#[macro_export]
macro_rules! create_set_flag_method {
    ($method:ident, $flag:expr, $platforms:expr) => (
        #[cfg(platforms)]
        pub fn $method(enabled: bool) -> Result<(), ()> {
            if enabled {
                self.flags = self.flags | flag;
            } else {
                self.flags = self.flags & !flag;
            }
            Ok(())
        }
        #[cfg(not(platforms))]
        pub fn $method(_enabled: bool) -> Result<(), ()> {
            Err(())
        }
    )
}


// ...

        create_set_flag_method!(
            set_nonblocking,
            MSG_DONTWAIT,
            any(target_os = "freebsd", target_os = "linux")
        );


// make fails with following error:


error[E0428]: a value named `set_nonblocking` has already been defined in this module
   --> src/transport.rs:217:9
    |
217 |            pub fn $method(_enabled: bool) -> Result<(), ()> {
    |   _________-
    |  |_________|
    | ||
218 | ||             Err(())
219 | ||         }
    | ||         -
    | ||_________|
    | |__________`set_nonblocking` already defined
    |            previous definition of `set_nonblocking` here