warning: unused variable ‘arrPixel’ [-Wunused-variable] - c++

Question

Main.cpp
#include <iostream>
#include <fstream>
#include "steganography.h" // call steganography class
const int arrSize = 30000;//array for contains pixels
using namespace std;
int main()
{
char FileName[20] = "new.txt";
char NewFile[20] = "new.ppm";
char arrPixel[arrSize] = {};
int count = 0;
int option;
Steganography A;//create the reference of steganopragpy class
cout<<"Choose Enocde/Decode[1/2]"; // take option from user
cin>>option;
switch(option)
{
case 1:
cout << "Enter PPM File Name" << endl;
cin>>FileName;
cout << "Enter Output File Name"<< endl;
cin>>NewFile;
A.readImage(FileName, arrPixel);//call readImage method
cout << "Encoded Successfully completed:" << endl;
A.printImage( NewFile, arrPixel);//write ppm
break;
case 2:
cout << "Enter Input File Name" << endl;
cin>>FileName;
cout << "Enter Output PPM File Name"<< endl;
cin>>NewFile;
A.readCipherText( NewFile, arrPixel);//call read file method
cout << "Decoded Successfully completed:" << endl;
A.printCipherText(FileName, arrPixel);//write ppm
break;
default:
cout<<"wrong choice";
}
// cout << NewFile << endl;
for(int ct = 0; ct > arrSize; ct++)
{
cout << arrPixel[ct];
}
return 0;
}
steganography.cpp
#include <iostream>
#include <fstream>
#include <string>
#include "steganography.h" // call steganography class
const int arrSize = 30000;//array for contains pixels
using namespace std;
Steganography::Steganography()//call steganography constructor
{
char arrPixel[arrSize] = {};
}
void Steganography::readImage(char* FileName, char* arrPixel)//read image
{
ifstream infile (FileName);//open file
if(infile.is_open())
{
for(int count = 0; count < arrSize; count++)
{
infile >> noskipws >> arrPixel[count];
}
}
else
{
cout << "Error opening new file." << endl;
//abort();
}
infile.close();
}
void Steganography::readCipherText(char* FileName, char* arrPixel)//read text file contains ppm info
{
ifstream infile (FileName);
if(infile.is_open())
{
for(int count = 0; count < arrSize; count++)
{
infile >> noskipws >> arrPixel[count];
}
}
else
{
cout << "Error opening new file." << endl;
//abort();
}
infile.close();
}
void Steganography::printImage(char* NewFile, char* arrPixel)//write image
{
ofstream outfile (NewFile);
if(outfile.is_open())
{
int count = arrSize;
for(int i = 0; i < (count - 1); i++)
{
outfile << arrPixel[i];
}
}
else
{
cout << "Error opening new file." << endl;
// abort();
}
outfile.close();
}
void Steganography::printCipherText(char* NewFile, char* arrPixel)//write ppm file
{
ofstream outfile (NewFile);
if(outfile.is_open())
{
int count = arrSize;
for(int i = 0; i < (count - 1); i++)
{
outfile << arrPixel[i];
}
}
else
{
cout << "Error opening new file." << endl;
// abort();
}
outfile.close();
}
steganography.h
#ifndef STEGANOGRAPHY_H
#define STEGANOGRAPHY_H
#include <string>
#include <vector>
class Steganography {
private:
// Image header
std::string image_type;
int width, height;
int max_color_depth;
// Image data
std::vector<int> color_data;
// Hidden data
std::string ciphertext;
int getNthBit(char cipher_char, int n);
public:
Steganography(void); //Constructor
void readImage(char*,char*);
void printImage(char*,char*);
void readCipherText(char*,char*);
void printCipherText(char*,char*);
void cleanImage();
void encipher();
void decipher();
};
#endif
When I compile, i get this warning:
steganography.cpp: In constructor ‘Steganography::Steganography()’:
steganography.cpp:11:10: warning: unused variable ‘arrPixel’ [-Wunused-variable]
Can someone help me figuring out the problem. Also,I have to write this line const int arrSize = 30000; in both Main.cpp and steganography.cpp to avoid getting errors, is there a way to write it only on steganography.cpp without getting errors?

Answer 1

Here:
Steganography::Steganography()//call steganography constructor
{
char arrPixel[arrSize] = {};
}
You declare a local variable called arrPixel and you don't use it. You can remove that line.
Note that you have a warning, not an error.