Finalizers: conclusion?

[Alastair Reid]

John Meacham <john at repetae.net> writes:
> here are my canidate suggestions:

> * add a subset of Weak pointers 

Can you spell this out in detail.  What are the functions?  What are
their semantics?

> - or -

> * add addForeignDependency :: ForeignPtr a -> ForeignPtr b -> IO ()

Again, could you spell out the semantics.

> note that breaking these dependencies might be tricky/impossible

This is something I don't understand.  

Why do you have to break dependencies?  Is it to break dependency
cycles?

Also, when do you break dependencies?  e.g., Do C finalizers need a
way to tell Haskell to break a dependency?  Do you manually detect
that some objects have not been collected and speculatively start
breaking dependencies?  If the problem is cycles, would it be helpful
if addForeignDependency detected when it created a cycle and raise an
exception/ set a flag/ etc.


--
Alastair