Attributes

Syntax

// apply to the whole crate
#![crate_attribute]
// apply to to a module or item
#[item_attribute]

#[attribute = "value"]
#[attribute(key = "value")]
#[attribute(value)]
#[attribute(value, value2)]
#[attribute(value, value2, value3,
            value4, value5)]

Common Attributes

allow

// disables the `dead_code` lint
#[allow(dead_code)]

#[allow(non_camel_case_types)]

#[allow(unconditional_panic, unused_must_use)]

cfg

// the cfg attribute: #[cfg(...)] in attribute position
// the cfg! macro: cfg!(...) in boolean expressions
// This function only gets compiled if the target OS is linux
#[cfg(target_os = "linux")]
// And this function only gets compiled if the target OS is *not* linux
#[cfg(not(target_os = "linux"))]
// same as this
    if cfg!(target_os = "linux") {
        println!("Yes. It's definitely linux!");
    }

Common #[cfg(...)] options
- test
- debug_assertions
- unix and windows
- target_pointer_width = "64" // other value is 32
- target_arch = "x86_64" // “x86”, “arm”, “aarch64” etc.
- target_os = "macos" // “windows”, “ios”, “android”, “linux”, “freebsd”, “openbsd” etc.
- feature= "robots" // user-defined feature declared in [features] section in Cargo.toml
- not(A) // #[cfg(X)] and #[cfg(not(X))]
- all(A,B) // both A and B satisfied
- any(A,B) // either or

inline

// inline expansion of functions
#[inline]