hellofunc.c
Undefined symbols for architecture x86_64:
  "_lua_setglobal", referenced from:
      _luaopen_power in hellofunc-c1ab9b.o
  "_lua_tonumberx", referenced from:
      _isquare in hellofunc-c1ab9b.o
      _icube in hellofunc-c1ab9b.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)