Fixes alloc::io by removing use String instead complex Error parameter.

library/alloc/src/io/buffered/mod.rs

@@ -179,14 +179,6 @@ impl<W> From<IntoInnerError<W>> for Error {
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<W: Send + fmt::Debug> error::Error for IntoInnerError<W> {
-    #[allow(deprecated, deprecated_in_future)]
-    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 {

library/alloc/src/io/error.rs

@@ -74,7 +74,7 @@ enum Repr {
 #[derive(Debug)]
 struct Custom {
     kind: ErrorKind,
-    error: Box<dyn error::Error + Send + Sync>,
+    error: String,
 }
 
 /// A list specifying general categories of I/O error.
@@ -177,6 +177,12 @@ pub enum ErrorKind {
     /// read.
     #[stable(feature = "read_exact", since = "1.6.0")]
     UnexpectedEof,
+
+    /// A marker variant that tells the compiler that users of this enum cannot
+    /// match it exhaustively.
+    #[doc(hidden)]
+    #[stable(feature = "read_exact", since = "1.6.0")]
+    __Nonexhaustive,
 }
 
 impl ErrorKind {
@@ -200,6 +206,7 @@ impl ErrorKind {
             ErrorKind::Interrupted => "operation interrupted",
             ErrorKind::Other => "other os error",
             ErrorKind::UnexpectedEof => "unexpected end of file",
+            _ => "unknown error",
         }
     }
 }
@@ -249,33 +256,15 @@ impl Error {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new<E>(kind: ErrorKind, error: E) -> Error
     where
-        E: Into<Box<dyn error::Error + Send + Sync>>,
+        E: Into<String>,
     {
         Self::_new(kind, error.into())
     }
 
-    fn _new(kind: ErrorKind, error: Box<dyn error::Error + Send + Sync>) -> Error {
+    fn _new(kind: ErrorKind, error: String) -> Error {
         Error { repr: Repr::Custom(Box::new(Custom { kind, 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.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use std::io::Error;
-    ///
-    /// println!("last OS error: {:?}", Error::last_os_error());
-    /// ```
-    #[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.
     ///
     /// # Examples
@@ -372,11 +361,11 @@ impl Error {
     /// }
     /// ```
     #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn get_ref(&self) -> Option<&(dyn error::Error + Send + Sync + 'static)> {
+    pub fn get_ref(&self) -> Option<&String> {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
-            Repr::Custom(ref c) => Some(&*c.error),
+            Repr::Custom(ref c) => Some(&c.error),
         }
     }
 
@@ -443,11 +432,11 @@ impl Error {
     /// }
     /// ```
     #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn get_mut(&mut self) -> Option<&mut (dyn error::Error + Send + Sync + 'static)> {
+    pub fn get_mut(&mut self) -> Option<&mut String> {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
-            Repr::Custom(ref mut c) => Some(&mut *c.error),
+            Repr::Custom(ref mut c) => Some(&mut c.error),
         }
     }
 
@@ -479,7 +468,7 @@ impl Error {
     /// }
     /// ```
     #[stable(feature = "io_error_inner", since = "1.3.0")]
-    pub fn into_inner(self) -> Option<Box<dyn error::Error + Send + Sync>> {
+    pub fn into_inner(self) -> Option<String> {
         match self.repr {
             Repr::Os(..) => None,
             Repr::Simple(..) => None,
@@ -508,7 +497,7 @@ impl 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,
             Repr::Simple(kind) => kind,
         }
@@ -521,8 +510,6 @@ impl fmt::Debug for Repr {
             Repr::Os(code) => fmt
                 .debug_struct("Os")
                 .field("code", &code)
-                .field("kind", &sys::decode_error_kind(code))
-                .field("message", &sys::os::error_string(code))
                 .finish(),
             Repr::Custom(ref c) => fmt::Debug::fmt(&c, fmt),
             Repr::Simple(kind) => fmt.debug_tuple("Kind").field(&kind).finish(),
@@ -535,43 +522,14 @@ 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),
             Repr::Simple(kind) => write!(fmt, "{}", kind.as_str()),
         }
     }
 }
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl error::Error for Error {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        match self.repr {
-            Repr::Os(..) | Repr::Simple(..) => self.kind().as_str(),
-            Repr::Custom(ref c) => c.error.description(),
-        }
-    }
-
-    #[allow(deprecated)]
-    fn cause(&self) -> Option<&dyn error::Error> {
-        match self.repr {
-            Repr::Os(..) => None,
-            Repr::Simple(..) => None,
-            Repr::Custom(ref c) => c.error.cause(),
-        }
-    }
-
-    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
-        match self.repr {
-            Repr::Os(..) => None,
-            Repr::Simple(..) => None,
-            Repr::Custom(ref c) => c.error.source(),
-        }
-    }
-}
-
 fn _assert_error_is_sync_send() {
     fn _is_sync_send<T: Sync + Send>() {}
     _is_sync_send::<Error>();

library/alloc/src/io/mod.rs

@@ -293,7 +293,7 @@ pub mod prelude;
 mod util;
 use crate::{vec::Vec, string::String};
 
-const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+const DEFAULT_BUF_SIZE: usize = 8 * 1024;
 
 struct Guard<'a> {
     buf: &'a mut Vec<u8>,
@@ -1003,7 +1003,10 @@ pub fn read_to_string<R: Read>(reader: &mut R) -> Result<String> {
 /// Windows.
 #[stable(feature = "iovec", since = "1.36.0")]
 #[repr(transparent)]
-pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>);
+pub struct IoSliceMut<'a> {
+    vec: iovec,
+    _p: PhantomData<&'a [u8]>,
+}
 
