RTTI

typeid.cc

#include <iostream>
#include <typeinfo>

class Base {
 public:
  Base() : x_(0) {}
  virtual void print() { std::cout << "Base" << std::endl; }
 private:
  int x_;
};

class Sub : public Base {
 public:
  Sub() : y_(0) {}
  virtual void print() { std::cout << "Sub" << std::endl; }
 private:
  int y_;
};

class NoVirtualBase {
 public:
  NoVirtualBase() : z_(0) {}
  void print() { std::cout << "NoVirtualBase" << std::endl; }
 private:
  int z_;
};

class NoVirtualSub: public NoVirtualBase {
 public:
  NoVirtualSub() : w_(0) {}
  void print() { std::cout << "NoVirtualSub" << std::endl; }
 private:
  int w_;
};

int main() {
  Base b;
  Sub s;
  Base* p = static_cast<Base*>(&s);

  NoVirtualBase nb;
  NoVirtualSub ns;
  NoVirtualBase* np = static_cast<NoVirtualBase*>(&ns);

  std::cout << typeid(  b).name() << std::endl; // 4Base
  std::cout << typeid(  s).name() << std::endl; // 3Sub
  std::cout << typeid( *p).name() << std::endl; // 3Sub

  std::cout << typeid( nb).name() << std::endl; // 13NoVirtualBase
  std::cout << typeid( ns).name() << std::endl; // 12NoVirtualSub
  std::cout << typeid(*np).name() << std::endl; // 13NoVirtualBase <= It's not NoVirtualSub!

  std::cout << typeid( &b).name() << std::endl; // P4Base
  std::cout << typeid( &s).name() << std::endl; // P3Sub
  std::cout << typeid(  p).name() << std::endl; // P4Base

  std::cout << typeid(&nb).name() << std::endl; // P13NoVirtualBase
  std::cout << typeid(&ns).name() << std::endl; // P12NoVirtualSub
  std::cout << typeid( np).name() << std::endl; // P13NoVirtualBase

  void* vb = &b;
  void* vs = &s;

  void* vnb = &nb;
  void* vns = &ns;

  std::cout << typeid( vb).name() << std::endl; // Pv
  std::cout << typeid( vs).name() << std::endl; // Pv

  std::cout << typeid(vnb).name() << std::endl; // Pv
  std::cout << typeid(vns).name() << std::endl; // Pv

  return 0;
}

Please look at the line 51 for RTTI and vtables.

typeid() looks type of any "variable" in source code. But, runtime object type is only available in objects with vtables.