From 9562c01879475a01e3ac5a147bc3724a9b5bd1dc Mon Sep 17 00:00:00 2001
From: DrMeepster <19316085+DrMeepster@users.noreply.github.com>
Date: Tue, 29 Jun 2021 15:13:28 -0700
Subject: [PATCH] add safety comments

---
 library/std/src/io/util.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/library/std/src/io/util.rs b/library/std/src/io/util.rs
index 0d4fd5fedf7..c1300cd67c0 100644
--- a/library/std/src/io/util.rs
+++ b/library/std/src/io/util.rs
@@ -131,12 +131,14 @@ impl Read for Repeat {
     }
 
     fn read_buf(&mut self, buf: &mut ReadBuf<'_>) -> io::Result<()> {
+        // SAFETY: No uninit bytes are being written
         for slot in unsafe { buf.unfilled_mut() } {
             slot.write(self.byte);
         }
 
         let remaining = buf.remaining();
 
+        // SAFETY: the entire unfilled portion of buf has been initialized
         unsafe {
             buf.assume_init(remaining);
         }