From bfda0a0a90bc37f683e99bbff75fbf59abe48991 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 14 Aug 2018 18:51:15 +0200
Subject: [PATCH] add a scary test case

---
 tests/run-pass/transmute_fat.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 tests/run-pass/transmute_fat.rs

diff --git a/tests/run-pass/transmute_fat.rs b/tests/run-pass/transmute_fat.rs
new file mode 100644
index 000000000000..ec887902d054
--- /dev/null
+++ b/tests/run-pass/transmute_fat.rs
@@ -0,0 +1,10 @@
+fn main() {
+    // If we are careful, we can exploit data layout...
+    let raw = unsafe {
+        std::mem::transmute::<&[u8], [usize; 2]>(&[42])
+    };
+    let ptr = raw[0] + raw[1];
+    let ptr = ptr as *const u8;
+    // The pointer is one-past-the end, but we decrement it into bounds before using it
+    assert_eq!(unsafe { *ptr.offset(-1) }, 42);
+}