c - First time working with opaque pointers -

i trying implement stack, not understanding use of opaque pointer. here declaration:

/* incomplete type */ typedef struct stack_t *stack;  /* create new stack, have call first */ stack new_stack(void); 

and here stack structure , new_stack function:

struct stack_t {     int count;     struct node_t {             void *data;             struct node_t *next;     } *head; };  stack new_stack(void) {     struct stack_t new;     new.count = 0;     new.head->next = null;     return new; } 

in eyes, returning address of new stack, throws error on compilation returning new. doing wrong?

you returning stack_t value, return type of stack_new function stack, typedef struct stack_t* stack.
need return pointer - change allocation of stack_t stack heap use malloc dynamic allocation.
don't remember free() stack when not needed anymore, because dynamically allocated.

stack new_stack(void) {     struct stack_t* new = malloc(sizeof(struct stack_t));     new->count = 0;     new->head = null;     return new; }