Re: expose m4_PACKAGE_VERSION,m4_version_compare

[Eric Blake]

Eric Blake <ebb9 <at> byu.net> writes:

> 
> Benoit SIGOURE <tsuna <at> lrde.epita.fr> writes:
> 
> > 
> > It looks great.  The name m4_PACKAGE_VERSION is somewhat misleading  
> > however (as I understand it, it contains the current version of  
> > autoconf right?  So why not name it like m4_AUTOCONF_VERSION or  
> > whatever?).
> 
> Good point.  There are other m4_PACKAGE_* macros that I did not document; 
> basically, they all perform a hard-wired mapping to the contents of the 
> PACKAGE_* macros from autoconf's configure script.  I like your idea of 
making 
> the public macro have a more obvious name.  I'll rework my patch accordingly 
> (as in, add m4_AUTOCONF_VERSION as the new documented alias, and leave 
> m4_PACKAGE_VERSION available, but undocumented).

It turns out that even Automake 1.10 uses m4_PACKAGE_VERSION, so I don't feel 
good obsoleting it just yet (at least, not until after one release of autoconf 
with both names, and a release of automake that prefers the newer name when 
available).  That, and obsoleting an m4sugar macro is not as simple as 
obsoleting a normal autoconf macro, since there is no AU_DEFUN in the m4sugar 
level.  It would involve something like the trick that lib/autoconf/autoconf.m4 
uses for discouraging the name m4_patsubst (users should either use patsubst or 
m4_bpatsubst).

So for now, I'm checking in this:

2007-09-12  Eric Blake  <address@hidden>

        Publish m4_ifndef, m4_version_compare, m4_AUTOCONF_VERSION.
        * doc/autoconf.texi (Text processing Macros): Document
        m4_version_compare, m4_AUTOCONF_VERSION, m4_PACKAGE_VERSION.
        (Redefined M4 Macros): Document m4_ifndef.
        * lib/m4sugar/m4sugar.m4 (m4_AUTOCONF_VERSION): New macro; we
        can't obsolete m4_PACKAGE_VERSION at this time since Autoconf 1.10
        used it while it was undocumented.
        * NEWS: Document this change.
        * lib/m4sugar/Makefile.am (version.m4): Update copyright dates.
        * lib/m4sugar/Makefile.in: Regenerate.
        * tests/m4sugar.at (m4@&address@hidden): New test.
        Reported by Bruno Haible.

Index: NEWS
===================================================================
RCS file: /sources/autoconf/autoconf/NEWS,v
retrieving revision 1.437
diff -u -p -r1.437 NEWS
--- NEWS        11 Sep 2007 17:13:13 -0000      1.437
+++ NEWS        13 Sep 2007 03:09:27 -0000
@@ -8,7 +8,7 @@ GNU Autoconf NEWS - User visible changes
    generated by autoconf under the license of your own program.
  FIXME - revisit this line once exception clause is finalized.
 
-** New macros AC_OPENMP, AC_PATH_PROGS_FEATURE_CHECK.
+** New Autoconf macros AC_OPENMP, AC_PATH_PROGS_FEATURE_CHECK.
 
 ** AC_C_BIGENDIAN now supports universal binaries a la Mac OS X.
 
@@ -47,6 +47,13 @@ GNU Autoconf NEWS - User visible changes
    Autoconf and Automake.  GNU M4 1.4.8 or later is recommended.  The
    configure search for a working M4 is improved.
 
+** New m4sugar macro m4_AUTOCONF_VERSION.  Also, document the m4sugar macros
+   m4_ifndef, m4_version_compare, and m4_PACKAGE_VERSION (available
+   without documentation since at least autoconf 2.53), in part so
+   that packages can make decisions based on the current version of
+   autoconf used to evaluate a given configure.ac.  The name
+   m4_PACKAGE_VERSION may be marked obsolescent in a future release.
+
 ** Warnings are now generated by default when an installer invokes
    'configure' with an unknown --enable-* or --with-* option.
    These warnings can be disabled with the new AC_DISABLE_OPTION_CHECKING
Index: lib/m4sugar/m4sugar.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/m4sugar/m4sugar.m4,v
retrieving revision 2.102
diff -u -p -r2.102 m4sugar.m4
--- lib/m4sugar/m4sugar.m4      20 Jul 2007 23:11:54 -0000      2.102
+++ lib/m4sugar/m4sugar.m4      13 Sep 2007 03:09:27 -0000
@@ -3,8 +3,8 @@ divert(-1)#                             
 # Base M4 layer.
 # Requires GNU M4.
 #
-# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
-# Foundation, Inc.
+# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 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
@@ -1725,6 +1725,15 @@ m4_define([m4_version_compare],
 m4_include([m4sugar/version.m4])
 
