Re: [PATCH] mac80211: fix "warning: ‘target_metric’ may be used uninitialized"

[Jeff Mahoney <jeffm@suse.com>]

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On 4/5/16 9:40 AM, Johannes Berg wrote:
> On Tue, 2016-04-05 at 09:33 -0400, Jeff Mahoney wrote:
>> On 4/5/16 5:43 AM, Johannes Berg wrote:
>>>
>>> On Mon, 2016-04-04 at 14:15 -0400, Jeff Mahoney wrote:
>>>>
>>>> This fixes:
>>>>
>>>> net/mac80211/mesh_hwmp.c:603:26: warning: ‘target_metric’ may be
>>>> used
>>>> uninitialized in this function
>>>>
>>>> target_metric is only consumed when reply = true so no bug exists
>>>> here,
>>>> but gcc doesn't notice that.  Initializing to 0 clears the
>>>> warning.
>>>>
>>> What gcc version are you using? Mine doesn't seem to have a problem
>>> following the logic here.
>> gcc version 4.8.5 (SUSE Linux)
> 
> Ok, mine's significantly newer:
> 
> gcc (Debian 5.3.1-10) 5.3.1 20160224
> 
> I do wonder though if we really should do this? It might hide errors
> later on?

AFAICT, the only way errors would be introduced is if someone added a
new case in which reply was true *and* needed a different target_metric
value (there are 3 cases it's used, 2 of which use 0).  Or if there was
a new case where the target_metric was used and reply wasn't true -- in
which case this code would have been broken anyway.

Also, using uninitalized_var would have a higher probability of hiding
an error later on.  Setting it to 0 seems the safest course.

-Jeff

-- 
Jeff Mahoney
SUSE Labs


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