#include <map>
#include <set>
#include <stack>
#include <utility>
#include <algorithm>

typedef std::stack<std::pair<short, std::set<short>>> stack_t;

int main()
{
    std::set<short> x = {0, 1, 2, 3};

    stack_t my_stack;
    auto iter = my_stack.top(); // error (segmentation fault)

    my_stack.push(std::make_pair(3, x));
    iter = my_stack.top();
    //...

    return 0;
}