+2001-02-21 Akim Demaille <akim@epita.fr>
+
+ * autoupdate.in: New. Replaces autoupdate.sh.
+
2001-02-21 Akim Demaille <akim@epita.fr>
* autoscan.pl (&find_configure_ac): New.
EXTRA_DIST = ChangeLog.0 ChangeLog.1 \
BUGS INSTALL.txt \
acversion.m4.in \
- autoconf.sh autoheader.sh autoreconf.sh autoupdate.sh ifnames.sh \
+ autoconf.sh autoheader.sh autoreconf.sh autoupdate.in ifnames.sh \
autoscan.pl \
$(distpkgdataDATA)
chmod +x autoreconf.tmp
mv autoreconf.tmp autoreconf
-autoupdate: $(srcdir)/autoupdate.sh $(srcdir)/configure.in
+autoupdate: $(srcdir)/autoupdate.in $(srcdir)/configure.in
rm -f autoupdate autoupdate.tmp
- $(edit) $(srcdir)/autoupdate.sh >autoupdate.tmp
+ $(edit) $(srcdir)/autoupdate.in >autoupdate.tmp
chmod +x autoupdate.tmp
mv autoupdate.tmp autoupdate
pkgdata_DATA = $(distpkgdataDATA) $(nodistpkgdataDATA)
-EXTRA_DIST = ChangeLog.0 ChangeLog.1 BUGS INSTALL.txt acversion.m4.in autoconf.sh autoheader.sh autoreconf.sh autoupdate.sh ifnames.sh autoscan.pl $(distpkgdataDATA)
+EXTRA_DIST = ChangeLog.0 ChangeLog.1 BUGS INSTALL.txt acversion.m4.in autoconf.sh autoheader.sh autoreconf.sh autoupdate.in ifnames.sh autoscan.pl $(distpkgdataDATA)
# Files that should be removed, but which Automake does not know:
chmod +x autoreconf.tmp
mv autoreconf.tmp autoreconf
-autoupdate: $(srcdir)/autoupdate.sh $(srcdir)/configure.in
+autoupdate: $(srcdir)/autoupdate.in $(srcdir)/configure.in
rm -f autoupdate autoupdate.tmp
- $(edit) $(srcdir)/autoupdate.sh >autoupdate.tmp
+ $(edit) $(srcdir)/autoupdate.in >autoupdate.tmp
chmod +x autoupdate.tmp
mv autoupdate.tmp autoupdate
--- /dev/null
+#! @PERL@ -w
+# autoupdate - modernize an Autoconf file.
+# Copyright 1994, 1999, 2000, 2001 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
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.
+# Rewritten by Akim Demaille <akim@freefriends.org>.
+
+use Getopt::Long;
+use strict;
+
+(my $me = $0) =~ s,.*/,,;
+
+# Lib files.
+my $autoconf_dir = $ENV{"AC_MACRODIR"} || "@datadir@";
+
+my $autoconf = '';
+my $debug = 0;
+my $localdir = '.';
+# m4.
+my $m4 = $ENV{"M4"} || "@M4@";
+my $status = 0;
+# FIXME: Ahem....
+my $tmp = '/tmp/autoupdate.tmp';
+mkdir $tmp, 0700;
+my $verbose = 0;
+my $SIMPLE_BACKUP_SUFFIX = $ENV{'SIMPLE_BACKUP_SUFFIX'} || '~';
+
+
+## ---------- ##
+## Routines. ##
+## ---------- ##
+
+
+# END
+# ---
+# Exit nonzero whenever closing STDOUT fails.
+sub END
+{
+ use POSIX qw (_exit);
+ # This is required if the code might send any output to stdout
+ # E.g., even --version or --help. So it's best to do it unconditionally.
+ close STDOUT
+ or (warn "$me: closing standard output: $!\n"), _exit (1);
+}
+
+
+# print_usage ()
+# --------------
+# Display usage (--help).
+sub print_usage ()
+{
+ print "\
+Usage: $0 [OPTION] ... [TEMPLATE-FILE...]
+
+Update the TEMPLATE-FILE... if given, or \`configure.ac' if present,
+or else \`configure.in', to the syntax of the current version of
+Autoconf. The original files are backed up.
+
+Operation modes:
+ -h, --help print this help, then exit
+ -V, --version print version number, then exit
+ -v, --verbose verbosely report processing
+ -d, --debug don't remove temporary files
+
+Library directories:
+ -A, --autoconf-dir=ACDIR Autoconf's macro files location (rarely needed)
+ -l, --localdir=DIR location of \`aclocal.m4' and \`acconfig.h'
+
+Environment variables:
+ M4 GNU M4 is required.
+ AUTOCONF autoconf.
+
+Report bugs to <bug-autoconf\@gnu.org>.
+";
+ exit 0;
+}
+
+
+# print_version ()
+# ----------------
+# Display version (--version).
+sub print_version
+{
+ print "\
+autoupdate (@PACKAGE_NAME@) @VERSION@
+Written by David J. MacKenzie and Akim Demaille.
+
+Copyright 1994, 1999, 2000, 2001 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.
+";
+ exit 0;
+}
+
+
+# $CONFIGURE_AC
+# &find_configure_ac ()
+# ---------------------
+sub find_configure_ac ()
+{
+ if (-f 'configure.ac')
+ {
+ if (-f 'configure.in')
+ {
+ warn "warning: `configure.ac' and `configure.in' both present.\n";
+ warn "warning: proceeding with `configure.ac'.\n";
+ }
+ return 'configure.ac';
+ }
+ elsif (-f 'configure.in')
+ {
+ return 'configure.in';
+ }
+ return;
+}
+
+
+# parse_args ()
+# -------------
+# Process any command line arguments.
+sub parse_args ()
+{
+ my $srcdir;
+ Getopt::Long::config ("bundling");
+ Getopt::Long::GetOptions ("A|autoconf-dir|m|macrodir=s" => \$autoconf_dir,
+ "h|help" => \&print_usage,
+ "V|version" => \&print_version,
+ "v|verbose" => \$verbose)
+ or exit 1;
+ if (! @ARGV)
+ {
+ my $configure_ac = find_configure_ac;
+ die 'no input file'
+ unless $configure_ac;
+ push @ARGV, $configure_ac;
+ }
+}
+
+
+# find_slaves
+# -----------
+# Find the lib files and autoconf.
+sub find_slaves ()
+{
+ # Some non-GNU m4's don't reject the --help option, so give them /dev/null.
+ die "Autoconf requires GNU m4 1.4 or later\n"
+ if system "$m4 --help </dev/null 2>&1 | fgrep reload-state >/dev/null";
+
+ # autoconf.
+ (my $dir = $0) =~ s,[^/]*$,,;
+
+ # We test "$dir/autoconf" in case we are in the build tree, in which case
+ # the names are not transformed yet.
+ foreach my $file ($ENV{"AUTOCONF"} || '',
+ "$dir/@autoconf-name@",
+ "$dir/autoconf",
+ "@bindir@/@autoconf-name@")
+ {
+ if (-x $file)
+ {
+ $autoconf = $file;
+ last;
+ }
+ }
+}
+
+
+## -------------- ##
+## Main program. ##
+## -------------- ##
+find_slaves;
+parse_args;
+$autoconf .= " -l $localdir";
+$ENV{'autoconf_dir'} = $autoconf_dir;
+
+# m4.txt -- the builtins of m4.
+system ("echo dumpdef | "
+ . "$m4 2>&1 >/dev/null | "
+ . "sed -n 's/:.*//p' "
+ . ">$tmp/m4.txt");
+
+# m4.m4 -- enable the m4 builtins.
+system ("sed 's/^.*\$/_au_define([&], _au_defn([_au_&]))/' $tmp/m4.txt "
+ . ">$tmp/m4.m4");
+
+# unm4.m4 -- disable the m4 builtins.
+system ("sed 's/^.*\$/_au_undefine([&])/' $tmp/m4.txt >$tmp/unm4.m4");
+
+# savem4.m4 -- save the m4 builtins.
+system ("sed 's/^.*\$/define([_au_&], defn([&]))/' $tmp/m4.txt "
+ . ">$tmp/m4save.m4");
+
+# au.txt -- list of all the AU macros.
+system ("$autoconf --trace AU_DEFUN:'\$1' -i /dev/null | "
+ . "sort -u "
+ . ">$tmp/au.txt");
+
+# au-del.sed -- delete the AU macro names.
+system ("sed \"s,^.*\$,/&/d,\" $tmp/au.txt "
+ . " >$tmp/au-del.sed");
+
+# au.m4 -- definitions the AU macros.
+system ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@,
+\@<:\@\$2\@:>\@)' -i /dev/null "
+ . ">$tmp/au.m4");
+
+# quote.sed -- enable the quote `[', `]' right before any AU macro.
+# Unfortunately, I can't see a solution which does not use `\b', which
+# is a GNU extension :(. Am I understanding we should use Perl?
+system ('sed \'s/^.*$/s!\\\\b&\\\\b!_au_changequote([,])\\&!/\'' . " $tmp/au.txt "
+ . ">$tmp/quote.sed");
+
+# ac.txt -- list of all the AC and m4sugar macros prefixed by the name
+# of the file which defines it.
+# Be carefull to remove the AU macros.
+system ("$autoconf --trace define:'\$f:\$1' -i /dev/null | "
+ . "sed -f $tmp/au-del.sed "
+ . ">$tmp/ac.txt");
+
+# ac.m4 -- autoquoting definitions of the AC macros.
+system ('sed -n \'/m4sugar.m4/!s/^[^:]*:\(.*\)$/_au_define([\1], [[$0($@)]])/p\''
+ . " $tmp/ac.txt"
+ . ">$tmp/ac.m4");
+
+# disable.m4 -- undefine the macros of AC and m4sugar.
+system ('sed \'s/^[^:]*:\\(.*\\)$/_au_undefine([\1])/\'' . " $tmp/ac.txt "
+ . ">$tmp/disable.m4");
+
+foreach my $file (@ARGV)
+ {
+ my $filename = $file;
+ # We need an actual file.
+ if ($file eq '-')
+ {
+ $file = "$tmp/stdin";
+ system "cat >$file";
+ }
+ elsif (! -r "$file")
+ {
+ die "$me: $file: No such file or directory";
+ }
+
+ # input.m4 -- m4 program to produce the updated file.
+ # Load the values, the dispatcher, neutralize m4, and the prepared
+ # input file.
+ my $input_m4 = <<EOF;
+ divert(-1) -*- Autoconf -*-
+ changequote([, ])
+
+ # Move all the builtins into the \`_au_' pseudo namespace
+ include([$tmp/m4save.m4])
+
+ # _au_defun(NAME, BODY)
+ # ---------------------
+ # Define NAME to BODY, plus AU activation/deactivation.
+ _au_define([_au_defun],
+ [_au_define([\$1],
+ [_au_enable()dnl
+ \$2[]dnl
+ _au_disable()])])
+
+ # Import the definition of the obsolete macros.
+ _au_include([$tmp/au.m4])
+
+
+ ## ------------------------ ##
+ ## _au_enable/_au_disable. ##
+ ## ------------------------ ##
+
+ # They work by pair: each time an AU macro is activated, it runs
+ # _au_enable, and at its end its runs _au_disable (see _au_defun
+ # above). But since AU macros might use AU macros, which should
+ # enable/disable only for the outter AU macros.
