Finalizers are not called on thread exit

[endragor]

When a thread exits, Nim simply deallocates GC heap without running finalizers. This results in resource leaking if the finalizers are supposed to free some foreign resources.

Finalizers must be called when:

1. A thread exits.
2. tearDownForeignThreadGc is called.

[Araq]

This is possible via deallocHeap.

[timotheecour]

@Araq wait but why wouldn't it be by default called automatically, eg when thread exits?

[Araq]

Days have only 24 hours and finalizers are "old runtime" cruft, my focus is on ARC that doesn't have this problem.

[endragor]

I guess the question was: isn't fixing this a matter of replacing deallocOsPages with deallocHeap(allowGcAfterwards = false) within the threads module?

This bug causes leaks for those who use threads, and it's not obvious you should call deallocHeap on your own. Even if you don't use finalizers, you may use a library that implements them, which makes the issue even more subtle.

[Araq]

Fine...