Spinning no_std feature

Fixes #44

Author: Ericson2314

Cargo.toml

@@ -11,5 +11,10 @@ documentation = "http://rust-lang-nursery.github.io/lazy-static.rs/lazy_static/i
 repository = "https://github.com/rust-lang-nursery/lazy-static.rs"
 keywords = ["macro", "lazy", "static"]
 
+[dependencies.spin]
+version = "0.4"
+optional = true
+
 [features]
 nightly = []
+no_std = ["nightly", "spin"]

src/core_lazy.rs

@@ -0,0 +1,27 @@
+extern crate spin;
+
+use self::spin::Once;
+
+pub struct Lazy<T: Sync>(Once<T>);
+
+impl<T: Sync> Lazy<T> {
+    #[inline(always)]
+    pub const fn new() -> Self {
+        Lazy(Once::new())
+    }
+
+    #[inline(always)]
+    pub fn get<F>(&'static self, builder: F) -> &T
+        where F: FnOnce() -> T
+    {
+        self.0.call_once(builder)
+    }
+}
+
+#[macro_export]
+#[allow_internal_unstable]
+macro_rules! __lazy_static_create {
+    ($NAME:ident, $T:ty) => {
+        static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();
+    }
+}

src/lib.rs

@@ -69,14 +69,19 @@ The `Deref` implementation uses a hidden static variable that is guarded by a at
 */
 
 #![cfg_attr(feature="nightly", feature(const_fn, allow_internal_unstable, core_intrinsics))]
+#![cfg_attr(feature="no_std", no_std)]
 
 #[cfg(not(feature="nightly"))]
 pub mod lazy;
 
-#[cfg(feature="nightly")]
+#[cfg(all(feature="nightly", not(feature="no_std")))]
 #[path="nightly_lazy.rs"]
 pub mod lazy;
 
+#[cfg(all(feature="nightly", feature="no_std"))]
+#[path="core_lazy.rs"]
+pub mod lazy;
+
 #[macro_export]
 #[cfg_attr(feature="nightly", allow_internal_unstable)]
 macro_rules! lazy_static {