7.53.cpp

#include <iostream>

class Debug {
public:
  constexpr Debug(bool b = true) : hw(b), io(b), other(b) {}
  constexpr Debug(bool h, bool i, bool o)
      : hw(h), io(i), other(o) {}

  constexpr bool any() const { return hw || io || other; }  // Add const (since C++14)
  void set_hw(bool b) { hw = b; }
  void set_io(bool b) { io = b; }
  void set_other(bool b) { other = b; }

private:
  bool hw;
  bool io;
  bool other;
};

int main() {
  constexpr Debug io_sub(false, true, false);
  if (io_sub.any())
    std::cout << "Error message 1" << std::endl;

  constexpr Debug nodbg = false;
  if (nodbg.any())
    std::cout << "Error message 2" << std::endl;
  //nodbg.set_hw(true);  // Error

  Debug dbg(false);
  if (dbg.any())
    std::cout << "Error message 3" << std::endl;
  dbg.set_other(true);
  if (dbg.any())
    std::cout << "Error message 4" << std::endl;


  return 0;
}