8021897: EXCEPTION_ACCESS_VIOLATION on debugging String.contentEquals()

Reviewed-by: alanb, sspitsyn

src/share/back/outStream.c

@@ -298,17 +298,15 @@ jdwpError
 outStream_writeString(PacketOutputStream *stream, char *string)
 {
     jdwpError error;
-    jint      length;
+    jint      length = string != NULL ? (int)strlen(string) : 0;
 
     /* Options utf8=y/n controls if we want Standard UTF-8 or Modified */
     if ( gdata->modifiedUtf8 ) {
-        length = (int)strlen(string);
         (void)outStream_writeInt(stream, length);
         error = writeBytes(stream, (jbyte *)string, length);
     } else {
         jint      new_length;
 
-        length = (int)strlen(string);
         new_length = (gdata->npt->utf8mToUtf8sLength)
                             (gdata->npt->utf, (jbyte*)string, length);
         if ( new_length == length ) {

test/com/sun/jdi/GetUninitializedStringValue.java

+/*
+ * 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 8021897
+ *  @summary Test getting the value for an uninitialized String object
+ *
+ *  @author Staffan Larsen
+ *
+ *  @run build TestScaffold VMConnection TargetListener TargetAdapter
+ *  @run compile -g GetUninitializedStringValue.java
+ *  @run main GetUninitializedStringValue
+ */
+import com.sun.jdi.ReferenceType;
+import com.sun.jdi.StackFrame;
+import com.sun.jdi.StringReference;
+import com.sun.jdi.ThreadReference;
+import com.sun.jdi.event.BreakpointEvent;
+
+ /********** target program **********/
+
+class GetUninitializedStringValueTarg {
+    public static void main(String[] args) {
+        new String("foo");
+        System.out.println("Goodbye from GetUninitializedStringValueTarg!");
+    }
+}
+
+ /********** test program **********/
+
+public class GetUninitializedStringValue extends TestScaffold {
+    ReferenceType targetClass;
+    ThreadReference mainThread;
+
+    GetUninitializedStringValue (String args[]) {
+        super(args);
+    }
+
+    public static void main(String[] args)
+        throws Exception
+    {
+        new GetUninitializedStringValue (args).startTests();
+    }
+
+    /********** test core **********/
+
+    protected void runTests()
+        throws Exception
+    {
+        /*
+         * Run to String.<init>
+         */
+        startUp("GetUninitializedStringValueTarg");
+        BreakpointEvent bpe = resumeTo("java.lang.String", "<init>", "(Ljava/lang/String;)V");
+
+        /*
+         * We've arrived. Look at 'this' - it will be uninitialized (the value field will not be set yet).
+         */
+        StackFrame frame = bpe.thread().frame(0);
+        StringReference sr = (StringReference)frame.thisObject();
+        if (!sr.value().equals("")) {
+            throw new Exception("Unexpected value for the uninitialized String");
+        }
+
+        /*
+         * resume the target listening for events
+         */
+        listenUntilVMDisconnect();
+    }
+}