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.

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) {
      cout << "Caught: bad_cast exception. A Shape is not a Circle.\n"; 
   }
}

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);

See Also

Concepts

dynamic_cast Operator

C++ Keywords

C++ Exception Handling