6691215: (coll) IdentityHashMap.containsValue(null) returns true when null value not present

[Martin Buchholz]

It's a little disconcerting to still keep finding basic correctness bugs in
core Collections classes.

Here's a fix (again demonstrating that the Mother Of All Collections Tests
is not thorough enough):

Review requested from Chris Hegarty, Doug Lea

# HG changeset patch
# User martin
# Date 1208733844 25200
# Node ID fd80580439549ed34473cfa973f34d29f9efd7a6
# Parent  8513593a57f180641d06cf535f1647cb9160f9e0
6691215: (coll) IdentityHashMap.containsValue(null) returns true when
null value not present
Reviewed-by:
Contributed-by: Scott Blum <scottb at google.com>

diff --git a/src/share/classes/java/util/IdentityHashMap.java
b/src/share/classes/java/util/IdentityHashMap.java
--- a/src/share/classes/java/util/IdentityHashMap.java
+++ b/src/share/classes/java/util/IdentityHashMap.java
@@ -188,7 +188,6 @@ public class IdentityHashMap<K,V>
     /**
      * Use NULL_KEY for key if it is null.
      */
-
     private static Object maskNull(Object key) {
         return (key == null ? NULL_KEY : key);
     }
@@ -378,8 +377,8 @@ public class IdentityHashMap<K,V>
      */
     public boolean containsValue(Object value) {
         Object[] tab = table;
-        for (int i = 1; i < tab.length; i+= 2)
-            if (tab[i] == value)
+        for (int i = 1; i < tab.length; i += 2)
+            if (tab[i] == value && tab[i - 1] != null)
                 return true;

         return false;
@@ -905,7 +904,6 @@ public class IdentityHashMap<K,V>
      * view the first time this view is requested.  The view is stateless,
      * so there's no reason to create more than one.
      */
-
     private transient Set<Map.Entry<K,V>> entrySet = null;

     /**
diff --git a/test/java/util/Collection/MOAT.java
b/test/java/util/Collection/MOAT.java
--- a/test/java/util/Collection/MOAT.java
+++ b/test/java/util/Collection/MOAT.java
@@ -25,7 +25,7 @@
  * @test
  * @bug     6207984 6272521 6192552 6269713 6197726 6260652 5073546 4137464
  *          4155650 4216399 4294891 6282555 6318622 6355327 6383475 6420753
- *          6431845 4802633 6570566 6570575 6570631 6570924 6691185
+ *          6431845 4802633 6570566 6570575 6570631 6570924 6691185 6691215
  * @summary Run many tests on many Collection and Map implementations
  * @author  Martin Buchholz
  */
@@ -247,6 +247,13 @@ public class MOAT {
         testEmptySet(m.keySet());
         testEmptySet(m.entrySet());
         testEmptyCollection(m.values());
+
+        try { check(! m.containsValue(null)); }
+        catch (NullPointerException _) { /* OK */ }
+        try { check(! m.containsKey(null)); }
+        catch (NullPointerException _) { /* OK */ }
+        check(! m.containsValue(1));
+        check(! m.containsKey(1));
     }

     private static void testImmutableMap(final Map<Integer,Integer> m) {

Martin

On Sun, Apr 20, 2008 at 3:07 AM, Alan Bateman <Alan.Bateman at sun.com> wrote:
> Joshua Bloch wrote:
>
> >
> > Folks,
> >
> > While we're at it, here's another Collections bug discovered recently by a
> Googler (Scott Blum).  The value of this expression should be false:
> >
> >    new IdentityHashMap().containsValue(null)
> >
> > Unfortunately, it's true.  Looking at the code for containsValue, it's
> obvious what's wrong:
> >
> >    /**
> >     * Tests whether the specified object reference is a value in this
> identity
> >     * hash map.
> >     *
> >     * @param value value whose presence in this map is to be tested
> >     * @return <tt>true</tt> if this map maps one or more keys to the
> >     *         specified object reference
> >     * @see     #containsKey(Object)
> >     */
> >    public boolean containsValue(Object value) {
> >        Object[] tab = table;
> >        for (int i = 1; i < tab.length; i+= 2)
> >            if (tab[i] == value)
> >                return true;
> >
> >        return false;
> >    }
> >
> > Empty entries are masquerading as entries mapping to null.  The fix is
> easy:
> >
> >            if (tab[i] == value)
> >
> > becomes:
> >
> >            if (tab[i] == value && tab[i -1] != null)
> >
> > (Recall that the null key (but not value) is proxied by NULL_KEY.)
> >
> >              Josh
> >
> >
>  I don't see this in the bug database so I've created the following so that
> it doesn't get lost:
>   6691215: (coll) IdentityHashMap.containsValue(null) returns true when null
> value not present
>
>  -Alan.
>