From 7b7c60a369c743170ca6f496ee44ad0750673281 Mon Sep 17 00:00:00 2001
From: Petros Angelatos <petrosagg@gmail.com>
Date: Sun, 20 Feb 2022 12:52:13 +0100
Subject: [PATCH] consolidation: fix UB from mutable pointer aliasing

Running the added testcase under miri without the equality check results
in Undefined Behaviour from creating two mutable references pointing to
the same location.

Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
---
 src/consolidation.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/consolidation.rs b/src/consolidation.rs
index 379d25256..69b5f4570 100644
--- a/src/consolidation.rs
+++ b/src/consolidation.rs
@@ -66,7 +66,7 @@ pub fn consolidate_slice<T: Ord, R: Semigroup>(slice: &mut [(T, R)]) -> usize {
                     offset += 1;
                 }
                 let ptr1 = slice.as_mut_ptr().offset(offset as isize);
-                std::mem::swap(&mut *ptr1, &mut *ptr2);
+                std::ptr::swap(ptr1, ptr2);
             }
         }
     }
@@ -129,7 +129,7 @@ pub fn consolidate_updates_slice<D: Ord, T: Ord, R: Semigroup>(slice: &mut [(D,
                     offset += 1;
                 }
                 let ptr1 = slice.as_mut_ptr().offset(offset as isize);
-                std::mem::swap(&mut *ptr1, &mut *ptr2);
+                std::ptr::swap(ptr1, ptr2);
             }
 
         }
@@ -164,6 +164,10 @@ mod tests {
                 vec![("a", 0), ("b", 0)],
                 vec![],
             ),
+            (
+                vec![("a", 1), ("b", 1)],
+                vec![("a", 1), ("b", 1)],
+            ),
         ];
 
         for (mut input, output) in test_cases {
@@ -192,6 +196,10 @@ mod tests {
                 vec![("a", 1, 0), ("b", 1, 0)],
                 vec![],
             ),
+            (
+                vec![("a", 1, 1), ("b", 2, 1)],
+                vec![("a", 1, 1), ("b", 2, 1)],
+            ),
         ];
 
         for (mut input, output) in test_cases {