This sounds cool! The first example has a pretty nasty typo. This: int *arr = malloc(9); does of course not allocate enough space to make it safe to index

This sounds cool! The first example has a pretty nasty typo. This: int *arr = malloc(9); does of course not allocate enough space to make it safe to index arr up to 8. It only allocates 9 bytes, which on a typical 32-bit int machine only gives you room for 2.25 ints. It should of course be: int *arr = malloc(9 * sizeof *arr); It's fixed in the second example, where they introduce the malloc_wrapper().