bad_cast Exception
The latest version of this topic can be found at bad_cast Exception.
The bad_cast exception is thrown by the dynamic_cast operator as the result of a failed cast to a reference type.
Syntax
catch (bad_cast)
statement
Remarks
The interface for bad_cast is:
class bad_cast : public exception {
public:
bad_cast(const char * _Message = "bad cast");
bad_cast(const bad_cast &);
virtual ~bad_cast();
};
The following code contains an example of a failed dynamic_cast that throws the bad_cast exception.
// expre_bad_cast_Exception.cpp
// compile with: /EHsc /GR
#include <typeinfo.h>
#include <iostream>
class Shape {
public:
virtual void virtualfunc() const {}
};
class Circle: public Shape {
public:
virtual void virtualfunc() const {}
};
using namespace std;
int main() {
Shape shape_instance;
Shape& ref_shape = shape_instance;
try {
Circle& ref_circle = dynamic_cast<Circle&>(ref_shape);
}
catch (bad_cast b) {
cout << "Caught: " << b.what();
}
}
The exception is thrown because the object being cast (a Shape) is not derived from the specified cast type (Circle). To avoid the exception, add these declarations to main:
Circle circle_instance;
Circle& ref_circle = circle_instance;
Then reverse the sense of the cast in the try block as follows:
Shape& ref_shape = dynamic_cast<Shape&>(ref_circle);