AIX 4.3 or later should use gethostbyname() and not the *_r() version.

#ifdef HAVE_GETHOSTBYNAME_R_3

    /* AIX, Digital Unix, HPUX 10, more? */

    /* For AIX 4.3 or later, we don't use gethostbyname_r() at all, because of

       the plain fact that it does not return unique full buffers on each

       call, but instead several of the pointers in the hostent structs will

       point to the same actual data! This have the unfortunate down-side that

       our caching system breaks down horribly. Luckily for us though, AIX 4.3

       and more recent versions have a completely thread-safe libc where all

       the data is stored in thread-specific memory areas making calls to the

       plain old gethostbyname() work fine even for multi-threaded programs.

       This AIX 4.3 or later detection is all made in the configure script.

       Troels Walsted Hansen helped us work this out on March 3rd, 2003. */

    if(CURL_NAMELOOKUP_SIZE >=

       (sizeof(struct hostent)+sizeof(struct hostent_data)))

      ret = gethostbyname_r(hostname,

                            (struct hostent *)buf,

                            (struct hostent_data *)((char *)buf + sizeof(struct hostent)));

                            (struct hostent_data *)((char *)buf +

                                                    sizeof(struct hostent)));

    else

      ret = -1; /* failure, too smallish buffer size */