title: How to use C++ 20 in g++
body: <p>I am trying to access <code>std::popcount</code>, but it seems like it's <a href="https://en.cppreference.com/w/cpp/numeric/popcount#:%7E:text=since%20C++20" rel="noreferrer">only there in C++ 20</a>.</p>
  <p>When I try compiling with <code>g++ -std=c++20 main.cpp</code>, it says <code>g++: error: unrecognized command line option '-std=c++20'; did you mean '-std=c++03'</code></p>
  <p>How do I tell g++ to use c++ 20?</p>
  <p>I am using Ubuntu 18.04</p>