SEGV in `_PyObject_ClearFreeLists` after exception in subinterpreter

What happened?

Executing the following two file python script with python3.14 -m src crashes the (sub?)interpreter with a SIGSEGV.

# src/executor.py
import importlib
import sys
import traceback

def execute_module():
    importlib.invalidate_caches()
    sys.modules = "xxx"
    importlib.import_module("zip")

# src/__main__,py
from concurrent import interpreters

sub_interpreter = interpreters.create()
queue = interpreters.create_queue()

def run_module(queue):
    import importlib
    execute_module_fn = importlib.import_module("src.executor").execute_module
    execute_module_fn()
    queue.put(True)

sub_interpreter.call(run_module, queue)
queue.get()
sub_interpreter.close()

Starting program: /nix/store/6p5sldsqcgn0x0al9h2hvqpd4xqi1wpm-user-environment/bin/python3.14 -m src
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/nix/store/km4g87jxsqxvcq344ncyb8h1i6f3cqxh-glibc-2.40-218/lib/libthread_db.so.1".
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/uli/DEV/python-segv/src/__main__.py", line 14, in <module>
    sub_interpreter.call(run_module, queue)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/python3.14/concurrent/interpreters/__init__.py", line 238, in call
    return self._call(callable, args, kwargs)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/python3.14/concurrent/interpreters/__init__.py", line 222, in _call
    raise ExecutionFailed(excinfo)
concurrent.interpreters.ExecutionFailed: AttributeError: 'str' object has no attribute 'get'
<sys>:0: RuntimeWarning: remaining subinterpreters; close them with Interpreter.close()

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7989bb9 in _PyObject_ClearFreeLists ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
(gdb) bt
#0  0x00007ffff7989bb9 in _PyObject_ClearFreeLists ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#1  0x00007ffff7adce4f in _PyGC_Collect ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#2  0x00007ffff7b1ace4 in finalize_modules.lto_priv ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#3  0x00007ffff7b24b57 in Py_EndInterpreter ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#4  0x00007ffff7c35451 in _Py_Finalize.part.0.constprop.0 ()
--Type <RET> for more, q to quit, c to continue without paging--
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#5  0x00007ffff7b5f8d8 in Py_RunMain ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#6  0x00007ffff7b60b81 in Py_BytesMain ()
   from /nix/store/w9f9jj6mbrk4146wm69qlyssjghildlf-python3-3.14.3/lib/libpython3.14.so.1.0
#7  0x00007ffff742a4d8 in __libc_start_call_main ()
   from /nix/store/km4g87jxsqxvcq344ncyb8h1i6f3cqxh-glibc-2.40-218/lib/libc.so.6
#8  0x00007ffff742a59b in __libc_start_main_impl ()
   from /nix/store/km4g87jxsqxvcq344ncyb8h1i6f3cqxh-glibc-2.40-218/lib/libc.so.6
#9  0x0000555555555085 in _start ()

The following reduction shows the same crashing behavior, I wasn't able to reproduce it while running in gdb however.

from concurrent import interpreters

sub_interpreter = interpreters.create()

def run_module():
    import importlib
    import sys
    import traceback

    importlib.invalidate_caches()
    sys.modules = "xxx"
    importlib.import_module("zip")

sub_interpreter.call(run_module)
sub_interpreter.close()

CPython versions tested on:

3.14

Operating systems tested on:

Linux

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

Python 3.14.3 (main, Feb 3 2026, 15:32:20) [GCC 14.3.0] on linux

Start with the reduced script using concurrent.interpreters, sys.modules = "xxx", and importlib.import_module("zip") on Python 3.14 Linux, then inspect the traceback through _PyObject_ClearFreeLists, _PyGC_Collect, finalize_modules, and Py_EndInterpreter. Done means the reproducer no longer causes a SIGSEGV during subinterpreter closure, with regression coverage for the reported exception path.