patches for DPDK stable branches
 help / color / mirror / Atom feed
From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Kevin Traynor <ktraynor@redhat.com>, dev@dpdk.org
Cc: stable@dpdk.org, allain.legacy@windriver.com,
	Steven Webster <steven.webster@windriver.com>,
	Matt Peters <matt.peters@windriver.com>,
	"Kilheeney, Louise" <louise.kilheeney@intel.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v2 1/2] net/avp: fix gcc 10 maybe-uninitialized warning
Date: Thu, 12 Mar 2020 16:47:49 +0000
Message-ID: <6abf293a-9007-c06f-c216-8d8331709b51@intel.com> (raw)
In-Reply-To: <24e2ec05-de5d-3251-ac63-f344ec09f44e@redhat.com>

On 3/12/2020 3:15 PM, Kevin Traynor wrote:
> On 12/03/2020 14:31, Ferruh Yigit wrote:
>> On 3/12/2020 2:18 PM, Kevin Traynor wrote:
>>> On 12/03/2020 13:25, Ferruh Yigit wrote:
>>>> On 3/11/2020 11:32 AM, Kevin Traynor wrote:
>>>>> gcc 10.0.1 reports:
>>>>>
>>>>> ../drivers/net/avp/avp_ethdev.c: In function ‘avp_xmit_scattered_pkts’:
>>>>> ../drivers/net/avp/avp_ethdev.c:1791:24:
>>>>> warning: ‘avp_bufs[count]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>>>>>  1791 |   tx_bufs[i] = avp_bufs[count];
>>>>>       |                ~~~~~~~~^~~~~~~
>>>>> ../drivers/net/avp/avp_ethdev.c:1791:24:
>>>>> warning: ‘avp_bufs[count]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>>>>>
>>>>> Fix by intializing the array.
>>>>>
>>>>> Fixes: 295abce2d25b ("net/avp: add packet transmit functions")
>>>>> Cc: stable@dpdk.org
>>>>>
>>>>> Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
>>>>> ---
>>>>> v2: no change
>>>>>
>>>>> note, commit log violates line length but I didn't want to split warning msg.
>>>>>
>>>>> Cc: allain.legacy@windriver.com
>>>>> Cc: Steven Webster <steven.webster@windriver.com>
>>>>> Cc: Matt Peters <matt.peters@windriver.com>
>>>>> ---
>>>>>  drivers/net/avp/avp_ethdev.c | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/net/avp/avp_ethdev.c b/drivers/net/avp/avp_ethdev.c
>>>>> index cd747b6be..1abe96ce5 100644
>>>>> --- a/drivers/net/avp/avp_ethdev.c
>>>>> +++ b/drivers/net/avp/avp_ethdev.c
>>>>> @@ -1695,5 +1695,5 @@ avp_xmit_scattered_pkts(void *tx_queue,
>>>>>  {
>>>>>  	struct rte_avp_desc *avp_bufs[(AVP_MAX_TX_BURST *
>>>>> -				       RTE_AVP_MAX_MBUF_SEGMENTS)];
>>>>> +				       RTE_AVP_MAX_MBUF_SEGMENTS)] = {};
>>>>>  	struct avp_queue *txq = (struct avp_queue *)tx_queue;
>>>>>  	struct rte_avp_desc *tx_bufs[AVP_MAX_TX_BURST];
>>>>>
>>>>
>>>> Isn't this a false positive, can there be any case 'avp_bufs[]' used
>>>> uninitialized? Or am I missing something.
>>>>
>>>
>>> I presume it's because it's not being initialized in the fn and there is
>>> some paths in fn's it's passed to that don't initialize it. Of course in
>>> practice with "normal" values this might not happen.
>>
>> 'avp_fifo_get(alloc_q, (void **)&avp_bufs, segments);' initializes it, and I am
>> not just talking about 'normal' case, I don't see any case that 'avp_bufs[]'
>> used uninitialized, can you see any?
>>
> 
> Well, it's initialization there is dependent on not hitting the first
> return and the loop executing.

If whole array not initialized, the next line, 'if (unlikely(n != segments))',
will catch it and function return without using 'avp_bufs[]' at all.

Anyway, as I said I can't see a case that 'avp_bufs[]' used uninitialized,
and not sure about additional zeroing out in datapath function if this is a
false positive, but if windriver guys are OK I won't object.

> 
>>>
>>>> If this is false positive, does it worth to report to issue to gcc?
>>>>
>>>
>>
> 


      reply	other threads:[~2020-03-12 16:47 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20  9:37 [dpdk-stable] [PATCH " Kevin Traynor
2020-02-20  9:37 ` [dpdk-stable] [PATCH 2/2] examples/ipsec-gw: " Kevin Traynor
2020-02-26  6:12   ` Akhil Goyal
2020-03-10 13:08   ` Ananyev, Konstantin
2020-03-10 18:52     ` Kevin Traynor
2020-03-10 19:03       ` Ananyev, Konstantin
2020-03-11 11:32 ` [dpdk-stable] [PATCH v2 1/2] net/avp: " Kevin Traynor
2020-03-11 11:33   ` [dpdk-stable] [PATCH v2 2/2] examples/ipsec-gw: " Kevin Traynor
2020-03-11 12:04     ` Ananyev, Konstantin
2020-05-06  9:18       ` [dpdk-stable] [dpdk-dev] " David Marchand
2020-03-11 23:56   ` [dpdk-stable] [PATCH v2 1/2] net/avp: " Webster, Steven
2020-05-06  9:18     ` David Marchand
2020-03-12 13:25   ` [dpdk-stable] [dpdk-dev] " Ferruh Yigit
2020-03-12 14:18     ` Kevin Traynor
2020-03-12 14:31       ` Ferruh Yigit
2020-03-12 15:15         ` Kevin Traynor
2020-03-12 16:47           ` Ferruh Yigit [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=6abf293a-9007-c06f-c216-8d8331709b51@intel.com \
    --to=ferruh.yigit@intel.com \
    --cc=allain.legacy@windriver.com \
    --cc=dev@dpdk.org \
    --cc=ktraynor@redhat.com \
    --cc=louise.kilheeney@intel.com \
    --cc=matt.peters@windriver.com \
    --cc=stable@dpdk.org \
    --cc=steven.webster@windriver.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

patches for DPDK stable branches

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/stable/0 stable/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 stable stable/ https://inbox.dpdk.org/stable \
		stable@dpdk.org
	public-inbox-index stable

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.stable


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git