Replaced std with core, and made std::error::Error optional through feature

Cargo.toml

@@ -27,8 +27,9 @@ path = "src/lib.rs"
 
 [features]
 unstable = []
-default = []
+default = ["std"]
 fuzztarget = []
+std = []
 
 [dev-dependencies]
 rand = "0.6"
@@ -38,7 +39,9 @@ serde_test = "1.0"
 [dependencies.rand]
 version = "0.6"
 optional = true
+default-features = false
 
 [dependencies.serde]
 version = "1.0"
 optional = true
+default-features = false

src/ecdh.rs

@@ -16,7 +16,7 @@
 //! Support for shared secret computations
 //!
 
-use std::{ops, ptr};
+use core::{ops, ptr};
 
 use key::{SecretKey, PublicKey};
 use ffi;

src/key.rs

@@ -17,7 +17,7 @@
 
 #[cfg(any(test, feature = "rand"))] use rand::Rng;
 
-use std::{fmt, mem, str};
+use core::{fmt, mem, str};
 
 use super::{from_hex, Secp256k1};
 use super::Error::{self, InvalidPublicKey, InvalidSecretKey};

src/lib.rs

@@ -133,15 +133,17 @@
 #![cfg_attr(feature = "dev", feature(plugin))]
 #![cfg_attr(feature = "dev", plugin(clippy))]
 
+#![cfg_attr(all(not(test), not(feature = "std")), no_std)]
 #![cfg_attr(all(test, feature = "unstable"), feature(test))]
 #[cfg(all(test, feature = "unstable"))] extern crate test;
 #[cfg(any(test, feature = "rand"))] pub extern crate rand;
 #[cfg(any(test))] extern crate rand_core;
 #[cfg(feature = "serde")] pub extern crate serde;
 #[cfg(all(test, feature = "serde"))] extern crate serde_test;
-
-use std::{error, fmt, ptr, str};
 #[cfg(any(test, feature = "rand"))] use rand::Rng;
+#[cfg(any(test, feature = "std"))] extern crate core;
+
+use core::{fmt, ptr, str};
 
 #[macro_use]
 mod macros;
@@ -152,7 +154,7 @@ pub mod key;
 
 pub use key::SecretKey;
 pub use key::PublicKey;
-use std::marker::PhantomData;
+use core::marker::PhantomData;
 
 /// A tag used for recovering the public key from a compact signature
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
@@ -519,15 +521,7 @@ pub enum Error {
 // Passthrough Debug to Display, since errors should be user-visible
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        f.write_str(error::Error::description(self))
+        let res = match *self {
-    }
-}
-
-impl error::Error for Error {
-    fn cause(&self) -> Option<&error::Error> { None }
-
-    fn description(&self) -> &str {
-        match *self {
             Error::IncorrectSignature => "secp: signature failed verification",
             Error::InvalidMessage => "secp: message was not 32 bytes (do you need to hash?)",
             Error::InvalidPublicKey => "secp: malformed public key",
@@ -535,9 +529,13 @@ impl error::Error for Error {
             Error::InvalidSecretKey => "secp: malformed or out-of-range secret key",
             Error::InvalidRecoveryId => "secp: bad recovery id",
             Error::InvalidTweak => "secp: bad tweak",
+        };
+        f.write_str(res)
     }
 }
-}
+
+#[cfg(feature = "std")]
+impl std::error::Error for Error {}
 
