nixpkgs/pkgs/build-support/cc-wrapper/add-hardening

hardeningFlags=(fortify stackprotector pic strictoverflow format relro bindnow)
hardeningFlags+=("${hardeningEnable[@]}")
hardeningCFlags=()
hardeningLDFlags=()

if [[ ! $hardeningDisable == "all" ]]; then
  for flag in "${hardeningFlags[@]}"
  do
    if [[ ! "$hardeningDisable" =~ "$flag" ]]; then
      case $flag in
        fortify)
          hardeningCFlags+=('-O2' '-D_FORTIFY_SOURCE=2')
          ;;
        stackprotector)
          hardeningCFlags+=('-fstack-protector-strong')
          ;;
        pie)
          hardeningCFlags+=('-fPIE')
          if [[ ! "$*" =~ "-shared" ]]; then
            hardeningLDFlags+=('-pie')
          fi
          ;;
        pic)
          hardeningCFlags+=('-fPIC')
          ;;
        strictoverflow)
          hardeningCFlags+=('-fno-strict-overflow')
          ;;
        format)
          hardeningCFlags+=('-Wformat' '-Wformat-security' '-Werror=format-security')
          ;;
        relro)
          hardeningLDFlags+=('-z relro')
          ;;
        bindnow)
          hardeningLDFlags+=('-z now')
          ;;
        *)
          echo "Hardening flag unknown: $flag"
          ;;
      esac
    fi
  done
fi