# std::bad_cast

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< cpp‎ | types

Defined in header `<typeinfo>` |  |
class bad_cast : public std::exception; |  |

An exception of this type is thrown when a `dynamic_cast` to a reference type fails the run-time check (e.g. because the types are not related by inheritance), and also from std::use_facet if the requested facet does not exist in the locale.

Inheritance diagram

### Member functions

(constructor) | constructs a new bad_cast object (public member function)

## Inherited from std::exception

### Member functions

(destructor) [virtual] | destroys the exception object (virtual public member function of `std::exception`)
what [virtual] | returns an explanatory string (virtual public member function of `std::exception`)

### Example

Run this code

    #include <iostream>
    #include <typeinfo>

    struct Foo { virtual ~Foo() {} };
    struct Bar { virtual ~Bar() {} };

    int main()
    {
        Bar b;
        try {
            Foo& f = dynamic_cast<Foo&>(b);
        } catch(const std::bad_cast& e)
        {
            std::cout << e.what() << '\n';
        }
    }

Possible output:

    Bad dynamic cast

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