Warn that platform-specific behavior may change

Author: sourcefrog

library/std/src/fs.rs

@@ -1739,7 +1739,7 @@ pub fn rename<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> io::Result<()>
 ///
 /// On MacOS, this function corresponds to `fclonefileat` and `fcopyfile`.
 ///
-/// Note that, this [may change in the future][changes].
+/// Note that platform-specific behavior [may change in the future][changes].
 ///
 /// [changes]: io#platform-specific-behavior
 ///

library/std/src/io/copy.rs

@@ -45,6 +45,10 @@ use crate::mem::MaybeUninit;
 /// On Linux (including Android), this function uses `copy_file_range(2)`,
 /// `sendfile(2)` or `splice(2)` syscalls to move data directly between file
 /// descriptors if possible.
+///
+/// Note that platform-specific behavior [may change in the future][changes].
+///
+/// [changes]: crate::io#platform-specific-behavior
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
 where