200 };

   201 

   202 // A version of ObjectClosure that is expected to be robust

   203 // in the face of possibly uninitialized objects.

   204 class ObjectClosureCareful : public ObjectClosure {

   205  public:

   206   virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;

   207   virtual size_t do_object_careful(oop p) = 0;

   208 };

   209 

   210 // The following are used in CompactibleFreeListSpace and

   211 // ConcurrentMarkSweepGeneration.

   212 

   213 // Blk closure (abstract class)

   214 class BlkClosure : public StackObj {

   215  public:

   216   virtual size_t do_blk(HeapWord* addr) = 0;

   217 };

   218 

   219 // A version of BlkClosure that is expected to be robust

   220 // in the face of possibly uninitialized objects.

   221 class BlkClosureCareful : public BlkClosure {

   222  public:

   223   size_t do_blk(HeapWord* addr) {

   224     guarantee(false, "call do_blk_careful instead");

   225     return 0;

   226   }

   227   virtual size_t do_blk_careful(HeapWord* addr) = 0;