using qsort to sort an array of long long int not working for large nos

Question

I am using this compare function to sort an array consisting of long long int nos.

int compare(const void * p1,const void * p2)
{
    return (* (long long int * )a-*(long long int * )b);
}
qsort(array,no of elements,sizeof(long long int),compare)

this works fine for small nos but when the array contains nos of the oreder of 10^10 it gives wrong results?

what is the mistake i am making?

Answer 1

explicitly return -1,1 or 0. This is the following code :

int cmpfunc (const void * a, const void * b)
{
    if( *(long long int*)a - *(long long int*)b < 0 )
        return -1;
    if( *(long long int*)a - *(long long int*)b > 0 )
        return 1;
    return 0;
}