I found this out trying to work around a problem with an object shared across threads (yes, it was bad programming, but I still had to work around it). By casting to the base class before dynamic_cast, the deletion of the vtable is detected. If the object was no longer valid (deleted by the other thread) it became detectable:
#include using namespace std;class A{public: A() {} virtual ~A() {}};class B : public A{public: B() {}};int main(){ B* pB = new B; cout << "dynamic_cast( pB) "; cout << ( dynamic_cast(pB) ? "worked" : "failed") << endl; cout << "dynamic_cast( (A*)pB) "; cout << ( dynamic_cast( (A*)pB) ? "worked" : "failed") << endl; delete pB; cout << "dynamic_cast( pB) "; cout << ( dynamic_cast(pB) ? "worked" : "failed") << endl; cout << "dynamic_cast( (A*)pB) "; cout << ( dynamic_cast( (A*)pB) ? "worked" : "failed") << endl; }the output:dynamic_cast( pB) workeddynamic_cast( (A*)pB) workeddynamic_cast( pB) workeddynamic_cast( (A*)pB) failed 
Charlie has over a decade of experience in website administration and technology management. As the site admin, he oversees all technical aspects of running a high-traffic online platform, ensuring optimal performance, security, and user experience.
