5 files changed, 33 insertions, 11 deletions
diff --git a/src/libstd/fs.rs b/src/libstd/fs.rs
index 7bd1adc411a..442a0873ae0 100644
--- a/src/libstd/fs.rs
+++ b/src/libstd/fs.rs
@@ -331,6 +331,7 @@ pub fn read_to_string<P: AsRef<Path>>(path: P) -> io::Result<String> {
 ///
 /// fn main() -> std::io::Result<()> {
 ///     fs::write("foo.txt", b"Lorem ipsum")?;
+///     fs::write("bar.txt", "dolor sit")?;
 ///     Ok(())
 /// }
 /// ```
@@ -1699,8 +1700,8 @@ pub fn read_link<P: AsRef<Path>>(path: P) -> io::Result<PathBuf> {
     fs_imp::readlink(path.as_ref())
 }
 
-/// Returns the canonical form of a path with all intermediate components
-/// normalized and symbolic links resolved.
+/// Returns the canonical, absolute form of a path with all intermediate
+/// components normalized and symbolic links resolved.
 ///
 /// # Platform-specific behavior
 ///
@@ -1708,7 +1709,14 @@ pub fn read_link<P: AsRef<Path>>(path: P) -> io::Result<PathBuf> {
 /// and the `CreateFile` and `GetFinalPathNameByHandle` functions on Windows.
 /// Note that, this [may change in the future][changes].
 ///
+/// On Windows, this converts the path to use [extended length path][path]
+/// syntax, which allows your program to use longer path names, but means you
+/// can only join backslash-delimited paths to it, and it may be incompatible
+/// with other applications (if passed to the application on the command-line,
+/// or written to a file another application may read).
+///
 /// [changes]: ../io/index.html#platform-specific-behavior
+/// [path]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
 ///
 /// # Errors
 ///
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 696711a70d4..86478f0a523 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1460,7 +1460,7 @@ impl<P: AsRef<Path>> iter::Extend<P> for PathBuf {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl fmt::Debug for PathBuf {
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         fmt::Debug::fmt(&**self, formatter)
     }
 }
@@ -2284,8 +2284,8 @@ impl Path {
         fs::symlink_metadata(self)
     }
 
-    /// Returns the canonical form of the path with all intermediate components
-    /// normalized and symbolic links resolved.
+    /// Returns the canonical, absolute form of the path with all intermediate
+    /// components normalized and symbolic links resolved.
     ///
     /// This is an alias to [`fs::canonicalize`].
     ///
diff --git a/src/libstd/sys/redox/syscall/error.rs b/src/libstd/sys/redox/syscall/error.rs
index d8d78d55016..1ef79547431 100644
--- a/src/libstd/sys/redox/syscall/error.rs
+++ b/src/libstd/sys/redox/syscall/error.rs
@@ -48,13 +48,13 @@ impl Error {
 }
 
 impl fmt::Debug for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> result::Result<(), fmt::Error> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(self.text())
     }
 }
 
 impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> result::Result<(), fmt::Error> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str(self.text())
     }
 }
diff --git a/src/libstd/sys/unix/fd.rs b/src/libstd/sys/unix/fd.rs
index 5dafc3251e7..67546d06b4e 100644
--- a/src/libstd/sys/unix/fd.rs
+++ b/src/libstd/sys/unix/fd.rs
@@ -75,8 +75,15 @@ impl FileDesc {
         unsafe fn cvt_pread64(fd: c_int, buf: *mut c_void, count: usize, offset: i64)
             -> io::Result<isize>
         {
+            use convert::TryInto;
             use libc::pread64;
-            cvt(pread64(fd, buf, count, offset as i32))
+            // pread64 on emscripten actually takes a 32 bit offset
+            if let Ok(o) = offset.try_into() {
+                cvt(pread64(fd, buf, count, o))
+            } else {
+                Err(io::Error::new(io::ErrorKind::InvalidInput,
+                                   "cannot pread >2GB"))
+            }
         }
 
         #[cfg(not(any(target_os = "android", target_os = "emscripten")))]
@@ -116,8 +123,15 @@ impl FileDesc {
         unsafe fn cvt_pwrite64(fd: c_int, buf: *const c_void, count: usize, offset: i64)
             -> io::Result<isize>
         {
+            use convert::TryInto;
             use libc::pwrite64;
-            cvt(pwrite64(fd, buf, count, offset as i32))
+            // pwrite64 on emscripten actually takes a 32 bit offset
+            if let Ok(o) = offset.try_into() {
+                cvt(pwrite64(fd, buf, count, o))
+            } else {
+                Err(io::Error::new(io::ErrorKind::InvalidInput,
+                                   "cannot pwrite >2GB"))
+            }
         }
 
         #[cfg(not(any(target_os = "android", target_os = "emscripten")))]
diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs
index fe7e058091e..14a2555adf9 100644
--- a/src/libstd/sys_common/wtf8.rs
+++ b/src/libstd/sys_common/wtf8.rs
@@ -56,7 +56,7 @@ pub struct CodePoint {
 /// Example: `U+1F4A9`
 impl fmt::Debug for CodePoint {
     #[inline]
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         write!(formatter, "U+{:04X}", self.value)
     }
 }
@@ -144,7 +144,7 @@ impl ops::DerefMut for Wtf8Buf {
 /// Example: `"a\u{D800}"` for a string with code points [U+0061, U+D800]
 impl fmt::Debug for Wtf8Buf {
     #[inline]
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         fmt::Debug::fmt(&**self, formatter)
     }
 }