As I understand it:
With Py_LIMITED_API set to be an older Python version (e.g. 0x030700) the reference counting macros don’t account for immortal objects due to the need to maintain backwards compatibility. That isn’t a disaster but it makes things less efficient.
If you use the reference counting functions (Py_IncRef) instead then they’re handled correctly.
My opinion was that if you changed to using functions, then you should change everything (so you don’t end up in a situation where the incref is skipped but the decref isn’t, for example).
However, there doesn’t seem to be function versions for XINCREF, XDECREF, CLEAR, (X)SETREF.
Any advice on using these in the limited API if I want immortal objects to be untouched?