Use build script to detect wasm

tokio/Cargo.toml

@@ -117,7 +117,7 @@ mio = { version = "0.8.4", optional = true }
 num_cpus = { version = "1.8.0", optional = true }
 parking_lot = { version = "0.12.0", optional = true }
 
-[target.'cfg(not(target_family = "wasm"))'.dependencies]
+[target.'cfg(not(any(target_arch = "wasm32", target_arch = "wasm64")))'.dependencies]
 socket2 = { version = "0.4.4", features = [ "all" ] }
 
 # Currently unstable. The API exposed by these features may be broken at any time.
@@ -150,14 +150,14 @@ mockall = "0.11.1"
 tempfile = "3.1.0"
 async-stream = "0.3"
 
-[target.'cfg(not(target_family = "wasm"))'.dev-dependencies]
+[target.'cfg(not(any(target_arch = "wasm32", target_arch = "wasm64")))'.dev-dependencies]
 proptest = "1"
 socket2 = "0.4"
 
-[target.'cfg(not(all(target_family = "wasm", target_os = "unknown")))'.dev-dependencies]
+[target.'cfg(not(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown")))'.dev-dependencies]
 rand = "0.8.0"
 
-[target.'cfg(all(target_family = "wasm", not(target_os = "wasi")))'.dev-dependencies]
+[target.'cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"), not(target_os = "wasi")))'.dev-dependencies]
 wasm-bindgen-test = "0.3.0"
 
 [target.'cfg(target_os = "freebsd")'.dev-dependencies]

tokio/build.rs

@@ -85,4 +85,17 @@ fn main() {
         // RUSTFLAGS="--cfg tokio_no_addr_of"
         autocfg::emit("tokio_no_addr_of")
     }
+
+    let target = ::std::env::var("TARGET").unwrap_or_default();
+
+    // We emit cfgs instead of using `target_family = "wasm"` that requires Rust 1.54.
+    // Note that these cfgs are unavailable in `Cargo.toml`.
+    if target.starts_with("wasm") {
+        autocfg::emit("tokio_wasm");
+        if target.contains("wasi") {
+            autocfg::emit("tokio_wasi");
+        } else {
+            autocfg::emit("tokio_wasm_not_wasi");
+        }
+    }
 }

tokio/src/coop.rs

@@ -207,7 +207,7 @@ cfg_coop! {
 mod test {
     use super::*;
 
-    #[cfg(all(target_family = "wasm", not(target_os = "wasi")))]
+    #[cfg(tokio_wasm_not_wasi)]
     use wasm_bindgen_test::wasm_bindgen_test as test;
 
     fn get() -> Budget {

tokio/src/io/driver/mod.rs

@@ -73,7 +73,7 @@ pub(super) struct Inner {
 
     /// Used to wake up the reactor from a call to `turn`.
     /// Not supported on Wasi due to lack of threading support.
-    #[cfg(not(target_os = "wasi"))]
+    #[cfg(not(tokio_wasi))]
     waker: mio::Waker,
 
     metrics: IoDriverMetrics,
@@ -117,7 +117,7 @@ impl Driver {
     /// creation.
     pub(crate) fn new() -> io::Result<Driver> {
         let poll = mio::Poll::new()?;
-        #[cfg(not(target_os = "wasi"))]
+        #[cfg(not(tokio_wasi))]
         let waker = mio::Waker::new(poll.registry(), TOKEN_WAKEUP)?;
         let registry = poll.registry().try_clone()?;
 
@@ -132,7 +132,7 @@ impl Driver {
             inner: Arc::new(Inner {
                 registry,
                 io_dispatch: RwLock::new(IoDispatcher::new(allocator)),
-                #[cfg(not(target_os = "wasi"))]
+                #[cfg(not(tokio_wasi))]
                 waker,
                 metrics: IoDriverMetrics::default(),
             }),
@@ -168,7 +168,7 @@ impl Driver {
         match self.poll.poll(&mut events, max_wait) {
             Ok(_) => {}
             Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {}
-            #[cfg(target_os = "wasi")]
+            #[cfg(tokio_wasi)]
             Err(e) if e.kind() == io::ErrorKind::InvalidInput => {
                 // In case of wasm32_wasi this error happens, when trying to poll without subscriptions
                 // just return from the park, as there would be nothing, which wakes us up.
@@ -310,7 +310,7 @@ impl Handle {
     /// blocked in `turn`, then the next call to `turn` will not block and
     /// return immediately.
     fn wakeup(&self) {
-        #[cfg(not(target_os = "wasi"))]
+        #[cfg(not(tokio_wasi))]
         self.inner.waker.wake().expect("failed to wake I/O driver");
     }
 }

tokio/src/io/driver/registration.rs

@@ -115,7 +115,7 @@ impl Registration {
 
     // Uses the poll path, requiring the caller to ensure mutual exclusion for
     // correctness. Only the last task to call this function is notified.
-    #[cfg(not(all(target_family = "wasm", target_os = "wasi")))]
+    #[cfg(not(tokio_wasi))]
     pub(crate) fn poll_read_io<R>(
         &self,
         cx: &mut Context<'_>,

tokio/src/io/mod.rs

@@ -211,11 +211,11 @@ cfg_io_driver_impl! {
         pub use driver::{Interest, Ready};
     }
 
