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- Committer: Bazaar Package Importer
- Author(s): Ben Pfaff
- Date: 2002-03-27 21:52:33 UTC
- Revision ID: james.westby@ubuntu.com-20020327215233-r3gmxall0x27s306
Tags: upstream-2.53
Import upstream version 2.53
- files added:
- bin
- config
- doc
- lib
- lib/Autom4te
- lib/autoconf
- lib/autoscan
- lib/autotest
- lib/emacs
- lib/m4sugar
- man
- tests
added
removed
bin/autoupdate.in
1
#! @PERL@ -w
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# -*- perl -*-
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# autoupdate - modernize an Autoconf file.
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# Copyright 1994, 1999, 2000, 2001 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2, or (at your option)
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# any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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# 02111-1307, USA.
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# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.
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# Rewritten by Akim Demaille <akim@freefriends.org>.
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eval 'exec @PERL@ -S $0 ${1+"$@"}'
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if 0;
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BEGIN
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{
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my $perllibdir = $ENV{'autom4te_perllibdir'} || "@datadir@";
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unshift @INC, "$perllibdir";
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}
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use File::Basename;
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use Autom4te::General;
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use Autom4te::XFile;
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use strict;
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# Lib files.
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my $autom4te = $ENV{'AUTOM4TE'} || '@autom4te-name@';
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my $autoconf = "$autom4te --language=autoconf";
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# We need to find m4sugar.
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my @include = ('@datadir@');
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my $force = 0;
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# m4.
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my $m4 = $ENV{"M4"} || "@M4@";
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# $HELP
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# -----
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$help = "Usage: $0 [OPTION] ... [TEMPLATE-FILE...]
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Update the TEMPLATE-FILE... if given, or `configure.ac' if present,
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or else `configure.in', to the syntax of the current version of
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Autoconf. The original files are backed up.
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Operation modes:
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-h, --help print this help, then exit
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-V, --version print version number, then exit
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-v, --verbose verbosely report processing
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-d, --debug don't remove temporary files
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-I, --include=DIR look for input files in DIR (cumulative)
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-f, --force consider all files obsolete
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Report bugs to <bug-autoconf\@gnu.org>.
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";
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# $VERSION
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# --------
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$version = "autoupdate (@PACKAGE_NAME@) @VERSION@
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Written by David J. MacKenzie and Akim Demaille.
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Copyright 2002 Free Software Foundation, Inc.
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This is free software; see the source for copying conditions. There is NO
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warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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";
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## ---------- ##
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## Routines. ##
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## ---------- ##
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# parse_args ()
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# -------------
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# Process any command line arguments.
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sub parse_args ()
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{
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my $srcdir;
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getopt ('I|include|A|autoconf-dir|m|macrodir|l|localdir=s' => \@include,
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'f|force' => \$force);
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if (! @ARGV)
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{
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my $configure_ac = find_configure_ac;
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die "$me: no input file\n"
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unless $configure_ac;
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push @ARGV, $configure_ac;
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}
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}
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# ------------- #
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# M4 builtins. #
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# ------------- #
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my @m4_builtins;
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# &handle_m4_symbols ()
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# ---------------------
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# Create the following $tmp files:
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# m4.m4 -- enable the m4 builtins.
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# unm4.m4 -- disable the m4 builtins.
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# savem4.m4 -- save the m4 builtins.
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sub handle_m4_macros ()
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{
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# Get the list of builtins.
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xsystem ("echo dumpdef | $m4 2>$tmp/m4.defs >/dev/null");
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my $m4_defs = new Autom4te::XFile "$tmp/m4.defs";
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while ($_ = $m4_defs->getline)
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{
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push @m4_builtins, $1
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if /^(\w+):/;
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}
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$m4_defs->close;
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# Output the files.
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my $m4_m4 = new Autom4te::XFile ">$tmp/m4.m4";
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print $m4_m4 "# m4.m4 -- enable the m4 builtins.\n";
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my $unm4_m4 = new Autom4te::XFile ">$tmp/unm4.m4";
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print $unm4_m4 "# unm4.m4 -- disable the m4 builtins.\n";
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print $unm4_m4 "# Because Autoconf, via M4sugar, redefines some of these\n";
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print $unm4_m4 "# macros, and therefore since unac.m4 disables them,\n";
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print $unm4_m4 "# disable only if defined.\n";
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my $m4save_m4 = new Autom4te::XFile ">$tmp/m4save.m4";
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print $m4save_m4 "# savem4.m4 -- save the m4 builtins.\n";
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foreach (@m4_builtins)
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{
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print $m4save_m4 "define([_au_$_], defn([$_]))\n";
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print $unm4_m4 "_au_ifdef([$_], [_au_undefine([$_])])\n";
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print $m4_m4 "_au_define([$_], _au_defn([_au_$_]))\n";
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}
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}
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# ----------------- #
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# Autoconf macros. #
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# ----------------- #
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# @AU_MACROS & AC_MACROS -- AU and AC macros and yet another useful comment.
