diff --git a/buffered.rs b/buffered.rs
index a92ca95..e23b74f 100644
--- a/buffered.rs
+++ b/buffered.rs
@@ -10,15 +10,13 @@
 
 //! Buffering wrappers for I/O traits
 
-use prelude::v1::*;
+use core::prelude::v1::*;
 use io::prelude::*;
 
-use marker::Reflect;
-use cmp;
-use error;
-use fmt;
+use core::cmp;
+use core::fmt;
 use io::{self, DEFAULT_BUF_SIZE, Error, ErrorKind, SeekFrom};
-use memchr;
+use io::memchr;
 
 /// The `BufReader` struct adds buffering to any reader.
 ///
@@ -44,7 +42,6 @@ use memchr;
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct BufReader<R> {
     inner: R,
     buf: Box<[u8]>,
@@ -67,7 +64,6 @@ impl<R: Read> BufReader<R> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(inner: R) -> BufReader<R> {
         BufReader::with_capacity(DEFAULT_BUF_SIZE, inner)
     }
@@ -88,7 +84,6 @@ impl<R: Read> BufReader<R> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn with_capacity(cap: usize, inner: R) -> BufReader<R> {
         BufReader {
             inner: inner,
@@ -116,7 +111,6 @@ impl<R: Read> BufReader<R> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_ref(&self) -> &R { &self.inner }
 
     /// Gets a mutable reference to the underlying reader.
@@ -137,7 +131,6 @@ impl<R: Read> BufReader<R> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut R { &mut self.inner }
 
     /// Unwraps this `BufReader`, returning the underlying reader.
@@ -158,11 +151,9 @@ impl<R: Read> BufReader<R> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_inner(self) -> R { self.inner }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<R: Read> Read for BufReader<R> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         // If we don't have any buffered data and we're doing a massive read
@@ -180,7 +171,6 @@ impl<R: Read> Read for BufReader<R> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<R: Read> BufRead for BufReader<R> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
         // If we've reached the end of our internal buffer then we need to fetch
@@ -197,7 +187,6 @@ impl<R: Read> BufRead for BufReader<R> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<R> fmt::Debug for BufReader<R> where R: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_struct("BufReader")
@@ -207,7 +196,6 @@ impl<R> fmt::Debug for BufReader<R> where R: fmt::Debug {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<R: Seek> Seek for BufReader<R> {
     /// Seek to an offset, in bytes, in the underlying reader.
     ///
@@ -296,7 +284,6 @@ impl<R: Seek> Seek for BufReader<R> {
 /// By wrapping the stream with a `BufWriter`, these ten writes are all grouped
 /// together by the buffer, and will all be written out in one system call when
 /// the `stream` is dropped.
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct BufWriter<W: Write> {
     inner: Option<W>,
     buf: Vec<u8>,
@@ -331,7 +318,6 @@ pub struct BufWriter<W: Write> {
 /// };
 /// ```
 #[derive(Debug)]
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoInnerError<W>(W, Error);
 
 impl<W: Write> BufWriter<W> {
@@ -345,7 +331,6 @@ impl<W: Write> BufWriter<W> {
     ///
     /// let mut buffer = BufWriter::new(TcpStream::connect("127.0.0.1:34254").unwrap());
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(inner: W) -> BufWriter<W> {
         BufWriter::with_capacity(DEFAULT_BUF_SIZE, inner)
     }
@@ -363,7 +348,6 @@ impl<W: Write> BufWriter<W> {
     /// let stream = TcpStream::connect("127.0.0.1:34254").unwrap();
     /// let mut buffer = BufWriter::with_capacity(100, stream);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn with_capacity(cap: usize, inner: W) -> BufWriter<W> {
         BufWriter {
             inner: Some(inner),
@@ -412,7 +396,6 @@ impl<W: Write> BufWriter<W> {
     /// // we can use reference just like buffer
     /// let reference = buffer.get_ref();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_ref(&self) -> &W { self.inner.as_ref().unwrap() }
 
     /// Gets a mutable reference to the underlying writer.
@@ -430,7 +413,6 @@ impl<W: Write> BufWriter<W> {
     /// // we can use reference just like buffer
     /// let reference = buffer.get_mut();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut W { self.inner.as_mut().unwrap() }
 
     /// Unwraps this `BufWriter`, returning the underlying writer.
@@ -448,7 +430,6 @@ impl<W: Write> BufWriter<W> {
     /// // unwrap the TcpStream and flush the buffer
     /// let stream = buffer.into_inner().unwrap();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_inner(mut self) -> Result<W, IntoInnerError<BufWriter<W>>> {
         match self.flush_buf() {
             Err(e) => Err(IntoInnerError(self, e)),
@@ -457,7 +438,6 @@ impl<W: Write> BufWriter<W> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write> Write for BufWriter<W> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         if self.buf.len() + buf.len() > self.buf.capacity() {
@@ -478,7 +458,6 @@ impl<W: Write> Write for BufWriter<W> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write> fmt::Debug for BufWriter<W> where W: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_struct("BufWriter")
@@ -488,7 +467,6 @@ impl<W: Write> fmt::Debug for BufWriter<W> where W: fmt::Debug {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write + Seek> Seek for BufWriter<W> {
     /// Seek to the offset, in bytes, in the underlying writer.
     ///
@@ -498,7 +476,6 @@ impl<W: Write + Seek> Seek for BufWriter<W> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write> Drop for BufWriter<W> {
     fn drop(&mut self) {
         if self.inner.is_some() && !self.panicked {
@@ -537,7 +514,6 @@ impl<W> IntoInnerError<W> {
     ///     }
     /// };
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn error(&self) -> &Error { &self.1 }
 
