cython: [BUG] Using types.CodeType in Python 3.11 fails with ValueError: types.CodeType size changed, may indicate binary incompatibility. Expected 168 from C header, got 160 from PyObject

Versions:

• Cython 0.29 branch: commit c0dfb9c2f592b7e0ece90ec83fbadcf6e6da3d47 (May 17, 2022)
• Python 3.11.0b3+: commit a848a9894d (Jun 6 2022)

Reproducer, myext.pyx:

# cython: language_level=3
cdef extern from "Python.h":
    ctypedef class types.CodeType [object PyCodeObject]:
        pass

Build the extension (I make the assumption that cythonize uses Python 3.11):

cythonize -i myext.pyx

Importing the C extension fails:

$ python3.11 -c 'import myext'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "myext.pyx", line 1, in init myext
    # cython: language_level=3
                               
ValueError: types.CodeType size changed, may indicate binary incompatibility. Expected 168 from C header, got 160 from PyObject

To get Python 3.11 with Cython, you can use for example:

wget https://www.python.org/ftp/python/3.11.0/Python-3.11.0b3.tar.xz
tar -xf Python-3.11.0b3.tar.xz
cd Python-3.11.0b3
./configure --prefix /opt/py311
make
make install
cd ..
/opt/py311/bin/python3.11 -m pip install Cython

Then use /opt/py311/bin/cythonize. You can use a different prefix.

---

The problem is that tp_basicsize of &PyCode_Type is 160 bytes, whereas and sizeof(PyCodeObject) is 168 bytes.

---

Issue discovered when on my PR to update gevent to Python 3.11: https://github.com/gevent/gevent/pull/1872#issuecomment-1146149244

@hroncok proposed a Cython pull request in Fedora: https://src.fedoraproject.org/rpms/Cython/pull-request/35

I am working on reworking @hroncok’s PR to propose a PR to the master branch of Cython.

cc @encukou who helped to debug this tedious issue.