From 5eaa7c2d7df58f186015a40778ea888428d008e8 Mon Sep 17 00:00:00 2001
From: Scott Olson <scott@solson.me>
Date: Thu, 9 Feb 2017 03:38:52 -0800
Subject: [PATCH] Fix unaligned load in librustc_metadata::index.

---
 src/librustc_metadata/index.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/librustc_metadata/index.rs b/src/librustc_metadata/index.rs
index 5b52b268849..db9fc870fa8 100644
--- a/src/librustc_metadata/index.rs
+++ b/src/librustc_metadata/index.rs
@@ -96,9 +96,17 @@ impl<'tcx> LazySeq<Index> {
 }
 
 #[repr(packed)]
-#[derive(Copy, Clone)]
+#[derive(Copy)]
 struct Unaligned<T>(T);
 
+// The derived Clone impl is unsafe for this packed struct since it needs to pass a reference to
+// the field to `T::clone`, but this reference may not be properly aligned.
+impl<T: Copy> Clone for Unaligned<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
 impl<T> Unaligned<T> {
     fn get(self) -> T { self.0 }
 }