CODEWITHSUNDEEP
c++c++11placement-newvirtual-destructor
CoffeDeveloper
CoffeDeveloper

Reputation: 8325

Destructor on polymorphic placed stuff

Is there a way to call destructor on objects if they are polymorphic types created with placement new?

class AbstractBase{
public:
    ~virtual AbstractBase(){}
    virtual void doSomething()=0;
};

class Implementation:public virtual AbstractBase{
public:
    virtual void doSomething()override{
        std::cout<<"hello!"<<std::endl;
    }
};

int main(){
    char array[sizeof(Implementation)];
    Implementation * imp = new (&array[0]) Implementation();
    AbstractBase * base = imp; //downcast
    //then how can I call destructor of Implementation from
    //base? (I know I can't delete base, I just want to call its destructor)
    return 0;
}

I want to destruct "Implementation" only thanks to a pointer to its virtual base... Is that possible?

Upvotes: 0

Views: 340

Answers (1)

Casey
Casey

Reputation: 42584

Overkill answer: with unique_ptr and a custom deleter!

struct placement_delete {
  template <typename T>
  void operator () (T* ptr) const {
    ptr->~T();
  }
};

std::aligned_storage<sizeof(Implementation)>::type space;
std::unique_ptr<AbstractBase,placement_delete> base{new (&space) Implementation};

Live at Coliru.

Upvotes: 3

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