gh-158842: Add Py_SETREF() and Py_XSETREF() to the limited C API

[vstinner]

Test these macros with the limited C API in _testlimitedcapi and test_cext.

Move also other tests (refcount, Py_CLEAR, etc.) to _testlimitedcapi.

• Issue: [C API] Add Py_SETREF() and Py_XSETREF() macros to the limited C API 3.16 #158842

[vstinner]

cc @ngoldbaum @serhiy-storchaka @encukou

[vstinner]

Note: _testlimitedcapi.test_py_setref() checks that Py_SETREF/Py_XSETREF() arguments are only evaluated once.

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #34945011 | 📁 Comparing e98478b against main (9112dae)

  🔍 Preview build  

2 files changed

± whatsnew/3.16.html
± whatsnew/changelog.html

[encukou]

Could you add them to stable_abi.toml, too?

[picnixz]

If this only moving code, then this LGTM.

[picnixz]

Could you add them to stable_abi.toml, too?

Oh right... I totally forgot about that. It's for the docs rendering right?

[vstinner]

Could you add them to stable_abi.toml, too?

Sure, done. I forgot that we also put macros in stable_abi.toml. I also added Py_CLEAR(). It seems like Py_CLEAR() was added to Python 2.4 (so it's available since limited C API 3.2).

[ngoldbaum]

It's for the docs rendering right?

I learned recently that abi3audit uses the toml table as input for a codegen script that generates the abi3audit implementation. I'd also like to use it in PyO3 for static checks. So downstream appreciates it being accurate and updated.