pub fn set_fieldtype_arg( fieldtype: FIELDTYPE, make_arg: unsafe extern "C" fn(_: *mut va_list) -> *mut c_void, copy_arg: Option<unsafe extern "C" fn(_: *const c_void) -> *mut c_void>, free_arg: Option<unsafe extern "C" fn(_: *mut c_void)>) -> Result<(), NCurseswFormError>