 /// Marker trait for indicating that an instance of `Secp256k1` can be used for signing.
 pub trait Signing {}

src/macros.rs

@@ -53,14 +53,14 @@ macro_rules! impl_array_newtype {
 
         impl PartialOrd for $thing {
             #[inline]
-            fn partial_cmp(&self, other: &$thing) -> Option<::std::cmp::Ordering> {
+            fn partial_cmp(&self, other: &$thing) -> Option<::core::cmp::Ordering> {
                 self[..].partial_cmp(&other[..])
             }
         }
 
         impl Ord for $thing {
             #[inline]
-            fn cmp(&self, other: &$thing) -> ::std::cmp::Ordering {
+            fn cmp(&self, other: &$thing) -> ::core::cmp::Ordering {
                 self[..].cmp(&other[..])
             }            
         }
@@ -69,8 +69,8 @@ macro_rules! impl_array_newtype {
             #[inline]
             fn clone(&self) -> $thing {
                 unsafe {
-                    use std::intrinsics::copy_nonoverlapping;
+                    use core::intrinsics::copy_nonoverlapping;
-                    use std::mem;
+                    use core::mem;
                     let mut ret: $thing = mem::uninitialized();
                     copy_nonoverlapping(self.as_ptr(),
                                         ret.as_mut_ptr(),
@@ -80,7 +80,7 @@ macro_rules! impl_array_newtype {
             }
         }
 
-        impl ::std::ops::Index<usize> for $thing {
+        impl ::core::ops::Index<usize> for $thing {
             type Output = $ty;
 
             #[inline]
@@ -90,41 +90,41 @@ macro_rules! impl_array_newtype {
             }
         }
 
-        impl ::std::ops::Index<::std::ops::Range<usize>> for $thing {
+        impl ::core::ops::Index<::core::ops::Range<usize>> for $thing {
             type Output = [$ty];
 
             #[inline]
-            fn index(&self, index: ::std::ops::Range<usize>) -> &[$ty] {
+            fn index(&self, index: ::core::ops::Range<usize>) -> &[$ty] {
                 let &$thing(ref dat) = self;
                 &dat[index]
             }
         }
 
-        impl ::std::ops::Index<::std::ops::RangeTo<usize>> for $thing {
+        impl ::core::ops::Index<::core::ops::RangeTo<usize>> for $thing {
             type Output = [$ty];
 
             #[inline]
-            fn index(&self, index: ::std::ops::RangeTo<usize>) -> &[$ty] {
+            fn index(&self, index: ::core::ops::RangeTo<usize>) -> &[$ty] {
                 let &$thing(ref dat) = self;
                 &dat[index]
             }
         }
 
-        impl ::std::ops::Index<::std::ops::RangeFrom<usize>> for $thing {
+        impl ::core::ops::Index<::core::ops::RangeFrom<usize>> for $thing {
             type Output = [$ty];
 
             #[inline]
-            fn index(&self, index: ::std::ops::RangeFrom<usize>) -> &[$ty] {
+            fn index(&self, index: ::core::ops::RangeFrom<usize>) -> &[$ty] {
                 let &$thing(ref dat) = self;
                 &dat[index]
             }
         }
 
-        impl ::std::ops::Index<::std::ops::RangeFull> for $thing {
+        impl ::core::ops::Index<::core::ops::RangeFull> for $thing {
             type Output = [$ty];
 
             #[inline]
-            fn index(&self, _: ::std::ops::RangeFull) -> &[$ty] {
+            fn index(&self, _: ::core::ops::RangeFull) -> &[$ty] {
                 let &$thing(ref dat) = self;
                 &dat[..]
             }
@@ -134,8 +134,8 @@ macro_rules! impl_array_newtype {
 
 macro_rules! impl_pretty_debug {
     ($thing:ident) => {
-        impl ::std::fmt::Debug for $thing {
+        impl ::core::fmt::Debug for $thing {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
                 try!(write!(f, "{}(", stringify!($thing)));
                 for i in self[..].iter().cloned() {
                     try!(write!(f, "{:02x}", i));
@@ -148,8 +148,8 @@ macro_rules! impl_pretty_debug {
 
 macro_rules! impl_raw_debug {
     ($thing:ident) => {
-        impl ::std::fmt::Debug for $thing {
+        impl ::core::fmt::Debug for $thing {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
                 for i in self[..].iter().cloned() {
                     try!(write!(f, "{:02x}", i));
                 }