  void write_pointer(const void *p) {
    spec_.flags_ = HASH_FLAG;
    spec_.type_ = 'x';
    writer_.write_int(reinterpret_cast<uintptr_t>(p), spec_);
  }
  void write_pointer(const void *p) {
    spec_.flags_ = HASH_FLAG;
    spec_.type_ = 'x';
    writer_.write_int(reinterpret_cast<uintptr_t>(p), spec_);
  }