Move semantics and function order evaluation

Question

Suppose I have the following:

#include 
struct A { int x; };

class B {
  B(int x, std::unique_ptr a);
};

class C : public B {
  C(st         


        

Answer 1

As alternative to Praetorian's answer, you can use constructor delegate:

class C : public B {
public:
    C(std::unique_ptr a) :
        C(a->x, std::move(a)) // this move doesn't nullify a.
    {}

private:
    C(int x, std::unique_ptr&& a) :
        B(x, std::move(a)) // this one does, but we already have copied x
    {}
};