Hi, I'm using MzScheme v4.2.4, and I'm trying to use the CUDD Binary Decision Diagram (BDD) library, which is implemented in C. CUDD manages all the BDDs with reference counting and its own garbage collector. In my scheme code I would like to have all the reference counting automated. What I did is have the functions create new BDDs to automatically increment the reference counts, and then use register-finalizer to decrement the reference count. I understand how to do all this, and it works.
The problem is that I need to sync up the CUDD garbage collector and the Scheme garbage collector. I want the Scheme garbage collector to be called right before the CUDD garbage collector is called, so that when BDD nodes are unreachable by Scheme, their reference counts go to 0, and CUDD can collect them. CUDD provides a hook to have a function called right before garbage collection occurs, so I thought this should be simple. The problem is that the collect-garbage calls in the hook appear to do nothing. None of the finalizers are called when I rely on the hook, but if I explicitly call collect-garbage, then the finalizers are called. I know the finalizers are called because I print a message in them, and I know the hook function is being called, because I print out a message in the hook function. I cannot just call collect-garbage myself, because the CUDD garbage collection is called by the package itself at unknown times. Operations internal to the package can cause a garbage collection at any time. I have tried to call scheme_collect_garbage from C, in a hook function implemented in C. And, I have implemented the hook in scheme, and had passed the function to the C procedure that registers the hook. For both methods, the hook is called, and collect-garbage doesn't work. Is garbage collection disabled or something during a FFI call? Is there another solution? Thanks, Nick _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
