How to cast sockaddr_storage and avoid breaking strict-aliasing rules

Question

I\'m using Beej\'s Guide to Networking and came across an aliasing issue. He proposes a function to return either the IPv4 or IPv6 address of a particular struct:

Answer 1

I tend to do this to get GCC do the right thing with type-punning, which is explicitly allowed with unions

I am pretty sure this (mis)use of union will not work (or only by accident) with GCC:

short type_pun2 (int i, int *pi, short *ps) {
    *pi = i;
    return *ps;
}

union U {
    int i;
    short s;
};

short type_pun (int i) {
    U u;
    return type_pun2 (i, &u.i, &u.s);
}

The correct way to do that is with memcpy, not union.