SI-8774 Null link fields in mutable hash maps on removal.

(cherry picked from commit 9a24860)
scala · adriaanm · Jan 6, 2017 · Jan 5, 2017 · Jul 21, 2016 · Nov 22, 2016
commit f31745ac9bc5d2fcad1ab52caf4a3b6169c7f9b4
diff --git a/src/library/scala/collection/mutable/HashTable.scala b/src/library/scala/collection/mutable/HashTable.scala
@@ -183,6 +183,7 @@ trait HashTable[A, Entry >: Null <: HashEntry[A, Entry]] extends HashTable.HashU
         table(h) = e.next
         tableSize = tableSize - 1
         nnSizeMapRemove(h)
+        e.next = null
         return e
       } else {
         var e1 = e.next
@@ -194,6 +195,7 @@ trait HashTable[A, Entry >: Null <: HashEntry[A, Entry]] extends HashTable.HashU
           e.next = e1.next
           tableSize = tableSize - 1
           nnSizeMapRemove(h)
+          e1.next = null
           return e1
         }
       }
@@ -227,8 +229,9 @@ trait HashTable[A, Entry >: Null <: HashEntry[A, Entry]] extends HashTable.HashU
     var es        = iterTable(idx)
 
     while (es != null) {
+      val next = es.next // Cache next in case f removes es.
       f(es.asInstanceOf[Entry])
-      es = es.next
+      es = next
 
       while (es == null && idx > 0) {
         idx -= 1

diff --git a/src/library/scala/collection/mutable/LinkedHashMap.scala b/src/library/scala/collection/mutable/LinkedHashMap.scala
@@ -81,6 +81,8 @@ class LinkedHashMap[A, B] extends AbstractMap[A, B]
       else e.earlier.later = e.later
       if (e.later eq null) lastEntry = e.earlier
       else e.later.earlier = e.earlier
+      e.earlier = null // Null references to prevent nepotism
+      e.later = null
       Some(e.value)
     }
   }

diff --git a/src/library/scala/collection/mutable/LinkedHashSet.scala b/src/library/scala/collection/mutable/LinkedHashSet.scala
@@ -73,6 +73,8 @@ class LinkedHashSet[A] extends AbstractSet[A]
       else e.earlier.later = e.later
       if (e.later eq null) lastEntry = e.earlier
       else e.later.earlier = e.earlier
+      e.earlier = null // Null references to prevent nepotism
+      e.later = null
       true
     }
   }