> As an alternative to that, we could also deprecate using any of those functions before initializing the runtime.   Instead of calling them, you would set the relevant info on the runtime "config" struct that you pass to the replacement for PyInitialize().

Currently, _PyCoreConfig is not complete: you cannot pass PYTHONPATH or PYTHONHOME. I'm working on patches to implement that.

Moreover, there is the question how to decode a bytes path (for PYTHONPATH) into a wchar_t* string.

Disallow calling Py_DecodeLocale() before Py_Initialize(): ok, but which alternative do you propose to decode OS data?