+ #
+ # \`_au_enabled' is used to this end, condionning whether we really
+ # enable/disable.
+
+
+ # __au_enable
+ # -----------
+ # Reenable the builtins, and m4sugar.
+ _au_define([__au_enable],
+ [_au_divert(-1)
+ # Enable special characters.
+ _au_changecom([#])
+
+ # Enable the m4 builtins, m4sugar and the autoquoting AC macros.
+ _au_include([$tmp/m4.m4])
+ _au_include([$autoconf_dir/m4sugar.m4])
+ _au_include([$tmp/ac.m4])
+
+ _au_divert(0)])
+
+ # _au_enable
+ # ----------
+ # Called at the beginning of all the obsolete macros. Reenable the
+ # builtins, and m4sugar if needed.
+ _au_define([_au_enable],
+ [_au_ifdef([_au_enabled],
+ [],
+ [__au_enable()])_au_dnl
+ _au_pushdef([_au_enabled])])
+
+
+ # __au_disable
+ # ------------
+ # Disable the builtins, and m4sugar.
+ _au_define([__au_disable],
+ [_au_divert(-1)
+ # Disable m4sugar, the AC autoquoting macros, and m4.
+ _au_include([$tmp/disable.m4])
+ _au_include([$tmp/unm4.m4])
+
+ # Disable special characters.
+ _au_changequote()
+ _au_changecom()
+
+ _au_divert(0)])
+
+ # _au_disable
+ # -----------
+ # Called at the end of all the obsolete macros. Disable the
+ # builtins, and m4sugar if needed..
+ _au_define([_au_disable],
+ [_au_popdef([_au_enabled])_au_dnl
+ _au_ifdef([_au_enabled],
+ [],
+ [__au_disable()])])
+
+
+ ## ------------------------------- ##
+ ## Disable, and process the file. ##
+ ## ------------------------------- ##
+ _au_disable()_au_dnl
+EOF
+
+ $input_m4 =~ s/^ //mg;
+
+ # prepared input -- input, but reenables the quote before each AU macro.
+ open INPUT_M4, ">$tmp/input.m4";
+ print INPUT_M4 "$input_m4\n";
+ close INPUT_M4;
+ system ("sed -f $tmp/quote.sed $file >>$tmp/input.m4");
+
+ # Now ask m4 to perform the update.
+ print STDERR "$me: running $m4 $tmp/input.m4"
+ if $verbose;
+ system ("$m4 $tmp/input.m4 >$tmp/updated") == 0
+ or die "$me: cannot update \`$filename'";
+
+ if ("$file" eq "$tmp/stdin")
+ {
+ system ("cat $tmp/updated");
+ }
+ elsif (! system ("cmp -s $tmp/updated $file"))
+ {
+ # File didn't change, so don't update its mod time.
+ print STDERR "$me: \`$file' is unchanged\n"
+ }
+ else
+ {
+ # Back up and install the new one.
+ if (system ("mv $file $file${SIMPLE_BACKUP_SUFFIX} && "
+ . "mv $tmp/updated $file") == 0)
+ {
+ print STDERR "$me: \`$file' is updated\n";
+ }
+ else
+ {
+ die "$me: cannot update \`$file'";
+ }
+ }
+ }
+
+exit 0;
+
+
+# ## ---------------------------- ##
+# ## How `autoupdate' functions. ##
+# ## ---------------------------- ##
+#
+# The task of `autoupdate' is not trivial: the biggest difficulty being
+# that you must limit the changes to the parts that really need to be
+# updated. Finding a satisfying implementation proved to be quite hard,
+# as this is the fourth implementation of `autoupdate'.
+#
+# Below, we will use a simple example of obsolete macro:
+#
+# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
+# AC_DEFUN([NEW], [echo "sum($1) = $2"])
+#
+# the input file contains
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Of course the expected output is
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0], [0])
+#
+#
+# # First implementation: sed
+# # =========================
+#
+# The first implementation was only able to change the name of obsolete
+# macros.
+#
+# The file `acoldnames.m4' defined the old names based on the new names.
+# It was simple then to produce a sed script such as:
+#
+# s/OLD/NEW/g
+#
+# Updating merely consisted in running this script on the file to
+# update.
+#
+# This scheme suffers an obvious limitation: that `autoupdate' was
+# unable to cope with new macros that just swap some of its arguments
+# compared to the old macro. Fortunately, that was enough to upgrade
+# from Autoconf 1 to Autoconf 2. (But I have no idea whether the
+# changes in Autoconf 2 were precisely limited by this constraint.)
+#
+#
+# # Second implementation: hooks
+# # ============================
+#
+# The version 2.15 of Autoconf brought a vast number of changes compared
+# to 2.13, so a solution was needed. One could think to extend the
+# `sed' scripts with specialized code for complex macros. But this
+# approach is of course full of flaws:
+#
+# a. the Autoconf maintainers have to write these snippets, which we
+# just don't want to,
+#
+# b. I really don't think you'll ever manage to handle the quoting of
+# m4 from sed.
+#
+# To satisfy a., let's remark that the code which implements the old
+# features in term of the new feature is exactly the code which should
+# replace the old code.
+#
+# To answer point b, as usual in the history of Autoconf, the answer, at
+# least on the paper, is simple: m4 is the best tool to parse m4, so
+# let's use m4.
+#
+# Therefore the specification is:
+#
+# I want to be able to tell Autoconf, well, m4, that the macro I
+# am currently defining is an obsolete macro (so that the user is
+# warned), which code is the code to use when running autoconf,
+# but that the very same code has to be used when running
+# autoupdate. To summarize, the interface I want is
+# `AU_DEFUN(OLD-NAME, NEW-CODE)'.
+#
+#
+# Now for the technical details.
+#
+# When running autoconf, except for the warning, AU_DEFUN is basically
+# AC_DEFUN.
+#
+# When running autoupdate, we want *only* OLD-NAMEs to be expanded.
+# This obviously means that acgeneral.m4 and acspecific.m4 must not be
+# loaded. Nonetheless, because we want to use a rich set of m4
+# features, m4sugar.m4 is needed. Please note that the fact that
+# Autoconf's macros are not loaded is positive on two points:
+#
+# - we do get an updated `configure.ac', not a `configure'!
+#
+# - the old macros are replaced by *calls* to the new-macros, not the
+# body of the new macros, since their body is not defined!!!
+# (Whoa, that's really beautiful!).
+#
+# Additionally we need to disable the quotes when reading the input for
+# two reasons: first because otherwise `m4' will swallow the quotes of
+# other macros:
+#
+# NEW([1, 2], 3)
+# => NEW(1, 2, 3)
+#
+# and second, because we want to update the macro calls which are
+# quoted, i.e., we want
+#
+# FOO([OLD(1, 2)])
+# => FOO([NEW([1, 2], [3])])
+#
+# If we don't disable the quotes, only the macros called at the top
+# level would be updated.
+#
+# So, let's disable the quotes.
+#
+# Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
+# Well, in this case, when running in autoupdate code, each macro first
+# reestablishes the quotes, expands itself, and disables the quotes.
+#
+# Thinking a bit more, you realize that in fact, people may use `define'
+# `ifelse' etc. in their files, and you certainly don't want to process
+# them. Another example is `dnl': you don't want to remove the
+# comments. You then realize you don't want exactly to import m4sugar:
+# you want to specify when it is enabled (macros active), and disabled.
+# m4sugar provides m4_disable/m4_enable to this end.
+#
+# You're getting close to it. Now remains one task: how to handle
+# twofold definitions?
+#
+# Remember that the same AU_DEFUN must be understood in two different
+# ways, the AC way, and the AU way.
+#
+# One first solution is to check whether acgeneral.m4 was loaded. But
+# that's definitely not cute. Another is simply to install `hooks',
+# that is to say, to keep in some place m4 knows, late `define' to be
+# triggered *only* in AU mode.
+#
+# You first think to design AU_DEFUN like this:
+#
+# 1. AC_DEFUN(OLD-NAME,
+# [Warn the user OLD-NAME is obsolete.
+# NEW-CODE])
+#
+# 2. Store for late AU binding([define(OLD_NAME,
+# [Reestablish the quotes.
+# NEW-CODE
+# Disable the quotes.])])
+#
+# but this will not work: NEW-CODE has probably $1, $2 etc. and these
+# guys will be replaced with the argument of `Store for late AU binding'
+# when you call it.
+#
+# I don't think there is a means to avoid this using this technology
+# (remember that $1 etc. are *always* expanded in m4). You may also try
+# to replace them with $[1] to preserve them for a later evaluation, but
+# if `Store for late AU binding' is properly written, it will remain
+# quoted till the end...
+#
+# You have to change technology. Since the problem is that `$1'
+# etc. should be `consumed' right away, one solution is to define now a
+# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
+# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By
+# the way, the same method was used in autoheader.
+#
+#
+# # Third implementation: m4 namespaces by m4sugar
+# # ==============================================
+#
+# Actually, this implementation was just a clean up of the previous
+# implementation: instead of defining hooks by hand, m4sugar was equipped
+# with `namespaces'. What are they?
+#
+# Sometimes we want to disable some *set* of macros, and restore them
+# later. We provide support for this via namespaces.
+#
+# There are basically three characters playing this scene: defining a
+# macro in a namespace, disabling a namespace, and restoring a namespace
+# (i.e., all the definitions it holds).
+#
+# Technically, to define a MACRO in NAMESPACE means to define the macro
+# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append
+# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
+# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
+# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of
+# NAMESPACE and to unbind them at will.
+#
+# Of course this implementation is really inefficient: m4 has to grow
+# strings which can become quickly huge, which slows it significantly.
+#
+# In particular one should avoid as much as possible to use `define' for
+# temporaries. Now that `define' as quite a complex meaning, it is an
+# expensive operations that should be limited to macros. Use
+# `m4_define' for temporaries.
+#
+# Private copies of the macros we used in entering / exiting the m4sugar
+# namespace. It is much more convenient than fighting with the renamed
+# version of define etc.
+#
+#
+#
+# Those two implementations suffered from serious problems:
+#
+# - namespaces were really expensive, and incurred a major performance
+# loss on `autoconf' itself, not only `autoupdate'. One solution
+# would have been the limit the use of namespaces to `autoupdate', but
+# that's again some complications on m4sugar, which really doesn't need
+# this. So we wanted to get rid of the namespaces.
+#
+# - since the quotes were disabled, autoupdate was sometimes making
+# wrong guesses, for instance on:
+#
+# foo([1, 2])
+#
+# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat
+# fragile, is to reestablish the quotes right before all the obsolete
+# macros, i.e., to use sed so that the previous text becomes
+#
+# changequote([, ])foo([1, 2])
+#
+# To this end, one wants to trace the definition of obsolete macros.
+#
+# It was there that the limitations of the namespace approach became
+# painful: because it was a complex machinery playing a lot with the
+# builtins of m4 (hence, quite fragile), tracing was almost impossible.
+#
+#
+# So this approach was dropped.
+#
+#
+# # The fourth implementation: two steps
+# # ====================================
+#
+# If you drop the uses of namespaces, you no longer can compute the
+# updated value, and replace the old call with it simultaneously.