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my (%ac_macros, %au_macros);
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# HANDLE_AUTOCONF_MACROS ()
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# -------------------------
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# @M4_BUILTINS -- M4 builtins and a useful comment.
158
sub handle_autoconf_macros ()
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{
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my $macros = new Autom4te::XFile ("$autoconf"
161
. " --trace AU_DEFUN:'AU:\$f:\$1'"
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. " --trace define:'AC:\$f:\$1'"
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. " --melt /dev/null |");
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while ($_ = $macros->getline)
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{
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chomp;
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my ($domain, $file, $macro) = /^(AC|AU):(.*):([^:]*)$/ or next;
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# ../lib/m4sugar/m4sugar.m4 -> m4sugar
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# ../lib/autoconf/general.m4 -> autoconf
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# aclocal.m4 -> ignore
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next
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if $file eq 'aclocal.m4';
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my $set = basename (dirname ($file));
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die "$me: unknown set: $set: $_\n"
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unless $set =~ /^(m4sugar|autoconf)$/;
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if ($domain eq "AC")
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{
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$ac_macros{$macro} = $set;
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}
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else
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{
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$au_macros{$macro} = $set;
183
}
184
}
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$macros->close;
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# Don't keep AU macros in @AC_MACROS.
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delete $ac_macros{$_}
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foreach (keys %au_macros);
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# Don't keep M4sugar macros which are redefined by Autoconf,
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# such as `builtin', `changequote' etc. See autoconf/autoconf.m4.
192
delete $ac_macros{$_}
193
foreach (@m4_builtins);
194
die "$me: no current Autoconf macros found\n"
195
unless keys %ac_macros;
196
die "$me: no obsolete Autoconf macros found\n"
197
unless keys %au_macros;
198
199
if ($debug)
200
{
201
print STDERR "Current Autoconf macros:\n";
202
print STDERR join (' ', sort keys %ac_macros) . "\n\n";
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print STDERR "Obsolete Autoconf macros:\n";
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print STDERR join (' ', sort keys %au_macros) . "\n\n";
205
}
206
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# ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded).
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# unac.m4 -- undefine the AC macros.
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my $ac_m4 = new Autom4te::XFile ">$tmp/ac.m4";
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print $ac_m4 "# ac.m4 -- autoquoting definitions of the AC macros.\n";
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my $unac_m4 = new Autom4te::XFile ">$tmp/unac.m4";
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print $unac_m4 "# unac.m4 -- undefine the AC macros.\n";
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foreach (sort grep { $ac_macros{$_} ne 'm4sugar' } keys %ac_macros)
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{
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print $ac_m4 "_au_define([$_], [[\$0(\$\@)]])\n";
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print $unac_m4 "_au_undefine([$_])\n";
217
}
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}
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## -------------- ##
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## Main program. ##
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## -------------- ##
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parse_args;
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$autoconf .= " --debug" if $debug;
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$autoconf .= " --force" if $force;
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$autoconf .= " --verbose" if $verbose;
229
$autoconf .= join (' --include=', '', @include);
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mktmpdir ('au');
232
handle_m4_macros;
233
handle_autoconf_macros;
234
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# $au_changequote -- enable the quote `[', `]' right before any AU macro.
236
my $au_changequote =
237
's/\b(' . join ('|', keys %au_macros) . ')\b/_au_changequote([,])$1/g';
238
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# au.m4 -- definitions the AU macros.
