From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 81546A052E for ; Mon, 9 Mar 2020 09:55:12 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 48CB31C000; Mon, 9 Mar 2020 09:55:12 +0100 (CET) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 0BE431C000; Mon, 9 Mar 2020 09:55:10 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Mar 2020 01:55:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,532,1574150400"; d="scan'208";a="230857331" Received: from fyigit-mobl.ger.corp.intel.com (HELO [10.237.221.20]) ([10.237.221.20]) by orsmga007.jf.intel.com with ESMTP; 09 Mar 2020 01:55:06 -0700 To: Gavin Hu , dev@dpdk.org Cc: nd@arm.com, david.marchand@redhat.com, thomas@monjalon.net, ktraynor@redhat.com, jerinj@marvell.com, honnappa.nagarahalli@arm.com, ruifeng.wang@arm.com, phil.yang@arm.com, joyce.kong@arm.com, stable@dpdk.org, Olivier MATZ , Konstantin Ananyev , Andrew Rybchenko References: <20200303162728.93744-1-gavin.hu@arm.com> <20200307155629.45021-1-gavin.hu@arm.com> From: Ferruh Yigit Autocrypt: addr=ferruh.yigit@intel.com; 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charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v2] mbuf: replace zero-length marker with unnamed union X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org Sender: "stable" On 3/7/2020 3:56 PM, Gavin Hu wrote: > Declaring zero-length arrays in other contexts, including as interior > members of structure objects or as non-member objects, is discouraged. > Accessing elements of zero-length arrays declared in such contexts is > undefined and may be diagnosed.[1] > > Fix by using unnamed union and struct. > > https://bugs.dpdk.org/show_bug.cgi?id=396 > > Bugzilla ID: 396 > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > > Fixes: 3e6181b07038 ("mbuf: use structure marker from EAL") > Cc: stable@dpdk.org > > Signed-off-by: Gavin Hu > --- > v2: > * change 'uint64_t rearm_data' to 'uint_64_t rearm_data[1]' to fix > the SFC PMD compiling error on x86. > --- > lib/librte_mbuf/rte_mbuf_core.h | 54 +++++++++++++++++++-------------- > 1 file changed, 32 insertions(+), 22 deletions(-) > > diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h > index b9a59c879..34cb152e2 100644 > --- a/lib/librte_mbuf/rte_mbuf_core.h > +++ b/lib/librte_mbuf/rte_mbuf_core.h > @@ -480,31 +480,41 @@ struct rte_mbuf { > rte_iova_t buf_physaddr; /**< deprecated */ > } __rte_aligned(sizeof(rte_iova_t)); > > - /* next 8 bytes are initialised on RX descriptor rearm */ > - RTE_MARKER64 rearm_data; > - uint16_t data_off; > - > - /** > - * Reference counter. Its size should at least equal to the size > - * of port field (16 bits), to support zero-copy broadcast. > - * It should only be accessed using the following functions: > - * rte_mbuf_refcnt_update(), rte_mbuf_refcnt_read(), and > - * rte_mbuf_refcnt_set(). The functionality of these functions (atomic, > - * or non-atomic) is controlled by the CONFIG_RTE_MBUF_REFCNT_ATOMIC > - * config option. > - */ > RTE_STD_C11 > union { > - rte_atomic16_t refcnt_atomic; /**< Atomically accessed refcnt */ > - /** Non-atomically accessed refcnt */ > - uint16_t refcnt; > - }; > - uint16_t nb_segs; /**< Number of segments. */ > + /* next 8 bytes are initialised on RX descriptor rearm */ > + uint64_t rearm_data[1]; We are using zero length array as markers only and know what we are doing with them, what would you think disabling the warning instead of increasing the complexity in mbuf struct?