incorrect output on vector assignment?

Below code snippet is From Herb Sutter's blog here

g++ outputs 10. MSVC also does output 10. Output could be different on different compilers.

I fail to understand how variable i is incremented. Can anyone explain me how come output is 10, Is 10 really correct output?

#include <iostream>
#include <vector>
#include <string>

int main()
{    
    std::vector<int> v = { 0, 0 };
    int i = 0;
    v[i++] = i++;
    std::cout << v[0] << v[1] << std::endl;
}