diff -r 5ac19bd3a1e2 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/memory/FileMapInfo.java
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/memory/FileMapInfo.java	Thu Mar 26 10:14:52 2020 -0700
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/memory/FileMapInfo.java	Fri Apr 10 17:36:40 2020 -0700
@@ -149,6 +149,9 @@
     }
 
     public boolean inCopiedVtableSpace(Address vptrAddress) {
+      if (vptrAddress == null) {
+	return false;
+      }
       if (vptrAddress.greaterThan(mcRegionBaseAddress) &&
           vptrAddress.lessThanOrEqual(mcRegionEndAddress)) {
         return true;
diff -r 5ac19bd3a1e2 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Metadata.java
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Metadata.java	Thu Mar 26 10:14:52 2020 -0700
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Metadata.java	Fri Apr 10 17:36:40 2020 -0700
@@ -71,6 +71,7 @@
   }
 
   public static Metadata instantiateWrapperFor(Address addr) {
+      System.err.println("instantiateWrapperFor:" + addr);
     return metadataConstructor.instantiateWrapperFor(addr);
   }
 
diff -r 5ac19bd3a1e2 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java	Thu Mar 26 10:14:52 2020 -0700
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Oop.java	Fri Apr 10 17:36:40 2020 -0700
@@ -190,13 +190,13 @@
   }
 
   public void printRawOn(PrintStream tty) {
-    tty.print("Dumping raw memory for ");
-    printValueOn(tty);
-    tty.println();
+    //tty.print("Dumping raw memory for ");
+    //printValueOn(tty);
+    //tty.println();
     long size = getObjectSize() * 4;
-    for (long i = 0; i < size; i += 4) {
-      long memVal = getHandle().getCIntegerAt(i, 4, true);
-      tty.println(Long.toHexString(memVal));
+    for (long i = 0; i < size; i += 8) {
+      long memVal = getHandle().getCIntegerAt(i, 8, true);
+      tty.format("@%3d: 0x%16x\n", i, memVal);
     }
   }
 
diff -r 5ac19bd3a1e2 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/types/basic/BasicTypeDataBase.java
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/types/basic/BasicTypeDataBase.java	Thu Mar 26 10:14:52 2020 -0700
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/types/basic/BasicTypeDataBase.java	Fri Apr 10 17:36:40 2020 -0700
@@ -296,6 +296,10 @@
 
     Address loc1 = addr.getAddressAt(0);
 
+    if (loc1 == null) {
+	System.err.println(addr.getClass() + "/" + Long.toHexString(addr.asLongValue()) + "/" + addr);
+    }
+
     if (VM.getVM().isSharingEnabled()) {
       // Check if the value falls in the _md_region
       FileMapInfo cdsFileMapInfo = VM.getVM().getFileMapInfo();
diff -r 5ac19bd3a1e2 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java
--- a/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java	Thu Mar 26 10:14:52 2020 -0700
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java	Fri Apr 10 17:36:40 2020 -0700
@@ -610,6 +610,8 @@
     }
 
     protected void writeClass(Instance instance) throws IOException {
+	System.err.println("writeClass: " + instance);
+	instance.printRawOn(System.err);
         Klass reflectedKlass = java_lang_Class.asKlass(instance);
         // dump instance record only for primitive type Class objects.
         // all other Class objects are covered by writeClassDumpRecords.