Sum of array elements in a dynamic array

[Night Rawk]

I'm trying to sum the elements in a dynamic array. This is the code thus far.

#include <iostream>
#include <cstdlib>
using namespace std;

void fillarray(int SIZE);

int main(int argc, char *argv[])
{
    int size;
    
    cout<<"\nEnter the desired size of the array: ";
    cin>>size;
    
    fillarray(size);
    
    system ("pause");
    return EXIT_SUCCESS;
}

void fillarray(int SIZE)
{
     int *arr;
     arr = new int[SIZE];
     int total = 0;
     int average;
     
     for (int i=0; i < SIZE; i++)
     {
         cout<<"\nEnter a number to be stored in array element "<<i+1<<": ";
         cin>>arr[i];
     }
     
     for (int i = 0; i < SIZE; i++, arr++)
     {
         cout<< *arr <<" ";
     }
     
     int *p = arr;
     for (int i = 0; i < SIZE; i++, p++)
     {
         total += *p;
     }
     cout<<"\n"<<total<<endl;   
     
     delete arr;
     arr = NULL;    
}

The problem lies with the output for "total." For some reason it's being output in machine code.

Enter the desired size of the array: 3

Enter a number to be stored in array element 1: 4

Enter a number to be stored in array element 2: 5

Enter a number to be stored in array element 3: 6
4 5 6
-1480403165
Press any key to continue . . . 

It would be helpful if anyone could shed light on this issue. Thanks!

[slicedpan]

When you increment the value of arr at line 33, this means the arr points beyond the last element of the array. Then you assign p to that. That means that p points beyond the last element also. When you try and dereference a pointer that points to unallocated memory, crazy things will happen. In this case, the value of (*p) will be uninitialised (essentially random). Instead of incrementing arr in line 33, use the same syntax you used in line 30 to input the numbers, i.e. arr[i]. This way doesn't change the value of arr.

[zb0S216C]

Night Rawk wrote:

delete arr;

Careful! This causes a memory leak. A call to new should have a corresponding call to delete. A call to new[] should have a corresponding call to delete[].

You've done something terrible here. In your second for loop in fillarray(), arr, which each cycle, is moved 1 place up through the array. When the loop ends, arr is pointing to the to the last element of the dynamically allocated array; thus, p points to the last element of the dynamically allocated array. As a consequence, the 3^rd loop moves p past the dynamically allocated array, and ultimately, reads uninitialised memory (usually contains values such as 82847324).

_Wazzak

[Night Rawk]

Thank you slicedpan! It now works perfectly!