Re: make -U

From: Garance A Drosihn (drosih_at_rpi.edu)
Date: 07/31/03

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    Date: Thu, 31 Jul 2003 17:49:55 -0400
To: naddy@mips.inka.de (Christian Weisgerber), freebsd-current@freebsd.org

    At 1:39 PM +0000 7/31/03, Christian Weisgerber wrote:
    >Juli Mallett <jmallett@FreeBSD.org> wrote:
    >
    > > Why go thru those contortions? I sometimes use "make FOO=" to
    > > define things. -U obviously has a place, if it not existing
    > > means I have to have all these contortions to do a fairly
    > > obvious thing, yeah?
    >
    >What are the exact semantics of -U supposed to be?

     From the message in freebsd-hackers which first introduced
    this patch:

    - Date: Tue, 29 Jul 2003 09:09:17 -0700
    - From: Faried Nawaz <fn@hungry.com>
    - Subject: patch to add make -U

         While working around a port issue (ports/55013), I discovered
         that make couldn't unset variables using make -U. I've written
         a small patch that adds -U functionality, but I haven't tested
         it extensively.

         http://web.nilpotent.org/tmp/make.diff.bz2 (~ 3KB unpacked)
         against yesterday's -CURRENT code.

         A simple Makefile I used to test it:

         -- cut here --
         FOO = bar

         .ifdef FOO
         SAY = y
         .else
         SAY = n
         .endif

         all:
                echo $(SAY)
         -- cut here --

         Try "make -U FOO".

    Personally I think this is a reasonable option to implement.
    An undefined variable is not the same as a variable which is
    defined to be a null string. 

    -- 
Garance Alistair Drosehn            =   gad@gilead.netel.rpi.edu
Senior Systems Programmer           or  gad@freebsd.org
Rensselaer Polytechnic Institute    or  drosih@rpi.edu
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