[dpdk-dev] [PATCH] checkpatch: re-enable warnings about split long strings

[Ferruh Yigit]

On 10/3/2017 11:56 AM, adrien.mazarguil at 6wind.com (Adrien Mazarguil) wrote:
> On Tue, Oct 03, 2017 at 11:38:13AM +0100, Bruce Richardson wrote:
>> On Mon, Oct 02, 2017 at 06:21:06PM +0200, Adrien Mazarguil wrote:
>>> On Mon, Oct 02, 2017 at 02:46:24PM +0100, Bruce Richardson wrote:
>>>> On Mon, Oct 02, 2017 at 01:53:17PM +0200, Adrien Mazarguil wrote:
>>>>> Hi Stephen,
>>>>>
>>>>> On Fri, Sep 29, 2017 at 08:37:49AM -0700, Stephen Hemminger wrote:
>>>>>> The Linux kernel style policy about strings is that strings should
>>>>>> be always put on one line. This makes sense since a typical use case
>>>>>> is for a user to type the error message into a search engine or
>>>>>> grep, and it won't be found if split across lines.  This patch just
>>>>>> re-enables that check.
>>>>>>
>>>>>> Yes, lots of DPDK code now splits strings, that doesn't make it
>>>>>> right.
>>>>>>
>>>>>> Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com> ---
>>>>>> devtools/checkpatches.sh | 1 - 1 file changed, 1 deletion(-)
>>>>>>
>>>>>> diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
>>>>>> index a56c41a301c0..3e6081dd673e 100755 ---
>>>>>> a/devtools/checkpatches.sh +++ b/devtools/checkpatches.sh @@ -44,7
>>>>>> +44,6 @@ options="$options --show-types" options="$options
>>>>>> --ignore=LINUX_VERSION_CODE,FILE_PATH_CHANGES,\
>>>>>> VOLATILE,PREFER_PACKED,PREFER_ALIGNED,PREFER_PRINTF,\
>>>>>> PREFER_KERNEL_TYPES,BIT_MACRO,CONST_STRUCT,\
>>>>>> -SPLIT_STRING,LONG_LINE_STRING,\
>>>>>> LINE_SPACING,PARENTHESIS_ALIGNMENT,NETWORKING_BLOCK_COMMENT_STYLE,\
>>>>>> NEW_TYPEDEFS,COMPARISON_TO_NULL"
>>>>>
>>>>> I'm not sure, given that the main reason for splitting strings in the
>>>>> first place is to avoid LONG_LINE_STRING warnings, I think we must
>>>>> choose between the two options. If split strings are not allowed, then
>>>>> long lines must be.
>>>>>
>>>>> Since checkpatches.sh is used by various automated scripts to complain
>>>>> loudly about problems in submissions, the above change prevents
>>>>> maintainers from writing long string at all (can't split and can't go
>>>>> past 80 columns).
>>>>>
>>>>> As a result, they will be tempted to cripple their code with nasty
>>>>> workarounds to shut up checkpatches.sh, we don't want that to happen.
>>>>>
>>>>> Also I think the reasons stated by original commit cf75514c8e2e are
>>>>> still relevant. My vote would be to keep things as is.
>>>>>
>>>> In my experience, checkpatch is smart enough to recognise when a long
>>>> line overflows the 80 character limit because of a single long string,
>>>> so the two options are not mutually exclusive. In other words, long
>>>> lines are not allowed except in the case where shortening the line
>>>> involves splitting a string. There may be a small amount of work in
>>>> getting checkpatch happy, i.e. by putting the string on a line on it's
>>>> own, but we can indeed have our cake and eat it too in this case.
>>>
>>> I can't seem to get around warnings without ignoring either SPLIT_STRING or
>>> LONG_LINE_STRING as of Linux v4.14-rc3's checkpatch.pl. I think you can only
>>> get around them by fooling it somehow. You really need to ignore at least
>>> LONG_LINE_STRING to meet the requirements of the commit log.
>>>
>>> However SPLIT_STRING still looks necessary to address part of cf75514c8e2e
>>> ("devtools: ignore warning on long log string"):
>>>
>>>  "...lines that make use of PRIx64 with string concatenation will still be
>>>   flagged if the beginning of the last string fragment begins after the 80
>>>   character threshold."
>>>
>>> It's not all that uncommon in my opinion.
>>>
>> If you have PRIx64 in it, it's not part of a literal string you would
>> grep, so it's reasonable to split there. The user cannot know what the
>> specific %x formatting character used is.
> 
> I agree, however in that case checkpatch would complain because our
> configuration doesn't specify to ignore SPLIT_STRING since there is no comma
> separator when concatenating them.
> 
> My point is that the occasional exception is still necessary for split
> strings, that ignoring LONG_LINE_STRING must remain either way and
> unnecessary warnings cause more harm than good (they need to be worked
> around if we enforce this rule).
> 
> In short, long/split strings acceptability assessment should be left to
> reviewers, as it cannot be automated in all cases through checkpatch.pl.
> 

This patch is waiting in patchwork for a long time now.

My experience is same with Adrien's, if 'LONG_LINE_STRING' is not ignored, it
will complain about long log messages, so removing 'LONG_LINE_STRING'
contradicts with the reason of the patch described in the commit log.

Perhaps it can be an option to remove only 'SPLIT_STRING' from ignore list, to
detect split messages.

But overall, I am updating this patch as "Change Requested", if there is a
demand for ignoring 'SPLIT_STRING' please send a new version.

Thanks,
ferruh