Macro warnp

macro_rules! warnp {
    ($path:expr, $fmt:expr) => { ... };
    ($path:expr, $fmt:expr, $($args:tt)*) => { ... };
}

Prints the formatted message to the standard error output (stderr). The program name, a colon, a pathname, another colon, and a space are output before the message, and a newline character follows.