netdev - Re: [patch net-next 0/8] Add support for pipeline debug (dpipe)

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Date:   Tue, 28 Mar 2017 10:10:23 +0200
From:   Ivan Vecera <ivecera@...hat.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        arkadis@...lanox.com, idosch@...lanox.com, mlxsw@...lanox.com,
        jhs@...atatu.com, roopa@...ulusnetworks.com, f.fainelli@...il.com,
        vivien.didelot@...oirfairelinux.com, john.fastabend@...il.com,
        andrew@...n.ch, simon.horman@...ronome.com
Subject: Re: [patch net-next 0/8] Add support for pipeline debug (dpipe)

Dne 28.3.2017 v 09:59 Jiri Pirko napsal(a):
> Tue, Mar 28, 2017 at 09:57:22AM CEST, jiri@...nulli.us wrote:
>> Tue, Mar 28, 2017 at 09:42:58AM CEST, ivecera@...hat.com wrote:
>>> Dne 28.3.2017 v 09:10 Jiri Pirko napsal(a):
>>>> Tue, Mar 28, 2017 at 12:48:34AM CEST, davem@...emloft.net wrote:
>>>>>
>>>>> Please fix up these warnings and resubmit:
>>>>>
>>>>> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c: In function ‘mlxsw_sp_rif_counter_free’:
>>>>> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:208:2: warning: ‘p_counter_index’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>>>>>  mlxsw_sp_rif_counter_edit(mlxsw_sp, rif->rif_index,
>>>>>  ^
>>>>
>>>> This is I believe also gcc bug. Code looks fine. I'm not getting the warning
>>>> with gcc 6
>>>>
>>> No it is not a gcc bug. The function mlxsw_sp_rif_counter_free() is not
>>> static so the compiler cannot know all its callers and so 'dir' parameter can
>>> be theoretically anything.
>>> You call mlxsw_sp_rif_p_counter_get() there it assumes dir can be only
>>> MLXSW_SP_RIF_COUNTER_EGRESS or MLXSW_SP_RIF_COUNTER_INGRESS so initializes
>>> *pp_counter_index only for them. For any other value the value is
>>> uninitialized.
>>
>> Interesting, why gcc 6.2.1 is silent then?
>
> Oh, I see that it is not :) My bad, will fix, thanks!
>
Probably because 'dir' is enumeration and this gcc assumes that any caller uses 
only defined enum values.

Ivan