That passing of threads between languages is highly uncommon (because many things could fail and make you crash / slow along the way and because if your language can create threads then it likely already has C-like performance so you will not introduce parallel libraries written in another language for performance reasons).
Anyways, it is cool if it's stable and works well. I guess there's a use case for such feature, even if it sounds strange to an outsider.
I understand Julia is much more dynamic language. But Java JNI can do this too. You have to attach the thread manually, and take care of pinned references.
Are there any safety reasons for it or is it just a sign of its age?
That's correct. As you said elsewhere, lot of it pins down (!) to design of Java. There's direct byte buffer, but you have to architect your code around nio APIs to utilize it.
But we were talking about working with native threads.
i know my usage of the word "just" might suggest otherwise but i am not trying to deminish this feat. i use common lisp for scientific work and whenever i hear about something cool in another language i ask myself can i do this with my toolset. this is the reason i am asking this.
ECL is not a rewrite of some THE compiler, it is a whole implementation. This actually goes toward your point that Julia cant do this because the language is not seperate from its compiler, but it is not because julia is more complicated than common lisp
Common Lisp has been called many things, rarely simple. Its spec is over 1000 pages
[0] https://ecl.common-lisp.dev/static/manual/Native-threads.htm...