From fe475ba0498b76c5848f365983a0df7e9be39f85 Mon Sep 17 00:00:00 2001
From: Thomas de Zeeuw <thomasdezeeuw@gmail.com>
Date: Sun, 13 Aug 2023 09:42:54 +0200
Subject: [PATCH] make `log` an optional dependency

Currently, Mio depends on `log`. In rust-lang/log#552, the `log`
maintainers aim to increase `log`'s MSRV to 1.60. This MSRV increase
would impact Mio, which in turn, would impact Tokio. As of 1.25, Tokio
supports Rust 1.49 with the intent of supporting it until March 2024.

This commit makes `log` an optional dependency for those who wish to
maintain a lower MSRV.

Backport of commit 44df449467af5b8b255f99b85f89d6bf666e1956
---
 Cargo.toml                      |  4 ++--
 src/macros.rs                   | 24 ++++++++++++++++++++++++
 src/poll.rs                     |  1 -
 src/sys/unix/selector/epoll.rs  |  1 -
 src/sys/unix/selector/kqueue.rs |  1 -
 5 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 041dc222b..bb84d24ba 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,7 +32,7 @@ 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 = []
@@ -50,7 +50,7 @@ pipe = ["os-ext"] # Replaced with "os-ext" feature.
 os-util = ["os-ext"]# Replaced with "os-ext" feature.
 
 [dependencies]
-log = "0.4.8"
+log = { version = "0.4.8", optional = true }
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2.86"
diff --git a/src/macros.rs b/src/macros.rs
index f97f90911..3d42bd20a 100644
--- a/src/macros.rs
+++ b/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)*);
+            }
+        }
+    }
+}
diff --git a/src/poll.rs b/src/poll.rs
index a6f4ab0b5..09124779b 100644
--- a/src/poll.rs
+++ b/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;
diff --git a/src/sys/unix/selector/epoll.rs b/src/sys/unix/selector/epoll.rs
index 38667d66c..e3af341a4 100644
--- a/src/sys/unix/selector/epoll.rs
+++ b/src/sys/unix/selector/epoll.rs
@@ -1,7 +1,6 @@
 use crate::{Interest, Token};
 
 use libc::{EPOLLET, EPOLLIN, EPOLLOUT, EPOLLRDHUP};
-use log::error;
 use std::os::unix::io::{AsRawFd, RawFd};
 #[cfg(debug_assertions)]
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
diff --git a/src/sys/unix/selector/kqueue.rs b/src/sys/unix/selector/kqueue.rs
index b7a01a51c..4937d57ac 100644
--- a/src/sys/unix/selector/kqueue.rs
+++ b/src/sys/unix/selector/kqueue.rs
@@ -1,5 +1,4 @@
 use crate::{Interest, Token};
-use log::error;
 use std::mem::MaybeUninit;
 use std::ops::{Deref, DerefMut};
 use std::os::unix::io::{AsRawFd, RawFd};