Hello configure hackers, have a look at this little thing:

This is plain Redhat 7.2 installation:

$ which curl
/usr/bin/curl
$ curl -V
curl 7.8 (i386-redhat-linux-gnu) libcurl 7.8 (OpenSSL 0.9.6b) (ipv6 enabled)

Aha! An IPv6 enabled libcurl is installed by default. Neato!

But then...

$ cd curl-7.9.3
$ ./configure
...
checking whether to enable ipv6... no
...

;-(

When I do the exact same operation on my 2.4.16 IPv6-enabled box it says:

checking whether to enable ipv6... yes
checking for working getaddrinfo... yes

Now, why does configure say this on the redhat 7.2-box? I can still make the
7.2 use ipv6 if I pass the --enable-ipv6 option to configure.

config.log on the failing machine says this:

configure:7840: checking whether to enable ipv6
configure:7879: gcc -o conftest -g -O2 conftest.c >&5
configure:7882: $? = 0
configure:7884: ./conftest
configure:7887: $? = 1
configure: program exited with status 1
configure: failed program was:
#line 7864 "configure"
#include "confdefs.h"
 /* is AF_INET6 available? */
#include <sys/types.h>
#include <sys/socket.h>
main()
{
 if (socket(AF_INET6, SOCK_STREAM, 0) < 0)
   exit(1);
 else
   exit(0);
}

configure:7896: result: no

The question is of course: why doesn't this tiny program work?

The same piece of log on my 2.4.16-box says:

configure:7840: checking whether to enable ipv6
configure:7879: gcc -o conftest -g -O2 conftest.c >&5
configure:7882: $? = 0
configure:7884: ./conftest
configure:7887: $? = 0
configure:7889: result: yes

-- 
    Daniel Stenberg -- curl groks URLs -- http://curl.haxx.se/