
to one specific object layout.  Two built-in kinds are uncollectable.
One (<TT>STUBBORN</tt>) is immutable without special precautions.
In spite of that, it is very likely that most C clients of the
collector currently
use at most two kinds: <TT>NORMAL</tt> and <TT>PTRFREE</tt> objects.
The <A HREF="http://gcc.gnu.org/java">gcj</a> runtime also makes
heavy use of a kind (allocated with GC_gcj_malloc) that stores
type information at a known offset in method tables.
<P>
The collector uses a two level allocat