std::bad_typeid - cppreference.com (original) (raw)

An exception of this type is thrown when a typeid operator is applied to a dereferenced null pointer value of a polymorphic type.

Inheritance diagram

Contents

• 1 Member functions
• 2 std::bad_typeid::bad_typeid
  • 2.1 Parameters
• 3 std::bad_typeid::operator=
  • 3.1 Parameters
  • 3.2 Return value
• 4 std::bad_typeid::what
  • 4.1 Return value
  • 4.2 Notes
• 5 Inherited from std::exception
  • 5.1 Member functions
  • 5.2 Notes
  • 5.3 Example

[edit] Member functions

| | constructs a new bad_typeid object (public member function) | | --------------------------------------------------------------- | | | replaces the bad_typeid object (public member function) | | | returns the explanatory string (public member function) |

std::bad_typeid::bad_typeid

| (1) | | | | ------------------------------------------------- | | ------------------------------------- | | bad_typeid() throw(); | | (until C++11) | | bad_typeid() noexcept; | | (since C++11) (constexpr since C++26) | | (2) | | | | bad_typeid( const bad_typeid& other ) throw(); | | (until C++11) | | bad_typeid( const bad_typeid& other ) noexcept; | | (since C++11) (constexpr since C++26) |

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

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) (constexpr since C++26) |

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

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) (constexpr since C++26) |

Returns the explanatory string.

Return value

Pointer to an implementation-defined 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

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

[edit] Notes

[edit] Example

#include #include   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!