From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:52944)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <armbru@redhat.com>) id 1Zgw3E-0003Oe-Ev
	for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:38:41 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <armbru@redhat.com>) id 1Zgw3B-0006yC-4s
	for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:38:40 -0400
Received: from mx1.redhat.com ([209.132.183.28]:50648)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <armbru@redhat.com>) id 1Zgw3A-0006y5-VP
	for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:38:37 -0400
From: Markus Armbruster <armbru@redhat.com>
References: <1443497249-15361-1-git-send-email-eblake@redhat.com>
	<1443497249-15361-17-git-send-email-eblake@redhat.com>
Date: Tue, 29 Sep 2015 16:38:33 +0200
In-Reply-To: <1443497249-15361-17-git-send-email-eblake@redhat.com> (Eric
	Blake's message of "Mon, 28 Sep 2015 21:27:29 -0600")
Message-ID: <87pp11guja.fsf@blackfin.pond.sub.org>
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [Qemu-devel] [PATCH v6 16/16] qapi: Share gen_visit_fields()
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: Eric Blake <eblake@redhat.com>
Cc: marcandre.lureau@redhat.com, qemu-devel@nongnu.org, ehabkost@redhat.com, Michael Roth <mdroth@linux.vnet.ibm.com>

Eric Blake <eblake@redhat.com> writes:

> Consolidate the code between visit, command marshalling, and
> event generation that iterates over the members of a struct.
> It reduces code duplication in the generator, so that a future
> patch can reduce the size of generated code while touching only
> one instead of three locations.
>
> There are no changes to generated marshal code.
>
> The visitor code is slightly more verbose, but semantically

Suggest "becomes slightly more verbose".

> equivalent, and actually easier to read as it follows a more
> common idiom:
>
> |     visit_optional(v, &(*obj)->has_device, "device", &err);
> |-    if (!err && (*obj)->has_device) {
> |-        visit_type_str(v, &(*obj)->device, "device", &err);
> |-    }
> |     if (err) {
> |         goto out;
> |     }
> |+    if ((*obj)->has_device) {
> |+        visit_type_str(v, &(*obj)->device, "device", &err);
> |+        if (err) {
> |+            goto out;
> |+        }
> |+    }
>
> The event code is slightly more verbose, but arguably a bug
> fix (although the visitors are not well documented, use of an
> optional member should not be attempted unless guarded by a
> prior call to visit_optional()) - we were lucky that the output
> qmp visitor has a no-op visit_optional():

Suggest "becomes slightly more verbose, but this is arguably a bug fix:
although [...] prior call to visit_optional().  Works only because the
output qmp visitor [...]".

>
> |+    visit_optional(v, &has_offset, "offset", &err);
> |+    if (err) {
> |+        goto out;
> |+    }
> |     if (has_offset) {
> |         visit_type_int(v, &offset, "offset", &err);
>
> Signed-off-by: Eric Blake <eblake@redhat.com>
>
> ---
> v6: retitle 10/46, split gen_err_check() to its own patch,
> improve commit message, use named parameters in gen_visit_fields()
> to minimize effort of callers

Interdiff to v5 looks sane.