How to install multiple versions of c++ (gcc, g++) and set up their aliass on ubuntu
Refer to https://tuxamito.com/wiki/index.php/Installing_newer_GCC_versions_in_Ubuntu

[ ] Add the repository
  [ ] sudo add-apt-repository ppa:ubuntu-toolchain-r/test
  [ ] sudo apt-get update

[ ] Install compilers
  [ ] sudo apt-get install gcc g++ gcc-7 g++-7 gcc-8 g++-8 gcc-9 g++-9

[ ] Clear any alternatives already in place
  [ ] sudo update-alternatives --remove-all gcc

[ ] Set up alternatives
  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 90 --slave /usr/bin/g++ g++ /usr/bin/g++-7
  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 80 --slave /usr/bin/g++ g++ /usr/bin/g++-8
  [ ] sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 70 --slave /usr/bin/g++ g++ /usr/bin/g++-9

[ ] Configure the compiler to use
  [ ] sudo update-alternatives --config gcc
      This will show choices along with the current selected compiler version
    [ ] Pick the compiler version you want to use
    [ ] Verify the choice
      [ ] g++ -v