Python 3.13.2 Compatibility Issue with vectorcall API

[brianfreud]

Description

When attempting to install pyroaring on Python 3.13.2t, compilation fails due to issues with the Python C API's vectorcall functionality. Although version 1.0.0 includes PR #119 for Python 3.13 support, there appear to be additional API changes in Python 3.13.2t that aren't yet accounted for.

Environment

• Python version: 3.13.2t
• Installation method: pip install pyroaring
• Operating system: Linux

Steps to Reproduce

1. Use Python 3.13.2t
2. Run pip install pyroaring

Error

The build fails with these key errors:

pyroaring/pyroaring.cpp:3094:80: error: '__pyx_vectorcallfunc' has not been declared
 3094 | static CYTHON_INLINE PyObject *__Pyx_PyVectorcall_FastCallDict(PyObject *func, __pyx_vectorcallfunc vc, PyObject *const *args, size_t nargs, PyObject *kw);
      |                                                                                ^~~~~~~~~~~~~~~~~~~~

pyroaring/pyroaring.cpp:66265:6: error: '__pyx_vectorcallfunc' was not declared in this scope; did you mean 'vectorcallfunc'?
66265 |      __pyx_vectorcallfunc vc = __Pyx_CyFunction_func_vectorcall(cyfunc);
      |      ^~~~~~~~~~~~~~~~~~~~
      |      vectorcallfunc

Possible Cause

The __pyx_vectorcallfunc type/macro is not properly defined for Python 3.13.2t. This might be due to changes in Python's C API between Python 3.13.0 (which PR #119 may have targeted) and Python 3.13.2t.

Potential Solutions

1. Update the Cython wrappers to use the new vectorcall API correctly for Python 3.13.2
2. Add appropriate typedefs or macro definitions to handle the API changes
3. Add a conditional check for Python version to adjust for the API differences

[Ezibenroc]

Hello,

Thanks for this detailed report, I overlooked this new python 3.13t (ref here for the record).

Ideally, I think this kind of things should be handled transparently by Cython, so I am not a fan of the potential solutions 2 and 3 you described.

It looks like Cython is adding support for free-threading in its version 3.1 (changelog here), but it is still in beta at the moment. Let's wait for a stable release maybe?

[rgommers]

This build error is resolved with Cython 3.1.0, which was released a few days ago.

By default, the build will not declare the extension modules free-threading compatible. To do so, you'll need the freethreading_compatible directive, which can be plumbed into setup.py like described at https://py-free-threading.github.io/porting-extensions/#__tabbed_1_2. That may only be the right thing to do if there's no global state or other thread-safety issues; pytest-run-parallel can be used as the first test tool for that, it'll smoke out a lot of potential issues (see https://py-free-threading.github.io/testing/).