Realloc pollfd - conversion to non-scalar

Question

I'm using the poll function. The library has a structure as so:

struct pollfd{
   int fd;
   short events;
   short revents;
}

Now, in my code I have an array of these events and I need to be able to realloc and give more memory space for more items. This is what I currently have:

#define NRCONNECTIONS 10
#define STEPSIZE 5

struct pollfd pollFd[NRCONNECTIONS];

int main(void){
   void * temp;
   temp = realloc((void *)pollFd, (sizeof(pollFd)/sizeof(pollFd[0])) + STEPSIZE);
   if(temp != NULL){
    pollFd = (struct pollfd *)temp;
   }
}

Now, I can't seem to get the code inside the if(temp != NULL) correct. I can't do it without a cast because then it's incorrect. I can't do it with a (struct pollfd) cast because that's non-scalar. Like this also isn't working. Is it because my pollFd variable is done without a malloc(), or is something else wrong?

Thanks in advance.

Update

struct pollfd *pollFd;

pollFd = malloc(NRCONNECTIONS * sizeof(struct pollfd));
if(pollFd == NULL){
    printf("Error malloc\n");
    fflush(stdout);
    exit(0);
}

This should be the correct initialization then? How do I then make it act like an array? I mean, how do I access eg the 0'th element?

Answer 1

The first argument of realloc must be a pointer that is earlier returned by a call to malloc, realloc or calloc, or a null pointer. In your case, it's not any of them.