std::tuple for non-copyable and non-movable object

Question

I have a class with copy & move ctor deleted.

struct A
{
    A(int a):data(a){}
    ~A(){ std::cout << \"~A()\" << this << \" : \" <<         


        

Answer 1

Your problem is that you explicitly asked for a tuple of rvalue references, and a rvalue reference is not that far from a pointer.

So auto q = std::tuple(A{100},A{200}); creates two A objects, takes (rvalue) references to them, build the tuple with the references... and destroys the temporary objects, leaving you with two dangling references

Even if it is said to be more secure than good old C and its dangling pointers, C++ still allows programmer to write wrong programs.

Anyway, the following would make sense (note usage of A& and not A&&):

int main() {
    A a(100), b(100); // Ok, a and b will leave as long as main
    auto q = tuple(a, b);  // ok, q contains references to a and b
    ...
    return 0; // Ok, q, a and b will be destroyed
}