no_std support

Changes references from std:: to core:: where applicable, ensuring the crate
builds in no_std environments.

.travis.yml

@@ -13,6 +13,12 @@ matrix:
     env: FEATURES=--features=nightly
   - rust: beta
     env: FEATURES=--features=nightly
+  include:
+  - rust: beta
+    script: cargo build --verbose --no-default-features --features=no_cc
+    script: cargo build --verbose --no-default-features --features=nightly
+    script: cargo build --verbose --release --no-default-features --features=no_cc
+    script: cargo build --verbose --release --no-default-features --features=nightly
 script:
   - cargo build --verbose $FEATURES
   - cargo test --verbose $FEATURES

Cargo.toml

@@ -12,10 +12,10 @@ license = "MIT OR Apache-2.0"
 build = "build.rs"
 
 [features]
+default = ["std"]
 no_cc = []
 nightly = ["no_cc"]
+std = []
 
 [build-dependencies]
 gcc = "0.3"
-
-[dependencies]

src/clear.rs

@@ -39,8 +39,8 @@
 //! assert!(!as_bytes(&place).contains(&0x41));
 //! ```
 
-use std::mem;
-use std::ptr;
+use core::mem;
+use core::ptr;
 
 use hide::hide_mem_impl;
 

src/clear_on_drop.rs

@@ -1,10 +1,10 @@
-use std::borrow::{Borrow, BorrowMut};
-use std::cmp::Ordering;
-use std::fmt;
-use std::hash::{Hash, Hasher};
-use std::mem;
-use std::ops::{Deref, DerefMut};
-use std::ptr;
+use core::borrow::{Borrow, BorrowMut};
+use core::cmp::Ordering;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::mem;
+use core::ops::{Deref, DerefMut};
+use core::ptr;
 
 use clear::Clear;
 
@@ -138,7 +138,7 @@ impl<P> Drop for ClearOnDrop<P>
     }
 }
 
-// std::convert traits
+// core::convert traits
 
 impl<P, T: ?Sized> AsRef<T> for ClearOnDrop<P>
     where P: DerefMut + AsRef<T>,
@@ -160,7 +160,7 @@ impl<P, T: ?Sized> AsMut<T> for ClearOnDrop<P>
     }
 }
 
-// std::borrow traits
+// core::borrow traits
 
 // The `T: Clear` bound avoids a conflict with the blanket impls
 // `impl<T> Borrow<T> for T` and `impl<T> BorrowMut<T> for T`, since
@@ -188,7 +188,7 @@ impl<P, T: ?Sized> BorrowMut<T> for ClearOnDrop<P>
     }
 }
 
-// std::hash traits
+// core::hash traits
 
 impl<P> Hash for ClearOnDrop<P>
     where P: DerefMut + Hash,
@@ -200,7 +200,7 @@ impl<P> Hash for ClearOnDrop<P>
     }
 }
 
-// std::cmp traits
+// core::cmp traits
 
 impl<P, Q> PartialEq<ClearOnDrop<Q>> for ClearOnDrop<P>
     where P: DerefMut + PartialEq<Q>,

src/hide.rs

@@ -25,7 +25,7 @@ pub fn hide_ptr<P>(mut ptr: P) -> P {
 #[cfg(feature = "nightly")]
 pub use self::nightly::*;
 
-#[cfg(not(feature = "no_cc"))]
+#[cfg(all(not(feature = "no_cc"), feature = "std"))]
 pub use self::cc::*;
 
 #[cfg(all(feature = "no_cc", not(feature = "nightly")))]
@@ -63,7 +63,7 @@ mod nightly {
 }
 
 // When a C compiler is available, a dummy C function can be used.
-#[cfg(not(feature = "no_cc"))]
+#[cfg(all(not(feature = "no_cc"), feature = "std"))]
 mod cc {
     use std::os::raw::c_void;
 
@@ -83,7 +83,7 @@ mod cc {
 // and hope this is enough to confuse the optimizer.
 #[cfg(all(feature = "no_cc", not(feature = "nightly")))]
 mod fallback {
-    use std::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};
+    use core::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};
 
     #[inline]
     pub fn hide_mem_impl<T: ?Sized>(ptr: *mut T) {

src/lib.rs

@@ -1,3 +1,4 @@
+#![cfg_attr(not(feature = "std"), no_std)]
 #![cfg_attr(feature = "nightly", feature(asm))]
 #![cfg_attr(feature = "nightly", feature(i128_type))]
 #![cfg_attr(feature = "nightly", feature(specialization))]
@@ -55,6 +56,9 @@
 //! the `no_cc` feature, works on stable Rust, and does not need a C
 //! compiler.
 
+#[cfg(feature = "std")]
+extern crate core;
+
 pub mod clear;
 mod clear_on_drop;
 mod clear_stack_on_return;