diff -r 3df2fe7c4451 -r 850fdf70db2b src/share/vm/runtime/globals.hpp
--- a/src/share/vm/runtime/globals.hpp	Fri Jul 25 11:29:03 2008 -0700
+++ b/src/share/vm/runtime/globals.hpp	Mon Jul 28 15:30:23 2008 -0700
@@ -589,9 +589,15 @@
   develop(bool, ZapJNIHandleArea, trueInDebug,                              \
           "Zap freed JNI handle space with 0xFEFEFEFE")                     \
                                                                             \
-  develop(bool, ZapUnusedHeapArea, false,                                   \
+  develop(bool, ZapUnusedHeapArea, trueInDebug,                             \
           "Zap unused heap space with 0xBAADBABE")                          \
                                                                             \
+  develop(bool, TraceZapUnusedHeapArea, false,                              \
+          "Trace zapping of unused heap space")                             \
+                                                                            \
+  develop(bool, CheckZapUnusedHeapArea, false,                              \
+          "Check zapping of unused heap space")                             \
+                                                                            \
   develop(bool, PrintVMMessages, true,                                      \
           "Print vm messages on console")                                   \
                                                                             \