From cppreference.com
classbad_cast:publicstd::exception;An exception of this type is thrown when a
to a reference type fails the run-time check (e.g., because the types are not related by inheritance), and also from
if the requested facet does not exist in the locale.
Inheritance diagram
Member functions
(constructor)
constructs a new bad_cast object
(public member function)operator=
replaces the bad_cast object
(public member function)what
returns the explanatory string
(public member function)std::bad_cast::bad_cast
bad_cast()throw(); (1)(until C++11)bad_cast()noexcept;(since C++11)bad_cast(constbad_cast&other)throw(); (2)(until C++11)bad_cast(constbad_cast&other)noexcept;(since C++11)Constructs a new bad_cast object with an implementation-defined null-terminated byte string which is accessible through
.
1) Default constructor.
2) Copy constructor. If *this and other both have dynamic type std::bad_cast then std::strcmp(what(),other.what())==0.(since C++11)
Parameters
other - another exception object to copy std::bad_cast::operator=
bad_cast&operator=(constbad_cast&other)throw();(until C++11)bad_cast&operator=(constbad_cast&other)noexcept;(since C++11)Assigns the contents with those of other. If *this and other both have dynamic type std::bad_cast 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_cast::what
virtualconstchar*what()constthrow();(until C++11)virtualconstchar*what()constnoexcept;(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
. 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.
The returned string is encoded with the ordinary literal encoding during constant evaluation.
(since C++26)Notes
Implementations are allowed but not required to override what().
Inherited from
Member functions
[virtual]
destroys the exception object
(virtual public member function of std::exception)
[virtual]
returns an explanatory string
(virtual public member function of std::exception)
Notes
macroValueStdFeature
__cpp_lib_constexpr_exceptions
(C++26)constexpr for exception types Example
Run this code
#include<iostream>#include<typeinfo>structFoo{virtual~Foo(){}};structBar{virtual~Bar(){std::cout<<"~Bar\n";}};structPub:Bar{~Pub()override{std::cout<<"~Pub\n";}};intmain(){Pubpub;try{Bar&r1=dynamic_cast<Bar&>(pub);// OK, upcastFoo&r2=dynamic_cast<Foo&>(pub);// throws}catch(conststd::bad_cast&e){std::cout<<"e.what(): "<<e.what()<<'\n';}}Possible output:
e.what(): std::bad_cast ~Pub ~Bar