add: REGISTER_SO(cache_ht);
context: void scheme_init_print(Scheme_Env *env){  int i;  REGISTER_SO(quick_buffer);  REGISTER_SO(quick_encode_buffer);    quick_buffer = (char *)scheme_malloc_atomic(100);  quick_encode_buffer = (char *)scheme_malloc_atomic(QUICK_ENCODE_BUFFER_SIZE);  REGISTER_SO(quote_link_symbol);    quote_link_symbol = scheme_intern_symbol("-q");    for (i = 0; i < _CPT_COUNT_; i++) {    compacts[i] = i;  }#ifdef MZ_PRECISE_GC  register_traversers();#endif}