Messages in this thread | | | Subject | Re: [PATCH v2] smp: kernel/panic.c - silence warnings | From | "heying (H)" <> | Date | Fri, 19 Mar 2021 09:39:50 +0800 |
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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. >> > .
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