From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Joe Perches <joe@perches.com>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Randy Dunlap <rdunlap@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] media: do not use C++ style comments in uapi headers
Date: Wed, 5 Jun 2019 13:10:41 +0900 [thread overview]
Message-ID: <CAK7LNARU+uT0aUBh5niwEafL8+Ok7=sOZYukptpDH1w7Cii3hQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a0bz8XYJOsmND2=CT_oTDmGMJGaRo9+QMroEhpekSMEaQ@mail.gmail.com>
On Wed, Jun 5, 2019 at 3:21 AM Arnd Bergmann <arnd@arndb.de> wrote:
> > > >
> > > > There are two ways to define fixed-width type.
> > > >
> > > > [1] #include <linux/types.h>, __u8, __u16, __u32, __u64
> > > >
> > > > vs
> > > >
> > > > [2] #include <stdint.h>, uint8_t, uint16_t, uint32_t, uint64_t
> > > >
> > > >
> > > > Both are used in UAPI headers.
> > > > IIRC, <stdint.h> was standardized by C99.
> > > >
> > > > So, we have already relied on C99 in user-space too.
>
> A related problem is that using the stdint.h types requires
> including stdint.h first, but the C library requires that including
> one standard header does not include another one recursively.
>
> So if sys/socket.h includes linux/socket.h, that must not include
> stdint.h or any other header file that does so.
This means we cannot reliably use uint{8,16,32,64}_t in UAPI headers.
[1] If we include <stdint.h> from linux/foo.h
If sys/foo.h includes <linux/foo.h> and <stdint.h>,
it violates the C library requirement.
[2] If we do not include <stdint.h> from linux/foo.h
If sys/foo.h includes <linux/foo.h>, but not <stdint.h>,
we get 'unknown type name' errors.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2019-06-05 4:11 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 11:13 [PATCH] media: do not use C++ style comments in uapi headers Masahiro Yamada
2019-06-04 11:23 ` Joe Perches
2019-06-04 11:48 ` Masahiro Yamada
2019-06-04 12:04 ` Joe Perches
2019-06-04 11:54 ` Arnd Bergmann
2019-06-04 12:48 ` Masahiro Yamada
2019-06-04 13:32 ` Masahiro Yamada
2019-06-04 13:42 ` Greg KH
2019-06-04 15:27 ` Masahiro Yamada
2019-06-04 18:20 ` Arnd Bergmann
2019-06-05 4:10 ` Masahiro Yamada [this message]
2019-06-05 5:10 ` Greg KH
2019-06-05 5:22 ` Joe Perches
2019-06-05 6:02 ` Greg KH
2019-06-05 10:08 ` Masahiro Yamada
2019-06-05 10:14 ` Mauro Carvalho Chehab
2019-06-05 17:03 ` Joe Perches
2019-06-09 7:14 ` Masahiro Yamada
2019-06-09 11:55 ` Joe Perches
2019-06-09 13:08 ` Masahiro Yamada
2019-06-09 13:35 ` Joe Perches
2019-06-09 17:19 ` Masahiro Yamada
2019-06-09 17:42 ` Pavel Machek
2019-06-16 15:48 ` Pavel Machek
2019-06-04 14:42 ` Mauro Carvalho Chehab
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