     /// Returns the buffered writer instance which generated the error.
@@ -570,23 +546,13 @@ impl<W> IntoInnerError<W> {
     ///     }
     /// };
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_inner(self) -> W { self.0 }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W> From<IntoInnerError<W>> for Error {
     fn from(iie: IntoInnerError<W>) -> Error { iie.1 }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<W: Reflect + Send + fmt::Debug> error::Error for IntoInnerError<W> {
-    fn description(&self) -> &str {
-        error::Error::description(self.error())
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W> fmt::Display for IntoInnerError<W> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.error().fmt(f)
@@ -641,7 +607,6 @@ impl<W> fmt::Display for IntoInnerError<W> {
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct LineWriter<W: Write> {
     inner: BufWriter<W>,
 }
@@ -661,7 +626,6 @@ impl<W: Write> LineWriter<W> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(inner: W) -> LineWriter<W> {
         // Lines typically aren't that long, don't use a giant buffer
         LineWriter::with_capacity(1024, inner)
@@ -682,7 +646,6 @@ impl<W: Write> LineWriter<W> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn with_capacity(cap: usize, inner: W) -> LineWriter<W> {
         LineWriter { inner: BufWriter::with_capacity(cap, inner) }
     }
@@ -703,7 +666,6 @@ impl<W: Write> LineWriter<W> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_ref(&self) -> &W { self.inner.get_ref() }
 
     /// Gets a mutable reference to the underlying writer.
@@ -726,7 +688,6 @@ impl<W: Write> LineWriter<W> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut W { self.inner.get_mut() }
 
     /// Unwraps this `LineWriter`, returning the underlying writer.
@@ -748,7 +709,6 @@ impl<W: Write> LineWriter<W> {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_inner(self) -> Result<W, IntoInnerError<LineWriter<W>>> {
         self.inner.into_inner().map_err(|IntoInnerError(buf, e)| {
             IntoInnerError(LineWriter { inner: buf }, e)
@@ -756,7 +716,6 @@ impl<W: Write> LineWriter<W> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write> Write for LineWriter<W> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         match memchr::memrchr(b'\n', buf) {
@@ -775,7 +734,6 @@ impl<W: Write> Write for LineWriter<W> {
     fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write> fmt::Debug for LineWriter<W> where W: fmt::Debug {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         fmt.debug_struct("LineWriter")
diff --git a/cursor.rs b/cursor.rs
index a1002fd..3a00ffe 100644
--- a/cursor.rs
+++ b/cursor.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use prelude::v1::*;
+use core::prelude::v1::*;
 use io::prelude::*;
 
-use cmp;
+use core::cmp;
 use io::{self, SeekFrom, Error, ErrorKind};
 
 /// A `Cursor` wraps another type and provides it with a
@@ -73,7 +73,6 @@ use io::{self, SeekFrom, Error, ErrorKind};
 ///     assert_eq!(&buff.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
 /// }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Clone, Debug)]
 pub struct Cursor<T> {
     inner: T,
@@ -92,7 +91,6 @@ impl<T> Cursor<T> {
     /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
     /// # force_inference(&buff);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(inner: T) -> Cursor<T> {
         Cursor { pos: 0, inner: inner }
     }
@@ -110,7 +108,6 @@ impl<T> Cursor<T> {
     ///
     /// let vec = buff.into_inner();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn into_inner(self) -> T { self.inner }
 
     /// Gets a reference to the underlying value in this cursor.
@@ -126,7 +123,6 @@ impl<T> Cursor<T> {
     ///
     /// let reference = buff.get_ref();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_ref(&self) -> &T { &self.inner }
 
     /// Gets a mutable reference to the underlying value in this cursor.
@@ -145,7 +141,6 @@ impl<T> Cursor<T> {
     ///
     /// let reference = buff.get_mut();
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn get_mut(&mut self) -> &mut T { &mut self.inner }
 
     /// Returns the current position of this cursor.
@@ -167,7 +162,6 @@ impl<T> Cursor<T> {
     /// buff.seek(SeekFrom::Current(-1)).unwrap();
     /// assert_eq!(buff.position(), 1);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn position(&self) -> u64 { self.pos }
 
     /// Sets the position of this cursor.
@@ -187,11 +181,9 @@ impl<T> Cursor<T> {
     /// buff.set_position(4);
     /// assert_eq!(buff.position(), 4);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn set_position(&mut self, pos: u64) { self.pos = pos; }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<T> io::Seek for Cursor<T> where T: AsRef<[u8]> {
     fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
         let pos = match style {
@@ -210,7 +202,6 @@ impl<T> io::Seek for Cursor<T> where T: AsRef<[u8]> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Read for Cursor<T> where T: AsRef<[u8]> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         let n = Read::read(&mut self.fill_buf()?, buf)?;
@@ -219,7 +210,6 @@ impl<T> Read for Cursor<T> where T: AsRef<[u8]> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<T> BufRead for Cursor<T> where T: AsRef<[u8]> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
         let amt = cmp::min(self.pos, self.inner.as_ref().len() as u64);
@@ -228,7 +218,6 @@ impl<T> BufRead for Cursor<T> where T: AsRef<[u8]> {
     fn consume(&mut self, amt: usize) { self.pos += amt as u64; }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> Write for Cursor<&'a mut [u8]> {
     fn write(&mut self, data: &[u8]) -> io::Result<usize> {
         let pos = cmp::min(self.pos, self.inner.len() as u64);
@@ -239,7 +228,6 @@ impl<'a> Write for Cursor<&'a mut [u8]> {
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl Write for Cursor<Vec<u8>> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         // Make sure the internal buffer is as least as big as where we
@@ -267,7 +255,6 @@ impl Write for Cursor<Vec<u8>> {
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }
 
