From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:50123)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1ab9XW-0004p4-T6
	for qemu-devel@nongnu.org; Wed, 02 Mar 2016 11:22:19 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1ab9XW-0006W5-2z
	for qemu-devel@nongnu.org; Wed, 02 Mar 2016 11:22:18 -0500
Date: Wed, 2 Mar 2016 17:22:08 +0100
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20160302162208.GE4494@noname.redhat.com>
References: <fcd74f168507a8ea9a76d1e85eed9f82f75f00c1.1456934833.git.jcody@redhat.com>
	<56D71109.7060009@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <56D71109.7060009@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2 1/1] block/sheepdog: fix argument passed
 to qemu_strtoul()
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-block@nongnu.org, mitake.hitoshi@lab.ntt.co.jp, Jeff Cody <jcody@redhat.com>, qemu-devel@nongnu.org, v.tolstov@selfip.ru, mreitz@redhat.com, namei.unix@gmail.com

Am 02.03.2016 um 17:12 hat Paolo Bonzini geschrieben:
> 
> 
> On 02/03/2016 17:09, Jeff Cody wrote:
> > +    ret = qemu_strtoul(snapshot_id, NULL, 10, &snap_id);
> > +    if (ret) {
> > +        error_setg_errno(errp, -ret, "Invalid snapshot ID: %s",
> > +                         snapshot_id ? snapshot_id : "<null>");
> > +        return ret;
> > +    }
> > +
> > +    if (snap_id > UINT32_MAX) {
> > +        error_setg_errno(errp, EINVAL, "Snapshot ID numeric value %" PRId64
> > +                         " exceeds Sheepdog maximum of %" PRId32, snap_id,
> > +                          UINT32_MAX);
> > +        return -EINVAL;
> >      }
> 
> I think including the errno produces a worse error message ("Invalid
> snapshot ID: foo: Invalid argument" or something like that)

Yes. Rule of thumb: If you call error_setg_errno() with a constant
errno, there's something wrong.

Kevin

> , and also
> the error should be the same for an id of 10^10 (within uint64_t bounds)
> or 10^30 (outside the bounds).  So you could just use
> 
>     if (ret < 0 || snap_id > UINT32_MAX) {
>         error_setg(errp, "Invalid snapshot ID: %s",
>                    snapshot_id ? snapshot_id : "<null>");
>         return -EINVAL;
>     }
> 
> Thanks,
> 
> Paolo