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
17