+#
+# Obviously you will use m4 to compute the updated values, but you may
+# use some other tool to achieve the replacement. Personally, I trust
+# nobody but m4 to parse m4, so below, m4 will perform the two tasks.
+#
+# How can m4 be used to replace *some* macros calls with newer values.
+# Well, that's dead simple: m4 should learn the definitions of obsolete
+# macros, forget its builtins, disable the quotes, and then run on the
+# input file, which amounts to doing this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# which will result in
+#
+# dnl The Unbelievable Truth
+# NEW(1, 2, m4_eval(1 + 2))
+# NEW([0, 0],
+# 0)
+#
+# Grpmh. Two problems. A minor problem: it would have been much better
+# to have the `m4_eval' computed, and a major problem: you lost the
+# quotation in the result.
+#
+# Let's address the big problem first. One solution is to define any
+# modern macro to rewrite its calls with the proper quotation, thanks to
+# `$@'. Again, tracing the `define's makes it possible to know which
+# are these macros, so you input is:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# define([NEW], [[NEW($@)]changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# changequote([, ])NEW([0, 0],
+# 0)
+#
+# which results in
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2],[m4_eval(1 + 2)])
+# NEW([0, 0],[0])
+#
+# Our problem is solved, i.e., the first call to `NEW' is properly
+# quoted, but introduced another problem: we changed the layout of the
+# second calls, which can be a drama in the case of huge macro calls
+# (think of `AC_TRY_RUN' for instance). This example didn't show it,
+# but we also introduced parens to macros which did not have some:
+#
+# AC_INIT
+# => AC_INIT()
+#
+# No big deal for the semantics (unless the macro depends upon $#, which
+# is bad), but the users would not be happy.
+#
+# Additionally, we introduced quotes that we not there before, which is
+# OK in most cases, but could change the semantics of the file.
+#
+# Cruel dilemma: we do want the auto-quoting definition of `NEW' when
+# evaluating `OLD', but we don't when we evaluate the second `NEW'.
+# Back to namespaces?
+#
+# No.
+#
+#
+# # Second step: replacement
+# # ------------------------
+#
+# No, as announced above, we will work in two steps: in a first step we
+# compute the updated values, and in a second step we replace them. Our
+# goal is something like this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([1, 2], [3])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., the new value of `OLD' is precomputed using the auto-quoting
+# definition of `NEW' and the m4 builtins. We'll see how afterwards,
+# let's finish with the replacement.
+#
+# Of course the solution above is wrong: if there were other calls to
+# `OLD' with different values, we would smash them to the same value.
+# But it is quite easy to generalize the scheme above:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# define([OLD], [defn([OLD($@)])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., for each call to obsolete macros, we build an array `call =>
+# value', and use a macro to dispatch these values. This results in:
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0],
+# 0)
+#
+# In French, we say `Youpi !', which you might roughly translate as
+# `yipeee!'.
+#
+#
+# # First step: computation
+# # -----------------------
+#
+# Let's study the anatomy of the file, and name its sections:
+#
+# prologue
+# divert(-1)dnl
+# changequote([, ])
+# values
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# dispatcher
+# define([OLD], [defn([OLD($@)])changequote()])
+# disabler
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# input
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+#
+# # Computing the `values' section
+# # ..............................
+#
+# First we need to get the list of all the AU macro uses. To this end,
+# first get the list of all the AU macros names by tracing `AU_DEFUN' in
+# the initialization of autoconf. This list is computed in the file
+# `au.txt' below.
+#
+# Then use this list to trace all the AU macro uses in the input. The
+# goal is obtain in the case of our example:
+#
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# This is the file `values.in' below.
+#
+# We want to evaluate this with only the builtins (in fact m4sugar), the
+# auto-quoting definitions of the new macros (`new.m4'), and the
+# definition of the old macros (`old.m4'). Computing these last two
+# files is easy: it's just a matter of using the right `--trace' option.
+#
+# So the content of `values.in' is:
+#
+# include($autoconf_dir/m4sugar.m4)
+# m4_include(new.m4)
+# m4_include(old.m4)
+# divert(0)dnl
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# We run m4 on it, which yields:
+#
+# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)
+#
+# Transform `@<<@' and `@>>@' into quotes and we get
+#
+# define([OLD([1],[2])],[NEW([1, 2], [3])])
+#
+# This is `values.m4'.
+#
+#
+# # Computing the `dispatcher' section
+# # ..................................
+#
+# The `prologue', and the `disabler' are simple and need no commenting.
+#
+# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple
+# matter of using the right `--trace'.
+#
+# Finally, the input is not exactly the input file, rather it is the
+# input file with the added `changequote'. To this end, we build
+# `quote.sed'.
+#
+#
+# # Putting it all together
+# # .......................
+#
+# We build the file `input.m4' which contains:
+#
+# divert(-1)dnl
+# changequote([, ])
+# include(values.m4)
+# include(dispatch.m4)
+# undefine([dnl])
+# undefine([eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui.
+#
+# Well, there are a few additional technicalities. For instance, we
+# rely on `changequote', `ifelse' and `defn', but we don't want to
+# interpret the changequotes of the user, so we simply use another name:
+# `_au_changequote' etc.
+#
+#
+# # Failure of the fourth approach
+# # ------------------------------
+#
+# This approach is heavily based on traces, but then there is an obvious
+# problem: non expanded code will never be seen/ In particular, the body
+# of a `define' definition is not seen, so on the input
+#
+# define([idem], [OLD(0, [$1])])
+#
+# autoupdate would never see the `OLD', and wouldn't have updated it.
+# Worse yet, if `idem(0)' was used later, then autoupdate sees that
+# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a
+# dispatcher for `OLD'. Since there was no computed value for `OLD(0,
+# [$1])', the dispatcher would have replaced with... nothinhg, leading
+# to
+#
+# define([idem], [])
+#
+# With some more thinking, you see that the two step approach is wrong,
+# the namespace approach was much saner.
+#
+# But you learned a lot, in particular you realized that using traces
+# can make it possible to simulate namespaces!
+#
+#
+#
+# # The fifth implementation: m4 namespaces by files
+# # ================================================
+#
+# The fourth implementation demonstrated something unsurprising: you
+# cannot precompute, i.e., the namespace approach was the right one.
+# Still, we no longer want them, they're too expensive. Let's have a
+# look at the way it worked.
+#
+# When updating
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# you evaluate `input.m4':
+#
+# divert(-1)
+# changequote([, ])
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+# ...
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes
+# and comments:
+#
+# define([m4_disable],
+# [undefine([__file__])
+# ...
+# changecom(#)
+# changequote()])
+#
+# `m4_enable' does the converse: reestablish quotes and comments
+# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and
+# reenable the builtins. This later task requires that you first save
+# the builtins. And BTW, the definition above of `m4_disable' cannot
+# work: you undefined `changequote' before using it! So you need to use
+# your privates copies of the builtins. Let's introduce three files for
+# this:
+#
+# `m4save.m4'
+# moves the m4 builtins into the `_au_' pseudo namespace
+# `unm4.m4'
+# undefines the builtins
+# `m4.m4'
+# restores them
+#
+# So `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+#
+# # Import AU.
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)])
+#
+# define([_au_disable],
+# [# Disable m4sugar.
+# # Disable the m4 builtins.
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Based on what we learned in the fourth implementation we know that we
+# have to enable the quotes *before* any AU macro, and we know we need
+# to build autoquoting versions of the AC macros. But the autoquoting
+# AC definitions must be disabled in the rest of the file, and enabled
+# inside AU macros.
+#
+# Using `autoconf --trace' it is easy to build the files
+#
+# `ac.m4'
+# define the autoquoting AC fake macros
+# `disable.m4'
+# undefine the m4sugar and AC autoquoting macros.
+# `au.m4'
+# definitions of the AU macros (such as `OLD' above).
+#
+# Now, `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+# # Import AU.
+# include([au.m4])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)
+# _au_include(ac.m4)])
+#
+# define([_au_disable],
+# [_au_include([disable.m4])
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# _au_changequote([, ])OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Finally, version V is ready.
+#
+# Well... almost.
+#
+# There is a slight problem that remains: if an AU macro OUTTER includes
+# an AU macro INNER, then _au_enable will be run when entering OUTTER
+# and when entering INNER (not good, but not too bad yet). But when
+# getting out of INNER, _au_disable will disable everything while we
+# were still in OUTTER. Badaboom.
+#
+# Therefore _au_enable and _au_disable have to be written to work by
+# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable
+# popdef's _au_enabled. And of course _au_enable and _au_disable are
+# effective when _au_enabled is *not* defined.
+#
+# Finally, version V' is ready. And there is much rejoicing. (And I
+# have free time again. I think. Yeah, right.)
--- /dev/null
+#! @PERL@ -w
+# autoupdate - modernize an Autoconf file.
+# Copyright 1994, 1999, 2000, 2001 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
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.
+# Rewritten by Akim Demaille <akim@freefriends.org>.
+
+use Getopt::Long;
+use strict;
+
+(my $me = $0) =~ s,.*/,,;
+
+# Lib files.
+my $autoconf_dir = $ENV{"AC_MACRODIR"} || "@datadir@";
+
+my $autoconf = '';
+my $debug = 0;
+my $localdir = '.';
+# m4.
+my $m4 = $ENV{"M4"} || "@M4@";
+my $status = 0;
+# FIXME: Ahem....
+my $tmp = '/tmp/autoupdate.tmp';
+mkdir $tmp, 0700;
+my $verbose = 0;
+my $SIMPLE_BACKUP_SUFFIX = $ENV{'SIMPLE_BACKUP_SUFFIX'} || '~';
+
+
+## ---------- ##
+## Routines. ##
+## ---------- ##
+
+
+# END
+# ---
+# Exit nonzero whenever closing STDOUT fails.
+sub END
+{
+ use POSIX qw (_exit);
+ # This is required if the code might send any output to stdout
+ # E.g., even --version or --help. So it's best to do it unconditionally.
+ close STDOUT
+ or (warn "$me: closing standard output: $!\n"), _exit (1);
+}
+
+
+# print_usage ()
+# --------------
+# Display usage (--help).
+sub print_usage ()
+{
+ print "\
+Usage: $0 [OPTION] ... [TEMPLATE-FILE...]
+
+Update the TEMPLATE-FILE... if given, or \`configure.ac' if present,
+or else \`configure.in', to the syntax of the current version of
+Autoconf. The original files are backed up.
+
+Operation modes:
+ -h, --help print this help, then exit
+ -V, --version print version number, then exit
+ -v, --verbose verbosely report processing
+ -d, --debug don't remove temporary files
+
+Library directories:
+ -A, --autoconf-dir=ACDIR Autoconf's macro files location (rarely needed)
+ -l, --localdir=DIR location of \`aclocal.m4' and \`acconfig.h'
+
+Environment variables:
+ M4 GNU M4 is required.
+ AUTOCONF autoconf.
+
+Report bugs to <bug-autoconf\@gnu.org>.
+";
+ exit 0;
+}
+
+
+# print_version ()
+# ----------------
+# Display version (--version).
+sub print_version
+{
+ print "\
+autoupdate (@PACKAGE_NAME@) @VERSION@
+Written by David J. MacKenzie and Akim Demaille.
+
+Copyright 1994, 1999, 2000, 2001 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.
