Re: Environment variable $U

[Eric Blake]

According to Ralf Wildenhues on 2/8/2010 11:32 PM:
> Sounds like a bug to me, $U should be initialized somewhere, or removed
> from the LIBOBJS/LTLIBOBJS variables if ansi2knr is not used.

Aha.  In many projects, U _is_ initialized, but by automake during
AM_C_PROTOTYPES, and not by autoconf.  IIUC, the problem can only occur if
you are using autoconf but not automake.  So one real fix would be to quit
using U in autoconf, and to teach automake how to override
_AC_LIBOBJS_NORMALIZE to re-support U; but that has the drawback of
requiring upgrades in both automake and autoconf simultaneously.  Here's a
less-invasive fix, that only affects autoconf.

tests/semantics.at:AC_REPLACE_FUNCS also uses $U, so we could see a
spurious test failure; I'm not sure what to do there.  Thoughts before I
apply this to autoconf?

>  Or we
> could also go ahead and remove ansi2knr support (after deprecating it
> suitably).

It's always been a desire of mine to switch to C89 as default and require
extra effort on the part of people still wanting K&R, rather than the
current situation of trying to support both by default.  But it takes lots
of time and energy to implement, and hasn't been a high priority for me.

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

Eric Blake             e...@byu.net

From 7bf5c4827f3d7edc7e139915690ce3a495410a07 Mon Sep 17 00:00:00 2001
From: Eric Blake <e...@byu.net>
Date: Tue, 9 Feb 2010 06:22:59 -0700
Subject: [PATCH] Avoid $U if it is not initialized.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* lib/autoconf/general.m4 (_AC_LIBOBJS_NORMALIZE): Ensure $U is
set if automake did not define it.
* THANKS: Update.
Reported by Julien Élie.

Signed-off-by: Eric Blake <e...@byu.net>
---
 ChangeLog               |    8 ++++++++
 lib/autoconf/general.m4 |    2 ++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 43a7101..c1b74f8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2010-02-09  Eric Blake  <e...@byu.net>
+
+       Avoid $U if it is not initialized.
+       * lib/autoconf/general.m4 (_AC_LIBOBJS_NORMALIZE): Ensure $U is
+       set if automake did not define it.
+       * THANKS: Update.
+       Reported by Julien Élie.
+
 2009-09-16  Eric Blake  <e...@byu.net>

        Optimize AC_REPLACE_FUNCS.
diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index 28fd972..15640c8 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -2919,6 +2919,8 @@ AC_DEFUN([AC_LIBOBJ],
 AC_DEFUN([_AC_LIBOBJS_NORMALIZE],
 [ac_libobjs=
 ac_ltlibobjs=
+m4_ifndef([AM_C_PROTOTYPES], [U=
+])dnl
 for ac_i in : $LIB@&t...@objs; do test "x$ac_i" = x: && continue
   # 1. Remove the extension, and $U if already installed.
   ac_script='s/\$U\././;s/\.o$//;s/\.obj$//'
-- 
1.6.6.1

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