C++ use of undeclared identifier IOKit Functions

I am getting an error building my c++ program on xcode. For each of the various fuctions of the IOKit I am getting "use of undeclared identifier". I really don't know why I am getting this error. Here is the code:

#include <iostream>
#include <xlnt/xlnt.hpp>
#include <xlnt/xlnt_config.hpp>
#include <IOKitLib.h>
#include <IOTypes.h>
#include <IOReturn.h>
#include <IOKitKeys.h>
#include <iokitmig.h>
#include <OSMessageNotification.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <paths.h>
#include <termios.h>
#include <sysexits.h>
#include <sys/param.h>
#include <sys/select.h>
#include <sys/time.h>
#include <time.h>
#include <CoreFoundation/CoreFoundation.h>
#include <IOKit/IOKitLib.h>
#include <IOKit/serial/IOSerialKeys.h>
#include <IOKit/IOBSD.h>

#define LOCAL_ECHO
#ifdef LOCAL_ECHO
#define kOKResponseString “AT\r\r\nOK\r\n”
#else
#define kOKResponseString “\r\nOK\r\n”
#endif


#define kATCommandString        "AT\r"
#define kMyErrReturn            -1
enum {
kNumRetries = 3
};

static struct termios gOriginalTTYAttrs;



int main()
{
char path;
char text;

int fileDescriptor;
kern_return_t kernResult;
io_iterator_t serialPortIterator;
char deviceFilePath[MAXPATHLEN];
kernResult = MyFindModems(&serialPortIterator);
kernResult = MyGetModemPath(serialPortIterator, deviceFilePath,
                            sizeof(deviceFilePath));

Here is the image with all the errors shown: https://i.sstatic.net/e1UZS.jpg Any advice would be more than appreciated. Is it because I haven't declared the functions? Thanks in advance Alex