Date: Wed, 12 May 2010 13:29:55 -0400
From: Nelson Elhage <nelhage@MIT.EDU>
To: Jameson Rollins <jrollins@finestructure.net>
Subject: Re: [PATCH] configure: Respect LDFLAGS from the environment.
Message-ID: <20100512172955.GB32152@mit.edu>
References: <1273682752-19140-1-git-send-email-nelhage@ksplice.com>
	<87wrv9caxg.fsf@servo.finestructure.net>
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Cc: notmuch@notmuchmail.org
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Hm. You're probably right that it should be ${LDFLAGS:-} for
consistency with the others, but what I wrote is functionally correct:

${LDFLAGS-FOO} means "If LDFLAGS is set at all (even to an empty
value), substitute $LDFLAGS; otherwise, substitute FOO".

${LDFLAGS:-FOO} is the same, except in the case where LDFLAGS is set
to the empty string, in which case it substitutes FOO.

So, for the case where FOO is the empty string, they're
identical. However, since I chose ${LDFLAGS-} out of habit, and not
particularly intentionally, and the other lines use :-, so it probably
makes sense to use that form instead.

(Of course, as long as the default is empty and we're not running
under 'set -u', we could just remove the line entirely. But I think
it's good for the sake of explicitness.)

- Nelson

(If you're morbidly curious,
http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02
defines all the different ${blah} forms you can use in sh)

On Wed, May 12, 2010 at 01:00:27PM -0400, Jameson Rollins wrote:
> On Wed, 12 May 2010 12:45:52 -0400, Nelson Elhage <nelhage@ksplice.com> wrote:
> > The configure usage string documents that it respects LDFLAGS, but
> > currently it doesn't do anything with the configure-time LDFLAGS
> > value.
> > ---
> >  configure |    4 ++++
> >  1 files changed, 4 insertions(+), 0 deletions(-)
> > 
> > diff --git a/configure b/configure
> > index c522ad8..90355e8 100755
> > --- a/configure
> > +++ b/configure
> > @@ -6,6 +6,7 @@ CC=${CC:-gcc}
> >  CXX=${CXX:-g++}
> >  CFLAGS=${CFLAGS:--O2}
> >  CXXFLAGS=${CXXFLAGS:-\$(CFLAGS)}
> > +LDFLAGS=${LDFLAGS-}
> 
> Hey, Nelson.  I'm not sure exactly what you're trying to do here, but
> I'm betting that this is not it.  If you're trying to get the LDFLAGS
> var from the existing environment, you probably want:
> 
> LDFLAGS=${LDFLAGS:-}
> 
> jamie.



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