Merge #673

673: Fix two memory leaks in crossbeam-skiplist r=taiki-e a=sticnarf

Closes #671. Closes #672.

The first one is like a6de0ca, but the previous commit missed fixing `RefRange`.

The second problem is that `remove` increases the ref count but not returning the entry when the tower is not marked by the current thread. So the leak should be fixed if we always return the entry once the ref count is increased.

Co-authored-by: Yilin Chen <[email protected]>

crossbeam-skiplist/src/base.rs

@@ -1123,9 +1123,8 @@ where
                             break;
                         }
                     }
-
-                    return Some(entry);
                 }
+                return Some(entry);
             }
         }
     }
@@ -1893,7 +1892,13 @@ where
     pub fn next(&mut self, guard: &Guard) -> Option<RefEntry<'a, K, V>> {
         self.parent.check_guard(guard);
         self.head = match self.head {
-            Some(ref e) => e.next(guard),
+            Some(ref e) => {
+                let next_head = e.next(guard);
+                unsafe {
+                    e.node.decrement(guard);
+                }
+                next_head
+            }
             None => try_pin_loop(|| self.parent.lower_bound(self.range.start_bound(), guard)),
         };
         let mut finished = false;
@@ -1904,6 +1909,9 @@ where
             };
             if !below_upper_bound(&bound, h.key().borrow()) {
                 finished = true;
+                unsafe {
+                    h.node.decrement(guard);
+                }
             }
         }
         if finished {
@@ -1917,7 +1925,13 @@ where
     pub fn next_back(&mut self, guard: &Guard) -> Option<RefEntry<'a, K, V>> {
         self.parent.check_guard(guard);
         self.tail = match self.tail {
-            Some(ref e) => e.prev(guard),
+            Some(ref e) => {
+                let next_tail = e.prev(guard);
+                unsafe {
+                    e.node.decrement(guard);
+                }
+                next_tail
+            }
             None => try_pin_loop(|| self.parent.upper_bound(self.range.start_bound(), guard)),
         };
         let mut finished = false;
@@ -1928,6 +1942,9 @@ where
             };
             if !above_lower_bound(&bound, t.key().borrow()) {
                 finished = true;
+                unsafe {
+                    t.node.decrement(guard);
+                }
             }
         }
         if finished {