C++ & Xcode8.3.3 : Apple Mach-O Linker error - xcode

Question

I am working on C++ code to read and write .bmp image.
Below is my code.
However, I encountered some problems that I couldn't fix. enter image description here
I have googled a lot but none of them solve my problem.
Sorry if my coding style doesn't look good to you, I'm new to Xcode and C++.
Please help me.
I will be really appreciated.
#include <iostream>
#include <stdio.h>
#pragma pack(2)
typedef struct // BMP file header structure
{
unsigned short bfType ; // Magic number for file
unsigned int bfSize ; // Size of file
unsigned short bfReserved1 ; // Reserved, usually set to 0
unsigned short bfReserved2 ; // Reserved, usually set to 0
unsigned int bfoffBits ; // Offset to bitmap data
}BITMAPFILEHEADER;
#pragma pack()
typedef struct
{
unsigned int biSize ; // Size of info header
int biWidth ; // Width of image
int biHeight ; // Height of image
unsigned short biPlanes ; // Number of color planes
unsigned short biBitCount ; // Number of bits per pixel
unsigned int biCompression ; // Type of compression to use, 0 if there is no compression
unsigned int biSizeImage ; // Size of image data
int biXPelsPerMeter ; // X pixels per meter
int biYPelsPerMeter ; // Y pixels per meter
unsigned int biClrUsed ; // Number of color used
unsigned int biClrImportant ; // Number of important color
}BITMAPINFOHEADER;
unsigned char *ReadBitmapFile(const char *filename, BITMAPINFOHEADER *bitmapInfoHeader)
{
FILE* file ; //file pointer
BITMAPFILEHEADER bitmapFileHeader ; //bitmap file header
unsigned char *bitmapimage ; //store image data
int imageIdx = 0 ;
unsigned char tempRGB ; //swap
// open file in read binary mode
file = fopen(filename, "rb");
if (file == NULL)
return NULL;
// read the bitmap file header
fread(&bitmapFileHeader, sizeof(BITMAPFILEHEADER), 1, file);
// read the bitmap info header
fread(bitmapInfoHeader, sizeof(BITMAPINFOHEADER),1,file);
//move file point to the begging of bitmap data
fseek(file, bitmapFileHeader.bfoffBits, SEEK_SET);
//allocate enough memory for the bitmap image data
bitmapimage = (unsigned char*)malloc(bitmapInfoHeader->biSizeImage);
//verify memory allocation
if(!bitmapimage)
{
free(bitmapimage);
fclose(file);
return NULL;
}
// read in the bitmap image data
fread(bitmapimage, bitmapInfoHeader->biSizeImage, 1, file);
//swap the r and b value to get RGB (bitmap is BGR)
for (imageIdx = 0; imageIdx < bitmapInfoHeader->biSizeImage; imageIdx+=3){
tempRGB = bitmapimage[imageIdx];
bitmapimage[imageIdx] = bitmapimage[imageIdx + 2];
bitmapimage[imageIdx + 2] = tempRGB;
}
//close file and return bitmap data
fclose(file);
return bitmapimage;
}
BITMAPINFOHEADER bitmapInfoHeader;
unsigned char *bitmapData = ReadBitmapFile("input1.bmp", &bitmapInfoHeader);
By the way, I am using Xcode8.3.3