Prepare tokio 1.20.1

README.md

@@ -56,7 +56,7 @@ Make sure you activated the full features of the tokio crate on Cargo.toml:
 
 ```toml
 [dependencies]
-tokio = { version = "1.20.0", features = ["full"] }
+tokio = { version = "1.20.1", features = ["full"] }
 ```
 Then, on your main.rs:
 

tokio/CHANGELOG.md

@@ -1,6 +1,15 @@
+# 1.20.1 (July 25, 2022)
+
+### Fixed
+
+- chore: fix version detection in build script ([#4860])
+
+[#4860]: https://github.com/tokio-rs/tokio/pull/4860
+
 # 1.20.0 (July 12, 2022)
+
 ### Added
-- tokio: add track_caller to public APIs ([#4772], [#4791], [#4793], [#4806], [#4808])
+- tokio: add `track_caller` to public APIs ([#4772], [#4791], [#4793], [#4806], [#4808])
 - sync: Add `has_changed` method to `watch::Ref` ([#4758])
 
 ### Changed
@@ -11,8 +20,6 @@
 - tokio: use const initialized thread locals where possible ([#4677])
 - task: various small improvements to LocalKey ([#4795])
 
-### Fixed
-
 ### Documented
 
 - fs: warn about performance pitfall ([#4762])

tokio/Cargo.toml

@@ -6,7 +6,7 @@ name = "tokio"
 #   - README.md
 # - Update CHANGELOG.md.
 # - Create "v1.0.x" git tag.
-version = "1.20.0"
+version = "1.20.1"
 edition = "2018"
 rust-version = "1.49"
 authors = ["Tokio Contributors <team@tokio.rs>"]

tokio/README.md

@@ -56,7 +56,7 @@ Make sure you activated the full features of the tokio crate on Cargo.toml:
 
 ```toml
 [dependencies]
-tokio = { version = "1.20.0", features = ["full"] }
+tokio = { version = "1.20.1", features = ["full"] }
 ```
 Then, on your main.rs:
 

tokio/build.rs

@@ -1,11 +1,38 @@
 use autocfg::AutoCfg;
 
+const CONST_THREAD_LOCAL_PROBE: &str = r#"
+{
+    thread_local! {
+        static MY_PROBE: usize = const { 10 };
+    }
+
+    MY_PROBE.with(|val| *val)
+}
+"#;
+
 fn main() {
+    let mut enable_const_thread_local = false;
+
     match AutoCfg::new() {
         Ok(ac) => {
-            // Const-initialized thread locals were stabilized in 1.59
-            if ac.probe_rustc_version(1, 59) {
-                autocfg::emit("tokio_const_thread_local")
+            // These checks prefer to call only `probe_rustc_version` if that is
+            // enough to determine whether the feature is supported. This is
+            // because the `probe_expression` call involves a call to rustc,
+            // which the `probe_rustc_version` call avoids.
+
+            // Const-initialized thread locals were stabilized in 1.59.
+            if ac.probe_rustc_version(1, 60) {
+                enable_const_thread_local = true;
+            } else if ac.probe_rustc_version(1, 59) {
+                // This compiler claims to be 1.59, but there are some nightly
+                // compilers that claim to be 1.59 without supporting the
+                // feature. Explicitly probe to check if code using them
+                // compiles.
+                //
+                // The oldest nightly that supports the feature is 2021-12-06.
+                if ac.probe_expression(CONST_THREAD_LOCAL_PROBE) {
+                    enable_const_thread_local = true;
+                }
             }
 
             if !ac.probe_rustc_version(1, 51) {
@@ -23,4 +50,12 @@ fn main() {
             );
         }
     }
+
+    if !enable_const_thread_local {
+        // To disable this feature on compilers that support it, you can
+        // explicitly pass this flag with the following environment variable:
+        //
+        // RUSTFLAGS="--cfg tokio_no_const_thread_local"
+        autocfg::emit("tokio_no_const_thread_local")
+    }
 }

tokio/src/macros/thread_local.rs

@@ -10,12 +10,14 @@ macro_rules! thread_local {
     ($($tts:tt)+) => { loom::thread_local!{ $($tts)+ } }
 }
 
-#[cfg(all(tokio_const_thread_local, not(all(loom, test))))]
+#[cfg(not(tokio_no_const_thread_local))]
+#[cfg(not(all(loom, test)))]
 macro_rules! thread_local {
     ($($tts:tt)+) => { ::std::thread_local!{ $($tts)+ } }
 }
 
-#[cfg(all(not(tokio_const_thread_local), not(all(loom, test))))]
+#[cfg(tokio_no_const_thread_local)]
+#[cfg(not(all(loom, test)))]
 macro_rules! thread_local {
     ($(#[$attrs:meta])* $vis:vis static $name:ident: $ty:ty = const { $expr:expr } $(;)?) => {
         ::std::thread_local! {

tokio/src/task/task_local.rs

@@ -47,7 +47,7 @@ macro_rules! task_local {
 }
 
 #[doc(hidden)]
-#[cfg(tokio_const_thread_local)]
+#[cfg(not(tokio_no_const_thread_local))]
 #[macro_export]
 macro_rules! __task_local_inner {
     ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty) => {
@@ -63,7 +63,7 @@ macro_rules! __task_local_inner {
 }
 
 #[doc(hidden)]
-#[cfg(not(tokio_const_thread_local))]
+#[cfg(tokio_no_const_thread_local)]
 #[macro_export]
 macro_rules! __task_local_inner {
     ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty) => {