Re: [dpdk-stable] [dpdk-dev] [PATCH v2 1/2] net/avp: fix gcc 10 maybe-uninitialized warning

[Ferruh Yigit <ferruh.yigit@intel.com>]

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?

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