240
xsystem ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@,
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\@<:\@\$2\@:>\@)' --melt /dev/null "
242
. ">$tmp/au.m4");
243
244
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## ------------------- ##
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## Process the files. ##
248
## ------------------- ##
249
250
foreach my $file (@ARGV)
251
{
252
my $filename = $file;
253
# We need an actual file.
254
if ($file eq '-')
255
{
256
$file = "$tmp/stdin";
257
system "cat >$file";
258
}
259
elsif (! -r "$file")
260
{
261
die "$me: $file: No such file or directory";
262
}
263
264
# input.m4 -- m4 program to produce the updated file.
265
# Load the values, the dispatcher, neutralize m4, and the prepared
266
# input file.
267
my $input_m4 = <<\EOF;
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divert(-1) -*- Autoconf -*-
269
changequote([, ])
270
271
# Move all the builtins into the `_au_' pseudo namespace
272
include([m4save.m4])
273
274
# _au_defun(NAME, BODY)
275
# ---------------------
276
# Define NAME to BODY, plus AU activation/deactivation.
277
_au_define([_au_defun],
278
[_au_define([$1],
279
[_au_enable()dnl
280
$2[]dnl
281
_au_disable()])])
282
283
# Import the definition of the obsolete macros.
284
_au_include([au.m4])
285
286
287
## ------------------------ ##
288
## _au_enable/_au_disable. ##
289
## ------------------------ ##
290
291
# They work by pair: each time an AU macro is activated, it runs
292
# _au_enable, and at its end its runs _au_disable (see _au_defun
293
# above). But since AU macros might use AU macros, which should
294
# enable/disable only for the outter AU macros.
295
#
296
# `_au_enabled' is used to this end, condionning whether we really
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# enable/disable.
298
299
300
# __au_enable
301
# -----------
302
# Reenable the builtins, and m4sugar.
303
_au_define([__au_enable],
304
[_au_divert(-1)
305
# Enable special characters.
306
_au_changecom([#])
307
308
# Enable the m4 builtins, m4sugar and the autoquoting AC macros.
309
_au_include([m4.m4])
310
_au_include([m4sugar/m4sugar.m4])
311
_au_include([ac.m4])
312
313
_au_divert(0)])
314
315
# _au_enable
316
# ----------
317
# Called at the beginning of all the obsolete macros. Reenable the
318
# builtins, and m4sugar if needed.
319
_au_define([_au_enable],
320
[_au_ifdef([_au_enabled],
321
[],
322
[__au_enable()])_au_dnl
323
_au_pushdef([_au_enabled])])
324
325
326
# __au_disable
327
# ------------
328
# Disable the builtins, and m4sugar.
329
_au_define([__au_disable],
330
[_au_divert(-1)
331
# Disable m4sugar, the AC autoquoting macros, and m4.
332
_au_include([unac.m4])
333
_au_include([unm4.m4])
334
335
# Disable special characters.
336
_au_changequote()
337
_au_changecom()
338
339
_au_divert(0)])
340
341
# _au_disable
342
# -----------
343
# Called at the end of all the obsolete macros. Disable the
344
# builtins, and m4sugar if needed..
345
_au_define([_au_disable],
346
[_au_popdef([_au_enabled])_au_dnl
347
_au_ifdef([_au_enabled],
348
[],
349
[__au_disable()])])
350
351
352
## ------------------------------- ##
353
## Disable, and process the file. ##
354
## ------------------------------- ##
355
_au_divert(-1)
356
# Disable m4: M4sugar and the AC autoquoting macros are not loaded yet,
357
# hence invoking `_au_disable' is wrong.
358
_au_include([unm4.m4])
359
360
# Disable special characters.
361
_au_changequote()
362
_au_changecom()
363
364
_au_divert(0)_au_dnl
365
EOF
366
367
$input_m4 =~ s/^ //mg;
368
369
# prepared input -- input, but reenables the quote before each AU macro.
370
open INPUT_M4, ">$tmp/input.m4"
371
or die "$me: cannot open: $!\n";
372
open FILE, "<$file"
373
or die "$me: cannot open: $!\n";
374
print INPUT_M4 "$input_m4";
375
while (<FILE>)
376
{
377
eval $au_changequote;
378
print INPUT_M4;
379
}
380
close FILE
381
or die "$me: cannot close $file: $!\n";
382
close INPUT_M4
383
or die "$me: cannot close $tmp/input.m4: $!\n";
384
385
# Now ask m4 to perform the update.
386
# M4 and I don't agree on the associativity of `--include': reverse!
387
xsystem ("$m4"
388
. join (' --include=', '', reverse (@include, $tmp))
389
. " $tmp/input.m4 >$tmp/updated");
390
update_file ("$tmp/updated",
391
"$file" eq "$tmp/stdin" ? '-' : "$file");
392
}
393
exit 0;
