C command line list sorting w/ sort function extensibility and comparator extensibility

extensible_sort.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

void die(const char *message)
{
  if(errno) {
    perror(message);
  } else {
    printf("ERROR: %s\n", message);
  }
  exit(1);
}

void swap(int* a, int* b) {
  int tmp = *a;
  *a = *b;
  *b = tmp;
}

typedef int (*compare_cb)(int a, int b);

typedef int *(*sort_function_cb)(int *numbers, int count, compare_cb cmp);

int increasing(int a, int b) {
  return a - b;
}

int decreasing(int a, int b) {
  return b - a;
}

int *insertion_sort(int *numbers, int count, compare_cb cmp) {
  int i = 0;
  int j = 0;
  int *result = malloc(count * sizeof(int));

  if(!result) die("Memory error");

  memcpy(result, numbers, sizeof(int) * count);

  for(i = 1; i < count; i++) {
    j = i;
    while(j > 0 && cmp(result[j-1], result[j]) > 0) {
      swap(&result[j-1], &result[j]);
      j--;
    }
  }

  return result;
}

int *bubble_sort(int *numbers, int count, compare_cb cmp) {

  int i = 0;
  int j = 0;
  
  int *result = malloc(count * sizeof(int));
  if(!result) die("Memory error.");

  memcpy(result, numbers, sizeof(int) * count);
  
  for(i = 0; i < count; i++) {
    for(j = 0; j < count - 1; j++) {
      if(cmp(result[j], result[j + 1]) > 0) {
        swap(&result[j], &result[j + 1]);
      }
    }
  }

  return result;
}

void print_array(int *numbers, int count) {
  int i = 0;

  for(i = 0; i < count; i++) {
    printf("%d ", numbers[i]);
  }
  printf("\n");
}

void test_sort(sort_function_cb sort_fn, int *numbers, int count, compare_cb cmp) {
  int *result = sort_fn(numbers, count, cmp);

  print_array(result, count);

  /* more good C citizenship */
  free(result);
}

int main(int argc, char* argv[])
{

  int i = 0;
  int count = argc - 1;
  int *numbers;
  
  if(argc < 2) die("Usage ./sort 5 1 4 2 3 6\n");

  /* allocate space for int array */
  numbers = malloc(count * sizeof(int));
  if (!numbers) die("Memory error.");
  
  /* take in command line arguments */
  /* convert into integer array */
  for(i = 0; i < count; i++) {
    numbers[i] = atoi(argv[i + 1]);
  }

  printf("Bubble sort:\n");
  
  /* sort them */
  test_sort(bubble_sort, numbers, count, increasing);
  test_sort(bubble_sort, numbers, count, decreasing);

  printf("Insertion sort:\n");
  
  test_sort(insertion_sort, numbers, count, increasing);
  test_sort(insertion_sort, numbers, count, decreasing);

  /* Be a good Citizen and free your mallocs. For America. */
  free(numbers);
  return 0;
}