linux-kernel - Re: [PATCH] HID: logitech: fix a used uninitialized GCC warning

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Date:   Thu, 13 Sep 2018 15:39:02 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
CC:     Jiri Kosina <jikos@...nel.org>, open list:
        HID CORE LAYER <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, ;
Subject: Re: [PATCH] HID: logitech: fix a used uninitialized GCC warning

On 2018/9/13 15:01, Benjamin Tissoires wrote:
> On Thu, Sep 13, 2018 at 6:04 AM zhong jiang <zhongjiang@...wei.com> wrote:
>> Fix the following compile warning:
>>
>> drivers/hid/hid-logitech-hidpp.c: In function ‘hi_res_scroll_enable’:
>> drivers/hid/hid-logitech-hidpp.c:2714:54: warning: ‘multiplier’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>>   hidpp->vertical_wheel_counter.resolution_multiplier = multiplier;
>>
>> Signed-off-by: zhong jiang <zhongjiang@...wei.com>
>> ---
>>  drivers/hid/hid-logitech-hidpp.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
>> index 5f0c080..83c43dd 100644
>> --- a/drivers/hid/hid-logitech-hidpp.c
>> +++ b/drivers/hid/hid-logitech-hidpp.c
>> @@ -2696,7 +2696,7 @@ static int hi_res_scroll_look_up_microns(__u32 product_id)
>>  static int hi_res_scroll_enable(struct hidpp_device *hidpp)
>>  {
>>         int ret;
>> -       u8 multiplier;
>> +       u8 uninitialized_var(multiplier);
> I think your patch is correct (multiplier will be set given the code
> path), but IMO, it feels terribly wrong to explicitly remove this
> warning this way. The problem is that if someone else adds a new piece
> of code, we might miss the fact that multiplier is not set and we
> might show garbage in the hid_info call.
Make sense.
>
> Why don't you initialize the value to 8 as in the 'else' statement and
> remove the now duplicated assignement in this else statement?
Will do in v2.  Thank you for your suggestion.

Thanks,
zhong jiang
> Cheers,
> Benjamin
>
>>         if (hidpp->quirks & HIDPP_QUIRK_HI_RES_SCROLL_X2121) {
>>                 ret = hidpp_hrw_set_wheel_mode(hidpp, false, true, false);
>> --
>> 1.7.12.4
>>
> .
>