std::bad_cast
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Defined in header <typeinfo> | ||
class bad_cast:publicstd::exception | ||
An exception of this type is thrown when adynamic_cast to a reference type fails the run-time check (e.g., because the types are not related by inheritance), and also fromstd::use_facet if the requested facet does not exist in the locale.
Inheritance diagram
Contents |
[edit]Member functions
(constructor) | constructs a newbad_cast object(public member function) |
operator= | replaces thebad_cast object(public member function) |
what | returns the explanatory string (public member function) |
std::bad_cast::bad_cast
| (1) | ||
bad_cast()throw(); | (until C++11) | |
bad_cast()noexcept; | (since C++11) (constexpr since C++26) | |
| (2) | ||
bad_cast(const bad_cast& other)throw(); | (until C++11) | |
bad_cast(const bad_cast& other)noexcept; | (since C++11) (constexpr since C++26) | |
Constructs a newbad_cast object with an implementation-defined null-terminated byte string which is accessible throughwhat().
std::bad_cast thenstd::strcmp(what(), other.what())==0.(since C++11)Parameters
| other | - | another exception object to copy |
std::bad_cast::operator=
bad_cast& operator=(const bad_cast& other)throw(); | (until C++11) | |
bad_cast& operator=(const bad_cast& other)noexcept; | (since C++11) (constexpr since C++26) | |
Assigns the contents with those ofother.If*this andother both have dynamic typestd::bad_cast thenstd::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 astd::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.
The returned string is encoded with the ordinary literal encoding during constant evaluation. | (since C++26) |
Notes
Implementations are allowed but not required to overridewhat().
Inherited fromstd::exception
Member functions
[virtual] | destroys the exception object (virtual public member function of std::exception)[edit] |
[virtual] | returns an explanatory string (virtual public member function of std::exception)[edit] |
[edit]Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_constexpr_exceptions | 202411L | (C++26) | constexpr for exception types |
[edit]Example
#include <iostream>#include <typeinfo> struct Foo{virtual ~Foo(){}};struct Bar{virtual ~Bar(){std::cout<<"~Bar\n";}};struct Pub: Bar{ ~Pub() override{std::cout<<"~Pub\n";}}; int main(){ Pub pub;try{[[maybe_unused]] Bar& r1=dynamic_cast<Bar&>(pub);// OK, upcast [[maybe_unused]] Foo& r2=dynamic_cast<Foo&>(pub);// throws}catch(const std::bad_cast& e){std::cout<<"e.what(): "<< e.what()<<'\n';}}
Possible output:
e.what(): std::bad_cast~Pub~Bar
