Friend function is unable to construct a unique pointer of the class

Question

I have a certain design strategy where the constructor of my class is private and can only be constructed by friends of the class. Inside the friend function, I am trying to cre

Answer 1

In your case the function make_unique is trying to create an instance of Spam and that function is not a friend. Calling a non-friend function from inside a friend function does not imbue the non-friend function with friend status.

To solve this you can write in Foo:

std::unique_ptr spam(new Spam(10));