 #[stable(feature = "iovec-send-sync", since = "1.44.0")]
 unsafe impl<'a> Send for IoSliceMut<'a> {}
@@ -1014,7 +1017,7 @@ unsafe impl<'a> Sync for IoSliceMut<'a> {}
 #[stable(feature = "iovec", since = "1.36.0")]
 impl<'a> fmt::Debug for IoSliceMut<'a> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(self.0.as_slice(), fmt)
+        fmt::Debug::fmt(self.as_slice(), fmt)
     }
 }
 
@@ -1027,7 +1030,13 @@ impl<'a> IoSliceMut<'a> {
     #[stable(feature = "iovec", since = "1.36.0")]
     #[inline]
     pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
-        IoSliceMut(sys::io::IoSliceMut::new(buf))
+        IoSliceMut {
+            vec: iovec {
+                iov_base: buf.as_mut_ptr() as *mut c_void,
+                iov_len: buf.len() as iov_len_t,
+            },
+            _p: PhantomData,
+        }
     }
 
     /// Advance the internal cursor of the slice.
@@ -1080,10 +1089,34 @@ impl<'a> IoSliceMut<'a> {
 
         let bufs = &mut bufs[remove..];
         if !bufs.is_empty() {
-            bufs[0].0.advance(n - accumulated_len)
+            bufs[0].advance_self(n - accumulated_len)
         }
         bufs
     }
+
+    #[inline]
+    fn advance_self(&mut self, n: usize) {
+        if (self.vec.iov_len as usize) < n {
+            panic!("advancing IoSliceMut beyond its length");
+        }
+
+        unsafe {
+            self.vec.iov_len -= n as iov_len_t;
+            self.vec.iov_base = self.vec.iov_base.add(n);
+        }
+    }
+
+    #[inline]
+    fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len as usize) }
+    }
+
+    #[inline]
+    fn as_mut_slice(&mut self) -> &mut [u8] {
+        unsafe {
+            slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len as usize)
+        }
+    }
 }
 
 #[stable(feature = "iovec", since = "1.36.0")]
@@ -1092,15 +1125,15 @@ impl<'a> Deref for IoSliceMut<'a> {
 
     #[inline]
     fn deref(&self) -> &[u8] {
-        self.0.as_slice()
+        self.as_slice()
     }
 }
 
 #[stable(feature = "iovec", since = "1.36.0")]
 impl<'a> DerefMut for IoSliceMut<'a> {
     #[inline]
     fn deref_mut(&mut self) -> &mut [u8] {
-        self.0.as_mut_slice()
+        self.as_mut_slice()
     }
 }
 
@@ -1112,7 +1145,10 @@ impl<'a> DerefMut for IoSliceMut<'a> {
 #[stable(feature = "iovec", since = "1.36.0")]
 #[derive(Copy, Clone)]
 #[repr(transparent)]
-pub struct IoSlice<'a>(sys::io::IoSlice<'a>);
+pub struct IoSlice<'a> {
+    vec: iovec,
+    _p: PhantomData<&'a [u8]>,
+}
 
 #[stable(feature = "iovec-send-sync", since = "1.44.0")]
 unsafe impl<'a> Send for IoSlice<'a> {}
@@ -1123,7 +1159,7 @@ unsafe impl<'a> Sync for IoSlice<'a> {}
 #[stable(feature = "iovec", since = "1.36.0")]
 impl<'a> fmt::Debug for IoSlice<'a> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(self.0.as_slice(), fmt)
+        fmt::Debug::fmt(self.as_slice(), fmt)
     }
 }
 
@@ -1136,7 +1172,13 @@ impl<'a> IoSlice<'a> {
     #[stable(feature = "iovec", since = "1.36.0")]
     #[inline]
     pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
-        IoSlice(sys::io::IoSlice::new(buf))
+        IoSlice {
+            vec: iovec {
+                iov_base: buf.as_ptr() as *mut u8 as *mut c_void,
+                iov_len: buf.len() as iov_len_t,
+            },
+            _p: PhantomData,
+        }
     }
 
     /// Advance the internal cursor of the slice.
@@ -1188,10 +1230,27 @@ impl<'a> IoSlice<'a> {
 
         let bufs = &mut bufs[remove..];
         if !bufs.is_empty() {
-            bufs[0].0.advance(n - accumulated_len)
+            bufs[0].advance_self(n - accumulated_len)
         }
         bufs
     }
+
+    #[inline]
+    fn advance_self(&mut self, n: usize) {
+        if (self.vec.iov_len as usize) < n {
+            panic!("advancing IoSlice beyond its length");
+        }
+
+        unsafe {
+            self.vec.iov_len -= n as iov_len_t;
+            self.vec.iov_base = self.vec.iov_base.add(n);
+        }
+    }
+
+    #[inline]
+    fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len as usize) }
+    }
 }
 
 #[stable(feature = "iovec", since = "1.36.0")]
@@ -1200,7 +1259,7 @@ impl<'a> Deref for IoSlice<'a> {
 
     #[inline]
     fn deref(&self) -> &[u8] {
-        self.0.as_slice()
+        self.as_slice()
     }
 }