From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1L2oXN-0004sP-Ag
	for qemu-devel@nongnu.org; Wed, 19 Nov 2008 10:00:13 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1L2oXL-0004qL-DE
	for qemu-devel@nongnu.org; Wed, 19 Nov 2008 10:00:12 -0500
Received: from [199.232.76.173] (port=50463 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1L2oXL-0004qI-3y
	for qemu-devel@nongnu.org; Wed, 19 Nov 2008 10:00:11 -0500
Received: from qb-out-0506.google.com ([72.14.204.233]:51282)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <anthony@codemonkey.ws>) id 1L2oXJ-0001TS-Jq
	for qemu-devel@nongnu.org; Wed, 19 Nov 2008 10:00:09 -0500
Received: by qb-out-0506.google.com with SMTP id e12so3194854qba.0
	for <qemu-devel@nongnu.org>; Wed, 19 Nov 2008 07:00:08 -0800 (PST)
Message-ID: <492429F3.3010202@codemonkey.ws>
Date: Wed, 19 Nov 2008 09:00:03 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 1/2] Add TAILQ_FOREACH_SAFE
References: <20081119134857.26075.2417.stgit@mchn012c.ww002.siemens.net>
	<20081119134857.26075.9428.stgit@mchn012c.ww002.siemens.net>
In-Reply-To: <20081119134857.26075.9428.stgit@mchn012c.ww002.siemens.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel@nongnu.org

Jan Kiszka wrote:
> Add TAILQ iterator that allows to safely remove elements while walking
> the list.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>
>  sys-queue.h |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/sys-queue.h b/sys-queue.h
> index 3d0773e..b92a77f 100644
> --- a/sys-queue.h
> +++ b/sys-queue.h
> @@ -210,6 +210,12 @@ struct {                                                                \
>                  (var);                                                  \
>                  (var) = ((var)->field.tqe_next))
>  
> +#define TAILQ_FOREACH_SAFE(var, head, field, next_var)                  \
> +        for ((var) = ((head)->tqh_first);                               \
> +                (var) ? ({ (next_var) = ((var)->field.tqe_next); 1; })  \
> +                      : 0;                                              \
> +                (var) = (next_var))
>   

So the Linux implementation of this is:

#define list_for_each_safe(pos, n, head) \
    for (pos = (head)->next, n = pos->next; pos != (head); \
        pos = n, n = pos->next)

I'd prefer something similar:

#define TAILQ_FOREACH_SAFE(var, head, field, next_var)
             for (var = (head)->tqh_first, next_var = var->field.tqe_next;
                   var;
                   var = next_var, next_var = var->field.tqe_next)

As it's functionally equivalent and avoids using a GCC-ism ({}).

Regards,

Anthony Liguori