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 recently had a similar alias warning on HPUX system when trying to write code to get the MAC address of the machine

The &(((struct sockaddr_in *)addr)->sin_addr) complains about strict-aliasing rules

This is the code in some context

 char ip[INET6_ADDRSTRLEN] = {0};
 strucut sockaddr *addr

 ...
 get addr from ioctl(socket,SOCGIFCONF...) call
 ...
 inet_ntop(AF_INET, &(((struct sockaddr_in *)addr)->sin_addr),ip,sizeof ip);

I overcame the aliasing warning by doing the following

struct sockaddr_in sin;
memcpy(&sin,addr,sizeof(struct sockaddr));
inet_ntop(AF_INET, &sin.sin_addr,ip,sizeof ip);

And whilst this is potentially dangerous I added the following lines before it

 static_assert(sizeof(sockaddr)==sizeof(sockaddr_in));

I'm not sure if that is something would be considered bad practice, but it worked and was cross platform to other *Nix flavors and compilers