linux-kernel - Re: [PATCH] media: do not use C++ style comments in uapi headers

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Message-ID: <2674b675063812e7c422a7964afdef6b7c712e4b.camel@perches.com>
Date:   Tue, 04 Jun 2019 05:04:55 -0700
From:   Joe Perches <joe@...ches.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-media@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] media: do not use C++ style comments in uapi headers

On Tue, 2019-06-04 at 20:48 +0900, Masahiro Yamada wrote:
> On Tue, Jun 4, 2019 at 8:24 PM Joe Perches <joe@...ches.com> wrote:
> > On Tue, 2019-06-04 at 20:13 +0900, Masahiro Yamada wrote:
> > > On the other hand, uapi headers are written in more strict C, where
> > > the C++ comment style is forbidden.
> > 
> > Is this a real problem for any toolchain?
> 
> I was waiting for this comment!
> 
> Which standard should UAPI headers follow?
> Is it defined somewhere?
> 
> If there is no rule, is it up to subsystem maintainers?
> 
> We have a certain of unknowledge in user-space,
> I do not know it it is a real problem.
> 
> Actually, this patch is related to this thread:
> https://lkml.org/lkml/2019/5/22/1441
> 
> Thomas and you agreed
> // should be avoided for SPDX tags in UAPI headers.

If it's really a generic issue, I think there are more
uses of // comments in uapi files.

$ git grep '//' include/uapi/ | grep -vP '(http://|https://|ftp:/)' | wc -l
101

> So, I just thought C99 was forbidden for user-space.

No idea, I just believe if it's really a problem
it likely would have been reported already.

> If C89/C90 is already fantasy,
> let's clearly say "Kernel requires C99 for user-space",
> and use // everywhere for SPDX tags?

OK by me.

I have a checkpatch patch waiting to submit to remove the
requirement to use the /* */ comment style in .h files.

The docs need to be updated too.

cheers, Joe