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std::bad_typeid(3) C++ Standard Libary std::bad_typeid(3)

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


constructor constructs a new bad_typeid object
(public member function)
operator= replaces the bad_typeid object
(public member function)
what returns the explanatory string
(public member function)

std::bad_typeid::bad_typeid


bad_typeid() throw(); (until C++11)
bad_typeid() noexcept; (1) (since C++11)
bad_typeid( const bad_typeid& other ) throw(); (2) (until C++11)
bad_typeid( const bad_typeid& other ) noexcept; (since C++11)


Constructs a new bad_typeid object with an implementation-defined null-terminated
byte string which is accessible through what().


1) Default constructor.
2) Copy constructor.
If *this and other both have dynamic type std::bad_typeid then std::strcmp(what(),
other.what()) == 0.
(since C++11)

Parameters


other - another exception object to copy

std::bad_typeid::operator=


bad_typeid& operator=( const bad_typeid& other ) throw(); (until C++11)
bad_typeid& operator=( const bad_typeid& other ) noexcept; (since C++11)


Assigns the contents with those of other.
If *this and other both have dynamic type std::bad_typeid then std::strcmp(what(),
other.what()) == 0 after assignment.
(since C++11)

Parameters


other - another exception object to assign with

Return value


*this

std::bad_typeid::what


virtual const char* what() const throw(); (until C++11)
virtual const char* what() const noexcept; (since C++11)


Returns the explanatory string.

Parameters


(none)

Return value


Pointer to a null-terminated string with explanatory information. The string is
suitable for conversion and display as a std::wstring. The pointer is guaranteed to
be valid at least until the exception object from which it is obtained is destroyed,
or until a non-const member function (e.g. copy assignment operator) on the
exception object is called.

Notes


Implementations are allowed but not required to override what().

Inherited from std::exception

Member functions


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

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';
}
}

Possible output:


Attempted a typeid of NULL pointer!

2024.06.10 http://cppreference.com