diff -r 0fa4c2b668b9 -r fc1c693e80bb src/share/vm/utilities/nativeCallStack.cpp
--- a/src/share/vm/utilities/nativeCallStack.cpp	Fri Jun 22 01:55:23 2018 -0700
+++ b/src/share/vm/utilities/nativeCallStack.cpp	Mon Jun 25 07:59:51 2018 -0700
@@ -55,6 +55,7 @@
   for (; index < NMT_TrackingStackDepth; index ++) {
     _stack[index] = NULL;
   }
+  _hash_value = 0;
 }
 
 // number of stack frames captured
@@ -69,19 +70,16 @@
 }
 
 // Hash code. Any better algorithm?
-int NativeCallStack::hash() const {
-  long hash_val = _hash_value;
+unsigned int NativeCallStack::hash() const {
+  uintptr_t hash_val = _hash_value;
   if (hash_val == 0) {
-    long pc;
-    int  index;
-    for (index = 0; index < NMT_TrackingStackDepth; index ++) {
-      pc = (long)_stack[index];
-      if (pc == 0) break;
-      hash_val += pc;
+    for (int index = 0; index < NMT_TrackingStackDepth; index++) {
+      if (_stack[index] == NULL) break;
+      hash_val += (uintptr_t)_stack[index];
     }
 
     NativeCallStack* p = const_cast<NativeCallStack*>(this);
-    p->_hash_value = (int)(hash_val & 0xFFFFFFFF);
+    p->_hash_value = (unsigned int)(hash_val & 0xFFFFFFFF);
   }
   return _hash_value;
 }