From: "heying (H)" <heying24@huawei.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>, <frederic@kernel.org>,
<paulmck@kernel.org>, <clg@kaod.org>, <qais.yousef@arm.com>,
<johnny.chenyi@huawei.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] smp: kernel/panic.c - silence warnings
Date: Fri, 19 Mar 2021 09:39:50 +0800 [thread overview]
Message-ID: <20180e8b-8cbe-e2d3-6ac6-da0e0b6e6d1f@huawei.com> (raw)
In-Reply-To: <f6cb47a6-45c9-ad8f-6657-90958a86c3e1@csgroup.eu>
Dear Ingo, Peter and Christophe,
I'm a bit confused. All of you have a good reason but have opposite
opinions.
If I don't add 'extern', can you accept it? Please let me know.
Thanks,
He Ying
在 2021/3/18 13:53, Christophe Leroy 写道:
>
>
> Le 17/03/2021 à 18:37, Peter Zijlstra a écrit :
>> On Wed, Mar 17, 2021 at 06:17:26PM +0100, Christophe Leroy wrote:
>>>
>>>
>>> Le 17/03/2021 à 13:23, Peter Zijlstra a écrit :
>>>> On Wed, Mar 17, 2021 at 12:00:29PM +0100, Christophe Leroy wrote:
>>>>> What do you mean ? 'extern' prototype is pointless for function
>>>>> prototypes
>>>>> and deprecated, no new function prototypes should be added with
>>>>> the 'extern'
>>>>> keyword.
>>>>>
>>>>> checkpatch.pl tells you: "extern prototypes should be avoided in
>>>>> .h files"
>>>>
>>>> I have a very strong preference for extern on function decls, to match
>>>> the extern on variable decl.
>>>
>>> You mean you also do 'static inline' variable declarations ?
>>
>> That's a func definition, not a declaration. And you _can_ do static
>> variable definitions in a header file just fine, although that's
>> typically not what you'd want. Although sometimes I've seen people do:
>>
>> static const int my_var = 10;
>>
>> inline is an attribute that obviously doesn't work on variables.
>>
>>> Using the extern keyword on function prototypes is superfluous visual
>>> noise so suggest removing it.
>>
>> I don't agree; and I think the C spec is actually wrong there (too).
>>
>> The thing is that it distinguishes between a forward declaration of a
>> function in the same TU and an external declaration for a function in
>> another TU.
>>
>> That is; if I see:
>>
>> void ponies(int legs);
>>
>> I expect that function to be defined later in the same TU. IOW it's a
>> forward declaration. OTOH if I see:
>>
>> extern void ponies(int legs);
>>
>> I know I won't find it in this TU and the linker will end up involved.
>
> Yes I can understand that for a .c file where you want to distinguish
> between forward declaration of functions defined in the file and
> functions declared outside. There, it is definitely an added value.
>
> But in .h, all functions must be defined somewhere else, otherwise you
> have another problem. So all functions would have the 'extern' keyword
> according to your reasoning. Therefore that's just useless and I fully
> agree with Checkpatch's commit that in that case that's "superfluous
> visual noise" impeding readability and making it more difficult to fit
> the prototype on a single line.
>
>
>>
>> Now, the C people figured that distinction was useless and allowed
>> sloppiness. But I still think there's merrit to that. And as mentioned
>> earlier, it is consistent with variable declarations.
>>
> .
next prev parent reply other threads:[~2021-03-19 1:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 8:41 [PATCH v2] smp: kernel/panic.c - silence warnings He Ying
2021-03-17 9:49 ` Ingo Molnar
2021-03-17 11:00 ` Christophe Leroy
2021-03-17 12:23 ` Peter Zijlstra
2021-03-17 17:17 ` Christophe Leroy
2021-03-17 17:37 ` Peter Zijlstra
2021-03-17 20:09 ` Ingo Molnar
2021-03-18 2:56 ` heying (H)
2021-03-18 6:11 ` Christophe Leroy
2021-03-18 6:04 ` Christophe Leroy
2021-03-18 5:53 ` Christophe Leroy
2021-03-19 1:39 ` heying (H) [this message]
2021-03-19 6:58 ` Christophe Leroy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180e8b-8cbe-e2d3-6ac6-da0e0b6e6d1f@huawei.com \
--to=heying24@huawei.com \
--cc=christophe.leroy@csgroup.eu \
--cc=clg@kaod.org \
--cc=frederic@kernel.org \
--cc=johnny.chenyi@huawei.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=qais.yousef@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).