394
395
396
# ## ---------------------------- ##
397
# ## How `autoupdate' functions. ##
398
# ## ---------------------------- ##
399
#
400
# The task of `autoupdate' is not trivial: the biggest difficulty being
401
# that you must limit the changes to the parts that really need to be
402
# updated. Finding a satisfying implementation proved to be quite hard,
403
# as this is the fourth implementation of `autoupdate'.
404
#
405
# Below, we will use a simple example of obsolete macro:
406
#
407
# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
408
# AC_DEFUN([NEW], [echo "sum($1) = $2"])
409
#
410
# the input file contains
411
#
412
# dnl The Unbelievable Truth
413
# OLD(1, 2)
414
# NEW([0, 0], [0])
415
#
416
# Of course the expected output is
417
#
418
# dnl The Unbelievable Truth
419
# NEW([1, 2], [3])
420
# NEW([0, 0], [0])
421
#
422
#
423
# # First implementation: sed
424
# # =========================
425
#
426
# The first implementation was only able to change the name of obsolete
427
# macros.
428
#
429
# The file `acoldnames.m4' defined the old names based on the new names.
430
# It was simple then to produce a sed script such as:
431
#
432
# s/OLD/NEW/g
433
#
434
# Updating merely consisted in running this script on the file to
435
# update.
436
#
437
# This scheme suffers an obvious limitation: that `autoupdate' was
438
# unable to cope with new macros that just swap some of its arguments
439
# compared to the old macro. Fortunately, that was enough to upgrade
440
# from Autoconf 1 to Autoconf 2. (But I have no idea whether the
441
# changes in Autoconf 2 were precisely limited by this constraint.)
442
#
443
#
444
# # Second implementation: hooks
445
# # ============================
446
#
447
# The version 2.15 of Autoconf brought a vast number of changes compared
448
# to 2.13, so a solution was needed. One could think to extend the
449
# `sed' scripts with specialized code for complex macros. But this
450
# approach is of course full of flaws:
451
#
452
# a. the Autoconf maintainers have to write these snippets, which we
453
# just don't want to,
454
#
455
# b. I really don't think you'll ever manage to handle the quoting of
456
# m4 from sed.
457
#
458
# To satisfy a., let's remark that the code which implements the old
459
# features in term of the new feature is exactly the code which should
460
# replace the old code.
461
#
462
# To answer point b, as usual in the history of Autoconf, the answer, at
463
# least on the paper, is simple: m4 is the best tool to parse m4, so
464
# let's use m4.
465
#
466
# Therefore the specification is:
467
#
468
# I want to be able to tell Autoconf, well, m4, that the macro I
469
# am currently defining is an obsolete macro (so that the user is
470
# warned), which code is the code to use when running autoconf,
471
# but that the very same code has to be used when running
472
# autoupdate. To summarize, the interface I want is
473
# `AU_DEFUN(OLD-NAME, NEW-CODE)'.
474
#
475
#
476
# Now for the technical details.
477
#
478
# When running autoconf, except for the warning, AU_DEFUN is basically
479
# AC_DEFUN.
480
#
481
# When running autoupdate, we want *only* OLD-NAMEs to be expanded.
482
# This obviously means that acgeneral.m4 and acspecific.m4 must not be
483
# loaded. Nonetheless, because we want to use a rich set of m4
484
# features, m4sugar.m4 is needed. Please note that the fact that
485
# Autoconf's macros are not loaded is positive on two points:
486
#
487
# - we do get an updated `configure.ac', not a `configure'!
488
#
489
# - the old macros are replaced by *calls* to the new-macros, not the
490
# body of the new macros, since their body is not defined!!!
491
# (Whoa, that's really beautiful!).
492
#
493
# Additionally we need to disable the quotes when reading the input for
494
# two reasons: first because otherwise `m4' will swallow the quotes of
495
# other macros:
496
#
497
# NEW([1, 2], 3)
498
# => NEW(1, 2, 3)
499
#
500
# and second, because we want to update the macro calls which are
501
# quoted, i.e., we want
502
#
503
# FOO([OLD(1, 2)])
504
# => FOO([NEW([1, 2], [3])])
505
#
506
# If we don't disable the quotes, only the macros called at the top
507
# level would be updated.
508
#
509
