c - undefined reference to avltree_init -

in code provided instructor there is:

typedef int (*avltree_cmp_fn_t)(const struct avltree_node *, const struct avltree_node *);  int avltree_init(struct avltree *tree, avltree_cmp_fn_t cmp, unsigned long flags); 

after define my_cmp function...

int my_cmp(const struct avltree_node *a, const struct avltree_node *b) {         struct my_struct *p = avltree_container_of(a, my_struct, node);         struct my_struct *q = avltree_container_of(b, my_struct, node);         return p->key - q->key; } 

and pass parameter avltree_init...

avltree_init(&tree, my_cmp, 0); 

i get:

 undefined reference `avltree_init(avltree*, int (*)(avltree_node const*, avltree_node const*), unsigned long)' 

could explain, please, why happens , did make mistake? thanks!

it seems error message you're not linking file contains avltree_init function. need link files, including file containing function, final application. error comes linking phase, not compiling phase.

furthermore, see error message you're using c++ compiler c code. don't need that: more optimal use c compiler.