-#[stable(feature = "cursor_box_slice", since = "1.5.0")]
 impl Write for Cursor<Box<[u8]>> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         let pos = cmp::min(self.pos, self.inner.len() as u64);
diff --git a/error.rs b/error.rs
index e142c78..eeb11d5 100644
--- a/error.rs
+++ b/error.rs
@@ -8,14 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use boxed::Box;
-use convert::Into;
-use error;
-use fmt;
-use marker::{Send, Sync};
-use option::Option::{self, Some, None};
-use result;
-use sys;
+#[cfg(feature="alloc")] use alloc::boxed::Box;
+#[cfg(not(feature="alloc"))] use ::FakeBox as Box;
+use core::convert::Into;
+use core::fmt;
+use core::marker::{Send, Sync};
+use core::option::Option::{self, Some, None};
+use core::result;
+#[cfg(feature="collections")] use collections::string::String;
+#[cfg(not(feature="collections"))] use ::ErrorString as String;
 
 /// A specialized [`Result`](../result/enum.Result.html) type for I/O
 /// operations.
@@ -47,7 +48,6 @@ use sys;
 ///     Ok(buffer)
 /// }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub type Result<T> = result::Result<T, Error>;
 
 /// The error type for I/O operations of the `Read`, `Write`, `Seek`, and
@@ -57,20 +57,22 @@ pub type Result<T> = result::Result<T, Error>;
 /// `Error` can be created with crafted error messages and a particular value of
 /// `ErrorKind`.
 #[derive(Debug)]
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Error {
     repr: Repr,
 }
 
 enum Repr {
     Os(i32),
+    #[cfg(feature="alloc")]
     Custom(Box<Custom>),
+    #[cfg(not(feature="alloc"))]
+    Custom(Custom),
 }
 
 #[derive(Debug)]
 struct Custom {
     kind: ErrorKind,
-    error: Box<error::Error+Send+Sync>,
+    error: String,
 }
 
 /// A list specifying general categories of I/O error.
@@ -78,47 +80,34 @@ struct Custom {
 /// This list is intended to grow over time and it is not recommended to
 /// exhaustively match against it.
 #[derive(Copy, PartialEq, Eq, Clone, Debug)]
-#[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated)]
 pub enum ErrorKind {
     /// An entity was not found, often a file.
-    #[stable(feature = "rust1", since = "1.0.0")]
     NotFound,
     /// The operation lacked the necessary privileges to complete.
-    #[stable(feature = "rust1", since = "1.0.0")]
     PermissionDenied,
     /// The connection was refused by the remote server.
-    #[stable(feature = "rust1", since = "1.0.0")]
     ConnectionRefused,
     /// The connection was reset by the remote server.
-    #[stable(feature = "rust1", since = "1.0.0")]
     ConnectionReset,
     /// The connection was aborted (terminated) by the remote server.
-    #[stable(feature = "rust1", since = "1.0.0")]
     ConnectionAborted,
     /// The network operation failed because it was not connected yet.
-    #[stable(feature = "rust1", since = "1.0.0")]
     NotConnected,
     /// A socket address could not be bound because the address is already in
     /// use elsewhere.
-    #[stable(feature = "rust1", since = "1.0.0")]
     AddrInUse,
     /// A nonexistent interface was requested or the requested address was not
     /// local.
-    #[stable(feature = "rust1", since = "1.0.0")]
     AddrNotAvailable,
     /// The operation failed because a pipe was closed.
-    #[stable(feature = "rust1", since = "1.0.0")]
     BrokenPipe,
     /// An entity already exists, often a file.
-    #[stable(feature = "rust1", since = "1.0.0")]
     AlreadyExists,
     /// The operation needs to block to complete, but the blocking operation was
     /// requested to not occur.
-    #[stable(feature = "rust1", since = "1.0.0")]
     WouldBlock,
     /// A parameter was incorrect.
-    #[stable(feature = "rust1", since = "1.0.0")]
     InvalidInput,
     /// Data not valid for the operation were encountered.
     ///
@@ -128,10 +117,8 @@ pub enum ErrorKind {
     ///
     /// For example, a function that reads a file into a string will error with
     /// `InvalidData` if the file's contents are not valid UTF-8.
-    #[stable(feature = "io_invalid_data", since = "1.2.0")]
     InvalidData,
     /// The I/O operation's timeout expired, causing it to be canceled.
-    #[stable(feature = "rust1", since = "1.0.0")]
     TimedOut,
     /// An error returned when an operation could not be completed because a
     /// call to `write` returned `Ok(0)`.
@@ -139,15 +126,12 @@ pub enum ErrorKind {
     /// This typically means that an operation could only succeed if it wrote a
     /// particular number of bytes but only a smaller number of bytes could be
     /// written.
-    #[stable(feature = "rust1", since = "1.0.0")]
     WriteZero,
     /// This operation was interrupted.
     ///
     /// Interrupted operations can typically be retried.
-    #[stable(feature = "rust1", since = "1.0.0")]
     Interrupted,
     /// Any I/O error not part of this list.
-    #[stable(feature = "rust1", since = "1.0.0")]
     Other,
 
     /// An error returned when an operation could not be completed because an
@@ -156,14 +140,9 @@ pub enum ErrorKind {
     /// This typically means that an operation could only succeed if it read a
     /// particular number of bytes but only a smaller number of bytes could be
     /// read.
-    #[stable(feature = "read_exact", since = "1.6.0")]
     UnexpectedEof,
 
     /// Any I/O error not part of this list.
-    #[unstable(feature = "io_error_internals",
-               reason = "better expressed through extensible enums that this \
-                         enum cannot be exhaustively matched against",
-               issue = "0")]
     #[doc(hidden)]
     __Nonexhaustive,
 }
@@ -187,14 +166,13 @@ impl Error {
     /// // errors can also be created from other errors
     /// let custom_error2 = Error::new(ErrorKind::Interrupted, custom_error);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new<E>(kind: ErrorKind, error: E) -> Error
-        where E: Into<Box<error::Error+Send+Sync>>
+        where E: Into<String>
     {
         Self::_new(kind, error.into())
     }
 
