[FEEDBACK] Issue with fd_set, FD_ZERO, FD_SET, FD_SETSIZE : Cygwin

[gs-cygwin.com@gluelogic.com]

On Tue, Feb 07, 2023 at 04:25:22AM +0800, Yeo Kai Wei via Cygwin wrote:
> 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 <stdio.h>//
> //#include <stdlib.h>//
> //#include <sys/time.h>//
> //#include <unistd.h>//
> / /
> //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

$ man select

#include <sys/select.h>