e collection, two additional functions are provided:

void PL_register_atom(atom_t atom)

Increment the reference count of the atom by one. PL_new_atom() performs this automatically, returning an atom with a reference count of at least one.^{216Otherwise asynchronous atom garbage collection might destroy the atom before it is used.}

void PL_unregister_atom(atom_t atom)

Decrement the reference count of the atom. If the reference count drops below zero, an assertion error is raised.