7105883: JDWP: agent crash if there exists a ThreadGroup with null name

Reviewed-by: sla, jbachorik

jdk/src/share/back/ThreadGroupReferenceImpl.c

@@ -47,7 +47,7 @@ name(PacketInputStream *in, PacketOutputStream *out)
 
         (void)memset(&info, 0, sizeof(info));
         threadGroupInfo(group, &info);
-        (void)outStream_writeString(out, info.name);
+        (void)outStream_writeString(out, info.name == NULL ? "" : info.name);
         if ( info.name != NULL )
             jvmtiDeallocate(info.name);
 

jdk/test/com/sun/jdi/NullThreadGroupNameTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2013 Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ *  @test
+ *  @bug 7105883
+ *  @summary Ensure that JDWP doesn't crash with a null thread group name
+ *
+ *  @run build TestScaffold VMConnection TargetListener TargetAdapter
+ *  @run main NullThreadGroupNameTest
+ */
+import com.sun.jdi.*;
+import com.sun.jdi.connect.*;
+import com.sun.jdi.event.*;
+import com.sun.jdi.request.*;
+import com.sun.jdi.VMDisconnectedException;
+import java.util.concurrent.CountDownLatch;
+import java.util.*;
+
+class DebugTarget {
+    public final static String DEBUG_THREAD_NAME = "DebugThread";
+
+    public static void main(String[] args) throws Exception {
+        DebugThread thread = new DebugThread();
+        thread.start();
+        thread.runningLatch.await();
+        breakpointHere();
+        thread.breakpointLatch.countDown();
+    }
+
+    public static void breakpointHere() {
+        System.out.println("Breakpoint finished!");
+    }
+
+    static class DebugThread extends Thread {
+        final CountDownLatch runningLatch = new CountDownLatch(1);
+        final CountDownLatch breakpointLatch = new CountDownLatch(1);
+
+        public DebugThread() {
+            super(new ThreadGroup(null), DEBUG_THREAD_NAME);
+        }
+
+        public void run() {
+            runningLatch.countDown();
+            try {
+                breakpointLatch.await();
+            } catch (InterruptedException ie) {
+                ie.printStackTrace();
+            }
+        }
+    }
+}
+
+public class NullThreadGroupNameTest extends TestScaffold {
+
+    NullThreadGroupNameTest(String args[]) {
+        super(args);
+    }
+
+    public static void main(String[] args) throws Exception {
+        new NullThreadGroupNameTest(args).startTests();
+    }
+
+    protected void runTests() throws Exception {
+        startTo("DebugTarget", "breakpointHere", "()V");
+
+        ThreadReference thread = findThread(DebugTarget.DEBUG_THREAD_NAME);
+        assertThreadGroupName(thread.threadGroup(), "");
+
+        listenUntilVMDisconnect();
+    }
+
+    private ThreadReference findThread(String name) {
+        for (ThreadReference thread : vm().allThreads()) {
+            if (name.equals(thread.name())) {
+                return thread;
+            }
+        }
+        throw new NoSuchElementException("Couldn't find " + name);
+    }
+
+    private void assertThreadGroupName(ThreadGroupReference threadGroup, String expectedName) {
+        try {
+            String name = threadGroup.name();
+            if (!expectedName.equals(name)) {
+                throw new AssertionError("Unexpected thread group name '" + name + "'");
+            }
+        } catch (VMDisconnectedException vmde) {
+            throw new AssertionError("Likely JVM crash with null thread group name", vmde);
+        }
+    }
+}