83 struct CustomFD  struct
85     CustomFD(const CustomFD&) = delete;
86     CustomFD& operator=(const CustomFD&) = delete;
87     CustomFD(CustomFD&&) = delete;
88     CustomFD& operator=(CustomFD&&) = delete;
90     CustomFD(int fd) : fd(fd) {}  in CustomFD()  function
92     ~CustomFD()  in ~CustomFD()  argument