library/std/src/sys/path/mod.rs

cfg_select! {
    target_os = "windows" => {
        mod windows;
        mod windows_prefix;
        pub use windows::*;
    }
    all(target_vendor = "fortanix", target_env = "sgx") => {
        mod sgx;
        pub use sgx::*;
    }
    target_os = "solid_asp3" => {
        mod unsupported_backslash;
        pub use unsupported_backslash::*;
    }
    target_os = "uefi" => {
        mod uefi;
        pub use uefi::*;
    }
    target_os = "cygwin" => {
        mod cygwin;
        mod windows_prefix;
        pub use cygwin::*;
    }
    _ => {
        mod unix;
        pub use unix::*;
    }
}