linux-kernel - Re: compiler

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Message-ID: <ZjiXLm9ZnJwMHiBP@smile.fi.intel.com>
Date: Mon, 6 May 2024 11:39:10 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: David Howells <dhowells@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: compiler_types.h in UAPI?

On Fri, May 03, 2024 at 09:34:13PM +0200, Arnd Bergmann wrote:
> On Fri, May 3, 2024, at 20:57, Andy Shevchenko wrote:

> > Today I have stumbled over use of __force and other compiler_types.h related
> > things in UAPI headers. Can anybody explain to me how do they suppose to work
> > outside of the kernel? Or did I miss something obvious? Or it was a mistake
> > during UAPI split to move swab.h and byteorder/ (most of the users of those)
> > to UAPI in the first place?
> 
> These get stripped out by scripts/headers_install.sh during
> the 'make headers_install' stage:
> 
> sed -E -e '
>         s/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g
>         s/__attribute_const__([[:space:]]|$)/\1/g
>         s@...nclude <linux/compiler(|_types).h>@@
>         s/(^|[^a-zA-Z0-9])__packed([^a-zA-Z0-9_]|$)/\1__attribute__((packed))\2/g
>         s/(^|[[:space:](])(inline|asm|volatile)([[:space:](]|$)/\1__\2__\3/g
>         s@#(ifndef|define|endif[[:space:]]*/[*])[[:space:]]*_UAPI@#\1 @
> ' $INFILE > $TMPFILE || exit 1

Thanks, Arnd, TIL!

But do we discourage using these in UAPI in general? I mean do we have
this somewhere being documented?

-- 
With Best Regards,
Andy Shevchenko