[kaffe] Object Allocation in the heap

Xu Bac xubacs at hotmail.com
Thu Apr 24 19:54:01 PDT 2003

Hello All,
  I was trying to trace through the life-time of an object: what calls the 
vm makes to allocate an object, and where the object is actually placed 
etc... one thing that puzzles me is this:
  in gc_heap_malloc(), essentially a block (small or large depending on 
size) is removed from the freelist, memset-ted to zero, and returned. but 
from the object data structure in java_lang_Object.h, i thought that the 
object was supposed to look like
   typedef struct Hjava_lang_Object {
     struct _dispatchTable*  dtable;
     struct _iLock*               lock;
     /* Data follows on immediately */
   } Hjava_lang_Object;
and there's a macro in object.h
#define OBJECT_DATA(OBJ) ((void*)((Hjava_lang_Object*)(OBJ)+1))

  so in essence, if we just take a block from the heap, and allocate it with 
just enough memory for the object data, and memset the whole of it to zero, 
then where does the metadata(the dtable and the lock) go? or even 
alternatively, given just a heap block how would i find the metadata for 
that object? i would be very grateful if someone could give me some pointers 

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