Why is data not being added to the stack (STL)?

Question

C++ / C#

When executing the code, data is not added to sorted, I look with a debugger.

#include <stack>
using namespace std;
int main() {

    stack<int> source;
    stack<int> sorted;

    source.push(17);
    source.push(11);
    source.push(1);
    source.push(9);
    while(!source.empty())
    {
        sorted.push(10);
        source.pop();
    }
    return 0;
}

Answer 1

are added)
print after source.pop();
std::cout<<"pop, stacksize"<<sorted.size()<<"\n";