main: swapcontext(&uctx_main, &uctx_func2)
func2: started (1, 2)
func2: swapcontext(&uctx_func2, &uctx_func1)
func1: started
func1: swapcontext(&uctx_func1, &uctx_func2)
func2: returning
func1: returning
main: exiting
