syscall_arg_fmt__scnprintf_val
printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx],
printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx], bf + printed, size - printed, &arg, val);
printed += syscall_arg_fmt__scnprintf_val(arg, bf + printed, size - printed, &syscall_arg, val);