Support for python interpreter free-threading mode

[vfdev-5]

I wonder whether there are plans to provide a support for free-threading mode for python >=3.13.
Similar support is provided for pybind11: pybind/pybind11#5148

Ref:

• https://py-free-threading.github.io/porting/

Context:

• we would like to provide free-threading support for JAX which uses nanobind: Add support nogil mode in JAX for Python 3.13 jax-ml/jax#23073

Thanks

[wjakob]

Yes, I plan to add free-threading support soon.

[vfdev-5]

Thanks for the answer @wjakob ! Would you like any help with that?

[wjakob]

I already started something in #695, but the implementation is still far from complete. An extra pair of eyes would not hurt.

[hawkinsp]

It looks good so far, and indeed it's far less invasive than I would have expected.

(Test cases that exercise nanobind concurrently are obviously needed as well.)

[wjakob]

This feature has now landed in the master branch. I will wait a bit more for it to stabilize and hear from users before releasing a new version of the library.

[vfdev-5]

Thanks @wjakob !