You need to add:
#include <stdlib.h>This file includes the declaration for the built-in function malloc. If you don't do that, the compiler thinks you want to define your own function named malloc and it warns you because:
- You don't explicitly declare it and
- There already is a built-in function by that name which has a different signature than the one that was implicitly declared (when a function is declared implicitly, its return and argument types are assumed to be
int, which isn't compatible with the built-inmalloc, which takes asize_tand returns avoid*).