From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124])
	by inbox.dpdk.org (Postfix) with ESMTP id 973554296E;
	Mon, 17 Apr 2023 17:16:36 +0200 (CEST)
Received: from mails.dpdk.org (localhost [127.0.0.1])
	by mails.dpdk.org (Postfix) with ESMTP id 6AFD240DFB;
	Mon, 17 Apr 2023 17:16:36 +0200 (CEST)
Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182])
 by mails.dpdk.org (Postfix) with ESMTP id 84CED40698
 for <dev@dpdk.org>; Mon, 17 Apr 2023 17:16:34 +0200 (CEST)
Received: by linux.microsoft.com (Postfix, from userid 1086)
 id 8723C21C1E67; Mon, 17 Apr 2023 08:16:33 -0700 (PDT)
DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 8723C21C1E67
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com;
 s=default; t=1681744593;
 bh=bPgXxsZ9WI8AkgGWI8kU7W7+rfee5B4HG71WT/5v/9k=;
 h=Date:From:To:Cc:Subject:References:In-Reply-To:From;
 b=h6/FlPejLvlNDwdE2l1r4xEfWeHQIGJbxtZ4QYXjZRiqrGaJRjHVoQ2bcwy6hgeRw
 6PMTk11psH4LNPaN6yS/ppAf6R/psQBkuDs1SGQbahSLOqFBDcKb8Gw/Ar0RVbfwe5
 OdTFZCzuJE3JbHmbSAugLI5SENWoRYK8KgXApUdI=
Date: Mon, 17 Apr 2023 08:16:33 -0700
From: Tyler Retzlaff <roretzla@linux.microsoft.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Morten =?iso-8859-1?Q?Br=F8rup?= <mb@smartsharesystems.com>,
 bruce.richardson@intel.com, david.marchand@redhat.com,
 thomas@monjalon.net, konstantin.ananyev@huawei.com, dev@dpdk.org
Subject: Re: [PATCH v5 11/14] eal: expand most macros to empty when using MSVC
Message-ID: <20230417151633.GB31948@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
References: <1680558751-17931-1-git-send-email-roretzla@linux.microsoft.com>
 <1681421163-18578-1-git-send-email-roretzla@linux.microsoft.com>
 <1681421163-18578-12-git-send-email-roretzla@linux.microsoft.com>
 <98CBD80474FA8B44BF855DF32C47DC35D87878@smartserver.smartshare.dk>
 <20230414170226.GA10264@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
 <98CBD80474FA8B44BF855DF32C47DC35D8787D@smartserver.smartshare.dk>
 <20230415205226.GA9699@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
 <98CBD80474FA8B44BF855DF32C47DC35D87880@smartserver.smartshare.dk>
 <20230415155227.28e647a2@hermes.local>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20230415155227.28e647a2@hermes.local>
User-Agent: Mutt/1.5.21 (2010-09-15)
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org

On Sat, Apr 15, 2023 at 03:52:27PM -0700, Stephen Hemminger wrote:
> On Sun, 16 Apr 2023 00:41:54 +0200
> Morten Brørup <mb@smartsharesystems.com> wrote:
> 
> > > > > > >  /**
> > > > > > >   * Force a structure to be packed
> > > > > > >   */
> > > > > > > +#ifndef RTE_TOOLCHAIN_MSVC
> > > > > > >  #define __rte_packed __attribute__((__packed__))
> > > > > > > +#else
> > > > > > > +#define __rte_packed
> > > > > > > +#endif  
> 
> Could there be cases this gets used for protocol headers or interacting with
> HW memory map, And if not packed then the code will not function correctly?

yes, that's one of the valid / correct use cases and it can't be avoided
if the structs are nested in recursively composed layout.

there are a few instances where we don't need compiler generated
static-stride. that is we don't need to force packing to get sizeof(T)
== offsetof(T.lastfield) + sizeof(T.lastfield).

anyway, this is more of an evaluate on a case by case basis for
candidates that aren't needed.

ty