c++ - Error calling FIONREAD under ioctl() function in Cygwin

Question

I have called the method ioctl to check the number of bytes available with the following code :

::ioctl(serial_port, FIONREAD, &available);

I'm compiling this from Cygwin under windows 10. But I get this error: error: ‘FIONREAD’ was not declared in this scope; did you mean ‘FREAD’?

How can I fix this? I want to check if there're bytes in the input buffer so when I poll, I don't get errors when it's empty. I have been having input/output error with error no.5.

if it's not possible to find the FIONREAD constant, is there another way to avoid the input/output error? I am using blocking mode too with VMIN = 0 and VTIME = 1. So it's waiting about 100ms with every read.

Those are my include files :

#include <string.h>
#include<iostream>
#include<stdio.h>
#include <string>

#include <fcntl.h> 

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/time.h>

#include <errno.h> 
#include <termios.h> 
#include <unistd.h> 

Answer 1

等待大神答复