-    fn _new(kind: ErrorKind, error: Box<error::Error+Send+Sync>) -> Error {
+    fn _new(kind: ErrorKind, error: String) -> Error {
         Error {
             repr: Repr::Custom(Box::new(Custom {
                 kind: kind,
@@ -203,18 +181,7 @@ impl Error {
         }
     }
 
-    /// Returns an error representing the last OS error which occurred.
-    ///
-    /// This function reads the value of `errno` for the target platform (e.g.
-    /// `GetLastError` on Windows) and will return a corresponding instance of
-    /// `Error` for the error code.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn last_os_error() -> Error {
-        Error::from_raw_os_error(sys::os::errno() as i32)
-    }
-
     /// Creates a new instance of an `Error` from a particular OS error code.
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn from_raw_os_error(code: i32) -> Error {
         Error { repr: Repr::Os(code) }
     }
@@ -224,7 +191,6 @@ impl Error {
     /// If this `Error` was constructed via `last_os_error` or
     /// `from_raw_os_error`, then this function will return `Some`, otherwise
     /// it will return `None`.
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn raw_os_error(&self) -> Option<i32> {
         match self.repr {
             Repr::Os(i) => Some(i),
@@ -236,11 +202,10 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn get_ref(&self) -> Option<&(error::Error+Send+Sync+'static)> {
+    pub fn get_ref(&self) -> Option<&String> {
         match self.repr {
             Repr::Os(..) => None,
-            Repr::Custom(ref c) => Some(&*c.error),
+            Repr::Custom(ref c) => Some(&c.error),
         }
     }
 
@@ -249,11 +214,10 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn get_mut(&mut self) -> Option<&mut (error::Error+Send+Sync+'static)> {
+    pub fn get_mut(&mut self) -> Option<&mut String> {
         match self.repr {
             Repr::Os(..) => None,
-            Repr::Custom(ref mut c) => Some(&mut *c.error),
+            Repr::Custom(ref mut c) => Some(&mut c.error),
         }
     }
 
@@ -261,8 +225,7 @@ impl Error {
     ///
     /// If this `Error` was constructed via `new` then this function will
     /// return `Some`, otherwise it will return `None`.
-    #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn into_inner(self) -> Option<Box<error::Error+Send+Sync>> {
+    pub fn into_inner(self) -> Option<String> {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Custom(c) => Some(c.error)
@@ -270,10 +233,9 @@ impl Error {
     }
 
     /// Returns the corresponding `ErrorKind` for this error.
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn kind(&self) -> ErrorKind {
         match self.repr {
-            Repr::Os(code) => sys::decode_error_kind(code),
+            Repr::Os(_code) => ErrorKind::Other,
             Repr::Custom(ref c) => c.kind,
         }
     }
@@ -283,63 +245,23 @@ impl fmt::Debug for Repr {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             Repr::Os(ref code) =>
-                fmt.debug_struct("Os").field("code", code)
-                   .field("message", &sys::os::error_string(*code)).finish(),
+                fmt.debug_struct("Os").field("code", code).finish(),
             Repr::Custom(ref c) => fmt.debug_tuple("Custom").field(c).finish(),
         }
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         match self.repr {
             Repr::Os(code) => {
-                let detail = sys::os::error_string(code);
-                write!(fmt, "{} (os error {})", detail, code)
+                write!(fmt, "os error {}", code)
             }
             Repr::Custom(ref c) => c.error.fmt(fmt),
         }
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        match self.repr {
-            Repr::Os(..) => match self.kind() {
-                ErrorKind::NotFound => "entity not found",
-                ErrorKind::PermissionDenied => "permission denied",
-                ErrorKind::ConnectionRefused => "connection refused",
-                ErrorKind::ConnectionReset => "connection reset",
-                ErrorKind::ConnectionAborted => "connection aborted",
-                ErrorKind::NotConnected => "not connected",
-                ErrorKind::AddrInUse => "address in use",
-                ErrorKind::AddrNotAvailable => "address not available",
-                ErrorKind::BrokenPipe => "broken pipe",
-                ErrorKind::AlreadyExists => "entity already exists",
-                ErrorKind::WouldBlock => "operation would block",
-                ErrorKind::InvalidInput => "invalid input parameter",
-                ErrorKind::InvalidData => "invalid data",
-                ErrorKind::TimedOut => "timed out",
-                ErrorKind::WriteZero => "write zero",
-                ErrorKind::Interrupted => "operation interrupted",
-                ErrorKind::Other => "other os error",
-                ErrorKind::UnexpectedEof => "unexpected end of file",
-                ErrorKind::__Nonexhaustive => unreachable!()
-            },
-            Repr::Custom(ref c) => c.error.description(),
-        }
-    }
-
-    fn cause(&self) -> Option<&error::Error> {
-        match self.repr {
-            Repr::Os(..) => None,
-            Repr::Custom(ref c) => c.error.cause(),
-        }
-    }
-}
-
 fn _assert_error_is_sync_send() {
     fn _is_sync_send<T: Sync+Send>() {}
     _is_sync_send::<Error>();
diff --git a/impls.rs b/impls.rs
index 3179938..291c69c 100644
--- a/impls.rs
+++ b/impls.rs
@@ -8,29 +8,31 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use boxed::Box;
-use cmp;
-use io::{self, SeekFrom, Read, Write, Seek, BufRead, Error, ErrorKind};
-use fmt;
-use mem;
-use string::String;
-use vec::Vec;
+#[cfg(feature="alloc")] use alloc::boxed::Box;
+use core::cmp;
+use io::{self, SeekFrom, Read, Write, Seek, Error, ErrorKind};
+#[cfg(feature="collections")] use io::BufRead;
+use core::fmt;
+use core::mem;
+#[cfg(feature="collections")] use collections::string::String;
+#[cfg(feature="collections")] use collections::vec::Vec;
 
