Creating Module With pymodule Cause Segmentation Fault In Free-Threaded Python 3.13 On Mac

[FlickerSoul]

Bug Description

The following code,

use pyo3::prelude::*;

#[pymodule]
fn test_lib(m: &Bound<'_, PyModule>) -> PyResult<()> {
    Ok(())
}

when built and run in the free-threaded version of Python 3.13, will cause segmentation fault.

❯ python3.13 -c 'import sysconfig; print(sysconfig.get_config_var("Py_GIL_DISABLED"))'
1
❯ python3.13 -c 'import test_lib'
[1]    20097 segmentation fault  python3.13 -c 'import test_lib'

I'm not entirely sure if it's because of PyO3's or CPython.

Steps to Reproduce

1. Clone https://github.com/FlickerSoul/pyo3-module-bug
2. Use free threaded version to create venv and activate it
3. Run maturin develop --target aarch64-apple-darwin
4. Run python3.13 -c "import test_lib"
5. See the segmentation fault

Backtrace

❯ lldb -- python -c "import test_lib"
(lldb) target create "python"
Current executable set to 'venv/bin/python' (arm64).
(lldb) settings set -- target.run-args  "-c" "import test_lib"
(lldb) run
Process 21042 launched: 'venv/bin/python' (arm64)
Process 21042 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x0000000184f888d0 libsystem_platform.dylib`_platform_strcmp$VARIANT$Base + 64
libsystem_platform.dylib`_platform_strcmp$VARIANT$Base:
->  0x184f888d0 <+64>: ldr    q0, [x0], #0x10
    0x184f888d4 <+68>: ldr    q1, [x1], #0x10
    0x184f888d8 <+72>: cmeq.16b v1, v0, v1
    0x184f888dc <+76>: and.16b v0, v0, v1
Target 0: (python) stopped.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x0000000184f888d0 libsystem_platform.dylib`_platform_strcmp$VARIANT$Base + 64
    frame #1: 0x00000001008970b8 libpython3.13t.dylib`_PyImport_ResolveNameWithPackageContext + 76
    frame #2: 0x0000000100775a40 libpython3.13t.dylib`_PyModule_CreateInitialized + 284
    frame #3: 0x00000001001e6d3c test_lib.cpython-313t-darwin.so`pyo3_ffi::modsupport::PyModule_Create::ha5da682c5748e8de(module=0x0000000100240298) at modsupport.rs:140:5
    frame #4: 0x00000001001e8ec4 test_lib.cpython-313t-darwin.so`pyo3::impl_::pymodule::ModuleDef::make_module::_$u7b$$u7b$closure$u7d$$u7d$::h19ffdd4137634f86 at pymodule.rs:148:25
    frame #5: 0x0000000100220560 test_lib.cpython-313t-darwin.so`pyo3::sync::GILOnceCell$LT$T$GT$::init::h4f5a3638ae166d78(self=0x0000000100240308, (null)=(__0 = core::marker::PhantomData<(&pyo3::gil::GILGuard, pyo3::impl_::not_send::NotSend)> @ 0x000000016fdfcdd7), f={closure_env#0} @ 0x000000016fdfcdd8) at sync.rs:157:21
    frame #6: 0x00000001001e5ba0 test_lib.cpython-313t-darwin.so`pyo3::sync::GILOnceCell$LT$T$GT$::get_or_try_init::h0ef029fbba9c4847(self=0x0000000100240308, (null)=(__0 = core::marker::PhantomData<(&pyo3::gil::GILGuard, pyo3::impl_::not_send::NotSend)> @ 0x000000016fdfce87), f={closure_env#0} @ 0x000000016fdfce88) at sync.rs:146:9
    frame #7: 0x00000001001e8e20 test_lib.cpython-313t-darwin.so`pyo3::impl_::pymodule::ModuleDef::make_module::h082db6c3d1962475(self=0x0000000100240290, (null)=(__0 = core::marker::PhantomData<(&pyo3::gil::GILGuard, pyo3::impl_::not_send::NotSend)> @ 0x000000016fdfceff)) at pymodule.rs:143:9
    frame #8: 0x00000001001dd838 test_lib.cpython-313t-darwin.so`test_lib::test_lib::__pyo3_init::_$u7b$$u7b$closure$u7d$$u7d$::h9de0cf31803401d2((null)=0x000000016fdfd03e, (null)=(__0 = core::marker::PhantomData<(&pyo3::gil::GILGuard, pyo3::impl_::not_send::NotSend)> @ 0x000000016fdfd01f)) at lib.rs:3:1
    frame #9: 0x00000001001dd6c8 test_lib.cpython-313t-darwin.so`core::ops::function::FnOnce::call_once::head2ac0736f5dc62((null)={closure_env#0} @ 0x000000016fdfd03e, (null)=(pyo3::marker::Python) @ 0x000000016fdfd03f) at function.rs:250:5
    frame #10: 0x00000001001ddb34 test_lib.cpython-313t-darwin.so`pyo3::impl_::trampoline::module_init::_$u7b$$u7b$closure$u7d$$u7d$::h8a2f9709624beab0((null)=(__0 = core::marker::PhantomData<(&pyo3::gil::GILGuard, pyo3::impl_::not_send::NotSend)> @ 0x000000016fdfd0af)) at trampoline.rs:22:21
    frame #11: 0x00000001001ddb00 test_lib.cpython-313t-darwin.so`pyo3::impl_::trampoline::trampoline::_$u7b$$u7b$closure$u7d$$u7d$::h654b5c2b83d193c8 at trampoline.rs:188:54
