Writing a network checker in C, but error handling troubles me

Question

I am still pretty new to pointers so need help with this. I am writing program that will list network adapter.

This is the whole code;

int main() {
    struct ifaddrs *addresses;
    
    if (getifaddrs(&addresses == -1)) {
        printf("getifaddrs call failed!\n");
        return -1;
    }

    struct ifaddrs *address = addresses;
    while (address) {
        int family = address->ifa_addr->sa_family;
        if (family == AF_INET || family == AF_INET6) {
            printf("%s\t", address->ifa_name);
            printf("%s\t", family == AF_INET ? "IPv4" : "IPv6");

            char ap[100];
            const int family_size = family == AF_INET ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6);
            getnameinfo(address->ifa_addr, family_size, ap, sizeof(ap), 0, 0, NI_NUMERICHOST);
            printf("\t%s\n", ap);
        }
        address = address->ifa_next;
    }

    freeifaddrs(addresses);
    
    return 0;
}    

My issue is with this part:

struct ifaddrs *addresses;
    
    if (getifaddrs(&addresses == -1)) {
        printf("getifaddrs call failed!\n");
        return -1;
    }

when compiling i get this error:

integer without a cast [-Wint-conversion]
   11 |     if (getifaddrs(&addresses == -1)) {
      |                    ~~~~~~~~~~~^~~~~
      |                               |
      |                               int
I fil inkluderet fra list_adapter.c:5:
/usr/include/ifaddrs.h:66:41: bemærk: expected »struct ifaddrs **« but argument is of type »int«
   66 | extern int getifaddrs (struct ifaddrs **__ifap) __THROW;
      |                        ~~~~~~~~~~~~~~~~~^~~~~~

I have tried to cast the address pointer to both int and char before using it, but it keeps giving the same error and if i outcomment the whole if-else that contains the error handling, then i get thrown a segmetation fault.

Also a void pointer didn't help.

Thanks

Answer 1

You have your closing parenthesis in the wrong place in this line:

if (getifaddrs(&addresses == -1)) {

It should be

if (getifaddrs(&addresses) == -1) {

The segmentation fault you get when you comment out the if else block is probably because you are trying to use the uninitialised pointer.