Merge pull request #55 from rust-lang-nursery/destructor_drop

Switch lazy_static over to mutable statics instead of UnsafeCell on nightly

Author: Kimundi

Cargo.toml

@@ -14,7 +14,7 @@ keywords = ["macro", "lazy", "static"]
 categories = [ "no-std", "rust-patterns", "memory-management" ]
 
 [dependencies.spin]
-version = "0.4"
+version = "0.4.6"
 optional = true
 
 [dependencies.compiletest_rs]

src/core_lazy.rs

@@ -26,8 +26,6 @@ impl<T: Sync> Lazy<T> {
 }
 
 #[macro_export]
-#[allow_internal_unstable]
-#[doc(hidden)]
 macro_rules! __lazy_static_create {
     ($NAME:ident, $T:ty) => {
         static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();

src/lazy.rs

@@ -9,6 +9,7 @@ extern crate std;
 
 use self::std::prelude::v1::*;
 use self::std::sync::Once;
+pub use self::std::sync::ONCE_INIT;
 
 pub struct Lazy<T: Sync>(pub *const T, pub Once);
 
@@ -31,10 +32,8 @@ impl<T: Sync> Lazy<T> {
 unsafe impl<T: Sync> Sync for Lazy<T> {}
 
 #[macro_export]
-#[doc(hidden)]
 macro_rules! __lazy_static_create {
     ($NAME:ident, $T:ty) => {
-        use std::sync::ONCE_INIT;
-        static mut $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy(0 as *const $T, ONCE_INIT);
+        static mut $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy(0 as *const $T, $crate::lazy::ONCE_INIT);
     }
 }

src/lib.rs

@@ -90,9 +90,10 @@ 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, const_unsafe_cell_new))]
+#![cfg_attr(feature="spin_no_std", feature(const_fn))]
+#![cfg_attr(feature="nightly", feature(unreachable))]
 
-#![doc(html_root_url = "https://docs.rs/lazy_static/0.2.8")]
+#![doc(html_root_url = "https://docs.rs/lazy_static/0.2.10")]
 #![no_std]
 
 #[cfg(not(feature="nightly"))]
@@ -113,7 +114,6 @@ pub mod lazy;
 pub use core::ops::Deref as __Deref;
 
 #[macro_export]
-#[cfg_attr(feature="nightly", allow_internal_unstable)]
 #[doc(hidden)]
 macro_rules! __lazy_static_internal {
     // optional visibility restrictions are wrapped in `()` to allow for
@@ -161,7 +161,6 @@ macro_rules! __lazy_static_internal {
 }
 
 #[macro_export]
-#[cfg_attr(feature="nightly", allow_internal_unstable)]
 macro_rules! lazy_static {
     ($(#[$attr:meta])* static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
         // use `()` to explicitly forward the information about private items

src/nightly_lazy.rs

@@ -8,29 +8,26 @@
 extern crate std;
 
 use self::std::prelude::v1::*;
-use self::std::cell::UnsafeCell;
-use self::std::sync::{Once, ONCE_INIT};
+use self::std::sync::Once;
+pub use self::std::sync::ONCE_INIT;
 
-pub struct Lazy<T: Sync>(UnsafeCell<Option<T>>, Once);
+pub struct Lazy<T: Sync>(pub Option<T>, pub Once);
 
 impl<T: Sync> Lazy<T> {
     #[inline(always)]
-    pub const fn new() -> Self {
-        Lazy(UnsafeCell::new(None), ONCE_INIT)
-    }
-
-    #[inline(always)]
-    pub fn get<F>(&'static self, f: F) -> &T
+    pub fn get<F>(&'static mut self, f: F) -> &T
         where F: FnOnce() -> T
     {
-        unsafe {
+        {
+            let r = &mut self.0;
             self.1.call_once(|| {
-                *self.0.get() = Some(f());
+                *r = Some(f());
             });
-
-            match *self.0.get() {
+        }
+        unsafe {
+            match self.0 {
                 Some(ref x) => x,
-                None => std::intrinsics::unreachable(),
+                None => std::mem::unreachable(),
             }
         }
     }
@@ -39,10 +36,8 @@ impl<T: Sync> Lazy<T> {
 unsafe impl<T: Sync> Sync for Lazy<T> {}
 
 #[macro_export]
-#[allow_internal_unstable]
-#[doc(hidden)]
 macro_rules! __lazy_static_create {
     ($NAME:ident, $T:ty) => {
-        static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::new();
+        static mut $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy(None, $crate::lazy::ONCE_INIT);
     }
 }

tests/compile-fail/static_is_sized.rs

@@ -0,0 +1,11 @@
+// error-pattern:the trait bound `str: std::marker::Sized` is not satisfied
+#[macro_use]
+extern crate lazy_static;
+
+lazy_static! {
+    pub static ref FOO: str = panic!();
+}
+
+
+fn main() {
+}