Re: toolchain/46750: make oddity expanding variables assigned to with +=

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR toolchain/46750; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: toolchain/46750: make oddity expanding variables assigned to
 with +=
Date: Wed, 22 Aug 2012 07:10:37 +0000

 On Mon, Jul 30, 2012 at 09:50:05AM +0000, Edgar Fu? wrote:
  >  > The problem is that it's doing this even if the old value is the empty 
  >  > string, so you get a leading space.
  >
  >  If we, for a moment, set aside how make internally handles lists (and 
  >  talk only about list elements not containing whitespace), the question is 
  >  what we expect "FOO=" to do.
  >  Either we expect it to set FOO to the empty list. Then, after "FOO+=foo", 
  >  the value should be "foo".
  >  Or we expect it to set FOO to a list containing an empty value. Then, 
  >  after "FOO+=foo", the value should indeed be " foo", but FOO:[1] should 
  >  return that empty value.
 
 Right.
 
  >  > Relatedly, if you do
  >
  >  Here, the question is whether we expect "FOO+=" to append an empty list 
  >  to FOO (e.g. don't change it) or whether we expext it to append an empty 
  >  value to the list.
 
 Right.
 
  >  Probably that should be discussed on tech-toolchain and then made
  >  consistent.
 
 The historic behavior of make has always been that variables hold
 strings which are whitespace-separated lists of words. There are no
 empty values. I don't think this needs discussion (nor can it be
 changed without risking a lot of fallout and incompatibility...)
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost