--- old/hotspot/src/share/vm/gc_implementation/parNew/parGCAllocBuffer.hpp	2009-08-01 04:10:43.982095514 +0100
+++ new/hotspot/src/share/vm/gc_implementation/parNew/parGCAllocBuffer.hpp	2009-08-01 04:10:43.897123752 +0100
@@ -2,7 +2,7 @@
 #pragma ident "@(#)parGCAllocBuffer.hpp	1.30 07/05/29 09:44:13 JVM"
 #endif
 /*
- * Copyright 2001-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * Copyright 2001-2008 Sun Microsystems, Inc.  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
@@ -44,8 +44,8 @@
   size_t    _allocated;     // in HeapWord units
   size_t    _wasted;        // in HeapWord units
   char tail[32];
-  static const size_t FillerHeaderSize;
-  static const size_t AlignmentReserve;
+  static size_t FillerHeaderSize;
+  static size_t AlignmentReserve;
 
 public:
   // Initializes the buffer to be empty, but with the given "word_sz".
@@ -66,9 +66,8 @@
   // return NULL.
   HeapWord* allocate(size_t word_sz) {
     HeapWord* res = _top;
-    HeapWord* new_top = _top + word_sz;
-    if (new_top <= _end) {
-      _top = new_top;
+    if (pointer_delta(_end, _top) >= word_sz) {
+      _top = _top + word_sz;
       return res;
     } else {
       return NULL;
@@ -78,10 +77,9 @@
   // Undo the last allocation in the buffer, which is required to be of the 
   // "obj" of the given "word_sz".
   void undo_allocation(HeapWord* obj, size_t word_sz) {
-    assert(_top - word_sz >= _bottom
-	   && _top - word_sz == obj,
-	   "Bad undo_allocation");
-    _top = _top - word_sz;
+    assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
+    assert(pointer_delta(_top, obj)     == word_sz, "Bad undo");
+    _top = obj;
   }
 
   // The total (word) size of the buffer, including both allocated and