Languaged bindings involving non-gced memory for languages without guaranteed destructors?

Question

When someone is making bindings from a C library to Java (or any other garbage-collected language without destructors that are guaranteed to run), how do they deal with proper deallocation of non-garbage-collected memory?

EDIT: What I'm thinking of (I know this isn't explicitly state in my original question) is when a piece of non-gc'ed memory holds references to other non-gc'ed resources that need to be freed when that object is freed. For example, if you have a non-gc'ed linked list node that is the head of a long list of such nodes and you want to have the gc system clean it up automatically eventually, how do you set that up?

Answer 1

In java, you have the finalize() concept. You can free the C-memory there.

However, probably a better way is to use PhantomReferences along with a ReferenceQueue. You can extend the PhantomReference class so that it holds some id or pointer or whatever to the C-side memory you need to free. When it is enqueued in the ReferenceQueue, you can then free the C-side memory that this id points to - the Java object is guaranteed to not be in existence "in Java" anymore.