>> I've experimented in the past with making a macro that would generate the
>> appropriate ffi code to create and manage c structs/unions/types.  The
>> challenge was to handle references obtained from accessors to fields
>> containing other structs/union/types within them in such a way that
>> - no copying was necessary, and
>> - the original structure wouldn't be released as long as derived references

>> existed
>
> Anyone know what guile does?  If anything?
>
> -- hendrik

Well, I was interested in how to make it work in Gambit as is.  If we consider modifications to Gambit, there is an easy solution: give foreign objects a 'data' field that holds a user-settable strong reference to a Scheme object.  Then, whenever you need to make sure that object A is not reclaimed while foreign object B is reachable, you just say (foreign-data-set! B A).

Indeed, after having tried hard, my current impression is that the above can't be done in a way that is robust and seamless to the user without modifying Gambit.  I'd be very happy to be proven wrong in this!

I have made a pull request proposing that change:

https://github.com/feeley/gambit/pull/59

but I don't know whether the cost of one extra pointer per foreign object is a showstopper here.

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