FYI: autoreconf: aclocal --force

[Akim Demaille]

Thanks to Alexandre Duret-Lutz for his preliminary proof-reading.

Index: ChangeLog
from  Akim Demaille  <address@hidden>

        Don't try to be smart with aclocal 1.8+ because (i) aclocal no
        longer updates aclocal.m4 if useless, (ii) if a file m4_included
        by aclocal.m4 is changed it might require the importing of another
        m4 extension file, i.e., aclocal must be run.

        * bin/autoreconf.in (&run_aclocal, $aclocal_supports_force): New.
        (&parse_args): Use --force with aclocal if required and supported.
        (&autoreconf_current_directory): Use &run_aclocal.

Index: bin/autoreconf.in
===================================================================
RCS file: /cvsroot/autoconf/autoconf/bin/autoreconf.in,v
retrieving revision 1.112
diff -u -u -r1.112 autoreconf.in
--- bin/autoreconf.in 28 Feb 2003 10:11:11 -0000 1.112
+++ bin/autoreconf.in 6 May 2003 15:06:28 -0000
@@ -6,7 +6,8 @@
     if 0;
 
 # autoreconf - install the GNU Build System in a directory tree
-# Copyright (C) 1994, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+# Copyright (C) 1994, 1999, 2000, 2001, 2002, 2003
+# Free Software Foundation, Inc.
 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -101,7 +102,7 @@
 $version = "autoreconf (@PACKAGE_NAME@) @VERSION@
 Written by David J. MacKenzie and Akim Demaille.
 
-Copyright 2002 Free Software Foundation, Inc.
+Copyright (C) 2003 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 ";
@@ -118,6 +119,8 @@
 my $install = 0;
 # symlink -- when --install, use symlinks instead.
 my $symlink = 0;
+# Does aclocal support --force?
+my $aclocal_supports_force = 0;
 
 my @prepend_include;
 my @include;
@@ -170,6 +173,8 @@
        }
     }
 
+  $aclocal_supports_force = `$aclocal --help` =~ /--force/;
+
   # Dispatch autoreconf's option to the tools.
   # --include;
   $autoconf   .= join (' --include=', '', @include);
@@ -187,6 +192,8 @@
   # --force;
   if ($force)
     {
+      $aclocal    .= ' --force'
+       if $aclocal_supports_force;
       $autoconf   .= ' --force';
       $autoheader .= ' --force';
       $automake   .= ' --force-missing';
@@ -217,6 +224,67 @@
 }
 
 
+# &run_aclocal ($ACLOCAL, $FLAGS)
+# -------------------------------
+# Update aclocal.m4 as lazily as possible, as aclocal pre-1.8 always
+# overwrites aclocal.m4, hence triggers autoconf, autoheader, automake
+# etc. uselessly.  aclocal 1.8+ does not need this.
+sub run_aclocal ($$)
+{
+  my ($aclocal, $flags) = @_;
+
+  # aclocal 1.8+ does all this for free.  It can be recognized by its
+  # --force support.
+  if ($aclocal_supports_force)
+    {
+      xsystem ("$aclocal $flags");
+    }
+  else
+    {
+      xsystem ("$aclocal $flags --output=aclocal.m4t");
+      # aclocal may produce no output.
+      if (-f 'aclocal.m4t')
+       {
+         update_file ('aclocal.m4t', 'aclocal.m4');
+         # Make sure that the local m4 files are older than
+         # aclocal.m4.
+         #
+         # Why is not always the case?  Because we already run
+         # aclocal at first (before tracing), which, for instance,
+         # can find Gettext's macros in .../share/aclocal, so we may
+         # have had the right aclocal.m4 already.  Then autopoint is
+         # run, and installs locally these M4 files.  Then
+         # autoreconf, via update_file, sees it is the _same_
+         # aclocal.m4, and doesn't change its timestamp.  But later,
+         # Automake's Makefile expresses that aclocal.m4 depends on
+         # these local files, which are newer, so it triggers aclocal
+         # again.
+         #
+         # To make sure aclocal.m4 is no older, we change the
+         # modification times of the local M4 files to be not newer
+         # than it.
+         #
+         # First, where are the local files?
+         my $aclocal_local_dir = '.';
+         if ($flags =~ /-I\s+(\S+)/)
+           {
+             $aclocal_local_dir = $1;
+           }
+         # All the local files newer than aclocal.m4 are to be
+         # made not newer than it.
+         my $aclocal_m4_mtime = mtime ('aclocal.m4');
+         for my $file (glob ("$aclocal_local_dir/*.m4"), 'acinclude.m4')
+           {
+             if ($aclocal_m4_mtime < mtime ($file))
+               {
+                 debug "aging $file to be not newer than aclocal.m4";
+                 utime $aclocal_m4_mtime, $aclocal_m4_mtime, $file;
+               }
+           }
+       }
+    }
+}
+
 # &autoreconf_current_directory
 # -----------------------------
 sub autoreconf_current_directory ()
@@ -337,10 +405,7 @@
       # fall.
       sleep 1;
 
-      xsystem ("$aclocal $aclocal_flags --output=aclocal.m4t");
-      # aclocal may produce no output.
-      update_file ('aclocal.m4t', 'aclocal.m4')
-       if -f 'aclocal.m4t';
+      run_aclocal ($aclocal, $aclocal_flags);
     }
 
   # We might have to rerun aclocal if Libtool (or others) imports new
@@ -437,47 +502,7 @@
        }
       else
        {
-         xsystem ("$aclocal $aclocal_flags --output=aclocal.m4t");
-         # aclocal may produce no output.
-         if (-f 'aclocal.m4t')
-           {
-             update_file ('aclocal.m4t', 'aclocal.m4');
-             # Make sure that the local m4 files are older than
-             # aclocal.m4.
-             #
-             # Why is not always the case?  Because we already run
-             # aclocal at first (before tracing), which, for instance,
-             # can find Gettext's macros in .../share/aclocal, so we
-             # may have had the right aclocal.m4 already.  Then
-             # autopoint is run, and installs locally these M4
-             # files.  Then autoreconf, via update_file, sees it is
-             # the _same_ aclocal.m4, and doesn't change its
-             # timestamp.  But later, Automake's Makefile expresses
-             # that aclocal.m4 depends on these local files, which
-             # are newer, so it triggers aclocal again.
-             #
-             # To make sure aclocal.m4 is no older, we change the
-             # modification times of the local M4 files to be
-             # not newer than it.
-             #
-             # First, where are the local files?
-             my $aclocal_local_dir = '.';
-             if ($aclocal_flags =~ /-I\s+(\S+)/)
-               {
-                 $aclocal_local_dir = $1;
-               }
-             # All the local files newer than aclocal.m4 are to be
-             # made not newer than it.
-             my $aclocal_m4_mtime = mtime ('aclocal.m4');
-             for my $file (glob ("$aclocal_local_dir/*.m4"), 'acinclude.m4')
-               {
-                 if ($aclocal_m4_mtime < mtime ($file))
-                   {
-                     debug "aging $file to be not newer than aclocal.m4";
-                     utime $aclocal_m4_mtime, $aclocal_m4_mtime, $file;
-                   }
-               }
-           }
+         run_aclocal ($aclocal, $aclocal_flags);
        }
     }