MCL ephemeral GC implementation

[gadbois@mcc.com (David Gadbois)]

A while back an MCL developer mentioned to me that the MCL EGC used
page-level read or write protections to trap memory references.  I am
now working on an application (not in MCL, sigh) that could make good
use of page-level protections.  If I understood the developer correctly,
is there an exported Mac OS interface to the page protection bits, and,
if so, is there any documentation on it?

Thanks,
--David Gadbois