[ace123]

First of all, I would HIGHLY recommend writing and using your own functions.

Are you using floating point powers (6^2.5) or only integers(6^3).

If you are using integer powers then it would be very easy to write your own function:

long powl(long y, int x) {
    long result=1;
    int i;
    for (i=0;i<x;++i) {
        result*=y;
    }
    return result;
}

(make sure to call a different name like powl instead of pow to avoid conflicts.)

That is much faster and better than using a function with floating point numbers (doubles), which are bad to use on these microprocessors and which one has little reason to use.

------------------------
Now, to answer your question about the hard way to do this:
The "old style" functions are when you do:

double pow(y,x)
double y, x;
{
    ...
}

The way to fix it is to change math.c:

double pow(double y,double x)
{
...
}

Do the same thing with ceil at line 71:

double ceil(double x)
{
...
}