Question

#include <vector>
#include <iostream>

int main()
{
    std::vector< int > v = { 1, 2, 3 };
    for ( auto it : v )
    {
        std::cout<<it<<std::endl;
    }
}

To what is auto expanding? Is it expanding to int& or int?

Answer 1

It expands to int. If you want a reference, you can use

for ( auto& it : v )
{
    std::cout<<it<<std::endl;
}

According to the C++11 standard, auto counts as a simple-type-specifier [7.1.6.2], thus the same rules apply to it as to other simple-type-specifiers. This means that declaring references with auto is no different from anything else.