On at least
one occasion they have been known to try to trace device memory that
could not safely be read in the manner the GC wanted to read it.
<P>
It is usually safer to walk the dynamic linker data structure, especially
if the linker exports an interface to do so.  But beware of poorly documented
locking behavior in this case.
<H2>Incremental GC support</h2>
For incremental and generational collection to work, <TT>os_dep.c</tt>
must contain a suitable "virtual dirty bit" implementation, which
allows the