-    #[cfg_attr(target_os = "wasi", allow(unused_imports))]
+    #[cfg_attr(tokio_wasi, allow(unused_imports))]
     mod poll_evented;
 
     #[cfg(not(loom))]
-    #[cfg_attr(target_os = "wasi", allow(unused_imports))]
+    #[cfg_attr(tokio_wasi, allow(unused_imports))]
     pub(crate) use poll_evented::PollEvented;
 }
 

tokio/src/lib.rs

@@ -393,9 +393,26 @@ compile_error! {
     "Tokio requires the platform pointer width to be 32, 64, or 128 bits"
 }
 
+// Ensure that our build script has correctly set cfg flags for wasm.
+//
+// Each condition is written all(a, not(b)). This should be read as
+// "if a, then we must also have b".
+#[cfg(any(
+    all(target_arch = "wasm32", not(tokio_wasm)),
+    all(target_arch = "wasm64", not(tokio_wasm)),
+    all(target_family = "wasm", not(tokio_wasm)),
+    all(target_os = "wasi", not(tokio_wasm)),
+    all(target_os = "wasi", not(tokio_wasi)),
+    all(target_os = "wasi", tokio_wasm_not_wasi),
+    all(tokio_wasm, not(any(target_arch = "wasm32", target_arch = "wasm64"))),
+    all(tokio_wasm_not_wasi, not(tokio_wasm)),
+    all(tokio_wasi, not(tokio_wasm))
+))]
+compile_error!("Tokio's build script has incorrectly detected wasm.");
+
 #[cfg(all(
     not(tokio_unstable),
-    target_family = "wasm",
+    tokio_wasm,
     any(
         feature = "fs",
         feature = "io-std",

tokio/src/macros/cfg.rs

@@ -61,7 +61,7 @@ macro_rules! cfg_fs {
     ($($item:item)*) => {
         $(
             #[cfg(feature = "fs")]
-            #[cfg(not(target_os = "wasi"))]
+            #[cfg(not(tokio_wasi))]
             #[cfg_attr(docsrs, doc(cfg(feature = "fs")))]
             $item
         )*
@@ -252,7 +252,7 @@ macro_rules! cfg_process {
             #[cfg(feature = "process")]
             #[cfg_attr(docsrs, doc(cfg(feature = "process")))]
             #[cfg(not(loom))]
-            #[cfg(not(target_os = "wasi"))]
+            #[cfg(not(tokio_wasi))]
             $item
         )*
     }
@@ -281,7 +281,7 @@ macro_rules! cfg_signal {
             #[cfg(feature = "signal")]
             #[cfg_attr(docsrs, doc(cfg(feature = "signal")))]
             #[cfg(not(loom))]
-            #[cfg(not(target_os = "wasi"))]
+            #[cfg(not(tokio_wasi))]
             $item
         )*
     }
@@ -341,7 +341,7 @@ macro_rules! cfg_not_rt {
 macro_rules! cfg_rt_multi_thread {
     ($($item:item)*) => {
         $(
-            #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+            #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
             #[cfg_attr(docsrs, doc(cfg(feature = "rt-multi-thread")))]
             $item
         )*
@@ -459,7 +459,7 @@ macro_rules! cfg_has_atomic_u64 {
                     target_arch = "mips",
                     target_arch = "powerpc",
                     target_arch = "riscv32",
-                    target_family = "wasm"
+                    tokio_wasm
                     )))]
             $item
         )*
@@ -474,7 +474,7 @@ macro_rules! cfg_not_has_atomic_u64 {
                     target_arch = "mips",
                     target_arch = "powerpc",
                     target_arch = "riscv32",
-                    target_family = "wasm"
+                    tokio_wasm
                     ))]
             $item
         )*
@@ -484,7 +484,7 @@ macro_rules! cfg_not_has_atomic_u64 {
 macro_rules! cfg_not_wasi {
     ($($item:item)*) => {
         $(
-            #[cfg(not(target_os = "wasi"))]
+            #[cfg(not(tokio_wasi))]
             $item
         )*
     }
@@ -493,7 +493,7 @@ macro_rules! cfg_not_wasi {
 macro_rules! cfg_is_wasm_not_wasi {
     ($($item:item)*) => {
         $(
-            #[cfg(all(target_family = "wasm", not(target_os = "wasi")))]
+            #[cfg(tokio_wasm_not_wasi)]
             $item
         )*
     }

tokio/src/net/tcp/listener.rs

@@ -275,7 +275,7 @@ impl TcpListener {
                 .map(|raw_socket| unsafe { std::net::TcpListener::from_raw_socket(raw_socket) })
         }
 
