Support for PEP 703 / Free-threaded Python

[lennart-bader]

In PEP 703 (Implemented in a beta state in Python 3.13), the GIL can be disabled to allow free-threaded Python programs.

This comes with required changes for imported C and C++ libraries to indicate that they support this GIL-free implementation.

For pybind11, this feature has been discussed as of April 2024 and, according to the respective compatibility tracking issue implemented in pybind 2.13 (?).

According to the [pybind11 documentation])(https://pybind11.readthedocs.io/en/stable/reference.html), the PYBIND11_MODULE can now be initialized with the py::mod_gil_not_used() parameter to indicate that the module can be safely used without the GIL.

Are there any plans to apply this to iec104-python or maybe even already considerations that prevent an adoption of this feature?

[m-unkel]

This should be a non-breaking change, so we’re planning to add experimental support and evaluate how it performs in practice.Since the change.
Please feel free to pull the latest changes or wait for the next release, and let us know if you encounter any further issues.

Best
Martin

[m-unkel]

I build a package for cp313t, but the interpreter crashes on importing c104. So there is more to do then just adding this argument.

[m-unkel]

Support for GIL-free Python has now been fixed. The CMakeLists.txt must explicitly define Py_GIL_DISABLED during configuration; otherwise, pybind11 will default to building with GIL required.

One known issue remains on Windows: the build process may fail to locate the correct library linking directory automatically. Some manual tweaks are still needed there. On Linux, the build should work out of the box using the provided CMakeLists.txt.

I've verified that the examples run as expected with a free-threaded Python 3.13 build. However, no additional testing has been performed at this stage. Feedback and further testing are very welcome!
I’ve uploaded working free-threaded wheels to the latest release assets. They aren't available via PyPI.

https://github.com/Fraunhofer-FIT-DIEN/iec104-python/releases/tag/v2.2.1