g-function with GC support example

merge2.c

Object merge2_(Object ctr, Object hda_, Object tla_) {
  struct {
    struct RootsBlock header;
    Object gcall_cnd;
    Object gcall_merge2;
    Object gcall_merge2_1;
    Object gcall_lss;
    Object ctr_Cons;
    Object ctr_Cons_1;
    Object ctr_Cons_2;
  } m = { { sll_roots, 7 } };
  sll_roots = &m.header;
  Object result = NULL;
  switch (SLL_get_ctr_id(ctr[0])) {
    case Cons_: {
      m.gcall_lss = lss_(hda_, (Object)ctr[1]);
      m.gcall_merge2 = merge2_(tla_, (Object)ctr[1], (Object)ctr[2]);
      m.ctr_Cons = create_object_2(Cons_, hda_, m.gcall_merge2);
      m.gcall_merge2_1 = merge2_((Object)ctr[2], hda_, tla_);
      m.ctr_Cons_1 = create_object_2(Cons_, (Object)ctr[1], m.gcall_merge2_1);
      m.gcall_cnd = cnd_(m.gcall_lss, m.ctr_Cons, m.ctr_Cons_1);
      result = m.gcall_cnd;
      break;
  } case Nil_: {
      m.ctr_Cons_2 = create_object_2(Cons_, hda_, tla_);
      result = m.ctr_Cons_2;
      break;
  } default:
      sll_fatal_error("Inexhaustive pattern matching");
  }
  sll_roots = m.header.next;
  return result;
}