记法 : 次级等于上级
TARGET_OS_WIN32 - Generated code will run under 32-bit Windows TARGET_OS_UNIX - Generated code will run under some Unix (not OSX) TARGET_OS_MAC - Generated code will run under Mac OS X variant/对于（可能）在Apple平台上运行的任何Cocoa应用程序，TARGET_OS_MAC将为1。 TARGET_OS_OSX - Generated code will run under OS X devices TARGET_OS_IPHONE - Generated code for firmware, devices, or simulator TARGET_OS_IOS - Generated code will run under iOS TARGET_OS_TV - Generated code will run under Apple TV OS TARGET_OS_WATCH - Generated code will run under Apple Watch OS TARGET_OS_BRIDGE - Generated code will run under Bridge devices TARGET_OS_SIMULATOR - Generated code will run under a simulator TARGET_OS_EMBEDDED - DEPRECATED: Use TARGET_OS_IPHONE and/or TARGET_OS_SIMULATOR instead TARGET_IPHONE_SIMULATOR - DEPRECATED: Same as TARGET_OS_SIMULATOR TARGET_OS_NANO - DEPRECATED: Same as TARGET_OS_WATCH