release/src-rt-6.x.4708/toolchains/hndtools-arm-linux-2.6.36-uclibc-4.5.3/bin/autoupdate

   1 #! /usr/bin/perl -w
   2 # -*- perl -*-
   3 # Generated from autoupdate.in; do not edit by hand.
   4
   5 # autoupdate - modernize an Autoconf file.
   6 # Copyright (C) 1994, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
   7 # 2007, 2008, 2009 Free Software Foundation, Inc.
   8
   9 # This program is free software: you can redistribute it and/or modify
  10 # it under the terms of the GNU General Public License as published by
  11 # the Free Software Foundation, either version 3 of the License, or
  12 # (at your option) any later version.
  13
  14 # This program is distributed in the hope that it will be useful,
  15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 # GNU General Public License for more details.
  18
  19 # You should have received a copy of the GNU General Public License
  20 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21
  22 # Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.
  23 # Rewritten by Akim Demaille <akim@freefriends.org>.
  24
  25 eval 'case $# in 0) exec /usr/bin/perl -S "$0";; *) exec /usr/bin/perl -S "$0" "$@";; esac'
  26     if 0;
  27
  28 BEGIN
  29 {
  30   my $pkgdatadir = $ENV{'autom4te_perllibdir'} || '/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/share/autoconf';
  31   unshift @INC, $pkgdatadir;
  32
  33   # Override SHELL.  On DJGPP SHELL may not be set to a shell
  34   # that can handle redirection and quote arguments correctly,
  35   # e.g.: COMMAND.COM.  For DJGPP always use the shell that configure
  36   # has detected.
  37   $ENV{'SHELL'} = '/bin/sh' if ($^O eq 'dos');
  38 }
  39
  40 use Autom4te::ChannelDefs;
  41 use Autom4te::Channels;
  42 use Autom4te::Configure_ac;
  43 use Autom4te::FileUtils;
  44 use Autom4te::General;
  45 use Autom4te::XFile;
  46 use File::Basename;
  47 use strict;
  48
  49 # Lib files.
  50 my $autom4te = $ENV{'AUTOM4TE'} || '/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/bin/autom4te';
  51 my $autoconf = "$autom4te --language=autoconf";
  52 # We need to find m4sugar.
  53 my @prepend_include;
  54 my @include = ('/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/share/autoconf');
  55 my $force = 0;
  56 # m4.
  57 my $m4 = $ENV{"M4"} || '/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/bin/m4';
  58
  59
  60 # $HELP
  61 # -----
  62 $help = "Usage: $0 [OPTION]... [TEMPLATE-FILE]...
  63
  64 Update each TEMPLATE-FILE if given, or `configure.ac' if present,
  65 or else `configure.in', to the syntax of the current version of
  66 Autoconf.  The original files are backed up.
  67
  68 Operation modes:
  69   -h, --help                 print this help, then exit
  70   -V, --version              print version number, then exit
  71   -v, --verbose              verbosely report processing
  72   -d, --debug                don't remove temporary files
  73   -f, --force                consider all files obsolete
  74
  75 Library directories:
  76   -B, --prepend-include=DIR  prepend directory DIR to search path
  77   -I, --include=DIR          append directory DIR to search path
  78
  79 Report bugs to <bug-autoconf\@gnu.org>.
  80 GNU Autoconf home page: <http://www.gnu.org/software/autoconf/>.
  81 General help using GNU software: <http://www.gnu.org/gethelp/>.
  82 ";
  83
  84 # $VERSION
  85 # --------
  86 $version = "autoupdate (GNU Autoconf) 2.65
  87 Copyright (C) 2009 Free Software Foundation, Inc.
  88 License GPLv3+/Autoconf: GNU GPL version 3 or later
  89 <http://gnu.org/licenses/gpl.html>, <http://gnu.org/licenses/exceptions.html>
  90 This is free software: you are free to change and redistribute it.
  91 There is NO WARRANTY, to the extent permitted by law.
  92
  93 Written by David J. MacKenzie and Akim Demaille.
  94 ";
  95
  96 ## ---------- ##
  97 ## Routines.  ##
  98 ## ---------- ##
  99
 100
 101 # parse_args ()
 102 # -------------
 103 # Process any command line arguments.
 104 sub parse_args ()
 105 {
 106   my $srcdir;
 107
 108   getopt ('I|include=s'         => \@include,
 109           'B|prepend-include=s' => \@prepend_include,
 110           'f|force'             => \$force);
 111
 112   if (! @ARGV)
 113     {
 114       my $configure_ac = require_configure_ac;
 115       push @ARGV, $configure_ac;
 116     }
 117 }
 118
 119
 120
 121 # ----------------- #
 122 # Autoconf macros.  #
 123 # ----------------- #
 124
 125 my (%ac_macros, %au_macros, %m4_builtins);
 126
 127 # HANDLE_AUTOCONF_MACROS ()
 128 # -------------------------
 129 # @M4_BUILTINS -- M4 builtins and a useful comment.
