1  
       2  int
       3  phoo();
       4  
       5  int
       6  bhar();
       7  
       8  #ifndef __has_include_next
       9  #  error "__has_include_next"
      10  #else
      11  #  if __has_include_next("phoobhar.h")
      12  #    include_next "phoobhar.h"
      13  #  else
      14  #    error "__has_include_next(\"phoobhar.h\")"
      15  #  endif
      16  #endif