Code shared from the Rust Playground

playground.rs

pub trait GetInt {
    fn get_int(&self) -> f32;
}

pub struct MagicLinux;

impl GetInt for MagicLinux {
    fn get_int(&self) -> f32 {
        5.0
    }
}

pub struct MagicWindows;

impl GetInt for MagicWindows {
    fn get_int(&self) -> f32 {
        std::f32::INFINITY
    }
}

pub struct Fallback;

impl GetInt for Fallback {
    fn get_int(&self) -> f32 {
        0.0
    }
}

fn cross_platform_for_sure() -> impl GetInt {
    #[cfg(windows)]
    return MagicWindows;

    #[cfg(unix)]
    return MagicLinux;

    #[cfg(not(any(unix, windows)))]
    return Fallback;
}

fn main() {
    println!(
        "My 100% crossplatform integer value: {}",
        cross_platform_for_sure().get_int()
    );
}