make log an optional dependency

Cargo.toml

@@ -29,7 +29,7 @@ include       = [
 # For documentation of features see the `mio::features` module.
 [features]
 # By default Mio only provides a shell implementation.
-default = []
+default = ["log"]
 
 # Enables the `Poll` and `Registry` types.
 os-poll = []
@@ -43,7 +43,7 @@ os-ext = [
 net = []
 
 [dependencies]
-log = "0.4.8"
+log = { version = "0.4.8", optional = true }
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2.121"

src/macros.rs

@@ -68,3 +68,27 @@ macro_rules! cfg_any_os_ext {
         )*
     }
 }
+
+macro_rules! trace {
+    ($($t:tt)*) => {
+        #[cfg(feature = "log")]
+        log::trace!($($t)*)
+    }
+}
+
+macro_rules! error {
+    ($($t:tt)*) => {
+        #[cfg(feature = "log")]
+        {
+            log::error!($($t)*)
+        }
+
+        // Silence warnings
+        #[cfg(not(feature = "log"))]
+        {
+            if false {
+                format!($($t)*);
+            }
+        }
+    }
+}

src/poll.rs

@@ -1,5 +1,4 @@
 use crate::{event, sys, Events, Interest, Token};
-use log::trace;
 #[cfg(unix)]
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::time::Duration;

src/sys/unix/selector/epoll.rs

@@ -1,7 +1,6 @@
 use crate::{Interest, Token};
 
 use libc::{EPOLLET, EPOLLIN, EPOLLOUT, EPOLLPRI, EPOLLRDHUP};
-use log::error;
 use std::os::unix::io::{AsRawFd, RawFd};
 #[cfg(debug_assertions)]
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

src/sys/unix/selector/kqueue.rs

@@ -1,5 +1,4 @@
 use crate::{Interest, Token};
-use log::error;
 use std::mem::{self, MaybeUninit};
 use std::ops::{Deref, DerefMut};
 use std::os::unix::io::{AsRawFd, RawFd};