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Evaluation
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iterator().remove() is sometimes causing size to be decremented twice,
leading to corrupted internal data structures.
Posted Date : 2007-10-03 08:24:48.0
Here's a simpler variant of the test case:
import java.util.*;
public class Bug6 {
static void remove(Map m, Iterator it) {
int size = m.size();
it.remove();
if (m.size() != size-1)
throw new Error(String.format("Incorrect size!%nmap=%s, size=%d%n",
m.toString(), m.size()));
}
public static void main(String[] args) {
while (true) {
final Map<Object, Object> m
= new IdentityHashMap<Object, Object>(16);
final Random r = new Random();
for (int i = 0; i < 10; i++)
m.put(r.nextInt(100), null);
Iterator it = m.keySet().iterator();
int size = m.size();
for (int j = 0; j < size - 2; j++)
it.next();
remove(m, it);
it.next();
remove(m, it);
}
}
}
Posted Date : 2007-10-03 19:06:34.0
Here's the obvious fix:
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
@@ -1,5 +1,5 @@
/*
- * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * Copyright 2000-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -749,7 +749,6 @@ public class IdentityHashMap<K,V>
expectedModCount = ++modCount;
int deletedSlot = lastReturnedIndex;
lastReturnedIndex = -1;
- size--;
// back up index to revisit new contents after deletion
index = deletedSlot;
indexValid = false;
@@ -781,6 +780,8 @@ public class IdentityHashMap<K,V>
expectedModCount = modCount;
return;
}
+
+ size--;
Object item;
for (int i = nextKeyIndex(d, len); (item = tab[i]) != null;
diff --git a/test/java/util/Map/LockStep.java b/test/java/util/Map/LockStep.java
new file mode 100644
--- /dev/null
+++ b/test/java/util/Map/LockStep.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright 2008 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug 6612102
+ * @summary Test Map implementations for mutual compatibility
+ */
+
+import java.util.*;
+import java.util.concurrent.*;
+
+/**
+ * Based on the strange scenario required to reproduce
+ * (coll) IdentityHashMap.iterator().remove() might decrement size twice
+ *
+ * It would be good to add more "Lockstep-style" tests to this file.
+ */
+public class LockStep {
+ void mapsEqual(Map m1, Map m2) {
+ equal(m1, m2);
+ equal(m2, m1);
+ equal(m1.size(), m2.size());
+ equal(m1.isEmpty(), m2.isEmpty());
+ equal(m1.keySet(), m2.keySet());
+ equal(m2.keySet(), m1.keySet());
+ }
+
+ void mapsEqual(List<Map> maps) {
+ Map first = maps.get(0);
+ for (Map map : maps)
+ mapsEqual(first, map);
+ }
+
+ void put(List<Map> maps, Object key, Object val) {
+ for (Map map : maps)
+ map.put(key, val);
+ mapsEqual(maps);
+ }
+
+ void removeLastTwo(List<Map> maps) {
+ Map first = maps.get(0);
+ int size = first.size();
+ Iterator fit = first.keySet().iterator();
+ for (int j = 0; j < size - 2; j++)
+ fit.next();
+ Object x1 = fit.next();
+ Object x2 = fit.next();
+
+ for (Map map : maps) {
+ Iterator it = map.keySet().iterator();
+ while (it.hasNext()) {
+ Object x = it.next();
+ if (x == x1 || x == x2)
+ it.remove();
+ }
+ }
+ mapsEqual(maps);
+ }
+
+ void remove(Map m, Iterator it) {
+ int size = m.size();
+ it.remove();
+ if (m.size() != size-1)
+ throw new Error(String.format("Incorrect size!%nmap=%s, size=%d%n",
+ m.toString(), m.size()));
+ }
+
+ void test(String[] args) throws Throwable {
+ final int iterations = 100;
+ final Random r = new Random();
+
+ for (int i = 0; i < iterations; i++) {
+ List<Map> maps = Arrays.asList(
+ new Map[] {
+ new IdentityHashMap(11),
+ new HashMap(16),
+ new LinkedHashMap(16),
+ new WeakHashMap(16),
+ new Hashtable(16),
+ new TreeMap(),
+ new ConcurrentHashMap(16),
+ new ConcurrentSkipListMap() });
+
+ for (int j = 0; j < 10; j++)
+ put(maps, r.nextInt(100), r.nextInt(100));
+ removeLastTwo(maps);
+ }
+ }
+
+ //--------------------- Infrastructure ---------------------------
+ volatile int passed = 0, failed = 0;
+ void pass() {passed++;}
+ void fail() {failed++; Thread.dumpStack();}
+ void fail(String msg) {System.err.println(msg); fail();}
+ void unexpected(Throwable t) {failed++; t.printStackTrace();}
+ void check(boolean cond) {if (cond) pass(); else fail();}
+ void equal(Object x, Object y) {
+ if (x == null ? y == null : x.equals(y)) pass();
+ else fail(x + " not equal to " + y);}
+ public static void main(String[] args) throws Throwable {
+ new LockStep().instanceMain(args);}
+ void instanceMain(String[] args) throws Throwable {
+ try {test(args);} catch (Throwable t) {unexpected(t);}
+ System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
+ if (failed > 0) throw new AssertionError("Some tests failed");}
+}
Posted Date : 2008-03-06 23:45:59.0
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