TODO: fix malloc.c, %zu format instead of %zi for size_t

man malloc:

malloc, free, calloc, realloc - allocate and free dynamic memory

  #include <stdlib.h>

  void *malloc(size_t size);
  void free(void *ptr);

  void *calloc(size_t nmemb, size_t size);
  void *realloc(void *ptr, size_t size);