Find root by Newton method

newton.c

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

typedef double (*func)(double);

double f(double x) {
  return x * x - 2.0 * x - 5.0;
}
double fd(double x) {
  return 2.0 * x - 2.0;
}
/**
 * find the x-intercept of a line given a point and slope
 */
double getIntercept(double x0, double y0, double m) {
  return x0 - y0 / m;
}
/*
 * return the estimated root, modify *iter by iteration count
 */
double newton(double x0, func f, func fd, double eps, double maxiter, int* iter) {
  for (*iter = 0; *iter < maxiter; ++*iter) {
    double y0 = f(x0);
    if (fabs(y0) < eps) return x0;
    x0 = getIntercept(x0, y0, fd(x0));
  }
  printf("max-iter reached");
  return x0;
}

int main() {
  double root;
  int* iter_count = (int *)malloc(sizeof(*iter_count));
  root = newton(5, f, fd, 0.001, 100, iter_count);
  printf("Case 1: root = %lf, iter_count = %d\n", root, *iter_count);
  root = newton(-3, f, fd, 0.001, 100, iter_count);
  printf("Case 2: root = %lf, iter_count = %d\n", root, *iter_count);
  free(iter_count);
  return 0;
}