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Re: confdefs.h not being included by AC_LANG_SOURCE()

From: Eric Blake
Subject: Re: confdefs.h not being included by AC_LANG_SOURCE()
Date: Tue, 02 Mar 2010 15:48:54 -0700
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20090812 Thunderbird/ Mnenhy/

According to Ralf Wildenhues on 3/2/2010 2:35 PM:
> Second, I do think this is a regression, as our documentation
> pretty clearly states that AC_LANG_SOURCE is the one expanding
> all the AC_DEFINEs seen so far.  I do however also think that
> the old code was ugly and hackish.  Not sure whether it would
> be better to go back, or go forward and announce the API change.

I'd rather go forward.  In other words, I'm thinking of the patch below.

> But what I do know is that we need better macro coverage here.

The change was made back on 2008-11-03 (commit 8e27cc7f5, contained in
autoconf 2.63b), so although it is somewhat of a regression
(AC_LANG_CONFTEST outputs defines now, when it did not do so previously),
there obviously aren't that many packages that try to mix-and-match their
own LANG_CONFTEST with autoconf's LANG_SOURCE, or we might have heard
about this issue sooner.  More test coverage is always welcome, but I'm
okay with just documentation patches for 2.66.

May I ask why LB_LANG_CONFTEST was created in the first place, rather than
sticking with the autoconf interface, or is that decision lost in history?
 Might it have something to do with the (ancient) bug where we tried to
output #line directives in the original conftest file corresponding to
locations in configure, which was later withdrawn when it was determined
that configure files often exceed 64k lines and it breaks some
preprocessors to have #line numbers that large?

Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden

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