[PATCH] Fix strict-aliasing warning in resolv/res_hconf.c

[Steve Ellcey]

On Tue, 2015-05-19 at 16:04 -0700, Paul Eggert wrote:
> On 05/19/2015 03:53 PM, Steve Ellcey wrote:
> > +      union
> > +	{
> > +	struct sockaddr *sa;
> > +	struct sockaddr_in *sin;
> > +	} ss;
> >         int sd, num, i;
> >         /* Save errno.  */
> >         int save = errno;
> > @@ -443,14 +448,14 @@ _res_hconf_reorder_addrs (struct hostent *hp)
> >   		continue;
> >   
> >   	      ifaddrs[new_num_ifs].addrtype = AF_INET;
> > -	      ifaddrs[new_num_ifs].u.ipv4.addr =
> > -		((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
> > +	      ss.sa = &cur_ifr->ifr_addr;
> > +	      ifaddrs[new_num_ifs].u.ipv4.addr = ss.sin->sin_addr.s_addr;
> 
> I'm afraid that's no better than casting.  It needs to be a union of 
> contents, not of pointers.

Hm, I am not sure I know how to do that.  I tried changing
sysdeps/gnu/net/if.h to include a 'struct sockaddr_in ifru_addr_in;'
entry in the ifru_data union but that won't compile.

In file included from ../include/net/if.h:3:0,
                 from ../sysdeps/generic/ifreq.h:22,
                 from ../sysdeps/unix/sysv/linux/ifreq.c:19:
../sysdeps/gnu/net/if.h:142:21: error: field 'ifru_addr_in' has
incomplete type
  struct sockaddr_in ifru_addr_in;

I am not sure if I am just missing an include or if I simply cannot use
the sockaddr_in struct in this header.

Steve Ellcey
sellcey@imgtec.com