std::bad_typeid (3) - Linux Manuals

std::bad_typeid: std::bad_typeid

NAME

std::bad_typeid - std::bad_typeid

Synopsis

Defined in header <typeinfo>
class bad_typeid : public std::exception;

An exception of this type is thrown when a typeid operator is applied to a dereferenced null pointer value of a polymorphic type.
 std-bad typeid-inheritance.svg
Inheritance diagram

Member functions

              constructs a new bad_typeid object
constructor (public member function)

Inherited from std::exception

Member functions

destructor destroys the exception object
             (virtual public member function of std::exception)
[virtual]

what returns an explanatory string
             (virtual public member function of std::exception)
[virtual]

Example

// Run this code

  #include <iostream>
  #include <typeinfo>

  struct S { // The type has to be polymorphic
      virtual void f();
  };

  int main()
  {
      S* p = nullptr;
      try {
          std::cout << typeid(*p).name() << '\n';
      } catch(const std::bad_typeid& e) {
          std::cout << e.what() << '\n';
      }
  }

Output:

  Attempted a typeid of NULL pointer!