# So, let's disable the quotes.
510
#
511
# Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
512
# Well, in this case, when running in autoupdate code, each macro first
513
# reestablishes the quotes, expands itself, and disables the quotes.
514
#
515
# Thinking a bit more, you realize that in fact, people may use `define'
516
# `ifelse' etc. in their files, and you certainly don't want to process
517
# them. Another example is `dnl': you don't want to remove the
518
# comments. You then realize you don't want exactly to import m4sugar:
519
# you want to specify when it is enabled (macros active), and disabled.
520
# m4sugar provides m4_disable/m4_enable to this end.
521
#
522
# You're getting close to it. Now remains one task: how to handle
523
# twofold definitions?
524
#
525
# Remember that the same AU_DEFUN must be understood in two different
526
# ways, the AC way, and the AU way.
527
#
528
# One first solution is to check whether acgeneral.m4 was loaded. But
529
# that's definitely not cute. Another is simply to install `hooks',
530
# that is to say, to keep in some place m4 knows, late `define' to be
531
# triggered *only* in AU mode.
532
#
533
# You first think to design AU_DEFUN like this:
534
#
535
# 1. AC_DEFUN(OLD-NAME,
536
# [Warn the user OLD-NAME is obsolete.
537
# NEW-CODE])
538
#
539
# 2. Store for late AU binding([define(OLD_NAME,
540
# [Reestablish the quotes.
541
# NEW-CODE
542
# Disable the quotes.])])
543
#
544
# but this will not work: NEW-CODE has probably $1, $2 etc. and these
545
# guys will be replaced with the argument of `Store for late AU binding'
546
# when you call it.
547
#
548
# I don't think there is a means to avoid this using this technology
549
# (remember that $1 etc. are *always* expanded in m4). You may also try
550
# to replace them with $[1] to preserve them for a later evaluation, but
551
# if `Store for late AU binding' is properly written, it will remain
552
# quoted till the end...
553
#
554
# You have to change technology. Since the problem is that `$1'
555
# etc. should be `consumed' right away, one solution is to define now a
556
# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
557
# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By
558
# the way, the same method was used in autoheader.
559
#
560
#
561
# # Third implementation: m4 namespaces by m4sugar
562
# # ==============================================
563
#
564
# Actually, this implementation was just a clean up of the previous
565
# implementation: instead of defining hooks by hand, m4sugar was equipped
566
# with `namespaces'. What are they?
567
#
568
# Sometimes we want to disable some *set* of macros, and restore them
569
# later. We provide support for this via namespaces.
570
#
571
# There are basically three characters playing this scene: defining a
572
# macro in a namespace, disabling a namespace, and restoring a namespace
573
# (i.e., all the definitions it holds).
574
#
575
# Technically, to define a MACRO in NAMESPACE means to define the macro
576
# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append
577
# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
578
# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
579
# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of
580
# NAMESPACE and to unbind them at will.
581
#
582
# Of course this implementation is really inefficient: m4 has to grow
583
# strings which can become quickly huge, which slows it significantly.
584
#
585
# In particular one should avoid as much as possible to use `define' for
586
# temporaries. Now that `define' as quite a complex meaning, it is an
587
# expensive operations that should be limited to macros. Use
588
# `m4_define' for temporaries.
589
#
590
# Private copies of the macros we used in entering / exiting the m4sugar
591
# namespace. It is much more convenient than fighting with the renamed
592
# version of define etc.
593
#
594
#
595
#
596
# Those two implementations suffered from serious problems:
597
#
598
# - namespaces were really expensive, and incurred a major performance
599
# loss on `autoconf' itself, not only `autoupdate'. One solution
600
# would have been the limit the use of namespaces to `autoupdate', but
601