+";
+ exit 0;
+}
+
+
+# $CONFIGURE_AC
+# &find_configure_ac ()
+# ---------------------
+sub find_configure_ac ()
+{
+ if (-f 'configure.ac')
+ {
+ if (-f 'configure.in')
+ {
+ warn "warning: `configure.ac' and `configure.in' both present.\n";
+ warn "warning: proceeding with `configure.ac'.\n";
+ }
+ return 'configure.ac';
+ }
+ elsif (-f 'configure.in')
+ {
+ return 'configure.in';
+ }
+ return;
+}
+
+
+# parse_args ()
+# -------------
+# Process any command line arguments.
+sub parse_args ()
+{
+ my $srcdir;
+ Getopt::Long::config ("bundling");
+ Getopt::Long::GetOptions ("A|autoconf-dir|m|macrodir=s" => \$autoconf_dir,
+ "h|help" => \&print_usage,
+ "V|version" => \&print_version,
+ "v|verbose" => \$verbose)
+ or exit 1;
+ if (! @ARGV)
+ {
+ my $configure_ac = find_configure_ac;
+ die 'no input file'
+ unless $configure_ac;
+ push @ARGV, $configure_ac;
+ }
+}
+
+
+# find_slaves
+# -----------
+# Find the lib files and autoconf.
+sub find_slaves ()
+{
+ # Some non-GNU m4's don't reject the --help option, so give them /dev/null.
+ die "Autoconf requires GNU m4 1.4 or later\n"
+ if system "$m4 --help </dev/null 2>&1 | fgrep reload-state >/dev/null";
+
+ # autoconf.
+ (my $dir = $0) =~ s,[^/]*$,,;
+
+ # We test "$dir/autoconf" in case we are in the build tree, in which case
+ # the names are not transformed yet.
+ foreach my $file ($ENV{"AUTOCONF"} || '',
+ "$dir/@autoconf-name@",
+ "$dir/autoconf",
+ "@bindir@/@autoconf-name@")
+ {
+ if (-x $file)
+ {
+ $autoconf = $file;
+ last;
+ }
+ }
+}
+
+
+## -------------- ##
+## Main program. ##
+## -------------- ##
+find_slaves;
+parse_args;
+$autoconf .= " -l $localdir";
+$ENV{'autoconf_dir'} = $autoconf_dir;
+
+# m4.txt -- the builtins of m4.
+system ("echo dumpdef | "
+ . "$m4 2>&1 >/dev/null | "
+ . "sed -n 's/:.*//p' "
+ . ">$tmp/m4.txt");
+
+# m4.m4 -- enable the m4 builtins.
+system ("sed 's/^.*\$/_au_define([&], _au_defn([_au_&]))/' $tmp/m4.txt "
+ . ">$tmp/m4.m4");
+
+# unm4.m4 -- disable the m4 builtins.
+system ("sed 's/^.*\$/_au_undefine([&])/' $tmp/m4.txt >$tmp/unm4.m4");
+
+# savem4.m4 -- save the m4 builtins.
+system ("sed 's/^.*\$/define([_au_&], defn([&]))/' $tmp/m4.txt "
+ . ">$tmp/m4save.m4");
+
+# au.txt -- list of all the AU macros.
+system ("$autoconf --trace AU_DEFUN:'\$1' -i /dev/null | "
+ . "sort -u "
+ . ">$tmp/au.txt");
+
+# au-del.sed -- delete the AU macro names.
+system ("sed \"s,^.*\$,/&/d,\" $tmp/au.txt "
+ . " >$tmp/au-del.sed");
+
+# au.m4 -- definitions the AU macros.
+system ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@,
+\@<:\@\$2\@:>\@)' -i /dev/null "
+ . ">$tmp/au.m4");
+
+# quote.sed -- enable the quote `[', `]' right before any AU macro.
+# Unfortunately, I can't see a solution which does not use `\b', which
+# is a GNU extension :(. Am I understanding we should use Perl?
+system ('sed \'s/^.*$/s!\\\\b&\\\\b!_au_changequote([,])\\&!/\'' . " $tmp/au.txt "
+ . ">$tmp/quote.sed");
+
+# ac.txt -- list of all the AC and m4sugar macros prefixed by the name
+# of the file which defines it.
+# Be carefull to remove the AU macros.
+system ("$autoconf --trace define:'\$f:\$1' -i /dev/null | "
+ . "sed -f $tmp/au-del.sed "
+ . ">$tmp/ac.txt");
+
+# ac.m4 -- autoquoting definitions of the AC macros.
+system ('sed -n \'/m4sugar.m4/!s/^[^:]*:\(.*\)$/_au_define([\1], [[$0($@)]])/p\''
+ . " $tmp/ac.txt"
+ . ">$tmp/ac.m4");
+
+# disable.m4 -- undefine the macros of AC and m4sugar.
+system ('sed \'s/^[^:]*:\\(.*\\)$/_au_undefine([\1])/\'' . " $tmp/ac.txt "
+ . ">$tmp/disable.m4");
+
+foreach my $file (@ARGV)
+ {
+ my $filename = $file;
+ # We need an actual file.
+ if ($file eq '-')
+ {
+ $file = "$tmp/stdin";
+ system "cat >$file";
+ }
+ elsif (! -r "$file")
+ {
+ die "$me: $file: No such file or directory";
+ }
+
+ # input.m4 -- m4 program to produce the updated file.
+ # Load the values, the dispatcher, neutralize m4, and the prepared
+ # input file.
+ my $input_m4 = <<EOF;
+ divert(-1) -*- Autoconf -*-
+ changequote([, ])
+
+ # Move all the builtins into the \`_au_' pseudo namespace
+ include([$tmp/m4save.m4])
+
+ # _au_defun(NAME, BODY)
+ # ---------------------
+ # Define NAME to BODY, plus AU activation/deactivation.
+ _au_define([_au_defun],
+ [_au_define([\$1],
+ [_au_enable()dnl
+ \$2[]dnl
+ _au_disable()])])
+
+ # Import the definition of the obsolete macros.
+ _au_include([$tmp/au.m4])
+
+
+ ## ------------------------ ##
+ ## _au_enable/_au_disable. ##
+ ## ------------------------ ##
+
+ # They work by pair: each time an AU macro is activated, it runs
+ # _au_enable, and at its end its runs _au_disable (see _au_defun
+ # above). But since AU macros might use AU macros, which should
+ # enable/disable only for the outter AU macros.
+ #
+ # \`_au_enabled' is used to this end, condionning whether we really
+ # enable/disable.
+
+
+ # __au_enable
+ # -----------
+ # Reenable the builtins, and m4sugar.
+ _au_define([__au_enable],
+ [_au_divert(-1)
+ # Enable special characters.
+ _au_changecom([#])
+
+ # Enable the m4 builtins, m4sugar and the autoquoting AC macros.
+ _au_include([$tmp/m4.m4])
+ _au_include([$autoconf_dir/m4sugar.m4])
+ _au_include([$tmp/ac.m4])
+
+ _au_divert(0)])
+
+ # _au_enable
+ # ----------
+ # Called at the beginning of all the obsolete macros. Reenable the
+ # builtins, and m4sugar if needed.
+ _au_define([_au_enable],
+ [_au_ifdef([_au_enabled],
+ [],
+ [__au_enable()])_au_dnl
+ _au_pushdef([_au_enabled])])
+
+
+ # __au_disable
+ # ------------
+ # Disable the builtins, and m4sugar.
+ _au_define([__au_disable],
+ [_au_divert(-1)
+ # Disable m4sugar, the AC autoquoting macros, and m4.
+ _au_include([$tmp/disable.m4])
+ _au_include([$tmp/unm4.m4])
+
+ # Disable special characters.
+ _au_changequote()
+ _au_changecom()
+
+ _au_divert(0)])
+
+ # _au_disable
+ # -----------
+ # Called at the end of all the obsolete macros. Disable the
+ # builtins, and m4sugar if needed..
+ _au_define([_au_disable],
+ [_au_popdef([_au_enabled])_au_dnl
+ _au_ifdef([_au_enabled],
+ [],
+ [__au_disable()])])
+
+
+ ## ------------------------------- ##
+ ## Disable, and process the file. ##
+ ## ------------------------------- ##
+ _au_disable()_au_dnl
+EOF
+
+ $input_m4 =~ s/^ //mg;
+
+ # prepared input -- input, but reenables the quote before each AU macro.
+ open INPUT_M4, ">$tmp/input.m4";
+ print INPUT_M4 "$input_m4\n";
+ close INPUT_M4;
+ system ("sed -f $tmp/quote.sed $file >>$tmp/input.m4");
+
+ # Now ask m4 to perform the update.
+ print STDERR "$me: running $m4 $tmp/input.m4"
+ if $verbose;
+ system ("$m4 $tmp/input.m4 >$tmp/updated") == 0
+ or die "$me: cannot update \`$filename'";
+
+ if ("$file" eq "$tmp/stdin")
+ {
+ system ("cat $tmp/updated");
+ }
+ elsif (! system ("cmp -s $tmp/updated $file"))
+ {
+ # File didn't change, so don't update its mod time.
+ print STDERR "$me: \`$file' is unchanged\n"
+ }
+ else
+ {
+ # Back up and install the new one.
+ if (system ("mv $file $file${SIMPLE_BACKUP_SUFFIX} && "
+ . "mv $tmp/updated $file") == 0)
+ {
+ print STDERR "$me: \`$file' is updated\n";
+ }
+ else
+ {
+ die "$me: cannot update \`$file'";
+ }
+ }
+ }
+
+exit 0;
+
+
+# ## ---------------------------- ##
+# ## How `autoupdate' functions. ##
+# ## ---------------------------- ##
+#
+# The task of `autoupdate' is not trivial: the biggest difficulty being
+# that you must limit the changes to the parts that really need to be
+# updated. Finding a satisfying implementation proved to be quite hard,
+# as this is the fourth implementation of `autoupdate'.
+#
+# Below, we will use a simple example of obsolete macro:
+#
+# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
+# AC_DEFUN([NEW], [echo "sum($1) = $2"])
+#
+# the input file contains
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Of course the expected output is
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0], [0])
+#
+#
+# # First implementation: sed
+# # =========================
+#
+# The first implementation was only able to change the name of obsolete
+# macros.
+#
+# The file `acoldnames.m4' defined the old names based on the new names.
+# It was simple then to produce a sed script such as:
+#
+# s/OLD/NEW/g
+#
+# Updating merely consisted in running this script on the file to
+# update.
+#
+# This scheme suffers an obvious limitation: that `autoupdate' was
+# unable to cope with new macros that just swap some of its arguments
+# compared to the old macro. Fortunately, that was enough to upgrade
+# from Autoconf 1 to Autoconf 2. (But I have no idea whether the
+# changes in Autoconf 2 were precisely limited by this constraint.)
+#
+#
+# # Second implementation: hooks
+# # ============================
+#
+# The version 2.15 of Autoconf brought a vast number of changes compared
+# to 2.13, so a solution was needed. One could think to extend the
+# `sed' scripts with specialized code for complex macros. But this
+# approach is of course full of flaws:
+#
+# a. the Autoconf maintainers have to write these snippets, which we
+# just don't want to,
+#
+# b. I really don't think you'll ever manage to handle the quoting of
+# m4 from sed.
