Module cfg_if

Compile-time conditional compilation as if / else blocks.

• Crate ::cfg_if.
• docs.rs
• crates.io
• GitHub

cfg_if provides the cfg_if! macro, which allows writing #[cfg] conditional compilation in a more readable if / else if / else style instead of repeating #[cfg] attributes with negated conditions.

This is especially useful when selecting between more than two configurations, where manually writing the correct combination of not(), any(), and all() becomes error-prone.

Example

use cfg_if::cfg_if;

cfg_if! {
    if #[cfg(unix)] {
        fn platform() -> &'static str { "unix" }
    } else if #[cfg(windows)] {
        fn platform() -> &'static str { "windows" }
    } else {
        fn platform() -> &'static str { "other" }
    }
}

let p = platform();
assert!(p == "unix" || p == "windows" || p == "other");