 // =============================================================================
 // Forwarding implementations
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, R: Read + ?Sized> Read for &'a mut R {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         (**self).read(buf)
     }
 
+    #[cfg(feature="collections")]
     #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         (**self).read_to_end(buf)
     }
 
+    #[cfg(feature="collections")]
     #[inline]
     fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
         (**self).read_to_string(buf)
@@ -41,7 +43,6 @@ impl<'a, R: Read + ?Sized> Read for &'a mut R {
         (**self).read_exact(buf)
     }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, W: Write + ?Sized> Write for &'a mut W {
     #[inline]
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }
@@ -59,12 +60,11 @@ impl<'a, W: Write + ?Sized> Write for &'a mut W {
         (**self).write_fmt(fmt)
     }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, S: Seek + ?Sized> Seek for &'a mut S {
     #[inline]
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<'a, B: BufRead + ?Sized> BufRead for &'a mut B {
     #[inline]
     fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }
@@ -83,18 +83,20 @@ impl<'a, B: BufRead + ?Sized> BufRead for &'a mut B {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="alloc")]
 impl<R: Read + ?Sized> Read for Box<R> {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         (**self).read(buf)
     }
 
+    #[cfg(feature="collections")]
     #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         (**self).read_to_end(buf)
     }
 
+    #[cfg(feature="collections")]
     #[inline]
     fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
         (**self).read_to_string(buf)
@@ -105,7 +107,7 @@ impl<R: Read + ?Sized> Read for Box<R> {
         (**self).read_exact(buf)
     }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="alloc")]
 impl<W: Write + ?Sized> Write for Box<W> {
     #[inline]
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { (**self).write(buf) }
@@ -123,12 +125,12 @@ impl<W: Write + ?Sized> Write for Box<W> {
         (**self).write_fmt(fmt)
     }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="alloc")]
 impl<S: Seek + ?Sized> Seek for Box<S> {
     #[inline]
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { (**self).seek(pos) }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<B: BufRead + ?Sized> BufRead for Box<B> {
     #[inline]
     fn fill_buf(&mut self) -> io::Result<&[u8]> { (**self).fill_buf() }
@@ -150,7 +152,6 @@ impl<B: BufRead + ?Sized> BufRead for Box<B> {
 // =============================================================================
 // In-memory buffer implementations
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> Read for &'a [u8] {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
@@ -174,7 +175,7 @@ impl<'a> Read for &'a [u8] {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<'a> BufRead for &'a [u8] {
     #[inline]
     fn fill_buf(&mut self) -> io::Result<&[u8]> { Ok(*self) }
@@ -183,7 +184,6 @@ impl<'a> BufRead for &'a [u8] {
     fn consume(&mut self, amt: usize) { *self = &self[amt..]; }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> Write for &'a mut [u8] {
     #[inline]
     fn write(&mut self, data: &[u8]) -> io::Result<usize> {
@@ -207,7 +207,7 @@ impl<'a> Write for &'a mut [u8] {
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl Write for Vec<u8> {
     #[inline]
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
diff --git a/memchr.rs b/memchr.rs
index 1d97611..110cfac 100644
--- a/memchr.rs
+++ b/memchr.rs
@@ -11,103 +11,12 @@
 // Original implementation taken from rust-memchr
 // Copyright 2015 Andrew Gallant, bluss and Nicolas Koch
 
-
-
-/// A safe interface to `memchr`.
-///
-/// Returns the index corresponding to the first occurrence of `needle` in
-/// `haystack`, or `None` if one is not found.
-///
-/// memchr reduces to super-optimized machine code at around an order of
-/// magnitude faster than `haystack.iter().position(|&b| b == needle)`.
-/// (See benchmarks.)
-///
-/// # Example
-///
-/// This shows how to find the first position of a byte in a byte string.
-///
-/// ```rust,ignore
-/// use memchr::memchr;
-///
-/// let haystack = b"the quick brown fox";
-/// assert_eq!(memchr(b'k', haystack), Some(8));
-/// ```
-pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
-    // libc memchr
-    #[cfg(not(target_os = "windows"))]
-    fn memchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> {
-        use libc;
-
-        let p = unsafe {
-            libc::memchr(
-                haystack.as_ptr() as *const libc::c_void,
-                needle as libc::c_int,
-                haystack.len() as libc::size_t)
-        };
-        if p.is_null() {
-            None
-        } else {
-            Some(p as usize - (haystack.as_ptr() as usize))
-        }
-    }
-
-    // use fallback on windows, since it's faster
-    #[cfg(target_os = "windows")]
-    fn memchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> {
-        fallback::memchr(needle, haystack)
-    }
-
-    memchr_specific(needle, haystack)
-}
-
-/// A safe interface to `memrchr`.
-///
-/// Returns the index corresponding to the last occurrence of `needle` in
-/// `haystack`, or `None` if one is not found.
-///
-/// # Example
-///
-/// This shows how to find the last position of a byte in a byte string.
-///
-/// ```rust,ignore
-/// use memchr::memrchr;
-///
-/// let haystack = b"the quick brown fox";
-/// assert_eq!(memrchr(b'o', haystack), Some(17));
-/// ```
-pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> {
-
-    #[cfg(target_os = "linux")]
-    fn memrchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> {
-        use libc;
-
-        // GNU's memrchr() will - unlike memchr() - error if haystack is empty.
-        if haystack.is_empty() {return None}
-        let p = unsafe {
-            libc::memrchr(
-                haystack.as_ptr() as *const libc::c_void,
-                needle as libc::c_int,
-                haystack.len() as libc::size_t)
-        };
-        if p.is_null() {
-            None
-        } else {
-            Some(p as usize - (haystack.as_ptr() as usize))
-        }
-    }
-
-    #[cfg(not(target_os = "linux"))]
-    fn memrchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> {
-        fallback::memrchr(needle, haystack)
-    }
-
-    memrchr_specific(needle, haystack)
-}
+pub use self::fallback::{memchr,memrchr};
 
 #[allow(dead_code)]
 mod fallback {
-    use cmp;
-    use mem;
+    use core::cmp;
+    use core::mem;
 
     const LO_U64: u64 = 0x0101010101010101;
     const HI_U64: u64 = 0x8080808080808080;
diff --git a/mod.rs b/mod.rs
index a058337..d190cba 100644
--- a/mod.rs
+++ b/mod.rs
@@ -247,49 +247,32 @@
 //! contract. The implementation of many of these functions are subject to change over
 //! time and may call fewer or more syscalls/library functions.
 
