On Wed, Feb 28, 2018 at 6:05 AM, A.M. <cis74...@gmail.com> wrote: > On Tuesday, 27 February 2018 19:21:03 UTC-5, Ben Noordhuis wrote: >> >> IIRC, it's a two-pass system: first pass should reset the persistent >> handle, second pass is the real finalizer. Preempting the question of >> why it works that way: I don't know. :-) > > Thanks for the insights. I think I see what you are saying, but even if I > set up the second pass callback, both internal fields within the second > callback are still `NULL`. How can I set up the weak callback to receive > internal fields of the object instance that is being destroyed?
I don't rightly know. We never used this mechanism in Node.js and I don't know if it's still used in Chromium. It might have been an experiment that didn't pan out. V8 still seems to use it internally for a few things (i18n, mostly) so I assume it must still be doing _something_. > I also noticed that the second pass callback is called much less frequent > than the first callback and if the actual clean-up is done in the second > callback, allocations would pile up at a higher rate. From the code it > appears that the second pass callbacks are done only if > `synchronous_second_pass` is set. Can you elaborate how second pass > callbacks are scheduled? >From a background thread, unless `--optimize_for_size` or `--predictable` is set, in which case they run on the foreground thread. > Further to this, my understanding is that in order to process phantom > handles generated by weak callbacks, I need to call `PumpMessageLoop` > periodically. The comment above this function says this: > >> The caller has to make sure that this is called from the right thread. > > What's the "right" thread in this context? If it's the same thread that runs > the script, how can one pump the message loop if the script never returns? > Am I supposed to synchronize with the script thread in v8 callbacks and pump > for messages? The foreground thread. If the script never yields control, you can't pump the message loop. -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
