expand-before-require bug

[Eric Blake]

I am about to patch autoconf to issue a syntax warning on instances of 
expanding a macro, then later requiring the same macro, from within the same 
defun'd body.  This is a bug in user code which can lead to silent out-of-order 
expansion in older autoconf, and which will cause duplicate expansion in newer 
autoconf once I implement Bruno's suggestion of re-expanding the macro as part 
of issuing the warning.

When I turned on the warning, I got this message:

configure.ac:35: warning: AC_REQUIRE: `AM_PROG_INSTALL_SH' was expanded before 
it was required
aclocal.m4:846: AM_PROG_INSTALL_STRIP is expanded from...
aclocal.m4:408: AM_INIT_AUTOMAKE is expanded from...
configure.ac:35: the top level

In this particular case, we happened to get lucky with no out-of-order 
expansion of AM_PROG_INSTALL_SH with older autoconf, because 
AM_PROG_INSTALL_STRIP was also directly expanded.  But to avoid duplicate 
expansion of AM_PROG_INSTALL_SH in newer autoconf, we will need this patch.  
Okay to apply to master and the branch?


From: Eric Blake <address@hidden>
Date: Tue, 20 Jan 2009 10:36:49 -0700
Subject: [PATCH] Avoid expand-before-require warning from newer autoconf.

* m4/init.m4 (AM_INIT_AUTOMAKE): Require, rather than directly
expand, AM_PROG_INSTALL_SH and AM_PROG_INSTALL_STRIP.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog  |    6 ++++++
 m4/init.m4 |    6 +++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d7a729f..4824872 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2009-01-20  Eric Blake  <address@hidden>
+
+       Avoid expand-before-require warning from newer autoconf.
+       * m4/init.m4 (AM_INIT_AUTOMAKE): Require, rather than directly
+       expand, AM_PROG_INSTALL_SH and AM_PROG_INSTALL_STRIP.
+
 2008-12-29  Chris Pickett  <address@hidden>  (tiny change)
 
        * doc/automake.texi (LIBOBJS): Clarify overriding of
diff --git a/m4/init.m4 b/m4/init.m4
index 7104dd3..51fe69a 100644
--- a/m4/init.m4
+++ b/m4/init.m4
@@ -1,7 +1,7 @@
 # Do all the work for Automake.                             -*- Autoconf -*-
 
 # Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
-# 2005, 2006, 2008 Free Software Foundation, Inc.
+# 2005, 2006, 2008, 2009 Free Software Foundation, Inc.
 #
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -75,8 +75,8 @@ AM_MISSING_PROG(AUTOCONF, autoconf)
 AM_MISSING_PROG(AUTOMAKE, automake-${am__api_version})
 AM_MISSING_PROG(AUTOHEADER, autoheader)
 AM_MISSING_PROG(MAKEINFO, makeinfo)
-AM_PROG_INSTALL_SH
-AM_PROG_INSTALL_STRIP
+AC_REQUIRE([AM_PROG_INSTALL_SH])dnl
+AC_REQUIRE([AM_PROG_INSTALL_STRIP])dnl
 AC_REQUIRE([AM_PROG_MKDIR_P])dnl
 # We need awk for the "check" target.  The system "awk" is bad on
 # some platforms.
-- 
1.6.0.4