macro(enable_arc)
  if(CMAKE_GENERATOR STREQUAL Xcode)
    set(CMAKE_XCODE_ATTRIBUTE_CLANG_ENABLE_OBJC_ARC YES)
  else()
    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fobjc-arc")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fobjc-arc")
  endif()
endmacro()