Add a new kind of write barrier, one which has a bit per field; the
mutator that sets the bit will need to add the field's location (the
edge) to a remembered set. Here we just have the fast-path
implementation.
In GC, request mutators to stop before doing anything else; changes the
order of the event listener interface. Also, refactor mmc to look more
like pcc.
* src/gc-ephemeron.c: Use key null-ness as dead ephemeron indicator;
works better with BDW-GC's disappearing link.
* src/bdw.c (gc_heap_ephemeron_trace_epoch): Fix to actually define the
epoch. Whoops!
Quoth gc_inline.h, which makes freelists:
/* Note that for these routines, it is the clients responsibility to */
/* add the extra byte at the end to deal with one-past-the-end pointers.*/
/* In the standard collector configuration, the collector assumes that */
/* such a byte has been added, and hence does not trace the last word */
/* in the resulting object. */
/* This is not an issue if the collector is compiled with */
/* DONT_ADD_BYTE_AT_END, or if GC_all_interior_pointers is not set. */
