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#[cfg(feature = "logging")] macro_rules! log { ( $fmt:expr ) => { println!($fmt); }; ( $fmt:expr, $($x:tt)* ) => { println!($fmt, $($x)*); } } #[cfg(not(feature = "logging"))] macro_rules! log { ( $fmt:expr ) => {}; ( $fmt:expr, $($x:tt)* ) => { if false { let _ = format!($fmt, $($x)*); } }; }