Add PyType_GetDict for Python 3.12

[cdce8p]

PyType_GetDict was added in Python 3.12 to safely access tp_dict.

PyAPI_FUNC(PyObject *) PyType_GetDict(PyTypeObject *);

https://github.com/python/cpython/blob/v3.12.0b4/Include/cpython/object.h#L286
https://github.com/python/cpython/blob/v3.12.0b4/Objects/typeobject.c#L241-L246

https://docs.python.org/3.12/c-api/type.html#c.PyType_GetDict
https://docs.python.org/3.12/c-api/typeobj.html#c.PyTypeObject.tp_dict
https://docs.python.org/3.12/whatsnew/changelog.html?highlight=pytype_getdict#c-api

[cdce8p]

Would it be possible to get this backported and released with 1.19.2? It's necessary to build some packages for 3.12. E.g. ijl/orjson#408

[adamreichold]

Would it be possible to get this backported and released with 1.19.2? It's necessary to build some packages for 3.12. E.g. ijl/orjson#408

We are still working on compatibility with Python 3.12 and plan a 0.19.x point release which contains mainly that. I suspect we will need to make use of this ourselves, so I am sure it will be cherry-picked into that release too. It might still take a while though.

[adamreichold]

(Note that while it should of course end up in a released version here, you can fix this in downstream crates by adding the extern "C" declaration there if you need this urgently. Not something I would generally recommend, but it should work as long as one of the dependencies pulls in the defining DSO.)