/in/hash.c:27:5: error: implicit declaration of function 'delete' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    delete (hashtable, size, key);
    ^
/in/hash.c:39:6: error: conflicting types for 'delete'
void delete(void* hashtable, int size, int key)
     ^
/in/hash.c:27:5: note: previous implicit declaration is here
    delete (hashtable, size, key);
    ^
2 errors generated.