#include <mach/thread_switch.h> also included by
<mach/mach.h>mach/thread_switch.h
macroSWITCH_OPTION_NONE
#define SWITCH_OPTION_NONE 0
macroSWITCH_OPTION_DEPRESS
#define SWITCH_OPTION_DEPRESS 1
macroSWITCH_OPTION_WAIT
#define SWITCH_OPTION_WAIT 2
macrovalid_switch_option
#define valid_switch_option(opt) (0 <= (opt) && (opt) <= 5)