From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1MGgSO-0004x1-4v
	for qemu-devel@nongnu.org; Tue, 16 Jun 2009 17:44:40 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1MGgSJ-0004v6-7G
	for qemu-devel@nongnu.org; Tue, 16 Jun 2009 17:44:39 -0400
Received: from [199.232.76.173] (port=36347 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1MGgSJ-0004v3-1S
	for qemu-devel@nongnu.org; Tue, 16 Jun 2009 17:44:35 -0400
Received: from mtaout03-winn.ispmail.ntl.com ([81.103.221.49]:23291)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <sdbrady@ntlworld.com>) id 1MGgSI-0007Gq-E9
	for qemu-devel@nongnu.org; Tue, 16 Jun 2009 17:44:34 -0400
Received: from aamtaout01-winn.ispmail.ntl.com ([81.103.221.35])
	by mtaout03-winn.ispmail.ntl.com
	(InterMail vM.7.08.04.00 201-2186-134-20080326) with ESMTP id
	<20090616214433.GMYO5579.mtaout03-winn.ispmail.ntl.com@aamtaout01-winn.ispmail.ntl.com>
	for <qemu-devel@nongnu.org>; Tue, 16 Jun 2009 22:44:33 +0100
Received: from miranda.arrow ([213.107.24.213])
	by aamtaout01-winn.ispmail.ntl.com
	(InterMail vG.2.02.00.01 201-2161-120-102-20060912) with ESMTP id
	<20090616214432.SQKQ13254.aamtaout01-winn.ispmail.ntl.com@miranda.arrow>
	for <qemu-devel@nongnu.org>; Tue, 16 Jun 2009 22:44:32 +0100
Received: from sdb by miranda.arrow with local (Exim 4.63)
	(envelope-from <sdbrady@ntlworld.com>) id 1MGgSE-0004bN-Dm
	for qemu-devel@nongnu.org; Tue, 16 Jun 2009 22:44:30 +0100
Date: Tue, 16 Jun 2009 22:44:29 +0100
From: Stuart Brady <sdbrady@ntlworld.com>
Subject: Re: [Qemu-devel] [PATCH 16/21] linux-user: implement pipe2 [v3]
Message-ID: <20090616214429.GA17638@miranda.arrow>
References: <cover.1244813287.git.riku.voipio@iki.fi>
	<6ed5b469e54f235bef136cbd65e5769e205a2464.1244813287.git.riku.voipio@iki.fi>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <6ed5b469e54f235bef136cbd65e5769e205a2464.1244813287.git.riku.voipio@iki.fi>
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

On Fri, Jun 12, 2009 at 04:50:26PM +0300, riku.voipio@iki.fi wrote:
> +static abi_long do_pipe2(int host_pipe[], int flags)
> +{
> +#ifdef CONFIG_PIPE2
> +    return pipe2(host_pipe, flags);
> +#else
> +    return -ENOSYS;
> +#endif
> +}
> +
> +static abi_long do_pipe(void *cpu_env, int pipedes, int flags)
> +{
> +    int host_pipe[2];
> +    abi_long ret;
> +    ret = flags ? do_pipe2(host_pipe, flags) : pipe(host_pipe);

This worries me slightly -- surely syscalls should be consistently
supported / not supported (where feasible), regardless of the precise
arguments that are supplied?  (Otherwise, any run-time check for pipe2
would get tricked if that check specifies 0 for flags.)

OTOH, I'm not sure what behaviour the library would provide for the
pipe2() function, if the pipe2 syscall is not available.  One could
that the pipe2() function is another matter entirely, and that QEMU
shouldn't be too concerned with its implementation, though.

Cheers,
-- 
Stuart Brady