Finalization provides a “hook” that is triggered when the garbage collector reclaims an object. It is usually used to recover non-Lisp resources that were allocated to implement the finalized Lisp object. For example, when a unix file-descriptor stream is collected, finalization is used to close the underlying file descriptor.
This function registers object for finalization. function is called with no arguments when object is reclaimed. Normally function will be a closure over the underlying state that needs to be freed, e.g. the unix file descriptor in the fd-stream case. Note that function must not close over object itself, as this prevents the object from ever becoming garbage.
This function cancel any finalization request for object.