+#
+# To satisfy a., let's remark that the code which implements the old
+# features in term of the new feature is exactly the code which should
+# replace the old code.
+#
+# To answer point b, as usual in the history of Autoconf, the answer, at
+# least on the paper, is simple: m4 is the best tool to parse m4, so
+# let's use m4.
+#
+# Therefore the specification is:
+#
+# I want to be able to tell Autoconf, well, m4, that the macro I
+# am currently defining is an obsolete macro (so that the user is
+# warned), which code is the code to use when running autoconf,
+# but that the very same code has to be used when running
+# autoupdate. To summarize, the interface I want is
+# `AU_DEFUN(OLD-NAME, NEW-CODE)'.
+#
+#
+# Now for the technical details.
+#
+# When running autoconf, except for the warning, AU_DEFUN is basically
+# AC_DEFUN.
+#
+# When running autoupdate, we want *only* OLD-NAMEs to be expanded.
+# This obviously means that acgeneral.m4 and acspecific.m4 must not be
+# loaded. Nonetheless, because we want to use a rich set of m4
+# features, m4sugar.m4 is needed. Please note that the fact that
+# Autoconf's macros are not loaded is positive on two points:
+#
+# - we do get an updated `configure.ac', not a `configure'!
+#
+# - the old macros are replaced by *calls* to the new-macros, not the
+# body of the new macros, since their body is not defined!!!
+# (Whoa, that's really beautiful!).
+#
+# Additionally we need to disable the quotes when reading the input for
+# two reasons: first because otherwise `m4' will swallow the quotes of
+# other macros:
+#
+# NEW([1, 2], 3)
+# => NEW(1, 2, 3)
+#
+# and second, because we want to update the macro calls which are
+# quoted, i.e., we want
+#
+# FOO([OLD(1, 2)])
+# => FOO([NEW([1, 2], [3])])
+#
+# If we don't disable the quotes, only the macros called at the top
+# level would be updated.
+#
+# So, let's disable the quotes.
+#
+# Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
+# Well, in this case, when running in autoupdate code, each macro first
+# reestablishes the quotes, expands itself, and disables the quotes.
+#
+# Thinking a bit more, you realize that in fact, people may use `define'
+# `ifelse' etc. in their files, and you certainly don't want to process
+# them. Another example is `dnl': you don't want to remove the
+# comments. You then realize you don't want exactly to import m4sugar:
+# you want to specify when it is enabled (macros active), and disabled.
+# m4sugar provides m4_disable/m4_enable to this end.
+#
+# You're getting close to it. Now remains one task: how to handle
+# twofold definitions?
+#
+# Remember that the same AU_DEFUN must be understood in two different
+# ways, the AC way, and the AU way.
+#
+# One first solution is to check whether acgeneral.m4 was loaded. But
+# that's definitely not cute. Another is simply to install `hooks',
+# that is to say, to keep in some place m4 knows, late `define' to be
+# triggered *only* in AU mode.
+#
+# You first think to design AU_DEFUN like this:
+#
+# 1. AC_DEFUN(OLD-NAME,
+# [Warn the user OLD-NAME is obsolete.
+# NEW-CODE])
+#
+# 2. Store for late AU binding([define(OLD_NAME,
+# [Reestablish the quotes.
+# NEW-CODE
+# Disable the quotes.])])
+#
+# but this will not work: NEW-CODE has probably $1, $2 etc. and these
+# guys will be replaced with the argument of `Store for late AU binding'
+# when you call it.
+#
+# I don't think there is a means to avoid this using this technology
+# (remember that $1 etc. are *always* expanded in m4). You may also try
+# to replace them with $[1] to preserve them for a later evaluation, but
+# if `Store for late AU binding' is properly written, it will remain
+# quoted till the end...
+#
+# You have to change technology. Since the problem is that `$1'
+# etc. should be `consumed' right away, one solution is to define now a
+# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
+# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By
+# the way, the same method was used in autoheader.
+#
+#
+# # Third implementation: m4 namespaces by m4sugar
+# # ==============================================
+#
+# Actually, this implementation was just a clean up of the previous
+# implementation: instead of defining hooks by hand, m4sugar was equipped
+# with `namespaces'. What are they?
+#
+# Sometimes we want to disable some *set* of macros, and restore them
+# later. We provide support for this via namespaces.
+#
+# There are basically three characters playing this scene: defining a
+# macro in a namespace, disabling a namespace, and restoring a namespace
+# (i.e., all the definitions it holds).
+#
+# Technically, to define a MACRO in NAMESPACE means to define the macro
+# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append
+# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
+# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
+# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of
+# NAMESPACE and to unbind them at will.
+#
+# Of course this implementation is really inefficient: m4 has to grow
+# strings which can become quickly huge, which slows it significantly.
+#
+# In particular one should avoid as much as possible to use `define' for
+# temporaries. Now that `define' as quite a complex meaning, it is an
+# expensive operations that should be limited to macros. Use
+# `m4_define' for temporaries.
+#
+# Private copies of the macros we used in entering / exiting the m4sugar
+# namespace. It is much more convenient than fighting with the renamed
+# version of define etc.
+#
+#
+#
+# Those two implementations suffered from serious problems:
+#
+# - namespaces were really expensive, and incurred a major performance
+# loss on `autoconf' itself, not only `autoupdate'. One solution
+# would have been the limit the use of namespaces to `autoupdate', but
+# that's again some complications on m4sugar, which really doesn't need
+# this. So we wanted to get rid of the namespaces.
+#
+# - since the quotes were disabled, autoupdate was sometimes making
+# wrong guesses, for instance on:
+#
+# foo([1, 2])
+#
+# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat
+# fragile, is to reestablish the quotes right before all the obsolete
+# macros, i.e., to use sed so that the previous text becomes
+#
+# changequote([, ])foo([1, 2])
+#
+# To this end, one wants to trace the definition of obsolete macros.
+#
+# It was there that the limitations of the namespace approach became
+# painful: because it was a complex machinery playing a lot with the
+# builtins of m4 (hence, quite fragile), tracing was almost impossible.
+#
+#
+# So this approach was dropped.
+#
+#
+# # The fourth implementation: two steps
+# # ====================================
+#
+# If you drop the uses of namespaces, you no longer can compute the
+# updated value, and replace the old call with it simultaneously.
+#
+# Obviously you will use m4 to compute the updated values, but you may
+# use some other tool to achieve the replacement. Personally, I trust
+# nobody but m4 to parse m4, so below, m4 will perform the two tasks.
+#
+# How can m4 be used to replace *some* macros calls with newer values.
+# Well, that's dead simple: m4 should learn the definitions of obsolete
+# macros, forget its builtins, disable the quotes, and then run on the
+# input file, which amounts to doing this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# which will result in
+#
+# dnl The Unbelievable Truth
+# NEW(1, 2, m4_eval(1 + 2))
+# NEW([0, 0],
+# 0)
+#
+# Grpmh. Two problems. A minor problem: it would have been much better
+# to have the `m4_eval' computed, and a major problem: you lost the
+# quotation in the result.
+#
+# Let's address the big problem first. One solution is to define any
+# modern macro to rewrite its calls with the proper quotation, thanks to
+# `$@'. Again, tracing the `define's makes it possible to know which
+# are these macros, so you input is:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# define([NEW], [[NEW($@)]changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# changequote([, ])NEW([0, 0],
+# 0)
+#
+# which results in
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2],[m4_eval(1 + 2)])
+# NEW([0, 0],[0])
+#
+# Our problem is solved, i.e., the first call to `NEW' is properly
+# quoted, but introduced another problem: we changed the layout of the
+# second calls, which can be a drama in the case of huge macro calls
+# (think of `AC_TRY_RUN' for instance). This example didn't show it,
+# but we also introduced parens to macros which did not have some:
+#
+# AC_INIT
+# => AC_INIT()
+#
+# No big deal for the semantics (unless the macro depends upon $#, which
+# is bad), but the users would not be happy.
+#
+# Additionally, we introduced quotes that we not there before, which is
+# OK in most cases, but could change the semantics of the file.
+#
+# Cruel dilemma: we do want the auto-quoting definition of `NEW' when
+# evaluating `OLD', but we don't when we evaluate the second `NEW'.
+# Back to namespaces?
+#
+# No.
+#
+#
+# # Second step: replacement
+# # ------------------------
+#
+# No, as announced above, we will work in two steps: in a first step we
+# compute the updated values, and in a second step we replace them. Our
+# goal is something like this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([1, 2], [3])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., the new value of `OLD' is precomputed using the auto-quoting
+# definition of `NEW' and the m4 builtins. We'll see how afterwards,
+# let's finish with the replacement.
+#
+# Of course the solution above is wrong: if there were other calls to
+# `OLD' with different values, we would smash them to the same value.
+# But it is quite easy to generalize the scheme above:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# define([OLD], [defn([OLD($@)])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., for each call to obsolete macros, we build an array `call =>
+# value', and use a macro to dispatch these values. This results in:
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0],
+# 0)
+#
+# In French, we say `Youpi !', which you might roughly translate as
+# `yipeee!'.
+#
+#
+# # First step: computation
+# # -----------------------
+#
+# Let's study the anatomy of the file, and name its sections:
+#
+# prologue
+# divert(-1)dnl
+# changequote([, ])
+# values
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# dispatcher
+# define([OLD], [defn([OLD($@)])changequote()])
+# disabler
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# input
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+#
+# # Computing the `values' section
+# # ..............................
+#
+# First we need to get the list of all the AU macro uses. To this end,
+# first get the list of all the AU macros names by tracing `AU_DEFUN' in
+# the initialization of autoconf. This list is computed in the file
+# `au.txt' below.
+#
+# Then use this list to trace all the AU macro uses in the input. The
+# goal is obtain in the case of our example:
+#
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# This is the file `values.in' below.
+#
+# We want to evaluate this with only the builtins (in fact m4sugar), the
+# auto-quoting definitions of the new macros (`new.m4'), and the
+# definition of the old macros (`old.m4'). Computing these last two
+# files is easy: it's just a matter of using the right `--trace' option.
+#
+# So the content of `values.in' is:
+#
+# include($autoconf_dir/m4sugar.m4)
+# m4_include(new.m4)
+# m4_include(old.m4)
+# divert(0)dnl
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# We run m4 on it, which yields:
+#
+# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)
+#
+# Transform `@<<@' and `@>>@' into quotes and we get
+#
+# define([OLD([1],[2])],[NEW([1, 2], [3])])
+#
+# This is `values.m4'.
+#
+#
+# # Computing the `dispatcher' section
+# # ..................................
+#
+# The `prologue', and the `disabler' are simple and need no commenting.
+#
+# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple
+# matter of using the right `--trace'.
+#
+# Finally, the input is not exactly the input file, rather it is the
+# input file with the added `changequote'. To this end, we build
+# `quote.sed'.
+#
+#
+# # Putting it all together
+# # .......................
+#
+# We build the file `input.m4' which contains:
+#
+# divert(-1)dnl
+# changequote([, ])
+# include(values.m4)
+# include(dispatch.m4)
+# undefine([dnl])
+# undefine([eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui.
+#
+# Well, there are a few additional technicalities. For instance, we
+# rely on `changequote', `ifelse' and `defn', but we don't want to
+# interpret the changequotes of the user, so we simply use another name:
+# `_au_changequote' etc.
