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Date: Fri, 09 Jun 2006 15:47:24 -0700
From: Darren Pilgrim <freebsd@bitfreak.org>
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To: "M. Warner Losh" <imp@bsdimp.com>
References: <20060609094052.GH1273@obiwan.tataz.chchile.org>	<20060609.074844.1324583587.imp@bsdimp.com>	<4489E354.5070201@bitfreak.org>
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Cc: freebsd-hackers@FreeBSD.ORG, jeremie@le-hen.org
Subject: Re: How to disable a src.conf on command-line
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M. Warner Losh wrote:
> In message: <4489E354.5070201@bitfreak.org>
>             Darren Pilgrim <darren.pilgrim@bitfreak.org> writes:
> : M. Warner Losh wrote:
> : > So if you make WITH_SSP off by default, then having WITH_SSP in the
> : > src.conf can't be overridden.  If you have it on by default, having
> : > WITHOUT_SSP in the src.conf file can't be overriden.  this appears to
> : > be an unintended flaw with the with/without stuff.  I'm not sure the
> : > right way to compensate.
> : 
> : I can't speak for the "right" way, but if you specify the variable in 
> : src.conf/make.conf with ?= instead of =, you can override it on the 
> : command-line:
> : 
> : # grep KERNCONF /etc/make.conf
> : KERNCONF?=TTPWEB
> : # make -V KERNCONF
> : TTPWEB
> : # env KERNCONF=SOMETHING_ELSE make -V KERNCONF
> : SOMETHING_ELSE
> 
> ?= doesn't mesh well with WITH/WITHOUT because then it will always be
> defined, thus defeating its purpose.

Use .ifndef to define WITH/WITHOUT iff its counterpart is undef:

.ifndef WITHOUT_FOO
WITH_FOO=def
.endif

-- 
Darren Pilgrim