Add no_std support to crossbeam-queue

ci/crossbeam-queue.sh

@@ -5,5 +5,6 @@ set -ex
 
 export RUSTFLAGS="-D warnings"
 
+cargo check --no-default-features
 cargo check --bins --examples --tests
 cargo test

crossbeam-queue/Cargo.toml

@@ -15,9 +15,18 @@ description = "Concurrent queues"
 keywords = ["queue", "mpmc", "lock-free", "producer", "consumer"]
 categories = ["concurrency", "data-structures"]
 
+[features]
+default = ["std"]
+std = ["crossbeam-utils/std"]
+alloc = ["crossbeam-utils/alloc"]
+
+[dependencies]
+cfg-if = "0.1.2"
+
 [dependencies.crossbeam-utils]
 version = "0.7"
 path = "../crossbeam-utils"
+default-features = false
 
 [dev-dependencies]
 rand = "0.6"

crossbeam-queue/src/array_queue.rs

@@ -8,12 +8,13 @@
 //!   - Simplified BSD License and Apache License, Version 2.0
 //!   - http://www.1024cores.net/home/code-license
 
-use std::cell::UnsafeCell;
-use std::fmt;
-use std::marker::PhantomData;
-use std::mem;
-use std::ptr;
-use std::sync::atomic::{self, AtomicUsize, Ordering};
+use alloc::vec::Vec;
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::marker::PhantomData;
+use core::mem;
+use core::ptr;
+use core::sync::atomic::{self, AtomicUsize, Ordering};
 
 use crossbeam_utils::{Backoff, CachePadded};
 

crossbeam-queue/src/err.rs

@@ -1,5 +1,4 @@
-use std::error;
-use std::fmt;
+use core::fmt;
 
 /// Error which occurs when popping from an empty queue.
 #[derive(Clone, Copy, Eq, PartialEq)]
@@ -17,7 +16,8 @@ impl fmt::Display for PopError {
     }
 }
 
-impl error::Error for PopError {
+#[cfg(features = "std")]
+impl std::error::Error for PopError {
     fn description(&self) -> &str {
         "popping from an empty queue"
     }
@@ -39,7 +39,8 @@ impl<T> fmt::Display for PushError<T> {
     }
 }
 
-impl<T: Send> error::Error for PushError<T> {
+#[cfg(features = "std")]
+impl<T: Send> std::error::Error for PushError<T> {
     fn description(&self) -> &str {
         "pushing into a full queue"
     }

crossbeam-queue/src/lib.rs

@@ -10,13 +10,31 @@
 
 #![warn(missing_docs)]
 #![warn(missing_debug_implementations)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[macro_use]
+extern crate cfg_if;
+#[cfg(feature = "std")]
+extern crate core;
+
+cfg_if! {
+    if #[cfg(feature = "alloc")] {
+        extern crate alloc;
+    } else if #[cfg(feature = "std")] {
+        extern crate std as alloc;
+    }
+}
 
 extern crate crossbeam_utils;
 
-mod array_queue;
-mod err;
-mod seg_queue;
+cfg_if! {
+    if #[cfg(any(feature = "alloc", feature = "std"))] {
+        mod array_queue;
+        mod err;
+        mod seg_queue;
 
-pub use self::array_queue::ArrayQueue;
-pub use self::err::{PopError, PushError};
-pub use self::seg_queue::SegQueue;
+        pub use self::array_queue::ArrayQueue;
+        pub use self::err::{PopError, PushError};
+        pub use self::seg_queue::SegQueue;
+    }
+}

crossbeam-queue/src/seg_queue.rs

@@ -1,9 +1,10 @@
-use std::cell::UnsafeCell;
-use std::fmt;
-use std::marker::PhantomData;
-use std::mem::{self, ManuallyDrop};
-use std::ptr;
-use std::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use alloc::boxed::Box;
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::marker::PhantomData;
+use core::mem::{self, ManuallyDrop};
+use core::ptr;
+use core::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
 
 use crossbeam_utils::{Backoff, CachePadded};