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Re: warnings expanding macros before they're required

From: Mike Frysinger
Subject: Re: warnings expanding macros before they're required
Date: Mon, 11 Jul 2011 17:06:55 -0400
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On Monday, July 11, 2011 16:44:25 Eric Blake wrote:
> On 07/11/2011 02:27 PM, Mike Frysinger wrote:
> > On Monday, July 11, 2011 15:50:42 Eric Blake wrote:
> >> 2.68 outputs a fixed configure, at the expense of
> >> outputting the code for AC_PROG_CC twice; the warning exists to tell you
> >> that you can shrink the size of your configure by fixing things to avoid
> >> the warning.
> > 
> > thanks ... the warning displayed didnt convey that's what was actually
> > happening.  perhaps it should be updated with the URL you provided here.
> At the time the code was written to produce the warning, the FAQ URL
> didn't exist.  I'm not sure if a patch would help now, as most projects
> have already had time to adjust, but it may be worth considering one if
> a patch is provided.

well, this isnt new code that i'm showing here.  it's been sitting around for 
quite a long time now.  i'll see about sending a patch to include the URL.

> It was already hard enough to coax m4 into displaying the warning when
> it output redundant code without exploding the execution time of
> autoconf.  I don't think it is possible to make autoconf any smarter
> than what it already is on this front - the best we can do is output a
> warning and rely on you to fix your configure.ac file to use AC_REQUIRE
> instead of direct expansion to avoid the redundancy in the first place.

so it's partially a limitation in the m4/autoconf base, and partially by 
design.  as you say, there are cases where the warning would be incorrect as 
it'd be desirable to have things expanded multiple times.  damned if you do, 
damned if you dont.

AC_REQUIRE seems to make things work, so i'll send a patch for that to the 
upstream project

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