--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Tue Mar 05 15:36:56 2013 -0800
@@ -4111,7 +4111,7 @@
         // bitmap knows by how much we need to move it as it knows its
         // granularity).
         assert(_finger < _region_limit, "invariant");
-        HeapWord* new_finger = _nextMarkBitMap->nextWord(_finger);
+        HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
         // Check if bitmap iteration was aborted while scanning the last object
         if (new_finger >= _region_limit) {
           giveup_current_region();

--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.hpp	Tue Mar 05 15:36:56 2013 -0800
@@ -97,7 +97,6 @@
                                        HeapWord* limit = NULL) const;
 
   // conversion utilities
-  // XXX Fix these so that offsets are size_t's...
   HeapWord* offsetToHeapWord(size_t offset) const {
     return _bmStartWord + (offset << _shifter);
   }
@@ -105,8 +104,13 @@
     return pointer_delta(addr, _bmStartWord) >> _shifter;
   }
   int heapWordDiffToOffsetDiff(size_t diff) const;
-  HeapWord* nextWord(HeapWord* addr) {
-    return offsetToHeapWord(heapWordToOffset(addr) + 1);
+
+  // The argument addr should be the start address of a valid object
+  HeapWord* nextObject(HeapWord* addr) {
+    oop obj = (oop) addr;
+    HeapWord* res =  addr + obj->size();
+    assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
+    return res;
   }
 
   // debugging

--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp	Mon Mar 04 22:39:00 2013 -0800
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp	Tue Mar 05 15:36:56 2013 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2013, Oracle and/or its affiliates. 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
@@ -252,12 +252,10 @@
 
     start_offset = _bm.get_next_one_offset(start_offset, end_offset);
     while (start_offset < end_offset) {
-      HeapWord* obj_addr = offsetToHeapWord(start_offset);
-      oop obj = (oop) obj_addr;
       if (!cl->do_bit(start_offset)) {
         return false;
       }
-      HeapWord* next_addr = MIN2(obj_addr + obj->size(), end_addr);
+      HeapWord* next_addr = MIN2(nextObject(offsetToHeapWord(start_offset)), end_addr);
       BitMap::idx_t next_offset = heapWordToOffset(next_addr);
       start_offset = _bm.get_next_one_offset(next_offset, end_offset);
     }