from ctypes import CDLL, c_char_p
from ctypes.util import find_library
from inspect import signature

def fn() -> None:
    pass

# prints () -> NoneType starting in python 3.10, () -> None before that
print(signature(fn))


libc = CDLL(find_library('c'))

# Works as expected
perror = libc.perror
perror.restype = None
perror.argtypes = [c_char_p]

perror(b"error")

# Causes TypeError: NoneType takes no arguments
perror = libc.perror
perror.restype = type(None)
perror.argtypes = [c_char_p]

perror(b"error")

# Thus the following would work on Python 3.9 but fail on 3.10

def error(message: c_char_p) -> None:
    pass

s = signature(error)
perror.restype = s.return_annotation
perror.argtypes = [v.annotation for v in s.parameters.values()]
perror(b"error")