Return type of a constructor in c++

Question

I am learning c++, and I came across following code segment:

class X
{
    int i;

public:
    X(int ii = 0);

    void modify();
};

X::X(int ii)
{ i = ii; }

void X::modify()
{ i++; }

X f5()
{ return X(); }

const X f6()
{ return X(); }

void f7(X& x) // Pass by non-const reference
{ x.modify(); }

int main()
{
    f5() = X(1);
    f5().modify();
}

I am stuck particularly in this segment-

X f5()
{ return X(); }

Does this part of code return an object of type x by value? Can a constructor return an object?

Answer 1

Does this part of code returns an object of type x by value?

Yes, it creates and value-initialises a temporary object of type X (by calling the constructor with the default value of zero) and returns that.

can a constructor can return an object?

No, that doesn't make any sense. But an conversion expression like X() does.

Answer 2

f5 is just function, not constructor. And it returns constructed object of type X .

Answer 3

simple, you misunderstand the constructor of the class and a function. your class class X have a constructor and it is X(int ii = 0); .

X f5() is not a constructor. Clearly understand that first.

Constructor of a class should have the same name as class and have no a return value. It does,t make any sense. (read further about class and constructor)

X f5() {
  return X();
}

This is a function which returns a X type of object. it returns the X().

X() creates a value-initialized temporary object of type X .