rflow.
Each time the stack overflows, an attempt is made to grow the mark stack.
All pieces of the collector that push regions onto the mark stack have to be
careful to ensure forward progress, even in case of repeated mark stack
overflows.  Every mark attempt results in additional marked objects.
<P>
Each mark stack entry is processed by examining all candidate pointers
in the range described by the entry.  If the region has no associated
type information, then this typically requires that each 4-byte alig