[Gd-hackers] Gwydion Dylan on MacOS X

[Thomas Christian Chust]

Bruce Hoult wrote:

> [...] Because the design in Boehm is to by default run
> finalizers synchronously from inside the garbage collector, *any*
> memory allocation call can (and will, one day) run finalizers.  If
> you're not incredibly careful in maintaining your cleanup list then
> this will eventually cause  corruption when finalizers are run
> removing things from that list in the middle of other code adding
> things to the list. [...]

Hello,

as far as I can see, there are two solutions to this problem:

  1) Create a list yourself which you update from the registered
     finalization functions with some mechanism like conditional-update!
     (as you said, locking data structures is not an option) and drain
     this list from a separate thread or from some kind of program main
     event loop -- this is what OpenDylan does, because the interface
     for the runtime is then uniform no matter whether MPS or the
     Boehm-Demers-Weiser collector are used.

  2) Set GC_finalize_on_demand = 1 and let the Boehm-Demers-Weiser
     collector maintain the finalization list for you. Then call
     GC_run_finalizers from a separate thread or from some kind of
     program main event loop to drain the list -- this is what my
     little library does.

Of course the automatic finalization thread cannot be enabled in single
threaded Dylan, so you have to call drain-finalization-queue manually
somewhere in your program -- presumably from the main loop of a GUI
application or in the initialization method of certain objects.

But this approach should be quite transparent also when debugging your
program.


cu,
Thomas