make array smaller...bad data i think

i need to make my array smaller to save memory and for some reason my program crashes when i call the print function i made to read out the numbers in the aray. i cant seem to find out why this only happens with the larger number because it works for making the array one size smaller just not 4 in the test I'm doing. when i do the test for re sizing 4 smaller it seems like it never saves the array because i put the print function be the realloc and it still crashes. also when i run the program with out pauses it crashes it would be nice to know why it did that too (same function)

here is the function

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void)
/******code******/

////////////////////////////////////////////////////////////////////////////////
//Preconditions:    p and q are pointers to struct integers.
//
//Postconditions:   A new struct integer is created that 
//                  stores the sum of the integers pointed to 
//                  by p and q and a pointer to it is 
//                  returned.
//
//Description:      
////////////////////////////////////////////////////////////////////////////////
struct integer* add(struct integer *p, struct integer *q)
{
    struct integer* big_number;
    int carry = 0;
    int test;
    int largest;
    int i;
    int j = 0;
    
    test = compare(p, q);
    
    if(test == 1)
    {
        largest = p->size;
    }
    else
    {
        largest = q->size;
    }
    big_number = malloc(sizeof(struct integer));
    big_number->digits = malloc(largest + 1 * sizeof(int));
    
    for(i = 0; i == largest; i++)
    {
        big_number->digits[i] = 0;
    }
    
    for(i = 0; i < largest +1; i++)
    {
        if(p->size <= i && q->size <= i)
        {
            big_number->digits[i] = carry;
            carry = 0;
            break;
        }
        else if(p->size <= i)
        {
            big_number->digits[i] = q->digits[i] + carry;
            carry = 0;
        }
        else if(q->size <= i)
        {
            printf("**test** i=%d", i);
            big_number->digits[i] = p->digits[i] + carry;
            carry = 0;
        }
        else
        {
            big_number->digits[i] = p->digits[i] + q->digits[i] +carry;
        
            if(big_number->digits[i] > 9)
            {
                big_number->digits[i] -= 10;
                carry = 1;
            }
            else
            {
                carry = 0;
            }
        }
        system("pause");
        //i have to put a pause here or the program will crash with no error message
    }
    for(i = largest, j = 0; big_number->digits[i] == 0 && i > 0; i--, j++);
    
    
    big_number->digits = (int*)realloc(big_number->digits,(largest-j) * sizeof(int));
    big_number->size = largest - j + 1;
    
    //the program crashes here with a windows message saying it "needs to close"
    print(big_number);
    
    return big_number;
}
////////////////////////////////////////////////////////////////////////////////
//Preconditions:    p is a pointer to a big integer.
//
//Postconditions:   The big integer pointed to by p is 
//                  printed out.
//
//Description:      
////////////////////////////////////////////////////////////////////////////////
void print(struct integer *p)
{
    int i;
    
    for(i = p->size -1 ; i >= 0; i--)
    {
        printf("%d", p->digits[i]);
    }
    printf("\n");
}

> for(i = 0; i == largest; i++)
This doesn't do anything useful. The condition is immediately false.

> big_number->digits = malloc(largest + 1 * sizeof(int));
Check your operator precedence.
Did you mean
big_number->digits = malloc( (largest + 1) * sizeof(int));

That at least would be consistent with your loop later on.

i knew it was something simple i just couldn't find it. thank you!