 
+# m4_AUTOCONF_VERSION
+# -------------------
+# A nicer synonym for the name m4_PACKAGE_VERSION.  However, since
+# automake 1.10 decided to use m4_PACKAGE_VERSION while it was still
+# undocumented, it will be a while before we can try to obsolete the
+# confusing name.
+m4_copy([m4_PACKAGE_VERSION], [m4_AUTOCONF_VERSION])
+
+
 # m4_version_prereq(VERSION, [IF-OK], [IF-NOT = FAIL])
 # ----------------------------------------------------
 # Check this Autoconf version against VERSION.
Index: lib/m4sugar/Makefile.am
===================================================================
RCS file: /sources/autoconf/autoconf/lib/m4sugar/Makefile.am,v
retrieving revision 1.16
diff -u -p -r1.16 Makefile.am
--- lib/m4sugar/Makefile.am     20 Jul 2007 23:11:53 -0000      1.16
+++ lib/m4sugar/Makefile.am     13 Sep 2007 03:09:27 -0000
@@ -1,6 +1,6 @@
 # Make Autoconf library for M4sugar.
 
-# Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.
+# Copyright (C) 2001, 2002, 2006, 2007 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
@@ -28,7 +28,7 @@ version.m4: $(top_srcdir)/configure.ac
        {                                       \
          echo '# This file is part of -*- Autoconf -*-.'; \
          echo '# Version of Autoconf.'; \
-         echo '# Copyright (C) 1999, 2000, 2001, 2002'; \
+         echo '# Copyright (C) 1999, 2000, 2001, 2002, 2006, 2007'; \
          echo '# Free Software Foundation, Inc.'; \
          echo ;\
          echo 'm4_define([m4_PACKAGE_NAME],      [$(PACKAGE_NAME)])'; \
Index: doc/autoconf.texi
===================================================================
RCS file: /sources/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.1173
diff -u -p -r1.1173 autoconf.texi
--- doc/autoconf.texi   13 Sep 2007 02:35:41 -0000      1.1173
+++ doc/autoconf.texi   13 Sep 2007 03:09:27 -0000
@@ -10050,6 +10050,14 @@ This macro corresponds to @code{m4exit}.
 This macro corresponds to @code{ifelse}.
 @end defmac
 
address@hidden m4_ifndef (@var{macro}, @var{if-not-defined}, @ovar{if-defined})
address@hidden
+This is shorthand for:
address@hidden
+m4_ifdef(address@hidden, address@hidden, address@hidden)
address@hidden example
address@hidden defmac
+
 @defmac m4_include (@var{file})
 @defmacx m4_sinclude (@var{file})
 @msindex{include}
@@ -10270,6 +10278,59 @@ added.  @code{m4_append} can be used to 
 @code{m4_append_uniq} to grow strings without duplicating substrings.
 @end defmac
 
