From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next] ipv4: use IS_ENABLED() macro to cleanup code
Date: Wed, 26 Oct 2011 08:34:34 +0200
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	 <20111025.193037.1312584002692004360.davem@davemloft.net>
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To: David Miller <davem@davemloft.net>
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Le mardi 25 octobre 2011 =C3=A0 19:30 -0400, David Miller a =C3=A9crit =
:

> net/ipv4/ip_sockglue.c: In function =E2=80=98do_ip_setsockopt=E2=80=99=
:
> net/ipv4/ip_sockglue.c:523:29: error: =E2=80=98LOOPBACK4_IPV6=E2=80=99=
 undeclared (first use in this function)
> net/ipv4/ip_sockglue.c:523:29: note: each undeclared identifier is re=
ported only once for each function it appears in
>=20
> This fails because ip_sockglue.c guards the net/transp_v6.h header
> inclusion with a real CPP guard.

Yep, it seems compiler was not able to perform optimisation of dead
code.

        if (IS_ENABLED(CONFIG_IPV6) &&
            (sk->sk_family =3D=3D PF_INET ||
             (!((1 << sk->sk_state) &
                (TCPF_LISTEN | TCPF_CLOSE)) &&
             inet->inet_daddr !=3D LOOPBACK4_IPV6))) {

Never mind, this will wait 3.3 :)