ref)        | 1.03x faster           |
+----------------+--------------+------------------------+

Ubuntu 24.04, build with --lto=full, same CPU:

+----------------+------------+------------------------+
| Benchmark      | main-linux | filter-linux           |
+================+============+========================+
| filter-1000    | 119 ms     | 120 ms: 1.01x slower   |
+----------------+------------+------------------------+
| filter-2000    | 242 ms     | 244 ms: 1.01x slower   |
+----------------+------------+------------------------+
| filter-4000    | 493 ms     | 497 ms: 1.01x slower   |
+----------------+------------+------------------------+
| filter-8000    | 1.01 sec   | 1.01 sec: 1.01x slower |
+----------------+------------+------------------------+
| filter-16000   | 2.02 sec   | 2.05 sec: 1.01x slower |
+----------------+------------+------------------------+
| Geometric mean | (ref)      | 1.01x slower           |
+----------------+------------+------------------------+

Microbenchmark

import pyperf
import functools
runner = pyperf.Runner()

def bench(loops):
    i = filter(bool, range(10000))
    for _ in range(loops):
        i = filter(bool, i)
    list(i)

for size in (1000, 2000, 4000, 8000, 16000):
    func = functools.partial(bench, size)
    runner.bench_func(f'filter-{size}', func)

Based on the results on Linux, I don't think it's worth adding yet.

Segmentation fault in Python 3.13 when chaining deep filter() iterators · Issue #137894 · python/cpython · GitHub

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Segmentation fault in Python 3.13 when chaining deep filter() iterators #137894

Crash report

What happened?

CPython versions tested on:

Operating systems tested on:

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

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Segmentation fault in Python 3.13 when chaining deep filter() iterators · Issue #137894 · python/cpython · GitHub

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Segmentation fault in Python 3.13 when chaining deep filter() iterators #137894

Description

Crash report

What happened?

CPython versions tested on:

Operating systems tested on:

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

Linked PRs

Activity

serhiy-storchaka commented on Aug 18, 2025

serhiy-storchaka commented on Aug 18, 2025

picnixz commented on Aug 18, 2025

sergey-miryanov commented on Nov 6, 2025

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