address@hidden m4_version_compare (@var{version-1}, @var{version-2})
address@hidden
+Introduced in autoconf 2.53.  Compare the version strings
address@hidden and @var{version-2}, and expand to @samp{-1} if
address@hidden is smaller, @samp{0} if they are the same, or @samp{1}
address@hidden is smaller.  Version strings must be a list of elements
+separated by @samp{.}, where each element is a number along with an
+optional letter.  The comparison stops at the leftmost element that
+contains a difference, although a 0 element compares equal to a missing
+element.
+
address@hidden
+m4_version_compare([1.1], [2.0])
address@hidden
+m4_version_compare([2.0b], [2.0a])
address@hidden
+m4_version_compare([1.1.1], [1.1.1a])
address@hidden
+m4_version_compare([1.2], [1.1.1a])
address@hidden
+m4_version_compare([1.0], [1])
address@hidden
address@hidden example
address@hidden defmac
+
address@hidden m4_AUTOCONF_VERSION
address@hidden m4_PACKAGE_VERSION
address@hidden
address@hidden
+These macros identify the version of Autoconf that is currently parsing
+the input file, in a format suitable for @code{m4_version_compare}.  The
+name @code{m4_AUTOCONF_VERSION} was introduced in Autoconf 2.62.  The
+synonym @code{m4_PACKAGE_VERSION} existed since Autoconf 2.53, but was
+undocumented for many years because it is not named very well, and it
+may be withdrawn in a future release.  One use of these macros is for
+writing conditional fallbacks based on when a feature was added to
+Autoconf, rather than using @code{AC_PREREQ} to require the newer
+version of Autoconf.
+
+For an example, @code{AC_USE_SYSTEM_EXTENSIONS} was only added in
+Autoconf 2.60 (@pxref{AC_USE_SYSTEM_EXTENSIONS}).  A @file{configure.ac}
+designed to work even with Autoconf 2.59 can do the following in a
+compatibility section, then use the newer macros elsewhere without
+worrying about Autoconf versions:
+
address@hidden
+m4_ifndef([m4_AUTOCONF_VERSION],
+          [m4_define([m4_AUTOCONF_VERSION],
+                     m4_defn([m4_PACKAGE_VERSION]))])
+m4_if(m4_version_compare(m4_AUTOCONF_VERSION, [2.60]), [-1],
+      [AC_DEFUN([AC_USE_SYSTEM_EXTENSIONS], [AC_GNU_SOURCE])])
address@hidden example
address@hidden defmac
 
 
 @node Forbidden Patterns
Index: tests/m4sugar.at
===================================================================
RCS file: /sources/autoconf/autoconf/tests/m4sugar.at,v
retrieving revision 1.34
diff -u -p -r1.34 m4sugar.at
--- tests/m4sugar.at    20 Jul 2007 23:11:54 -0000      1.34
+++ tests/m4sugar.at    13 Sep 2007 03:09:27 -0000
@@ -2,7 +2,7 @@
 
 AT_BANNER([M4sugar.])
 
-# Copyright (C) 2000, 2001, 2002, 2005, 2006 Free Software Foundation, Inc.
+# Copyright (C) 2000, 2001, 2002, 2005, 2006, 2007 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
@@ -117,10 +117,6 @@ AT_CLEANUP
 
 AT_SETUP([m4@&address@hidden: circular dependencies])
 
-# m4_text_wrap is used to display the help strings.  Also, check that
-# commas are not swallowed.  This can easily happen because of
-# m4-listification.
-
 AT_DATA_M4SUGAR([script.4s],
 [[m4_defun([foo], [m4_require([bar])])
 
@@ -191,6 +187,41 @@ AT_CHECK_M4SUGAR([-o-], 0, [expout])
 
 AT_CLEANUP
 
+## -------------------- ##
+## m4_version_compare.  ##
+## -------------------- ##
+
+AT_SETUP([m4@&address@hidden)
+
+# In addition to version checks, also check m4_AUTOCONF_VERSION, added
+# for autoconf 2.62.
+
+AT_CHECK_M4SUGAR_TEXT(
+[[m4_version_compare([1.1], [2.0])
+m4_version_compare([2.0b], [2.0a])
+m4_version_compare([2.0z], [2.0y])
+m4_version_compare([1.1.1], [1.1.1a])
+m4_version_compare([1.2], [1.1.1a])
+m4_version_compare([1.0], [1])
+m4_version_compare([1.0a], [1.0a])
+m4_version_compare([1.1a], [1.1a.1])
+m4_version_compare(m4_AUTOCONF_VERSION, [2.61])
+m4_version_compare(m4_defn([m4_AUTOCONF_VERSION]), [2.61])
+]],
+[[-1
+1
+1
+-1
+1
+0
+0
+-1
+1
+1
+]])
+
+AT_CLEANUP
+
 ## ------------------------------ ##
 ## Standard regular expressions.  ##
 ## ------------------------------ ##