+#
+#
+# # Failure of the fourth approach
+# # ------------------------------
+#
+# This approach is heavily based on traces, but then there is an obvious
+# problem: non expanded code will never be seen/ In particular, the body
+# of a `define' definition is not seen, so on the input
+#
+# define([idem], [OLD(0, [$1])])
+#
+# autoupdate would never see the `OLD', and wouldn't have updated it.
+# Worse yet, if `idem(0)' was used later, then autoupdate sees that
+# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a
+# dispatcher for `OLD'. Since there was no computed value for `OLD(0,
+# [$1])', the dispatcher would have replaced with... nothinhg, leading
+# to
+#
+# define([idem], [])
+#
+# With some more thinking, you see that the two step approach is wrong,
+# the namespace approach was much saner.
+#
+# But you learned a lot, in particular you realized that using traces
+# can make it possible to simulate namespaces!
+#
+#
+#
+# # The fifth implementation: m4 namespaces by files
+# # ================================================
+#
+# The fourth implementation demonstrated something unsurprising: you
+# cannot precompute, i.e., the namespace approach was the right one.
+# Still, we no longer want them, they're too expensive. Let's have a
+# look at the way it worked.
+#
+# When updating
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# you evaluate `input.m4':
+#
+# divert(-1)
+# changequote([, ])
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+# ...
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes
+# and comments:
+#
+# define([m4_disable],
+# [undefine([__file__])
+# ...
+# changecom(#)
+# changequote()])
+#
+# `m4_enable' does the converse: reestablish quotes and comments
+# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and
+# reenable the builtins. This later task requires that you first save
+# the builtins. And BTW, the definition above of `m4_disable' cannot
+# work: you undefined `changequote' before using it! So you need to use
+# your privates copies of the builtins. Let's introduce three files for
+# this:
+#
+# `m4save.m4'
+# moves the m4 builtins into the `_au_' pseudo namespace
+# `unm4.m4'
+# undefines the builtins
+# `m4.m4'
+# restores them
+#
+# So `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+#
+# # Import AU.
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)])
+#
+# define([_au_disable],
+# [# Disable m4sugar.
+# # Disable the m4 builtins.
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Based on what we learned in the fourth implementation we know that we
+# have to enable the quotes *before* any AU macro, and we know we need
+# to build autoquoting versions of the AC macros. But the autoquoting
+# AC definitions must be disabled in the rest of the file, and enabled
+# inside AU macros.
+#
+# Using `autoconf --trace' it is easy to build the files
+#
+# `ac.m4'
+# define the autoquoting AC fake macros
+# `disable.m4'
+# undefine the m4sugar and AC autoquoting macros.
+# `au.m4'
+# definitions of the AU macros (such as `OLD' above).
+#
+# Now, `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+# # Import AU.
+# include([au.m4])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)
+# _au_include(ac.m4)])
+#
+# define([_au_disable],
+# [_au_include([disable.m4])
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# _au_changequote([, ])OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Finally, version V is ready.
+#
+# Well... almost.
+#
+# There is a slight problem that remains: if an AU macro OUTTER includes
+# an AU macro INNER, then _au_enable will be run when entering OUTTER
+# and when entering INNER (not good, but not too bad yet). But when
+# getting out of INNER, _au_disable will disable everything while we
+# were still in OUTTER. Badaboom.
+#
+# Therefore _au_enable and _au_disable have to be written to work by
+# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable
+# popdef's _au_enabled. And of course _au_enable and _au_disable are
+# effective when _au_enabled is *not* defined.
+#
+# Finally, version V' is ready. And there is much rejoicing. (And I
+# have free time again. I think. Yeah, right.)
--- /dev/null
+#! @PERL@ -w
+# autoupdate - modernize an Autoconf file.
+# Copyright 1994, 1999, 2000, 2001 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
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.
+# Rewritten by Akim Demaille <akim@freefriends.org>.
+
+use Getopt::Long;
+use strict;
+
+(my $me = $0) =~ s,.*/,,;
+
+# Lib files.
+my $autoconf_dir = $ENV{"AC_MACRODIR"} || "@datadir@";
+
+my $autoconf = '';
+my $debug = 0;
+my $localdir = '.';
+# m4.
+my $m4 = $ENV{"M4"} || "@M4@";
+my $status = 0;
+# FIXME: Ahem....
+my $tmp = '/tmp/autoupdate.tmp';
+mkdir $tmp, 0700;
+my $verbose = 0;
+my $SIMPLE_BACKUP_SUFFIX = $ENV{'SIMPLE_BACKUP_SUFFIX'} || '~';
+
+
+## ---------- ##
+## Routines. ##
+## ---------- ##
+
+
+# END
+# ---
+# Exit nonzero whenever closing STDOUT fails.
+sub END
+{
+ use POSIX qw (_exit);
+ # This is required if the code might send any output to stdout
+ # E.g., even --version or --help. So it's best to do it unconditionally.
+ close STDOUT
+ or (warn "$me: closing standard output: $!\n"), _exit (1);
+}
+
+
+# print_usage ()
+# --------------
+# Display usage (--help).
+sub print_usage ()
+{
+ print "\
+Usage: $0 [OPTION] ... [TEMPLATE-FILE...]
+
+Update the TEMPLATE-FILE... if given, or \`configure.ac' if present,
+or else \`configure.in', to the syntax of the current version of
+Autoconf. The original files are backed up.
+
+Operation modes:
+ -h, --help print this help, then exit
+ -V, --version print version number, then exit
+ -v, --verbose verbosely report processing
+ -d, --debug don't remove temporary files
+
+Library directories:
+ -A, --autoconf-dir=ACDIR Autoconf's macro files location (rarely needed)
+ -l, --localdir=DIR location of \`aclocal.m4' and \`acconfig.h'
+
+Environment variables:
+ M4 GNU M4 is required.
+ AUTOCONF autoconf.
+
+Report bugs to <bug-autoconf\@gnu.org>.
+";
+ exit 0;
+}
+
+
+# print_version ()
+# ----------------
+# Display version (--version).
+sub print_version
+{
+ print "\
+autoupdate (@PACKAGE_NAME@) @VERSION@
+Written by David J. MacKenzie and Akim Demaille.
+
+Copyright 1994, 1999, 2000, 2001 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.
+";
+ exit 0;
+}
+
+
+# $CONFIGURE_AC
+# &find_configure_ac ()
+# ---------------------
+sub find_configure_ac ()
+{
+ if (-f 'configure.ac')
+ {
+ if (-f 'configure.in')
+ {
+ warn "warning: `configure.ac' and `configure.in' both present.\n";
+ warn "warning: proceeding with `configure.ac'.\n";
+ }
+ return 'configure.ac';
+ }
+ elsif (-f 'configure.in')
+ {
+ return 'configure.in';
+ }
+ return;
+}
+
+
+# parse_args ()
+# -------------
+# Process any command line arguments.
+sub parse_args ()
+{
+ my $srcdir;
+ Getopt::Long::config ("bundling");
+ Getopt::Long::GetOptions ("A|autoconf-dir|m|macrodir=s" => \$autoconf_dir,
+ "h|help" => \&print_usage,
+ "V|version" => \&print_version,
+ "v|verbose" => \$verbose)
+ or exit 1;
+ if (! @ARGV)
+ {
+ my $configure_ac = find_configure_ac;
+ die 'no input file'
+ unless $configure_ac;
+ push @ARGV, $configure_ac;
+ }
+}
+
+
+# find_slaves
+# -----------
+# Find the lib files and autoconf.
+sub find_slaves ()
+{
+ # Some non-GNU m4's don't reject the --help option, so give them /dev/null.
+ die "Autoconf requires GNU m4 1.4 or later\n"
+ if system "$m4 --help </dev/null 2>&1 | fgrep reload-state >/dev/null";
+
+ # autoconf.
+ (my $dir = $0) =~ s,[^/]*$,,;
+
+ # We test "$dir/autoconf" in case we are in the build tree, in which case
+ # the names are not transformed yet.
+ foreach my $file ($ENV{"AUTOCONF"} || '',
+ "$dir/@autoconf-name@",
+ "$dir/autoconf",
+ "@bindir@/@autoconf-name@")
+ {
+ if (-x $file)
+ {
+ $autoconf = $file;
+ last;
+ }
+ }
+}
+
+
+## -------------- ##
+## Main program. ##
+## -------------- ##
+find_slaves;
+parse_args;
+$autoconf .= " -l $localdir";
+$ENV{'autoconf_dir'} = $autoconf_dir;
+
+# m4.txt -- the builtins of m4.
+system ("echo dumpdef | "
+ . "$m4 2>&1 >/dev/null | "
+ . "sed -n 's/:.*//p' "
+ . ">$tmp/m4.txt");
+
+# m4.m4 -- enable the m4 builtins.
+system ("sed 's/^.*\$/_au_define([&], _au_defn([_au_&]))/' $tmp/m4.txt "
+ . ">$tmp/m4.m4");
+
+# unm4.m4 -- disable the m4 builtins.
+system ("sed 's/^.*\$/_au_undefine([&])/' $tmp/m4.txt >$tmp/unm4.m4");
+
+# savem4.m4 -- save the m4 builtins.
+system ("sed 's/^.*\$/define([_au_&], defn([&]))/' $tmp/m4.txt "
+ . ">$tmp/m4save.m4");
+
+# au.txt -- list of all the AU macros.
+system ("$autoconf --trace AU_DEFUN:'\$1' -i /dev/null | "
+ . "sort -u "
+ . ">$tmp/au.txt");
+
+# au-del.sed -- delete the AU macro names.
+system ("sed \"s,^.*\$,/&/d,\" $tmp/au.txt "
+ . " >$tmp/au-del.sed");
+
+# au.m4 -- definitions the AU macros.
+system ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@,
+\@<:\@\$2\@:>\@)' -i /dev/null "
+ . ">$tmp/au.m4");
+
+# quote.sed -- enable the quote `[', `]' right before any AU macro.
+# Unfortunately, I can't see a solution which does not use `\b', which
+# is a GNU extension :(. Am I understanding we should use Perl?
+system ('sed \'s/^.*$/s!\\\\b&\\\\b!_au_changequote([,])\\&!/\'' . " $tmp/au.txt "
+ . ">$tmp/quote.sed");
+
+# ac.txt -- list of all the AC and m4sugar macros prefixed by the name
+# of the file which defines it.
+# Be carefull to remove the AU macros.
+system ("$autoconf --trace define:'\$f:\$1' -i /dev/null | "
+ . "sed -f $tmp/au-del.sed "
+ . ">$tmp/ac.txt");
+
+# ac.m4 -- autoquoting definitions of the AC macros.
+system ('sed -n \'/m4sugar.m4/!s/^[^:]*:\(.*\)$/_au_define([\1], [[$0($@)]])/p\''
+ . " $tmp/ac.txt"
+ . ">$tmp/ac.m4");
+
+# disable.m4 -- undefine the macros of AC and m4sugar.
+system ('sed \'s/^[^:]*:\\(.*\\)$/_au_undefine([\1])/\'' . " $tmp/ac.txt "
+ . ">$tmp/disable.m4");
+
+foreach my $file (@ARGV)
+ {
+ my $filename = $file;
+ # We need an actual file.
