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

void *errorchecked_malloc(unsigned int);

int main(int argc, const char *argv[])
{
  char *char_ptr;
  int *int_ptr;
  int mem_size;

  if (argc < 2)
    mem_size = 50;
  else
    mem_size = atoi(argv[1]);

  printf("\t[+] allocating %d bytes of memory on the heap for char_ptr\n", mem_size);
  char_ptr = (char *) errorchecked_malloc(mem_size);

  strcpy(char_ptr, "this memory is located on the heap.");
  printf("char_ptr (%p) --> '%s'\n", char_ptr, char_ptr);

  printf("\t[+] allocating 12 bytes of memory on the heap for int_ptr\n");
  int_ptr = (int *) errorchecked_malloc(12);

  *int_ptr = 31337;
  printf("int_ptr (%p) --> %d\n", int_ptr, *int_ptr);

  printf("\t[-] freeing char_ptr's heap memory...\n");
  free(char_ptr);

  printf("\t[+] allocating another 15 bytes for char_ptr\n");
  char_ptr = (char *)errorchecked_malloc(15);

  strcpy(char_ptr, "new memory");
  printf("char_ptr (%p) --> '%s'\n", char_ptr, char_ptr);

  printf("\t[-] freeing int_ptr's heap memory...\n");
  free(int_ptr);
  printf("\t[-] freeing char_ptr's heap memory...\n");
  free(char_ptr);

  return 0;
}

void *errorchecked_malloc(unsigned int size)
{
  void *ptr;
  ptr = malloc(size);
  if (ptr == NULL) {
    fprintf(stderr, "Error: could not allocate heap memory.\n");
    exit(-1);
  }
  return ptr;
}