linux-kernel - Re: RFC: kconfig select warnings bogus?

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Message-ID: <4650AB9B.9060800@s5r6.in-berlin.de>
Date:	Sun, 20 May 2007 22:12:11 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Trent Piepho <xyzzy@...akeasy.org>
CC:	Satyam Sharma <satyam.sharma@...il.com>,
	Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Kumar Gala <galak@...nel.crashing.org>,
	Simon Horman <horms@...ge.net.au>
Subject: Re: RFC: kconfig select warnings bogus?

Trent Piepho wrote:
> config A
> 	bool "A"
> 
> config B
> 	bool "B"
> 	depends on A
> 
> config C
> 	bool "C"
> 	select B
> 
> In this case, it's possible to turn C on and A off.  B will be on, even
> though it depends on A and A is off.
> 
> The kconfig docs say that "B..  depends on A" sets the maximum value of B
> to be that of A.  Since A=0, the max value of B is 0.
> 
> The kconfig docs also say that "C..  select B" sets the minimum value of B
> to be that of C.  Since C=2, the minimum value of B is 2.
> 
> So we have B>=2 and B<=0, which is obviously impossible.  Yet *config has
> no problem with this, and will set B=2 even the 'depends' means B must be
> 0.  It seems like "select" will override any other dependencies.

If that's so, then we have /a/ an incomplete definition of the Kconfig
language (what is supposed to happen if "select" attempts to set an
impossible value?) and /b/ a bug in the make xyzconfig programs (they
generate invalid configs).
-- 
Stefan Richter
-=====-=-=== -=-= =-=--
http://arcgraph.de/sr/
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