> I think the basic implementation problem is that by the time you get to get_hash_info() in sysmodule.c, you no longer have access to the _PyCoreConfig object, nor the _PyMain object that it's generally attached to.

An interpreter now keeps a copy of _PyCoreConfig and _PyMainInterpreterConfig.

See for example make_flags() in sysmodule.c:

_PyCoreConfig *core_config = &_PyGILState_GetInterpreterStateUnsafe()->core_config;
...
PyStructSequence_SET_ITEM(seq, pos++, PyBool_FromLong(core_config->dev_mode));

The interpreter really owns the copy of these configs and they are kept until the interpreter object is destroyed.

Another example:

static PyObject *
import_find_and_load(PyObject *abs_name)
{
    ...
    int import_time = interp->core_config.import_time;
    ...
}