-#![stable(feature = "rust1", since = "1.0.0")]
-
-use cmp;
+use core::cmp;
 use rustc_unicode::str as core_str;
-use error as std_error;
-use fmt;
-use iter::{Iterator};
-use marker::Sized;
-use ops::{Drop, FnOnce};
-use option::Option::{self, Some, None};
-use result::Result::{Ok, Err};
-use result;
-use string::String;
-use str;
-use vec::Vec;
-use memchr;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::buffered::{BufReader, BufWriter, LineWriter};
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::buffered::IntoInnerError;
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::cursor::Cursor;
-#[stable(feature = "rust1", since = "1.0.0")]
+use core::fmt;
+use core::iter::{Iterator};
+use core::marker::Sized;
+#[cfg(feature="collections")] use core::ops::{Drop, FnOnce};
+use core::option::Option::{self, Some, None};
+use core::result::Result::{Ok, Err};
+use core::result;
+#[cfg(feature="collections")] use collections::string::String;
+use core::str;
+#[cfg(feature="collections")] use collections::vec::Vec;
+mod memchr;
+
+#[cfg(feature="collections")] pub use self::buffered::{BufReader, BufWriter, LineWriter};
+#[cfg(feature="collections")] pub use self::buffered::IntoInnerError;
+#[cfg(feature="collections")] pub use self::cursor::Cursor;
 pub use self::error::{Result, Error, ErrorKind};
-#[stable(feature = "rust1", since = "1.0.0")]
 pub use self::util::{copy, sink, Sink, empty, Empty, repeat, Repeat};
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::stdio::{stdin, stdout, stderr, _print, Stdin, Stdout, Stderr};
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::stdio::{StdoutLock, StderrLock, StdinLock};
-#[unstable(feature = "libstd_io_internals", issue = "0")]
-#[doc(no_inline, hidden)]
-pub use self::stdio::{set_panic, set_print};
 
 pub mod prelude;
-mod buffered;
-mod cursor;
+#[cfg(feature="collections")] mod buffered;
+#[cfg(feature="collections")] mod cursor;
 mod error;
 mod impls;
-mod lazy;
 mod util;
-mod stdio;
 
 const DEFAULT_BUF_SIZE: usize = 8 * 1024;
 
@@ -311,6 +294,7 @@ const DEFAULT_BUF_SIZE: usize = 8 * 1024;
 // 2. We're passing a raw buffer to the function `f`, and it is expected that
 //    the function only *appends* bytes to the buffer. We'll get undefined
 //    behavior if existing bytes are overwritten to have non-UTF-8 data.
+#[cfg(feature="collections")]
 fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize>
     where F: FnOnce(&mut Vec<u8>) -> Result<usize>
 {
@@ -342,6 +326,7 @@ fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize>
 // of data to return. Simply tacking on an extra DEFAULT_BUF_SIZE space every
 // time is 4,500 times (!) slower than this if the reader has a very small
 // amount of data to return.
+#[cfg(feature="collections")]
 fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize> {
     let start_len = buf.len();
     let mut len = start_len;
@@ -424,7 +409,6 @@ fn read_to_end<R: Read + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> Result<usize>
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub trait Read {
     /// Pull some bytes from this source into the specified buffer, returning
     /// how many bytes were read.
@@ -474,7 +458,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
 
     /// Read all bytes until EOF in this source, placing them into `buf`.
@@ -516,7 +499,7 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg(feature="collections")]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
         read_to_end(self, buf)
     }
@@ -554,7 +537,7 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg(feature="collections")]
     fn read_to_string(&mut self, buf: &mut String) -> Result<usize> {
         // Note that we do *not* call `.read_to_end()` here. We are passing
         // `&mut Vec<u8>` (the raw contents of `buf`) into the `read_to_end`
@@ -615,7 +598,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "read_exact", since = "1.6.0")]
     fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<()> {
         while !buf.is_empty() {
             match self.read(buf) {
@@ -667,7 +649,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
 
     /// Transforms this `Read` instance to an `Iterator` over its bytes.
@@ -697,7 +678,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn bytes(self) -> Bytes<Self> where Self: Sized {
         Bytes { inner: self }
     }
@@ -734,10 +714,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[unstable(feature = "io", reason = "the semantics of a partial read/write \
-                                         of where errors happen is currently \
-                                         unclear and may change",
-               issue = "27802")]
     fn chars(self) -> Chars<Self> where Self: Sized {
         Chars { inner: self }
     }
@@ -772,7 +748,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn chain<R: Read>(self, next: R) -> Chain<Self, R> where Self: Sized {
         Chain { first: self, second: next, done_first: false }
     }
@@ -806,7 +781,6 @@ pub trait Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn take(self, limit: u64) -> Take<Self> where Self: Sized {
         Take { inner: self, limit: limit }
     }
@@ -842,7 +816,6 @@ pub trait Read {
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub trait Write {
     /// Write a buffer into this object, returning how many bytes were written.
     ///
@@ -882,7 +855,6 @@ pub trait Write {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn write(&mut self, buf: &[u8]) -> Result<usize>;
 
     /// Flush this output stream, ensuring that all intermediately buffered
@@ -908,7 +880,6 @@ pub trait Write {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn flush(&mut self) -> Result<()>;
 
