For more advanced gc concepts it would be nice to keep a set a objects in a weak key hash table and at gc loop over the alive ones the various gc hooks that is available for the c coder.
The problem is that current guile data structure would hang on folding because inside the guile weak folder gc is assumed to be prevented. Not sure what to do here. This might be a feature request or a bug report dependning on how you view it.
Regards