# that's again some complications on m4sugar, which really doesn't need
602
# this. So we wanted to get rid of the namespaces.
603
#
604
# - since the quotes were disabled, autoupdate was sometimes making
605
# wrong guesses, for instance on:
606
#
607
# foo([1, 2])
608
#
609
# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat
610
# fragile, is to reestablish the quotes right before all the obsolete
611
# macros, i.e., to use sed so that the previous text becomes
612
#
613
# changequote([, ])foo([1, 2])
614
#
615
# To this end, one wants to trace the definition of obsolete macros.
616
#
617
# It was there that the limitations of the namespace approach became
618
# painful: because it was a complex machinery playing a lot with the
619
# builtins of m4 (hence, quite fragile), tracing was almost impossible.
620
#
621
#
622
# So this approach was dropped.
623
#
624
#
625
# # The fourth implementation: two steps
626
# # ====================================
627
#
628
# If you drop the uses of namespaces, you no longer can compute the
629
# updated value, and replace the old call with it simultaneously.
630
#
631
# Obviously you will use m4 to compute the updated values, but you may
632
# use some other tool to achieve the replacement. Personally, I trust
633
# nobody but m4 to parse m4, so below, m4 will perform the two tasks.
634
#
635
# How can m4 be used to replace *some* macros calls with newer values.
636
# Well, that's dead simple: m4 should learn the definitions of obsolete
637
# macros, forget its builtins, disable the quotes, and then run on the
638
# input file, which amounts to doing this:
639
#
640
# divert(-1)dnl
641
# changequote([, ])
642
# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
643
# undefine([dnl])
644
# undefine([m4_eval])
645
# # Some more undefines...
646
# changequote()
647
# divert(0)dnl
648
# dnl The Unbelievable Truth
649
# changequote([, ])OLD(1, 2)
650
# NEW([0, 0],
651
# 0)
652
#
653
# which will result in
654
#
655
# dnl The Unbelievable Truth
656
# NEW(1, 2, m4_eval(1 + 2))
657
# NEW([0, 0],
658
# 0)
659
#
660
# Grpmh. Two problems. A minor problem: it would have been much better
661
# to have the `m4_eval' computed, and a major problem: you lost the
662
# quotation in the result.
663
#
664
# Let's address the big problem first. One solution is to define any
665
# modern macro to rewrite its calls with the proper quotation, thanks to
666
# `$@'. Again, tracing the `define's makes it possible to know which
667
# are these macros, so you input is:
668
#
669
# divert(-1)dnl
670
# changequote([, ])
671
# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
672
# define([NEW], [[NEW($@)]changequote()])
673
# undefine([dnl])
674
# undefine([m4_eval])
675
# # Some more undefines...
676
# changequote()
677
# divert(0)dnl
678
# dnl The Unbelievable Truth
679
# changequote([, ])OLD(1, 2)
680
# changequote([, ])NEW([0, 0],
681
# 0)
682
#
683
# which results in
684
#
685
# dnl The Unbelievable Truth
686
# NEW([1, 2],[m4_eval(1 + 2)])
687
# NEW([0, 0],[0])
688
#
689
# Our problem is solved, i.e., the first call to `NEW' is properly
690
# quoted, but introduced another problem: we changed the layout of the
691
# second calls, which can be a drama in the case of huge macro calls
692
# (think of `AC_TRY_RUN' for instance). This example didn't show it,
693
# but we also introduced parens to macros which did not have some:
694
#
695
# AC_INIT
696
# => AC_INIT()
697
#
698
# No big deal for the semantics (unless the macro depends upon $#, which
699
# is bad), but the users would not be happy.
700
#
701
# Additionally, we introduced quotes that we not there before, which is
702
# OK in most cases, but could change the semantics of the file.
703
#
704
# Cruel dilemma: we do want the auto-quoting definition of `NEW' when
705
# evaluating `OLD', but we don't when we evaluate the second `NEW'.
706
# Back to namespaces?
707
#
708
# No.
709
#
710
#
711
# # Second step: replacement
712
# # ------------------------
713
#
714
# No, as announced above, we will work in two steps: in a first step we
715
# compute the updated values, and in a second step we replace them. Our
716
# goal is something like this:
717
#
718
# divert(-1)dnl
719
# changequote([, ])
720
# define([OLD], [NEW([1, 2], [3])changequote()])
721
