testing if auto uses refs

auto.cc

#include <vector>
#include <iostream>

struct Foo {
    Foo() : x(0) { };
  int x;
};

int main() {
  std::vector<Foo> v(5);
  for (auto c : v) { std::cout << c.x << " "; }
  std::cout << std::endl;
  for (auto c : v) { c.x++; }
  for (auto c : v) { std::cout << c.x << " "; }
  std::cout << std::endl;
  for (auto & c : v) { c.x++; }
  for (auto & c : v) { std::cout << c.x << " "; }
  std::cout << std::endl;
}

out.txt

mrvn@frosties:~% ./auto                                         
0 0 0 0 0 
0 0 0 0 0 
1 1 1 1 1