std::bad_cast
Defined in header <typeinfo>
|
||
|
class bad_cast :
public
std::exception
;
|
||
An exception of this type is thrown when a dynamic_cast to a reference type fails the run-time check (e.g. because the types are not related by inheritance), and also from std::use_facet
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
| (1) | ||
bad_cast() throw(); |
(until C++11) | |
bad_cast() noexcept; |
(since C++11) | |
| (2) | ||
|
bad_cast(
const bad_cast& other )
throw
(
)
;
|
(until C++11) | |
|
bad_cast( const bad_cast& other ) noexcept;
|
(since C++11) | |
Constructs a new bad_cast object with an implementation-defined null-terminated byte string which is accessible through what().
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=
(
const bad_cast& other )
throw
(
)
;
|
(until C++11) | |
|
bad_cast& operator=
(
const bad_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
(since C++11)
Parameters
| other | - | another exception object to assign with |
Return value
*this
std::bad_cast::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 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 std::exception
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
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_constexpr_exceptions |
202411L |
(C++26) | constexpr for exception types |
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