unsigned long long int pow

I have the following power function which operates on integers and it works fine:

int ipow( int base, int exp )
{
    int result = 1;
    while( exp )
    {
        if ( exp & 1 )
        {
            result *= base;
        }
        exp >>= 1;
        base *= base;
    }
    return result;
}

Now I'd like to have a version which allows exp > 32. So I use unsigned long long ints:

unsigned long long int ipow( int base, int exp )
{
    unsigned long long int result = 1ULL;
    while( exp )
    {
        if ( exp & 1 )
        {
            result *= (unsigned long long int)base;
        }
        exp >>= 1;
        base *= base;
    }
    return result;
}

But this second version doesn't seem to work:

unsigned long long int x;
x = ipow( 2, 35 );
printf( "%llu\n", x );

this will output 0.

What's the problem with my unsigned long long int implementation?

Your base variable is too small. Change it to unsigned long long int, like the others, since it holds numbers greater than 2^32.