Beyond Boundaries of a Pointer Array

[phztfte1]

Write your question here.
The program work. However, see questions starting from line 59.

  /*
*	Chapter 14
*
*
*
*
*/

#include <iostream>

using namespace std;

int* growArray(int* p_values, int* size);
void printArray(int* p_values, int size, int elements_set);

int main()
{
	int next_element = 0;
	int size = 10;;
	int* p_values = new int[size];
	int val;
	cout << "Please enter a number: ";
	cin >> val;
	while (val > 0)
	{
		if (size == next_element + 1)
		{
			p_values = growArray(p_values, &size);
		}
		p_values[next_element] = val;
		next_element++;;
		cout << "Current array values are: " << endl;
		printArray(p_values, size, next_element);
		cout << "Please enter a number (or 0 to exit): ";
		cin >> val;
	}
	delete[] p_values;;
}


void printArray(int* p_values, int size, int elements_set)
{
	cout << "The total size of the array is: " << size << endl;
	cout << "Number of slots set so far: " << elements_set << endl;
	cout << "Values in the array: " << endl;
	for (int i = 0; i < elements_set; i++)
	{
		cout << "p_values[" << i << "] = " << p_values[i] << endl;
	}
}


int* growArray(int* p_values, int* size)
{
	*size *= 2;
	int* p_new_values = new int[*size];
	for (int i = 0; i < *size; i++)
	{
		p_new_values[i] = p_values[i];  // The first pass through the
                                                // function the size of p_values
                                               // is 10.  Yet, the for loop
                                               // cycles 20 times.  Why no
                                               // compiler error?  Is there a 
                                               // possible memory conflict
                                               // where, say p_values[18], 
                                          // is occupied by another variable? 
	}
	delete[] p_values;
	return p_new_values;
}

[AbstractionAnon]

At line 53, lets assume that p_values has 10 entries and *size is 10.
At line 55, you modify *size so that it is now 20. p_values still has only 10 entries.
Line 56, You're using *size (which now contains 20) as the termination condition of your loop, so your loop will execute 20 times. However, p_array still only has 10 entries. What do p_array[10]-[19] contain? Probably garbage, if they don't cause your program to crash.

[phztfte1]

Thank you. You confirmed what I thought would happen.

I fixed the program as follows:

int* growArray(int* p_values, int* size)
{
	int old_size = *size;                   //  Added variable to store old size
	*size *= 2
	int* p_new_values = new int[*size];
	for (int i = 0; i < old_size; i++)        // Used old_size to terminate for loop
	{
		p_new_values[i] = p_values[i];
		cout << "old_size[" << i << "] = "  << endl;
	}
	delete[] p_values;
	return p_new_values;
}