ardupilot/libraries/AP_HAL_SITL/AP_HAL_SITL_Main.h

#ifndef __AP_HAL_SITL_MAIN_H__
#define __AP_HAL_SITL_MAIN_H__

#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
#define AP_HAL_MAIN() extern "C" {\
    int main (int argc, char * const argv[]) {	\
	hal.init(argc, argv); \
        setup(); \
        hal.scheduler->system_initialized(); \
        for(;;) { \
		loop(); \
	} \
        return 0;\
    }\
    }
#endif

#endif // __AP_HAL_SITL_MAIN_H__