log::log_enabled!

macro_rules! log_enabled {
    ($lvl:expr) => { ... };
}

Unstable (rustc_private)

: use the crates.io log library instead

A macro to test whether a log level is enabled for the current module.

Examples

#![feature(rustc_private)] #[macro_use] extern crate log; struct Point { x: i32, y: i32 } fn some_expensive_computation() -> Point { Point { x: 1, y: 2 } } fn main() { if log_enabled!(log::DEBUG) { let x = some_expensive_computation(); debug!("x.x = {}, x.y = {}", x.x, x.y); } }

#[macro_use] extern crate log;

struct Point { x: i32, y: i32 }
fn some_expensive_computation() -> Point { Point { x: 1, y: 2 } }

fn main() {
    if log_enabled!(log::DEBUG) {
        let x = some_expensive_computation();
        debug!("x.x = {}, x.y = {}", x.x, x.y);
    }
}

Assumes the binary is main:

$ RUST_LOG=error ./main

$ RUST_LOG=debug ./main
DEBUG:main: x.x = 1, x.y = 2