Hi, I would like to report an issue with Cygwin 3.4.2 on Windows. It doesn't seem to be able to work with  fd_set, FD_ZERO, FD_SET, FD_SETSIZE macros. The code is in italics. The filename was selectStdIn.c. The terminal command used was "gcc -o selectStdIn selectStdIn.c" Thank you. / / /CODE / /#include // //#include // //#include // //#include // / / //void main()// //{// //    fd_set fds; //set of file descriptors// / / //    struct timeval tv;// / / //    int flag;// / / //    char byte;// / / //    FD_ZERO(&fds);// / / //    FD_SET(0, &fds);// / / //    tv.tv_sec = 5;// / / //    tv.tv_usec = 0;// / / //    flag = select(FD_SETSIZE, // //            &fds,// //            NULL,// //            NULL,// //            &tv);// / / //    if(-1 == flag)// //        perror("select error");// //    else if(flag)// //    {// //        read(0,&byte,1);// / / //        puts("data read");// //    }// / / //    if(flag)// //        printf("The byte value is %c\n", byte);// //// //}/ TERMINAL COMMANDS $ gcc -o selectStdIn selectStdIn.c selectStdIn.c: In function 'main': selectStdIn.c:8:2: error: unknown type name 'fd_set'; did you mean 'fpos_t'?   fd_set fds; //set of file descriptors   ^~~~~~   fpos_t selectStdIn.c:16:2: warning: implicit declaration of function 'FD_ZERO' [-Wimpli cit-function-declaration]   FD_ZERO(&fds);   ^~~~~~~ selectStdIn.c:18:2: warning: implicit declaration of function 'FD_SET' [-Wimplic it-function-declaration]   FD_SET(0, &fds);   ^~~~~~ selectStdIn.c:24:9: warning: implicit declaration of function 'select'; did you mean 'sleep'? [-Wimplicit-function-declaration]   flag = select(FD_SETSIZE,          ^~~~~~          sleep selectStdIn.c:24:16: error: 'FD_SETSIZE' undeclared (first use in this function)   flag = select(FD_SETSIZE,                 ^~~~~~~~~~ selectStdIn.c:24:16: note: each undeclared identifier is reported only once for each function it appears in