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From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com>
Message-Id: <199504221911.MAA02245@gndrsh.aac.dev.com>
Subject: Re: Any objection to adding a .undef(VARNAME) to make?
To: paul@isl.cf.ac.uk (Paul Richards)
Date: Sat, 22 Apr 1995 12:11:44 -0700 (PDT)
Cc: nate@trout.sri.MT.net, jkh@freefall.cdrom.com, hackers@freefall.cdrom.com
In-Reply-To: <199504221907.UAA28460@isl.cf.ac.uk> from "Paul Richards" at Apr 22, 95 08:07:25 pm
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> 
> In reply to Nate Williams who said
> > 
> > > I've long been bothered by bmake's inability to programmatically unset
> > > a variable.  Assuming that nobody feels it to be too evil a hack to
> > > live, are there any objections to using the keyword `.undef'?
> > 
> > I'm kind of partial to '.undefine' myself, but I think the functionality
> > is a good addition to the utility.  Too bad we couldn't find a way
> > similar to how something is defined to undefine it.
> > 
> > FOO= 1
> > 
> > FOO= undefined
> 
> Anyone see a problem with FOO=
> Seems to make sense to me. How many things would that break?

Anything that tried to do a:

FOO=
.if defined(FOO)
BAR=${FOO}
.else
BAR=/usr/lib
.endif

would probably break.  This behaves much differently than:
.undef FOO
.if defined(FOO)
BAR=${FOO}
.else
BAR=/usr/lib
.endif

Note this whole question become a non issue when I pointed out the
fact that our make alread has .undef implemented and tested to work.

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                   Custom computers for FreeBSD