* libguile/finalizers.h:
* libguile/finalizers.c (scm_i_register_weak_gc_callback): New internal
helper, from weak-set.c.
Relative to the previous weak-set.c version, prefer the
finalizer-based implementation. Fix bug regarding confusion between
scm_before_gc_c_hook and scm_after_gc_hook. Fix bug regarding
referencing weak values outside of the alloc lock.
* libguile/weak-set.c (GC_move_disappearing_link): New stub.
GC_move_disappearing_link is only available in libgc 7.3.
(move_weak_entry): Use the new stub instead of ifdeffery.
(resize_set): Now that we run finalizers from a separate thread or
async, we can keep the lock while reallocating the set vector.
(do_vacuum_weak_set): For the same reason, always lock the set.
Remove implementation of scm_c_register_weak_gc_callback in preference
of the new copy in finalizers.c.
(scm_c_make_weak_set): Use the new scm_i_register_weak_gc_callback.
* libguile/finalizers.c: New excitement! We'll be running finalizers in
threads, if that's available. If it's not available, during early
boot, we can run finalizers in asyncs. This will make it safer to
allocate while holding a mutex.
* libguile/posix.c (scm_fork): Shut down the finalizer thread before
forking.
* libguile/init.c (scm_i_init_guile): Init the async finalizer mechanism
during boot and, if available, initialialize the finalizer thread at
the very end.
* libguile/gc.c (scm_storage_prehistory): Tell libgc we'll be finalizing
on demand.
(scm_gc): Explicitly run finalizers here. If you're calling this
function, you probably want synchronous GC.
