I've just been doing some exercises with move semantic, and I can't seem to figure out why my move assignment operator is not being called
My class is as follows (please ignore any bad practice that is not relevant to the question):
private:
int sz;
double* elems;
public:
Vector(int size):sz(size), elems(new double[size])
{
for(int i=0; i!=sz; ++i)
{
elems[i] = i;
}
}
~Vector()
{
std::cout << "Destruct " << std::endl; delete [] elems;
}
double& operator[](int i)
{
return elems[i];
}
const double& operator[](int i)const
{
return elems[i];
}
//operator+ to add vectors
friend Vector operator+(const Vector& a, const Vector& b)
{
Vector ret(a.sz);
if(a.sz!=b.sz)
return 0;
std::cout << "Adding" << std::endl;
for(int i=0; i!=a.sz; ++i)
{
ret[i] = a[i] + b[i];
}
return ret;
}
//move constructor
Vector(Vector&& a): sz(a.sz),elems(a.elems)
{
std::cout << "Move constructor"<< std::endl;
a.elems = nullptr;
a.sz = 0;
}
//move assignment
Vector& operator=(Vector&& a)
{
std::cout << "Moveeee" << std::endl;
delete [] elems;
elems = a.elems;
sz = a.sz;
a.elems = nullptr;
a.sz = 0;
return *this;
}
Now my test case is as follows:
Vector v1(3);
Vector v2(3);
Vector v3(3);
Vector v4 = v1+v2;
The output is as follows:
Adding
Move constructor
Destruct
Destruct
Destruct
Destruct
Destruct
What I expect is line Vector v4 = v1+v2;
to call the move assignment, but it doesn't. Instead it calls the move constructor.
I even tried Vector v4 = std::move(v2);
, but that also didn't work and called the move constructor.
Any idea why the move assignment is not being called?