c - How to realloc an array of structs -

using c, i'm trying input stuff array of structs, , once array filled, double size of array , keep going, using realloc.

i know there's been several question asked already, hoping explain since didn't create array way questions did , getting bit confused.

i have struct

struct data {     // variables } 

and initialised array using

struct data entries[100]; int curentries = 100; int counter = 1; // index, use (counter - 1) when accessing 

to realloc, i'm using

if(counter == curentries){  // counter = index of array, curentries = total     entries = realloc(entries, curentries * 2); } 

i know need cast realloc right? i'm not sure how or i'm meant casting to, don't have anything, of course gives me error "assignment expression array type"

thanks!

struct data entries[100];// memory allocated 

you need declare entries pointer like:

struct data *entries=null; entries = malloc(curentries  * sizeof(struct data)); //when time reallocate entries = realloc(entries, (curentries * 2 * sizeof(struct data)));