Update canonicalize docs

src/libstd/fs.rs

@@ -1699,16 +1699,23 @@ 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
 ///
 /// This function currently corresponds to the `realpath` function on Unix
 /// 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
 ///

src/libstd/path.rs

@@ -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`].
     ///