     /// Attempts to write an entire buffer into this write.
@@ -935,7 +906,6 @@ pub trait Write {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
         while !buf.is_empty() {
             match self.write(buf) {
@@ -987,7 +957,6 @@ pub trait Write {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn write_fmt(&mut self, fmt: fmt::Arguments) -> Result<()> {
         // Create a shim which translates a Write to a fmt::Write and saves
         // off I/O errors. instead of discarding them
@@ -1043,7 +1012,6 @@ pub trait Write {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn by_ref(&mut self) -> &mut Self where Self: Sized { self }
 }
 
@@ -1073,7 +1041,6 @@ pub trait Write {
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub trait Seek {
     /// Seek to an offset, in bytes, in a stream.
     ///
@@ -1087,35 +1054,31 @@ pub trait Seek {
     /// # Errors
     ///
     /// Seeking to a negative offset is considered an error.
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
 }
 
 /// Enumeration of possible methods to seek within an I/O object.
 #[derive(Copy, PartialEq, Eq, Clone, Debug)]
-#[stable(feature = "rust1", since = "1.0.0")]
 pub enum SeekFrom {
     /// Set the offset to the provided number of bytes.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    Start(#[stable(feature = "rust1", since = "1.0.0")] u64),
+    Start(u64),
 
     /// Set the offset to the size of this object plus the specified number of
     /// bytes.
     ///
     /// It is possible to seek beyond the end of an object, but it's an error to
     /// seek before byte 0.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    End(#[stable(feature = "rust1", since = "1.0.0")] i64),
+    End(i64),
 
     /// Set the offset to the current position plus the specified number of
     /// bytes.
     ///
     /// It is possible to seek beyond the end of an object, but it's an error to
     /// seek before byte 0.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    Current(#[stable(feature = "rust1", since = "1.0.0")] i64),
+    Current(i64),
 }
 
+#[cfg(feature="collections")]
 fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>)
                                    -> Result<usize> {
     let mut read = 0;
@@ -1195,7 +1158,7 @@ fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>)
 /// # }
 /// ```
 ///
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 pub trait BufRead: Read {
     /// Fills the internal buffer of this object, returning the buffer contents.
     ///
@@ -1240,7 +1203,6 @@ pub trait BufRead: Read {
     /// // ensure the bytes we worked with aren't returned again later
     /// stdin.consume(length);
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn fill_buf(&mut self) -> Result<&[u8]>;
 
     /// Tells this buffer that `amt` bytes have been consumed from the buffer,
@@ -1262,7 +1224,6 @@ pub trait BufRead: Read {
     ///
     /// Since `consume()` is meant to be used with [`fill_buf()`][fillbuf],
     /// that method's example includes an example of `consume()`.
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn consume(&mut self, amt: usize);
 
     /// Read all bytes into `buf` until the delimiter `byte` is reached.
@@ -1303,7 +1264,6 @@ pub trait BufRead: Read {
     /// # Ok(())
     /// # }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize> {
         read_until(self, byte, buf)
     }
@@ -1351,7 +1311,6 @@ pub trait BufRead: Read {
     ///     buffer.clear();
     /// }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn read_line(&mut self, buf: &mut String) -> Result<usize> {
         // Note that we are not calling the `.read_until` method here, but
         // rather our hardcoded implementation. For more details as to why, see
@@ -1384,7 +1343,6 @@ pub trait BufRead: Read {
     ///     println!("{:?}", content.unwrap());
     /// }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn split(self, byte: u8) -> Split<Self> where Self: Sized {
         Split { buf: self, delim: byte }
     }
@@ -1409,7 +1367,6 @@ pub trait BufRead: Read {
     ///     println!("{}", line.unwrap());
     /// }
     /// ```
-    #[stable(feature = "rust1", since = "1.0.0")]
     fn lines(self) -> Lines<Self> where Self: Sized {
         Lines { buf: self }
     }
@@ -1421,14 +1378,12 @@ pub trait BufRead: Read {
 /// Please see the documentation of `chain()` for more details.
 ///
 /// [chain]: trait.Read.html#method.chain
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Chain<T, U> {
     first: T,
     second: U,
     done_first: bool,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Read, U: Read> Read for Chain<T, U> {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
         if !self.done_first {
@@ -1441,7 +1396,7 @@ impl<T: Read, U: Read> Read for Chain<T, U> {
     }
 }
 
-#[stable(feature = "chain_bufread", since = "1.9.0")]
+#[cfg(feature="collections")]
 impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
     fn fill_buf(&mut self) -> Result<&[u8]> {
         if !self.done_first {
@@ -1468,7 +1423,6 @@ impl<T: BufRead, U: BufRead> BufRead for Chain<T, U> {
 /// Please see the documentation of `take()` for more details.
 ///
 /// [take]: trait.Read.html#method.take
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Take<T> {
     inner: T,
     limit: u64,
@@ -1482,11 +1436,9 @@ impl<T> Take<T> {
     ///
     /// This instance may reach EOF after reading fewer bytes than indicated by
     /// this method if the underlying `Read` instance reaches EOF.
-    #[stable(feature = "rust1", since = "1.0.0")]
     pub fn limit(&self) -> u64 { self.limit }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Read> Read for Take<T> {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
         // Don't call into inner reader at all at EOF because it may still block
@@ -1501,7 +1453,7 @@ impl<T: Read> Read for Take<T> {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<T: BufRead> BufRead for Take<T> {
     fn fill_buf(&mut self) -> Result<&[u8]> {
         // Don't call into inner reader at all at EOF because it may still block
@@ -1528,12 +1480,10 @@ impl<T: BufRead> BufRead for Take<T> {
 /// Please see the documentation of `bytes()` for more details.
 ///
 /// [bytes]: trait.Read.html#method.bytes
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Bytes<R> {
     inner: R,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl<R: Read> Iterator for Bytes<R> {
     type Item = Result<u8>;
 
