Heap Corruption Error

[mlholder]

Hi all,

I am working on a simple program using dynamic arrays. The program adds two positive integers in dynamic character arrays and stores the sum into a dynamic character array. However, I am getting a "Heap Corruption Detected" error. From a few Google searches, I have found that basically this error means that I am writing to memory that I have not allocated space for, more or less. The IDE I am using is Microsoft Visual C++ 2010 Express. I have tried multiple ways of doing this program and each way works for a few inputs, but then it seems like the error comes when the input is a large integer. I would appreciate if someone with more experience in debugging would look at my code and possibly tell me why I am getting this error, as well as possibly where the error is. Thank you for your time.

#include <iostream>
#include <string>
#include <cstring>

#define CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>

//Type Definitions
//===============================================================
typedef char* CharArrayPtr;
//===============================================================

//Function Prototypes
//===============================================================
bool finished();
void getNum(CharArrayPtr &);
void align(CharArrayPtr &, CharArrayPtr &);
void add(CharArrayPtr, CharArrayPtr, CharArrayPtr &);
void output(CharArrayPtr);
//===============================================================

int main()
{
	using namespace std;

	CharArrayPtr num1, num2, sum;

	cout << "This is a program that adds two positive integers.\n\n";

	do
	{
		cout << "Enter the first integer.\n";
		getNum(num1);
		cout << endl;
		cout << "Enter the second integer.\n";
		getNum(num2);
		cout << endl;

		align(num1, num2);
		add(num1, num2, sum);
		output(sum);

	}while(!finished());

	delete [] num1;
	delete [] num2; //This is where the error occurs
	delete [] sum;

	_CrtDumpMemoryLeaks();

	return 0;
}

//Function Definitions
//===============================================================
bool finished()
{
	using namespace std;

	string answer;

	do
	{
		cout << "Would you like to repeat the program? (Y/N): ";
		getline(cin, answer);
		cout << endl;

		if( (answer.find_first_not_of("YyNn") != string::npos) || (answer.length() > 1) )
			cout << "Response is not valid!\n";

	}while( (answer.find_first_not_of("YyNn") != string::npos) || (answer.length() > 1) );

	if(answer.find_first_of("Yy") != string::npos)
		return false;

	return true;
}
void getNum(CharArrayPtr &arr)
{
	using namespace std;

	char ch;
	int size(5), index(0);

	arr = new char[size];

	cin.get(ch);
	while(ch != '\n')
	{
		if(index == size)
		{
			CharArrayPtr temp = new char[size + 5];
			strncpy(temp, arr, index);
			temp[index] = ch;
			size += 5;
			index++;
			delete [] arr;
			arr = temp;
		}
		else
		{
			arr[index] = ch;
			index++;
		}

		cin.get(ch);
	}

	arr[index] = '\0';
}
void align(CharArrayPtr &n1, CharArrayPtr &n2)
{
	if(strlen(n1) > strlen(n2))
	{
		int difference = strlen(n1) - strlen(n2), tempIndex = 0, n2Index = 0;
		CharArrayPtr temp = new char[strlen(n1) + 1];

		while(tempIndex < difference)
		{
			temp[tempIndex] = '0';
			tempIndex++;
		}

		while(n2[n2Index] != '\0')
		{
			temp[tempIndex] = n2[n2Index];
			tempIndex++;
			n2Index++;
		}

		delete [] n2;
		n2 = temp;
		n2[tempIndex] = '\0';
	}
	else if(strlen(n2) > strlen(n1))
	{
		int difference = strlen(n2) - strlen(n1), tempIndex = 0, n1Index = 0;
		CharArrayPtr temp = new char[strlen(n2) + 1];

		while(tempIndex < difference)
		{
			temp[tempIndex] = '0';
			tempIndex++;
		}

		while(n1[n1Index] != '\0')
		{
			temp[tempIndex] = n1[n1Index];
			tempIndex++;
			n1Index++;
		}

		delete [] n1;
		n1 = temp;
		n1[tempIndex] = '\0';
	}
}
void add(CharArrayPtr n1, CharArrayPtr n2, CharArrayPtr &sum)
{
	int answer, carry(0);

	sum = new char[strlen(n1) + 1];

	for(int index = strlen(n1) - 1; index >= 0; index--)
	{
		answer = (n1[index] - '0') + (n2[index] - '0') + carry;
		if(answer >= 10)
		{
			answer -= 10;
			carry = 1;
		}
		else
			carry = 0;

		sum[index] = answer + '0';
	}

	if(carry == 1)
	{
		CharArrayPtr temp = new char[strlen(n1) + 2];
		int tempIndex = 0, index = 0;
		temp[tempIndex] = carry + '0';
		tempIndex++;

		while(index < strlen(n1))
		{
			temp[tempIndex] = sum[index];
			index++;
			tempIndex++;
		}

		delete [] sum;
		sum = temp;
		sum[tempIndex] = '\0';
		return;
	}

	sum[strlen(n1)] = '\0';
}
void output(CharArrayPtr sum)
{
	using namespace std;

	cout << "The sum of the integers is\n";
	for(int index = 0; index < strlen(sum); index++)
		cout << sum[index];
	cout << endl << endl;
}
//=============================================================== 

[ne555]

//getNum()
	while (ch != '\n')
	{
		if (index == size)
		{
			CharArrayPtr temp = new char[size + 5];
			strncpy (temp, arr, index);
			temp[index] = ch;
			size += 5;
			index++;
			delete[] arr;
			arr = temp;
		}
		else
		{
			arr[index] = ch;
			index++; //¿what if `index' == `size' here?
		}

		cin.get (ch); //and now you read a '\n'
	}

	arr[index] = '\0'; //out of bounds access 

> the error comes when the input is a large integer.
¿by instance?

> someone with more experience in debugging
¿have you at least tried to run it through a debugger?
I would point you to the line where it crashes, we can analyse from there.

[mlholder]

Yes, I've run the program through a debugger with no success in pinpointing where the error is. So I just scrapped the whole thing and we wrote it, being careful to make sure that each allocation is accounted for. Thank you for the reply and help.