    frame #12: 0x00000001001dd5b0 test_lib.cpython-313t-darwin.so`std::panicking::try::do_call::h7f28577fa69c1c21(data="\U00000010\xd3\xdfo\U00000001") at panicking.rs:559:40
    frame #13: 0x00000001001dd680 test_lib.cpython-313t-darwin.so`__rust_try + 32
    frame #14: 0x00000001001dd4f4 test_lib.cpython-313t-darwin.so`std::panicking::try::hfebe6c5ab5c7e583(f={closure_env#0}<pyo3::impl_::trampoline::module_init::{closure_env#0}, *mut pyo3_ffi::object::PyObject> @ 0x000000016fdfd208) at panicking.rs:523:19
    frame #15: 0x00000001001dd8ac test_lib.cpython-313t-darwin.so`std::panic::catch_unwind::ha70320dc9581b60c(f={closure_env#0}<pyo3::impl_::trampoline::module_init::{closure_env#0}, *mut pyo3_ffi::object::PyObject> @ 0x000000016fdfd248) at panic.rs:149:14
    frame #16: 0x00000001001dda7c test_lib.cpython-313t-darwin.so`pyo3::impl_::trampoline::trampoline::h91958361332b5c32(body={closure_env#0} @ 0x000000016fdfd2e0) at trampoline.rs:188:9
    frame #17: 0x00000001001dd710 test_lib.cpython-313t-darwin.so`pyo3::impl_::trampoline::module_init::h28307e976c4ec7a8(f=(test_lib.cpython-313t-darwin.so`core::ops::function::FnOnce::call_once::head2ac0736f5dc62 at function.rs:250)) at trampoline.rs:22:5
    frame #18: 0x00000001001dd730 test_lib.cpython-313t-darwin.so`PyInit_test_lib at lib.rs:3:1
    frame #19: 0x000000010089e2d8 libpython3.13t.dylib`_PyImport_RunModInitFunc + 60
    frame #20: 0x000000010089b808 libpython3.13t.dylib`import_run_extension + 116
    frame #21: 0x000000010089d2cc libpython3.13t.dylib`_imp_create_dynamic + 492
    frame #22: 0x0000000100774530 libpython3.13t.dylib`cfunction_vectorcall_FASTCALL + 268
    frame #23: 0x000000010084facc libpython3.13t.dylib`_PyEval_EvalFrameDefault + 13648
    frame #24: 0x0000000100712520 libpython3.13t.dylib`object_vacall + 304
    frame #25: 0x0000000100712320 libpython3.13t.dylib`PyObject_CallMethodObjArgs + 104
    frame #26: 0x0000000100899cf0 libpython3.13t.dylib`PyImport_ImportModuleLevelObject + 1064
    frame #27: 0x00000001008542a0 libpython3.13t.dylib`_PyEval_EvalFrameDefault + 32036
    frame #28: 0x000000010084c274 libpython3.13t.dylib`PyEval_EvalCode + 360
    frame #29: 0x000000010084834c libpython3.13t.dylib`builtin_exec + 1228
    frame #30: 0x0000000100774614 libpython3.13t.dylib`cfunction_vectorcall_FASTCALL_KEYWORDS + 164
    frame #31: 0x000000010084facc libpython3.13t.dylib`_PyEval_EvalFrameDefault + 13648
    frame #32: 0x0000000100712520 libpython3.13t.dylib`object_vacall + 304
    frame #33: 0x0000000100712320 libpython3.13t.dylib`PyObject_CallMethodObjArgs + 104
    frame #34: 0x0000000100899cf0 libpython3.13t.dylib`PyImport_ImportModuleLevelObject + 1064
    frame #35: 0x00000001008542a0 libpython3.13t.dylib`_PyEval_EvalFrameDefault + 32036
    frame #36: 0x000000010084c274 libpython3.13t.dylib`PyEval_EvalCode + 360
    frame #37: 0x00000001008c3ef4 libpython3.13t.dylib`run_eval_code_obj + 180
    frame #38: 0x00000001008c3994 libpython3.13t.dylib`run_mod + 224
    frame #39: 0x00000001008c1818 libpython3.13t.dylib`_PyRun_SimpleStringFlagsWithName + 176
    frame #40: 0x00000001008e6588 libpython3.13t.dylib`Py_RunMain + 1760
    frame #41: 0x00000001008e6d10 libpython3.13t.dylib`pymain_main + 324
    frame #42: 0x00000001008e6db0 libpython3.13t.dylib`Py_BytesMain + 40
    frame #43: 0x0000000184bcf274 dyld`start + 2840
(lldb)

Your operating system and version

macOS 15.0 24A5279h arm64

Your Python version (python --version)

Python 3.13.0b3

Your Rust version (rustc --version)

rustc 1.79.0 (129f3b996 2024-06-10)

Your PyO3 version

0.22.0

How did you install python? Did you use a virtualenv?

To install: pyenv install 3.13.0b3t
To create virtualenv: python -m venv ./venv
Then activate with source ./venv/bin/activate and then run maturin develop

Additional Info

The non-free-threaded version of 3.13.0b3, installed with pyenv install 3.13.0b3 works fine.

[davidhewitt]

This is not a huge surprise, we need to make PyO3 compatible with the free-threaded builds yet. It's probably my highest priority thing to look at now. The failure mode could be better (e.g. we could at least give you an error on build).

[alex]

#4265 is a tracking issue for free-threading