# undefine([dnl])
722
# undefine([m4_eval])
723
# # Some more undefines...
724
# changequote()
725
# divert(0)dnl
726
# dnl The Unbelievable Truth
727
# changequote([, ])OLD(1, 2)
728
# NEW([0, 0],
729
# 0)
730
#
731
# i.e., the new value of `OLD' is precomputed using the auto-quoting
732
# definition of `NEW' and the m4 builtins. We'll see how afterwards,
733
# let's finish with the replacement.
734
#
735
# Of course the solution above is wrong: if there were other calls to
736
# `OLD' with different values, we would smash them to the same value.
737
# But it is quite easy to generalize the scheme above:
738
#
739
# divert(-1)dnl
740
# changequote([, ])
741
# define([OLD([1],[2])], [NEW([1, 2], [3])])
742
# define([OLD], [defn([OLD($@)])changequote()])
743
# undefine([dnl])
744
# undefine([m4_eval])
745
# # Some more undefines...
746
# changequote()
747
# divert(0)dnl
748
# dnl The Unbelievable Truth
749
# changequote([, ])OLD(1, 2)
750
# NEW([0, 0],
751
# 0)
752
#
753
# i.e., for each call to obsolete macros, we build an array `call =>
754
# value', and use a macro to dispatch these values. This results in:
755
#
756
# dnl The Unbelievable Truth
757
# NEW([1, 2], [3])
758
# NEW([0, 0],
759
# 0)
760
#
761
# In French, we say `Youpi !', which you might roughly translate as
762
# `yipeee!'.
763
#
764
#
765
# # First step: computation
766
# # -----------------------
767
#
768
# Let's study the anatomy of the file, and name its sections:
769
#
770
# prologue
771
# divert(-1)dnl
772
# changequote([, ])
773
# values
774
# define([OLD([1],[2])], [NEW([1, 2], [3])])
775
# dispatcher
776
# define([OLD], [defn([OLD($@)])changequote()])
777
# disabler
778
# undefine([dnl])
779
# undefine([m4_eval])
780
# # Some more undefines...
781
# changequote()
782
# divert(0)dnl
783
# input
784
# dnl The Unbelievable Truth
785
# changequote([, ])OLD(1, 2)
786
# NEW([0, 0],
787
# 0)
788
#
789
#
790
# # Computing the `values' section
791
# # ..............................
792
#
793
# First we need to get the list of all the AU macro uses. To this end,
794
# first get the list of all the AU macros names by tracing `AU_DEFUN' in
795
# the initialization of autoconf. This list is computed in the file
796
# `au.txt' below.
797
#
798
# Then use this list to trace all the AU macro uses in the input. The
799
# goal is obtain in the case of our example:
800
#
801
# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
802
#
803
# This is the file `values.in' below.
804
#
805
# We want to evaluate this with only the builtins (in fact m4sugar), the
806
# auto-quoting definitions of the new macros (`new.m4'), and the
807
# definition of the old macros (`old.m4'). Computing these last two
808
# files is easy: it's just a matter of using the right `--trace' option.
809
#
810
# So the content of `values.in' is:
811
#
812
# include($autoconf_dir/m4sugar.m4)
813
# m4_include(new.m4)
814
# m4_include(old.m4)
815
# divert(0)dnl
816
# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
817
#
818
# We run m4 on it, which yields:
819
#
820
# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)
821
#
822
# Transform `@<<@' and `@>>@' into quotes and we get
823
#
824
# define([OLD([1],[2])],[NEW([1, 2], [3])])
825
#
826
# This is `values.m4'.
827
#
828
#
829
# # Computing the `dispatcher' section
830
# # ..................................
831
#
832
# The `prologue', and the `disabler' are simple and need no commenting.
833
#
834
# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple
835
# matter of using the right `--trace'.
836
#
837
# Finally, the input is not exactly the input file, rather it is the
838
# input file with the added `changequote'. To this end, we build
839
# `quote.sed'.
840
#
841
#
842
# # Putting it all together
843
# # .......................
844
#
845
# We build the file `input.m4' which contains:
846
#
847
# divert(-1)dnl
848
# changequote([, ])
849
# include(values.m4)
850
# include(dispatch.m4)
851
# undefine([dnl])
852
# undefine([eval])
853
# # Some more undefines...
854
# changequote()
855
# divert(0)dnl
856
# dnl The Unbelievable Truth
857
# changequote([, ])OLD(1, 2)
858
# NEW([0, 0],
859
# 0)
860
#
861
# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui.
