[RFA/JDWP] Fix ReferenceType.ClassLoader

[Kyle Galloway <kgallowa at redhat dot com>]

Whenever this operation was attempted with a class loaded by the boot 
class loader, the null value would crash the communication thread 
causing the VM to stop responding to debugger commands.  This patch, the 
contents of which are already in the reference implementation in 
Classpath, properly returns NullObjectIds which avoids the crash and 
allows the debugger to continue correctly.  It also will correctly 
return a NullObjectId if get is called with id = 0.

ChangeLog
2007-04-11  Kyle Galloway  <kgallowa@redhat.com>

   * gnu/classpath/jdwp/VMIdManager.java (getObjectId): Deal with null 
objects.
   (get): Deal with ObjectId of 0.

Questions/comments/concerns?

Thanks,
Kyle

Index: gnu/classpath/jdwp/VMIdManager.java
===================================================================
--- gnu/classpath/jdwp/VMIdManager.java	(revision 123715)
+++ gnu/classpath/jdwp/VMIdManager.java	(working copy)
@@ -1,7 +1,7 @@
 /* VMIdManager.java -- A reference/example implementation of a manager for
    JDWP object/reference type IDs
 
-   Copyright (C) 2005, 2006 Free Software Foundation
+   Copyright (C) 2005, 2006, 2007 Free Software Foundation
 
 This file is part of GNU Classpath.
 
@@ -337,6 +337,10 @@
    */
   public ObjectId getObjectId (Object theObject)
   {
+    // Special case: null object.
+    if (theObject == null)
+      return new NullObjectId ();
+	  
     ReferenceKey ref = new ReferenceKey (theObject, _refQueue);
     ObjectId id = (ObjectId) _oidTable.get (ref);
     if (id == null)
@@ -364,6 +368,10 @@
   public ObjectId get (long id)
     throws InvalidObjectException
   {
+    // Special case: null object id.
+    if (id == 0)
+      return new NullObjectId ();
+    
     ObjectId oid = (ObjectId) _idTable.get (new Long (id));
     if (oid == null)
       throw new InvalidObjectException (id);