+ if ($file eq '-')
+ {
+ $file = "$tmp/stdin";
+ system "cat >$file";
+ }
+ elsif (! -r "$file")
+ {
+ die "$me: $file: No such file or directory";
+ }
+
+ # input.m4 -- m4 program to produce the updated file.
+ # Load the values, the dispatcher, neutralize m4, and the prepared
+ # input file.
+ my $input_m4 = <<EOF;
+ divert(-1) -*- Autoconf -*-
+ changequote([, ])
+
+ # Move all the builtins into the \`_au_' pseudo namespace
+ include([$tmp/m4save.m4])
+
+ # _au_defun(NAME, BODY)
+ # ---------------------
+ # Define NAME to BODY, plus AU activation/deactivation.
+ _au_define([_au_defun],
+ [_au_define([\$1],
+ [_au_enable()dnl
+ \$2[]dnl
+ _au_disable()])])
+
+ # Import the definition of the obsolete macros.
+ _au_include([$tmp/au.m4])
+
+
+ ## ------------------------ ##
+ ## _au_enable/_au_disable. ##
+ ## ------------------------ ##
+
+ # They work by pair: each time an AU macro is activated, it runs
+ # _au_enable, and at its end its runs _au_disable (see _au_defun
+ # above). But since AU macros might use AU macros, which should
+ # enable/disable only for the outter AU macros.
+ #
+ # \`_au_enabled' is used to this end, condionning whether we really
+ # enable/disable.
+
+
+ # __au_enable
+ # -----------
+ # Reenable the builtins, and m4sugar.
+ _au_define([__au_enable],
+ [_au_divert(-1)
+ # Enable special characters.
+ _au_changecom([#])
+
+ # Enable the m4 builtins, m4sugar and the autoquoting AC macros.
+ _au_include([$tmp/m4.m4])
+ _au_include([$autoconf_dir/m4sugar.m4])
+ _au_include([$tmp/ac.m4])
+
+ _au_divert(0)])
+
+ # _au_enable
+ # ----------
+ # Called at the beginning of all the obsolete macros. Reenable the
+ # builtins, and m4sugar if needed.
+ _au_define([_au_enable],
+ [_au_ifdef([_au_enabled],
+ [],
+ [__au_enable()])_au_dnl
+ _au_pushdef([_au_enabled])])
+
+
+ # __au_disable
+ # ------------
+ # Disable the builtins, and m4sugar.
+ _au_define([__au_disable],
+ [_au_divert(-1)
+ # Disable m4sugar, the AC autoquoting macros, and m4.
+ _au_include([$tmp/disable.m4])
+ _au_include([$tmp/unm4.m4])
+
+ # Disable special characters.
+ _au_changequote()
+ _au_changecom()
+
+ _au_divert(0)])
+
+ # _au_disable
+ # -----------
+ # Called at the end of all the obsolete macros. Disable the
+ # builtins, and m4sugar if needed..
+ _au_define([_au_disable],
+ [_au_popdef([_au_enabled])_au_dnl
+ _au_ifdef([_au_enabled],
+ [],
+ [__au_disable()])])
+
+
+ ## ------------------------------- ##
+ ## Disable, and process the file. ##
+ ## ------------------------------- ##
+ _au_disable()_au_dnl
+EOF
+
+ $input_m4 =~ s/^ //mg;
+
+ # prepared input -- input, but reenables the quote before each AU macro.
+ open INPUT_M4, ">$tmp/input.m4";
+ print INPUT_M4 "$input_m4\n";
+ close INPUT_M4;
+ system ("sed -f $tmp/quote.sed $file >>$tmp/input.m4");
+
+ # Now ask m4 to perform the update.
+ print STDERR "$me: running $m4 $tmp/input.m4"
+ if $verbose;
+ system ("$m4 $tmp/input.m4 >$tmp/updated") == 0
+ or die "$me: cannot update \`$filename'";
+
+ if ("$file" eq "$tmp/stdin")
+ {
+ system ("cat $tmp/updated");
+ }
+ elsif (! system ("cmp -s $tmp/updated $file"))
+ {
+ # File didn't change, so don't update its mod time.
+ print STDERR "$me: \`$file' is unchanged\n"
+ }
+ else
+ {
+ # Back up and install the new one.
+ if (system ("mv $file $file${SIMPLE_BACKUP_SUFFIX} && "
+ . "mv $tmp/updated $file") == 0)
+ {
+ print STDERR "$me: \`$file' is updated\n";
+ }
+ else
+ {
+ die "$me: cannot update \`$file'";
+ }
+ }
+ }
+
+exit 0;
+
+
+# ## ---------------------------- ##
+# ## How `autoupdate' functions. ##
+# ## ---------------------------- ##
+#
+# The task of `autoupdate' is not trivial: the biggest difficulty being
+# that you must limit the changes to the parts that really need to be
+# updated. Finding a satisfying implementation proved to be quite hard,
+# as this is the fourth implementation of `autoupdate'.
+#
+# Below, we will use a simple example of obsolete macro:
+#
+# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
+# AC_DEFUN([NEW], [echo "sum($1) = $2"])
+#
+# the input file contains
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Of course the expected output is
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0], [0])
+#
+#
+# # First implementation: sed
+# # =========================
+#
+# The first implementation was only able to change the name of obsolete
+# macros.
+#
+# The file `acoldnames.m4' defined the old names based on the new names.
+# It was simple then to produce a sed script such as:
+#
+# s/OLD/NEW/g
+#
+# Updating merely consisted in running this script on the file to
+# update.
+#
+# This scheme suffers an obvious limitation: that `autoupdate' was
+# unable to cope with new macros that just swap some of its arguments
+# compared to the old macro. Fortunately, that was enough to upgrade
+# from Autoconf 1 to Autoconf 2. (But I have no idea whether the
+# changes in Autoconf 2 were precisely limited by this constraint.)
+#
+#
+# # Second implementation: hooks
+# # ============================
+#
+# The version 2.15 of Autoconf brought a vast number of changes compared
+# to 2.13, so a solution was needed. One could think to extend the
+# `sed' scripts with specialized code for complex macros. But this
+# approach is of course full of flaws:
+#
+# a. the Autoconf maintainers have to write these snippets, which we
+# just don't want to,
+#
+# b. I really don't think you'll ever manage to handle the quoting of
+# m4 from sed.
+#
+# To satisfy a., let's remark that the code which implements the old
+# features in term of the new feature is exactly the code which should
+# replace the old code.
+#
+# To answer point b, as usual in the history of Autoconf, the answer, at
+# least on the paper, is simple: m4 is the best tool to parse m4, so
+# let's use m4.
+#
+# Therefore the specification is:
+#
+# I want to be able to tell Autoconf, well, m4, that the macro I
+# am currently defining is an obsolete macro (so that the user is
+# warned), which code is the code to use when running autoconf,
+# but that the very same code has to be used when running
+# autoupdate. To summarize, the interface I want is
+# `AU_DEFUN(OLD-NAME, NEW-CODE)'.
+#
+#
+# Now for the technical details.
+#
+# When running autoconf, except for the warning, AU_DEFUN is basically
+# AC_DEFUN.
+#
+# When running autoupdate, we want *only* OLD-NAMEs to be expanded.
+# This obviously means that acgeneral.m4 and acspecific.m4 must not be
+# loaded. Nonetheless, because we want to use a rich set of m4
+# features, m4sugar.m4 is needed. Please note that the fact that
+# Autoconf's macros are not loaded is positive on two points:
+#
+# - we do get an updated `configure.ac', not a `configure'!
+#
+# - the old macros are replaced by *calls* to the new-macros, not the
+# body of the new macros, since their body is not defined!!!
+# (Whoa, that's really beautiful!).
+#
+# Additionally we need to disable the quotes when reading the input for
+# two reasons: first because otherwise `m4' will swallow the quotes of
+# other macros:
+#
+# NEW([1, 2], 3)
+# => NEW(1, 2, 3)
+#
+# and second, because we want to update the macro calls which are
+# quoted, i.e., we want
+#
+# FOO([OLD(1, 2)])
+# => FOO([NEW([1, 2], [3])])
+#
+# If we don't disable the quotes, only the macros called at the top
+# level would be updated.
+#
+# So, let's disable the quotes.
+#
+# Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
+# Well, in this case, when running in autoupdate code, each macro first
+# reestablishes the quotes, expands itself, and disables the quotes.
+#
+# Thinking a bit more, you realize that in fact, people may use `define'
+# `ifelse' etc. in their files, and you certainly don't want to process
+# them. Another example is `dnl': you don't want to remove the
+# comments. You then realize you don't want exactly to import m4sugar:
+# you want to specify when it is enabled (macros active), and disabled.
+# m4sugar provides m4_disable/m4_enable to this end.
+#
+# You're getting close to it. Now remains one task: how to handle
+# twofold definitions?
+#
+# Remember that the same AU_DEFUN must be understood in two different
+# ways, the AC way, and the AU way.
+#
+# One first solution is to check whether acgeneral.m4 was loaded. But
+# that's definitely not cute. Another is simply to install `hooks',
+# that is to say, to keep in some place m4 knows, late `define' to be
+# triggered *only* in AU mode.
+#
+# You first think to design AU_DEFUN like this:
+#
+# 1. AC_DEFUN(OLD-NAME,
+# [Warn the user OLD-NAME is obsolete.
+# NEW-CODE])
+#
+# 2. Store for late AU binding([define(OLD_NAME,
+# [Reestablish the quotes.
+# NEW-CODE
+# Disable the quotes.])])
+#
+# but this will not work: NEW-CODE has probably $1, $2 etc. and these
+# guys will be replaced with the argument of `Store for late AU binding'
+# when you call it.
+#
+# I don't think there is a means to avoid this using this technology
+# (remember that $1 etc. are *always* expanded in m4). You may also try
+# to replace them with $[1] to preserve them for a later evaluation, but
+# if `Store for late AU binding' is properly written, it will remain
+# quoted till the end...
+#
+# You have to change technology. Since the problem is that `$1'
+# etc. should be `consumed' right away, one solution is to define now a
+# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
+# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By
+# the way, the same method was used in autoheader.
+#
+#
+# # Third implementation: m4 namespaces by m4sugar
+# # ==============================================
+#
+# Actually, this implementation was just a clean up of the previous
+# implementation: instead of defining hooks by hand, m4sugar was equipped
+# with `namespaces'. What are they?
+#
+# Sometimes we want to disable some *set* of macros, and restore them
+# later. We provide support for this via namespaces.
+#
+# There are basically three characters playing this scene: defining a
+# macro in a namespace, disabling a namespace, and restoring a namespace
+# (i.e., all the definitions it holds).
+#
+# Technically, to define a MACRO in NAMESPACE means to define the macro
+# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append
+# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
+# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
+# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of
+# NAMESPACE and to unbind them at will.
+#
+# Of course this implementation is really inefficient: m4 has to grow
+# strings which can become quickly huge, which slows it significantly.
+#
+# In particular one should avoid as much as possible to use `define' for
+# temporaries. Now that `define' as quite a complex meaning, it is an
+# expensive operations that should be limited to macros. Use
+# `m4_define' for temporaries.
+#
+# Private copies of the macros we used in entering / exiting the m4sugar
+# namespace. It is much more convenient than fighting with the renamed
+# version of define etc.
