Support shared futures on no_std

futures-util/Cargo.toml

@@ -43,6 +43,7 @@ futures_01 = { version = "0.1.25", optional = true, package = "futures" }
 tokio-io = { version = "0.1.9", optional = true }
 pin-utils = "0.1.0"
 pin-project-lite = "0.2.6"
+spin = "0.9.8"
 
 [dev-dependencies]
 futures = { path = "../futures", features = ["async-await", "thread-pool"] }

futures-util/src/future/future/mod.rs

@@ -107,9 +107,9 @@ mod remote_handle;
 #[cfg(feature = "std")]
 pub use self::remote_handle::{Remote, RemoteHandle};
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 mod shared;
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 pub use self::shared::{Shared, WeakShared};
 
 impl<T: ?Sized> FutureExt for T where T: Future {}
@@ -474,7 +474,7 @@ pub trait FutureExt: Future {
     /// join_handle.join().unwrap();
     /// # });
     /// ```
-    #[cfg(feature = "std")]
+    #[cfg(feature = "alloc")]
     fn shared(self) -> Shared<Self>
     where
         Self: Sized,

futures-util/src/future/future/shared.rs

@@ -1,15 +1,20 @@
 use crate::task::{waker_ref, ArcWake};
+use alloc::sync::{Arc, Weak};
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::hash::Hasher;
+use core::pin::Pin;
+use core::ptr;
+use core::sync::atomic::AtomicUsize;
+use core::sync::atomic::Ordering::{Acquire, SeqCst};
 use futures_core::future::{FusedFuture, Future};
 use futures_core::task::{Context, Poll, Waker};
 use slab::Slab;
-use std::cell::UnsafeCell;
-use std::fmt;
-use std::hash::Hasher;
-use std::pin::Pin;
-use std::ptr;
-use std::sync::atomic::AtomicUsize;
-use std::sync::atomic::Ordering::{Acquire, SeqCst};
-use std::sync::{Arc, Mutex, Weak};
+
+#[cfg(feature = "std")]
+type Mutex<T> = std::sync::Mutex<T>;
+#[cfg(not(feature = "std"))]
+type Mutex<T> = spin::Mutex<T>;
 
 /// Future for the [`shared`](super::FutureExt::shared) method.
 #[must_use = "futures do nothing unless you `.await` or poll them"]

futures-util/src/future/mod.rs

@@ -35,7 +35,7 @@ pub use self::future::CatchUnwind;
 #[cfg(feature = "std")]
 pub use self::future::{Remote, RemoteHandle};
 
-#[cfg(feature = "std")]
+#[cfg(feature = "alloc")]
 pub use self::future::{Shared, WeakShared};
 
 mod try_future;