void main()
main: scope:[main]  from
  [0] phi()
  to:main::@1
main::@1: scope:[main]  from main
  [1] *main::SCREEN = 'a'
  to:main::@2
main::@2: scope:[main]  from main::@1
  [2] *(main::SCREEN+1) = 'b'
  to:main::@return
main::@return: scope:[main]  from main::@2
  [3] return 
  to:@return