The class describes an exception that can be thrown from an unexpected handler.

class bad_exception : public exception {};

bad_exception();
bad_exception(const bad_exception&);
bad_exception& operator=(const bad_exception&);
const char* what() const override;

unexpected will throw a bad_exception instead of terminating or instead of calling another function specified with set_unexpected if bad_exception is included in the throw list of a function.

The value returned by what is an implementation-defined C string. None of the member functions throw any exceptions.

For a list of members inherited by the bad_exception class, see exception Class.

See set_unexpected for an example of the use of unexpected throwing a bad_exception.