ked
objects.  In this case <TT>GC_objects_are_marked</tt> will simultaneously
be false, so the mark state is advanced to
<LI> <TT>MS_PUSH_UNCOLLECTABLE</tt> indicating that it suffices to push
uncollectable objects, roots, and then mark everything reachable from them.
<TT>Scan_ptr</tt> is advanced through the heap until all uncollectable
objects are pushed, and objects reachable from them are marked.
At that point, the next call to <TT>GC_mark_some</tt> calls
<TT>GC_push_roots</tt> to push the roots.  It th