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[PATCH v2] Remove MULTI_PTRS_ARE_ALIASES to fix Wundef warning

On Fri, Jun 27, 2014 at 09:34:19PM -0700, Roland McGrath wrote:
> I guess for now the inconsistency just makes me want to have the other code
> forks around as documentation.  I suppose comments would do it just as
> well.  Still my inclination is to make these something like:
> /* Insert long new comment about the weirdness and referring to the other
>    file where the opposite fork is used in equivalent code.  */
> #if 0 /* was MULTI_PTRS_ARE_ALIASES */

After reading further, I don't think there is any inconsistency in
functionality.  The gethostbyaddr function also uses the dns-host.c
bits and gethnamaddr.c is currently not used at all.  The only
reference it has is in resolv/README:

    The files gethnamaddr.c, mapv4v6addr.h and mapv4v6hostent.h are
    leftovers from BIND 4.9.7.

Given this newly discovered fact, how about the following patch
instead?  I don't modify gethnamaddr.c because it's not even used.  I
wonder - given that we have decided to own the resolver bits now - if
we should just get rid of gethnamaddr.c and other unused files.  I
could add a note in the README mentioning this.


	* resolv/nss_dns/dns-host.c (getanswer_r)

commit 8e2ad63093a3c1e18122acdb50db5883770a3fc5
Author: Siddhesh Poyarekar <>
Date:   Mon Jun 30 11:17:51 2014 +0530

    Remove MULTI_PTRS_ARE_ALIASES in dns-hosts.c
    The code in gethnamaddr.c for gethostbyaddr used and set this macro to
    allow multiple PTR records to be added as aliases.  This was useful
    for gethostbyaddr since it returns a hostent structure, which can
    return aliases.
    The gethnamaddr.c source however is unused in glibc since pretty much
    forever.  Instead, the DNS lookup bits for gethostbyaddr (as well as
    getnameinfo) are implemented in dns-hosts.c and in that implementation
    all but one (the first one) of the multiple PTR records are ignored.
    Since gethnamaddr.c is essentially dead code, ignore that
    implementation and replace the MULTI_PTRS_ARE_ALIASES bit with a
    comment mentioning that bind adds PTR records as aliases while we

diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index a5f2c0a..3258e70 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -869,27 +869,8 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
-	  cp += n;
-	  if (haveanswer == 0)
-	    result->h_name = bp;
-	  else if (ap < &host_data->aliases[MAXALIASES-1])
-	    *ap++ = bp;
-	  else
-	    n = -1;
-	  if (n != -1)
-	    {
-	      n = strlen (bp) + 1;	/* for the \0 */
-	      if (__builtin_expect (n, 0) >= MAXHOSTNAMELEN)
-		{
-		  ++had_error;
-		  break;
-		}
-	      bp += n;
-	      linebuflen -= n;
-	    }
-	  break;
+	  /* bind would put multiple PTR records as aliases, but we don't do
+	     that.  */
 	  result->h_name = bp;
 	  if (have_to_map)
@@ -906,7 +887,6 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
 	  *h_errnop = NETDB_SUCCESS;
 	case T_A:
 	case T_AAAA:
 	  if (__builtin_expect (strcasecmp (result->h_name, bp), 0) != 0)

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