Why is this power calculating function crashing?-CodePudding

I tried following function (as suggested on these forums) to calculate power. However, it is causing program to hang up.

static long ipow(int b, int e) {
    long r = 1;
    while (e--) r *= b;
    return r;
}

double cfilefn(int a, int b, int c) {
    return (ipow(a, b) / (double)c); 
}

cfilefn(2,3,4);

The function looks all right. Where is the error and how can it be solved?

CodePudding user response：

The ipow function will misbehave if the second argument is a negative number: it will run for a while and have implementation defined behavior when e reaches INT_MIN. You should modify the test while (e--) r *= b; as:

static long ipow(int b, int e) {
    long r = 1;
    while (e-- > 0)
        r *= b;
    return r;
}

Note however that ipow will cause arithmetic overflow for moderately large values of e and since you want a double result from cfilefn, you should use double arithmetics for the power function:

#include <math.h>

double cfilefn(int a, int b, int c) {
    return pow(a, b) / c; 
}