-        #[cfg(target_os = "wasi")]
+        #[cfg(tokio_wasi)]
         {
             use std::os::wasi::io::{FromRawFd, IntoRawFd};
             self.io
@@ -403,7 +403,7 @@ mod sys {
 }
 
 cfg_unstable! {
-    #[cfg(target_os = "wasi")]
+    #[cfg(tokio_wasi)]
     mod sys {
         use super::TcpListener;
         use std::os::wasi::prelude::*;

tokio/src/net/tcp/stream.rs

@@ -252,7 +252,7 @@ impl TcpStream {
                 .map(|raw_socket| unsafe { std::net::TcpStream::from_raw_socket(raw_socket) })
         }
 
-        #[cfg(target_os = "wasi")]
+        #[cfg(tokio_wasi)]
         {
             use std::os::wasi::io::{FromRawFd, IntoRawFd};
             self.io
@@ -1334,7 +1334,7 @@ mod sys {
     }
 }
 
-#[cfg(all(tokio_unstable, target_os = "wasi"))]
+#[cfg(all(tokio_unstable, tokio_wasi))]
 mod sys {
     use super::TcpStream;
     use std::os::wasi::prelude::*;

tokio/src/park/thread.rs

@@ -65,9 +65,9 @@ impl Park for ParkThread {
 
     fn park_timeout(&mut self, duration: Duration) -> Result<(), Self::Error> {
         // Wasi doesn't have threads, so just sleep.
-        #[cfg(not(target_os = "wasi"))]
+        #[cfg(not(tokio_wasi))]
         self.inner.park_timeout(duration);
-        #[cfg(target_os = "wasi")]
+        #[cfg(tokio_wasi)]
         std::thread::sleep(duration);
         Ok(())
     }

tokio/src/runtime/blocking/pool.rs

@@ -125,7 +125,7 @@ const KEEP_ALIVE: Duration = Duration::from_secs(10);
 /// Tasks will be scheduled as non-mandatory, meaning they may not get executed
 /// in case of runtime shutdown.
 #[track_caller]
-#[cfg_attr(target_os = "wasi", allow(dead_code))]
+#[cfg_attr(tokio_wasi, allow(dead_code))]
 pub(crate) fn spawn_blocking<F, R>(func: F) -> JoinHandle<R>
 where
     F: FnOnce() -> R + Send + 'static,

tokio/src/runtime/builder.rs

@@ -174,7 +174,7 @@ pub(crate) type ThreadNameFn = std::sync::Arc<dyn Fn() -> String + Send + Sync +
 
 pub(crate) enum Kind {
     CurrentThread,
-    #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+    #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
     MultiThread,
 }
 
@@ -619,7 +619,7 @@ impl Builder {
     pub fn build(&mut self) -> io::Result<Runtime> {
         match &self.kind {
             Kind::CurrentThread => self.build_basic_runtime(),
-            #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+            #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
             Kind::MultiThread => self.build_threaded_runtime(),
         }
     }
@@ -628,7 +628,7 @@ impl Builder {
         driver::Cfg {
             enable_pause_time: match self.kind {
                 Kind::CurrentThread => true,
-                #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+                #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
                 Kind::MultiThread => false,
             },
             enable_io: self.enable_io,

tokio/src/runtime/mod.rs

@@ -174,7 +174,7 @@
 
 // At the top due to macros
 #[cfg(test)]
-#[cfg(not(target_family = "wasm"))]
+#[cfg(not(tokio_wasm))]
 #[macro_use]
 mod tests;
 
@@ -204,7 +204,7 @@ cfg_rt! {
 
     mod blocking;
     use blocking::BlockingPool;
-    #[cfg_attr(target_os = "wasi", allow(unused_imports))]
+    #[cfg_attr(tokio_wasi, allow(unused_imports))]
     pub(crate) use blocking::spawn_blocking;
 
     cfg_trace! {
@@ -304,7 +304,7 @@ cfg_rt! {
         CurrentThread(BasicScheduler),
 
         /// Execute tasks across multiple threads.
-        #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+        #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
         ThreadPool(ThreadPool),
     }
 
@@ -484,7 +484,7 @@ cfg_rt! {
 
             match &self.kind {
                 Kind::CurrentThread(exec) => exec.block_on(future),
-                #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+                #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
                 Kind::ThreadPool(exec) => exec.block_on(future),
             }
         }
@@ -614,7 +614,7 @@ cfg_rt! {
                         },
                     }
                 },
-                #[cfg(all(feature = "rt-multi-thread", not(target_os = "wasi")))]
+                #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
                 Kind::ThreadPool(_) => {
                     // The threaded scheduler drops its tasks on its worker threads, which is
                     // already in the runtime's context.