linux-kernel - [PATCH 0/3] RFC v2: strip 15,000 lines from a typical autoconf.h

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Date:	Thu, 12 Apr 2012 19:46:31 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	linux-kbuild@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, davem@...emloft.net,
	tony@...eyournoodle.com, mmarek@...e.cz, lacombar@...il.com,
	sfr@...b.auug.org.au, Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [PATCH 0/3] RFC v2: strip 15,000 lines from a typical autoconf.h

[Re: [PATCH 0/5] RFC: strip 15,000 lines from a typical autoconf.h] On 12/04/2012 (Thu 12:29) Linus Torvalds wrote:

> On Wed, Apr 11, 2012 at 8:10 PM, Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> >
> > Can we leave the CONFIG_ part in the caller, so they are still grepable, please?
> >
> > So:
> >
> >	#define config_enabled(x)	(__stringify(x)[0] == '1')
> 
> Sure. Except G+ came through, and we now have an even better hack for
> this, that works entirely in the preprocessor.
> 
> That also means that you can use it for static initializers etc, so you can do
> 
>    int some_value = config_enabled(CONFIG_ENABLE_XYZ_BY_DEFAULT);
> 
> Paul, do you want to write the patch to change IS_ENABLED() to use this trick?

Sure -- I've done this in patch #1 of the (now) three patches.

I've dropped all the patches relating to phasing out the users
of IS_ENABLED within C code, since now they should just work.

> 
> Trick courtesy of "comex ." on G+ (please do give him credit even if
> he doesn't seem to use his real name):
> 
>   #define is_set(macro) is_set_(macro)
>   #define macrotest_1 ,
>   #define is_set_(value) is_set__(macrotest_##value)
>   #define is_set__(comma) is_set___(comma 1, 0)
>   #define is_set___(_, v, ...) v
> 
> and now "is_set(CONFIG_xyzzy)" works, and gives either 1 or 0 directly
> in the preprocessor.
> 
> Obviously the names have to be changed here (let's not use
> "macrotest_1" - make it something more internal), but the concept is
> solid, and I would actually suggest having this as a generic "is this
> macro set to 1" helper first, and then implement IS_ENABLED() in terms
> of that.

Hopefully the names I've chosen are OK.  Please have a look.

Thanks,
Paul.

> 
> My likee.
> 
>                        Linus

Paul Gortmaker (3):
  kconfig: fix IS_ENABLED to not require all options to be defined
  Revert "kconfig: fix __enabled_ macros definition for invisible and
    un-selected symbols"
  kconfig: delete last traces of __enabled_ from autoconf.h

 include/linux/kconfig.h    |   22 ++++++++++++++++++----
 scripts/kconfig/confdata.c |   38 ++------------------------------------
 2 files changed, 20 insertions(+), 40 deletions(-)

-- 
1.7.9.1

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