@@ -1553,8 +1503,6 @@ impl<R: Read> Iterator for Bytes<R> {
 /// Please see the documentation of `chars()` for more details.
 ///
 /// [chars]: trait.Read.html#method.chars
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
 pub struct Chars<R> {
     inner: R,
 }
@@ -1562,8 +1510,6 @@ pub struct Chars<R> {
 /// An enumeration of possible errors that can be generated from the `Chars`
 /// adapter.
 #[derive(Debug)]
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
 pub enum CharsError {
     /// Variant representing that the underlying stream was read successfully
     /// but it did not contain valid utf8 data.
@@ -1573,8 +1519,6 @@ pub enum CharsError {
     Other(Error),
 }
 
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
 impl<R: Read> Iterator for Chars<R> {
     type Item = result::Result<char, CharsError>;
 
@@ -1606,25 +1550,6 @@ impl<R: Read> Iterator for Chars<R> {
     }
 }
 
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
-impl std_error::Error for CharsError {
-    fn description(&self) -> &str {
-        match *self {
-            CharsError::NotUtf8 => "invalid utf8 encoding",
-            CharsError::Other(ref e) => std_error::Error::description(e),
-        }
-    }
-    fn cause(&self) -> Option<&std_error::Error> {
-        match *self {
-            CharsError::NotUtf8 => None,
-            CharsError::Other(ref e) => e.cause(),
-        }
-    }
-}
-
-#[unstable(feature = "io", reason = "awaiting stability of Read::chars",
-           issue = "27802")]
 impl fmt::Display for CharsError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
@@ -1643,13 +1568,13 @@ impl fmt::Display for CharsError {
 /// `BufRead`. Please see the documentation of `split()` for more details.
 ///
 /// [split]: trait.BufRead.html#method.split
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 pub struct Split<B> {
     buf: B,
     delim: u8,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<B: BufRead> Iterator for Split<B> {
     type Item = Result<Vec<u8>>;
 
@@ -1674,12 +1599,12 @@ impl<B: BufRead> Iterator for Split<B> {
 /// `BufRead`. Please see the documentation of `lines()` for more details.
 ///
 /// [lines]: trait.BufRead.html#method.lines
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 pub struct Lines<B> {
     buf: B,
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl<B: BufRead> Iterator for Lines<B> {
     type Item = Result<String>;
 
diff --git a/prelude.rs b/prelude.rs
index 8772d0f..49d66c9 100644
--- a/prelude.rs
+++ b/prelude.rs
@@ -18,7 +18,8 @@
 //! use std::io::prelude::*;
 //! ```
 
-#![stable(feature = "rust1", since = "1.0.0")]
+pub use super::{Read, Write, Seek};
+#[cfg(feature="collections")] pub use super::BufRead;
 
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use super::{Read, Write, BufRead, Seek};
+#[cfg(feature="collections")] pub use alloc::boxed::Box;
+#[cfg(feature="collections")] pub use collections::vec::Vec;
diff --git a/util.rs b/util.rs
index 2815c01..1edcae5 100644
--- a/util.rs
+++ b/util.rs
@@ -10,7 +10,8 @@
 
 #![allow(missing_copy_implementations)]
 
-use io::{self, Read, Write, ErrorKind, BufRead};
+use io::{self, Read, Write, ErrorKind};
+#[cfg(feature="collections")] use io::BufRead;
 
 /// Copies the entire contents of a reader into a writer.
 ///
@@ -42,7 +43,6 @@ use io::{self, Read, Write, ErrorKind, BufRead};
 /// # Ok(())
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> io::Result<u64>
     where R: Read, W: Write
 {
@@ -66,7 +66,6 @@ pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> io::Result<
 /// the documentation of `empty()` for more details.
 ///
 /// [empty]: fn.empty.html
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Empty { _priv: () }
 
 /// Constructs a new handle to an empty reader.
@@ -87,14 +86,12 @@ pub struct Empty { _priv: () }
 /// # Ok(buffer)
 /// # }
 /// ```
-#[stable(feature = "rust1", since = "1.0.0")]
 pub fn empty() -> Empty { Empty { _priv: () } }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl Read for Empty {
     fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> { Ok(0) }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(feature="collections")]
 impl BufRead for Empty {
     fn fill_buf(&mut self) -> io::Result<&[u8]> { Ok(&[]) }
     fn consume(&mut self, _n: usize) {}
@@ -106,17 +103,14 @@ impl BufRead for Empty {
 /// see the documentation of `repeat()` for more details.
 ///
 /// [repeat]: fn.repeat.html
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Repeat { byte: u8 }
 
 /// Creates an instance of a reader that infinitely repeats one byte.
 ///
 /// All reads from this reader will succeed by filling the specified buffer with
 /// the given byte.
-#[stable(feature = "rust1", since = "1.0.0")]
 pub fn repeat(byte: u8) -> Repeat { Repeat { byte: byte } }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl Read for Repeat {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         for slot in &mut *buf {
@@ -132,17 +126,14 @@ impl Read for Repeat {
 /// see the documentation of `sink()` for more details.
 ///
 /// [sink]: fn.sink.html
-#[stable(feature = "rust1", since = "1.0.0")]
 pub struct Sink { _priv: () }
 
 /// Creates an instance of a writer which will successfully consume all data.
 ///
 /// All calls to `write` on the returned instance will return `Ok(buf.len())`
 /// and the contents of the buffer will not be inspected.
-#[stable(feature = "rust1", since = "1.0.0")]
 pub fn sink() -> Sink { Sink { _priv: () } }
 
-#[stable(feature = "rust1", since = "1.0.0")]
 impl Write for Sink {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> { Ok(buf.len()) }
     fn flush(&mut self) -> io::Result<()> { Ok(()) }