How to disable a src.conf on command-line

[Darren Pilgrim]

M. Warner Losh wrote:
> In message: <4489E354.5070201 at bitfreak.org>
>             Darren Pilgrim <darren.pilgrim at 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