862
#
863
# Well, there are a few additional technicalities. For instance, we
864
# rely on `changequote', `ifelse' and `defn', but we don't want to
865
# interpret the changequotes of the user, so we simply use another name:
866
# `_au_changequote' etc.
867
#
868
#
869
# # Failure of the fourth approach
870
# # ------------------------------
871
#
872
# This approach is heavily based on traces, but then there is an obvious
873
# problem: non expanded code will never be seen/ In particular, the body
874
# of a `define' definition is not seen, so on the input
875
#
876
# define([idem], [OLD(0, [$1])])
877
#
878
# autoupdate would never see the `OLD', and wouldn't have updated it.
879
# Worse yet, if `idem(0)' was used later, then autoupdate sees that
880
# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a
881
# dispatcher for `OLD'. Since there was no computed value for `OLD(0,
882
# [$1])', the dispatcher would have replaced with... nothinhg, leading
883
# to
884
#
885
# define([idem], [])
886
#
887
# With some more thinking, you see that the two step approach is wrong,
888
# the namespace approach was much saner.
889
#
890
# But you learned a lot, in particular you realized that using traces
891
# can make it possible to simulate namespaces!
892
#
893
#
894
#
895
# # The fifth implementation: m4 namespaces by files
896
# # ================================================
897
#
898
# The fourth implementation demonstrated something unsurprising: you
899
# cannot precompute, i.e., the namespace approach was the right one.
900
# Still, we no longer want them, they're too expensive. Let's have a
901
# look at the way it worked.
902
#
903
# When updating
904
#
905
# dnl The Unbelievable Truth
906
# OLD(1, 2)
907
# NEW([0, 0], [0])
908
#
909
# you evaluate `input.m4':
910
#
911
# divert(-1)
912
# changequote([, ])
913
# define([OLD],
914
# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
915
# ...
916
# m4_disable()
917
# dnl The Unbelievable Truth
918
# OLD(1, 2)
919
# NEW([0, 0], [0])
920
#
921
# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes
922
# and comments:
923
#
924
# define([m4_disable],
925
# [undefine([__file__])
926
# ...
927
# changecom(#)
928
# changequote()])
929
#
930
# `m4_enable' does the converse: reestablish quotes and comments
931
# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and
932
# reenable the builtins. This later task requires that you first save
933
# the builtins. And BTW, the definition above of `m4_disable' cannot
934
# work: you undefined `changequote' before using it! So you need to use
935
# your privates copies of the builtins. Let's introduce three files for
936
# this:
937
#
938
# `m4save.m4'
939
# moves the m4 builtins into the `_au_' pseudo namespace
940
# `unm4.m4'
941
# undefines the builtins
942
# `m4.m4'
943
# restores them
944
#
945
# So `input.m4' is:
946
#
947
# divert(-1)
948
# changequote([, ])
949
#
950
# include([m4save.m4])
951
#
952
# # Import AU.
953
# define([OLD],
954
# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
955
#
956
# define([_au_enable],
957
# [_au_changecom([#])
958
# _au_include([m4.m4])
959
# _au_include(m4sugar.m4)])
960
#
961
# define([_au_disable],
962
# [# Disable m4sugar.
963
# # Disable the m4 builtins.
964
# _au_include([unm4.m4])
965
# # 1. Disable special characters.
966
# _au_changequote()
967
# _au_changecom()])
968
#
969
# m4_disable()
970
# dnl The Unbelievable Truth
971
# OLD(1, 2)
972
# NEW([0, 0], [0])
973
#
974
# Based on what we learned in the fourth implementation we know that we
975
# have to enable the quotes *before* any AU macro, and we know we need
976
# to build autoquoting versions of the AC macros. But the autoquoting
977
# AC definitions must be disabled in the rest of the file, and enabled
978
# inside AU macros.
979
#
980
# Using `autoconf --trace' it is easy to build the files
981
#
982
# `ac.m4'
983
# define the autoquoting AC fake macros
984
# `disable.m4'
985
# undefine the m4sugar and AC autoquoting macros.
986
# `au.m4'
987
# definitions of the AU macros (such as `OLD' above).
988
#
989
# Now, `input.m4' is:
990
#
991
# divert(-1)
992
# changequote([, ])
993
#
994
# include([m4save.m4])
995
# # Import AU.
996
# include([au.m4])
997
#
998
# define([_au_enable],
999
# [_au_changecom([#])
1000
# _au_include([m4.m4])
1001
# _au_include(m4sugar.m4)
1002
# _au_include(ac.m4)])
1003
#
1004
# define([_au_disable],
1005
# [_au_include([disable.m4])
1006
# _au_include([unm4.m4])
1007
# # 1. Disable special characters.
1008
# _au_changequote()
1009
# _au_changecom()])
1010
#
1011
# m4_disable()
1012
# dnl The Unbelievable Truth
1013
# _au_changequote([, ])OLD(1, 2)
1014
# NEW([0, 0], [0])
1015
#
1016
# Finally, version V is ready.
1017
#
1018
# Well... almost.
1019
#
1020
# There is a slight problem that remains: if an AU macro OUTTER includes
1021
# an AU macro INNER, then _au_enable will be run when entering OUTTER
1022
# and when entering INNER (not good, but not too bad yet). But when
1023
# getting out of INNER, _au_disable will disable everything while we
1024
# were still in OUTTER. Badaboom.
1025
#
1026
# Therefore _au_enable and _au_disable have to be written to work by
1027
# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable
1028
# popdef's _au_enabled. And of course _au_enable and _au_disable are
1029
# effective when _au_enabled is *not* defined.
1030
#
1031
# Finally, version V' is ready. And there is much rejoicing. (And I
1032
# have free time again. I think. Yeah, right.)
Loggerhead is a web-based interface for Breezy
Version: 2.0.1