+#
+#
+#
+# Those two implementations suffered from serious problems:
+#
+# - namespaces were really expensive, and incurred a major performance
+# loss on `autoconf' itself, not only `autoupdate'. One solution
+# would have been the limit the use of namespaces to `autoupdate', but
+# that's again some complications on m4sugar, which really doesn't need
+# this. So we wanted to get rid of the namespaces.
+#
+# - since the quotes were disabled, autoupdate was sometimes making
+# wrong guesses, for instance on:
+#
+# foo([1, 2])
+#
+# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat
+# fragile, is to reestablish the quotes right before all the obsolete
+# macros, i.e., to use sed so that the previous text becomes
+#
+# changequote([, ])foo([1, 2])
+#
+# To this end, one wants to trace the definition of obsolete macros.
+#
+# It was there that the limitations of the namespace approach became
+# painful: because it was a complex machinery playing a lot with the
+# builtins of m4 (hence, quite fragile), tracing was almost impossible.
+#
+#
+# So this approach was dropped.
+#
+#
+# # The fourth implementation: two steps
+# # ====================================
+#
+# If you drop the uses of namespaces, you no longer can compute the
+# updated value, and replace the old call with it simultaneously.
+#
+# Obviously you will use m4 to compute the updated values, but you may
+# use some other tool to achieve the replacement. Personally, I trust
+# nobody but m4 to parse m4, so below, m4 will perform the two tasks.
+#
+# How can m4 be used to replace *some* macros calls with newer values.
+# Well, that's dead simple: m4 should learn the definitions of obsolete
+# macros, forget its builtins, disable the quotes, and then run on the
+# input file, which amounts to doing this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# which will result in
+#
+# dnl The Unbelievable Truth
+# NEW(1, 2, m4_eval(1 + 2))
+# NEW([0, 0],
+# 0)
+#
+# Grpmh. Two problems. A minor problem: it would have been much better
+# to have the `m4_eval' computed, and a major problem: you lost the
+# quotation in the result.
+#
+# Let's address the big problem first. One solution is to define any
+# modern macro to rewrite its calls with the proper quotation, thanks to
+# `$@'. Again, tracing the `define's makes it possible to know which
+# are these macros, so you input is:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
+# define([NEW], [[NEW($@)]changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# changequote([, ])NEW([0, 0],
+# 0)
+#
+# which results in
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2],[m4_eval(1 + 2)])
+# NEW([0, 0],[0])
+#
+# Our problem is solved, i.e., the first call to `NEW' is properly
+# quoted, but introduced another problem: we changed the layout of the
+# second calls, which can be a drama in the case of huge macro calls
+# (think of `AC_TRY_RUN' for instance). This example didn't show it,
+# but we also introduced parens to macros which did not have some:
+#
+# AC_INIT
+# => AC_INIT()
+#
+# No big deal for the semantics (unless the macro depends upon $#, which
+# is bad), but the users would not be happy.
+#
+# Additionally, we introduced quotes that we not there before, which is
+# OK in most cases, but could change the semantics of the file.
+#
+# Cruel dilemma: we do want the auto-quoting definition of `NEW' when
+# evaluating `OLD', but we don't when we evaluate the second `NEW'.
+# Back to namespaces?
+#
+# No.
+#
+#
+# # Second step: replacement
+# # ------------------------
+#
+# No, as announced above, we will work in two steps: in a first step we
+# compute the updated values, and in a second step we replace them. Our
+# goal is something like this:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD], [NEW([1, 2], [3])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., the new value of `OLD' is precomputed using the auto-quoting
+# definition of `NEW' and the m4 builtins. We'll see how afterwards,
+# let's finish with the replacement.
+#
+# Of course the solution above is wrong: if there were other calls to
+# `OLD' with different values, we would smash them to the same value.
+# But it is quite easy to generalize the scheme above:
+#
+# divert(-1)dnl
+# changequote([, ])
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# define([OLD], [defn([OLD($@)])changequote()])
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# i.e., for each call to obsolete macros, we build an array `call =>
+# value', and use a macro to dispatch these values. This results in:
+#
+# dnl The Unbelievable Truth
+# NEW([1, 2], [3])
+# NEW([0, 0],
+# 0)
+#
+# In French, we say `Youpi !', which you might roughly translate as
+# `yipeee!'.
+#
+#
+# # First step: computation
+# # -----------------------
+#
+# Let's study the anatomy of the file, and name its sections:
+#
+# prologue
+# divert(-1)dnl
+# changequote([, ])
+# values
+# define([OLD([1],[2])], [NEW([1, 2], [3])])
+# dispatcher
+# define([OLD], [defn([OLD($@)])changequote()])
+# disabler
+# undefine([dnl])
+# undefine([m4_eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# input
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+#
+# # Computing the `values' section
+# # ..............................
+#
+# First we need to get the list of all the AU macro uses. To this end,
+# first get the list of all the AU macros names by tracing `AU_DEFUN' in
+# the initialization of autoconf. This list is computed in the file
+# `au.txt' below.
+#
+# Then use this list to trace all the AU macro uses in the input. The
+# goal is obtain in the case of our example:
+#
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# This is the file `values.in' below.
+#
+# We want to evaluate this with only the builtins (in fact m4sugar), the
+# auto-quoting definitions of the new macros (`new.m4'), and the
+# definition of the old macros (`old.m4'). Computing these last two
+# files is easy: it's just a matter of using the right `--trace' option.
+#
+# So the content of `values.in' is:
+#
+# include($autoconf_dir/m4sugar.m4)
+# m4_include(new.m4)
+# m4_include(old.m4)
+# divert(0)dnl
+# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
+#
+# We run m4 on it, which yields:
+#
+# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)
+#
+# Transform `@<<@' and `@>>@' into quotes and we get
+#
+# define([OLD([1],[2])],[NEW([1, 2], [3])])
+#
+# This is `values.m4'.
+#
+#
+# # Computing the `dispatcher' section
+# # ..................................
+#
+# The `prologue', and the `disabler' are simple and need no commenting.
+#
+# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple
+# matter of using the right `--trace'.
+#
+# Finally, the input is not exactly the input file, rather it is the
+# input file with the added `changequote'. To this end, we build
+# `quote.sed'.
+#
+#
+# # Putting it all together
+# # .......................
+#
+# We build the file `input.m4' which contains:
+#
+# divert(-1)dnl
+# changequote([, ])
+# include(values.m4)
+# include(dispatch.m4)
+# undefine([dnl])
+# undefine([eval])
+# # Some more undefines...
+# changequote()
+# divert(0)dnl
+# dnl The Unbelievable Truth
+# changequote([, ])OLD(1, 2)
+# NEW([0, 0],
+# 0)
+#
+# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui.
+#
+# Well, there are a few additional technicalities. For instance, we
+# rely on `changequote', `ifelse' and `defn', but we don't want to
+# interpret the changequotes of the user, so we simply use another name:
+# `_au_changequote' etc.
+#
+#
+# # Failure of the fourth approach
+# # ------------------------------
+#
+# This approach is heavily based on traces, but then there is an obvious
+# problem: non expanded code will never be seen/ In particular, the body
+# of a `define' definition is not seen, so on the input
+#
+# define([idem], [OLD(0, [$1])])
+#
+# autoupdate would never see the `OLD', and wouldn't have updated it.
+# Worse yet, if `idem(0)' was used later, then autoupdate sees that
+# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a
+# dispatcher for `OLD'. Since there was no computed value for `OLD(0,
+# [$1])', the dispatcher would have replaced with... nothinhg, leading
+# to
+#
+# define([idem], [])
+#
+# With some more thinking, you see that the two step approach is wrong,
+# the namespace approach was much saner.
+#
+# But you learned a lot, in particular you realized that using traces
+# can make it possible to simulate namespaces!
+#
+#
+#
+# # The fifth implementation: m4 namespaces by files
+# # ================================================
+#
+# The fourth implementation demonstrated something unsurprising: you
+# cannot precompute, i.e., the namespace approach was the right one.
+# Still, we no longer want them, they're too expensive. Let's have a
+# look at the way it worked.
+#
+# When updating
+#
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# you evaluate `input.m4':
+#
+# divert(-1)
+# changequote([, ])
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+# ...
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes
+# and comments:
+#
+# define([m4_disable],
+# [undefine([__file__])
+# ...
+# changecom(#)
+# changequote()])
+#
+# `m4_enable' does the converse: reestablish quotes and comments
+# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and
+# reenable the builtins. This later task requires that you first save
+# the builtins. And BTW, the definition above of `m4_disable' cannot
+# work: you undefined `changequote' before using it! So you need to use
+# your privates copies of the builtins. Let's introduce three files for
+# this:
+#
+# `m4save.m4'
+# moves the m4 builtins into the `_au_' pseudo namespace
+# `unm4.m4'
+# undefines the builtins
+# `m4.m4'
+# restores them
+#
+# So `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+#
+# # Import AU.
+# define([OLD],
+# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)])
+#
+# define([_au_disable],
+# [# Disable m4sugar.
+# # Disable the m4 builtins.
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Based on what we learned in the fourth implementation we know that we
+# have to enable the quotes *before* any AU macro, and we know we need
+# to build autoquoting versions of the AC macros. But the autoquoting
+# AC definitions must be disabled in the rest of the file, and enabled
+# inside AU macros.
+#
+# Using `autoconf --trace' it is easy to build the files
+#
+# `ac.m4'
+# define the autoquoting AC fake macros
+# `disable.m4'
+# undefine the m4sugar and AC autoquoting macros.
+# `au.m4'
+# definitions of the AU macros (such as `OLD' above).
+#
+# Now, `input.m4' is:
+#
+# divert(-1)
+# changequote([, ])
+#
+# include([m4save.m4])
+# # Import AU.
+# include([au.m4])
+#
+# define([_au_enable],
+# [_au_changecom([#])
+# _au_include([m4.m4])
+# _au_include(m4sugar.m4)
+# _au_include(ac.m4)])
+#
+# define([_au_disable],
+# [_au_include([disable.m4])
+# _au_include([unm4.m4])
+# # 1. Disable special characters.
+# _au_changequote()
+# _au_changecom()])
+#
+# m4_disable()
+# dnl The Unbelievable Truth
+# _au_changequote([, ])OLD(1, 2)
+# NEW([0, 0], [0])
+#
+# Finally, version V is ready.
+#
+# Well... almost.
+#
+# There is a slight problem that remains: if an AU macro OUTTER includes
+# an AU macro INNER, then _au_enable will be run when entering OUTTER
+# and when entering INNER (not good, but not too bad yet). But when
+# getting out of INNER, _au_disable will disable everything while we
+# were still in OUTTER. Badaboom.
+#
+# Therefore _au_enable and _au_disable have to be written to work by
+# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable
+# popdef's _au_enabled. And of course _au_enable and _au_disable are
+# effective when _au_enabled is *not* defined.
+#
+# Finally, version V' is ready. And there is much rejoicing. (And I
+# have free time again. I think. Yeah, right.)
# when running `sh PROG'.
AT_CHECK([/bin/sh -n ../autoconf], 0)
AT_CHECK([/bin/sh -n ../autoreconf], 0)
- AT_CHECK([/bin/sh -n ../autoupdate], 0)
AT_CHECK([/bin/sh -n ../ifnames], 0)
# These are not built, they are in the src tree.
projects / thirdparty / autoconf.git / commitdiff
