Question

#include <iostream>
using namespace std;

class ClassA {
    int k;
public:
    ClassA(int i) : k(i) 
    {
    }

    ~ClassA()
    {
        cout << "A destroyed" << " k=" << k << endl;
    }

    ClassA copyAndModify() 
    { 
        ClassA a(k*2);
        return a; 
    }

    void taunt() 
    {
        cout << k << endl;
    }
};

int main (int argc, char * const argv[]) {
    ClassA original(1)
    ClassA modified = original.copyAndModify();
    modified.taunt();
    return 0;
}

I thought that the object ‘a’ (inside method copyAndModify) was deconstructed when the method returned, but it didn’t. Does this mean all objects, created inside a method, that are being returned don’t get deconstructed? Is this true for all compilers?

Answer 1

You have encountered the Return Value Optimization. No, it is not going to be the same on all compilers.