 130 sub handle_autoconf_macros ()
 131 {
 132   # Get the builtins.
 133   xsystem ("echo dumpdef | $m4 2>" . shell_quote ("$tmp/m4.defs") . " >/dev/null");
 134   my $m4_defs = new Autom4te::XFile "< " . open_quote ("$tmp/m4.defs");
 135   while ($_ = $m4_defs->getline)
 136     {
 137       $m4_builtins{$1} = 1
 138         if /^(\w+):/;
 139     }
 140   $m4_defs->close;
 141
 142   my $macros = new Autom4te::XFile ("$autoconf"
 143                                     . " --trace AU_DEFINE:'AU:\$f:\$1'"
 144                                     . " --trace define:'AC:\$f:\$1'"
 145                                     . " --melt /dev/null |");
 146   while ($_ = $macros->getline)
 147     {
 148       chomp;
 149       my ($domain, $file, $macro) = /^(AC|AU):(.*):([^:]*)$/ or next;
 150       if ($domain eq "AU")
 151         {
 152           $au_macros{$macro} = 1;
 153         }
 154       elsif ($file =~ /(^|\/)m4sugar\/(m4sugar|version)\.m4$/)
 155         {
 156           # Add the m4sugar macros to m4_builtins.
 157           $m4_builtins{$macro} = 1;
 158         }
 159       else
 160         {
 161           # Autoconf, aclocal, and m4sh macros.
 162           $ac_macros{$macro} = 1;
 163         }
 164     }
 165   $macros->close;
 166
 167
 168   # Don't keep AU macros in @AC_MACROS.
 169   delete $ac_macros{$_}
 170     foreach (keys %au_macros);
 171   # Don't keep M4sugar macros which are redefined by Autoconf,
 172   # such as `builtin', `changequote' etc.  See autoconf/autoconf.m4.
 173   delete $ac_macros{$_}
 174     foreach (keys %m4_builtins);
 175   error "no current Autoconf macros found"
 176     unless keys %ac_macros;
 177   error "no obsolete Autoconf macros found"
 178     unless keys %au_macros;
 179
 180   if ($debug)
 181     {
 182       print STDERR "Current Autoconf macros:\n";
 183       print STDERR join (' ', sort keys %ac_macros) . "\n\n";
 184       print STDERR "Obsolete Autoconf macros:\n";
 185       print STDERR join (' ', sort keys %au_macros) . "\n\n";
 186     }
 187
 188   # ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded).
 189   # unac.m4 -- undefine the AC macros.
 190   my $ac_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/ac.m4");
 191   print $ac_m4 "# ac.m4 -- autoquoting definitions of the AC macros.\n";
 192   my $unac_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/unac.m4");
 193   print $unac_m4 "# unac.m4 -- undefine the AC macros.\n";
 194   foreach (sort keys %ac_macros)
 195     {
 196       print $ac_m4   "_au_m4_define([$_], [m4_if(\$#, 0, [[\$0]], [[\$0(\$\@)]])])\n";
 197       print $unac_m4 "_au_m4_undefine([$_])\n";
 198     }
 199
 200   # m4save.m4 -- save the m4 builtins.
 201   # unm4.m4 -- disable the m4 builtins.
 202   # m4.m4 -- enable the m4 builtins.
 203   my $m4save_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/m4save.m4");
 204   print $m4save_m4 "# m4save.m4 -- save the m4 builtins.\n";
 205   my $unm4_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/unm4.m4");
 206   print $unm4_m4 "# unm4.m4 -- disable the m4 builtins.\n";
 207   my $m4_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/m4.m4");
 208   print $m4_m4 "# m4.m4 -- enable the m4 builtins.\n";
 209   foreach (sort keys %m4_builtins)
 210     {
 211       print $m4save_m4 "_au__save([$_])\n";
 212       print $unm4_m4   "_au__undefine([$_])\n";
 213       print $m4_m4     "_au__restore([$_])\n";
 214     }
 215 }
 216
 217
 218 ## -------------- ##
 219 ## Main program.  ##
 220 ## -------------- ##
 221
 222 parse_args;
 223 $autoconf .= " --debug" if $debug;
 224 $autoconf .= " --force" if $force;
 225 $autoconf .= " --verbose" if $verbose;
 226 $autoconf .= join (' --include=', '', map { shell_quote ($_) } @include);
 227 $autoconf .= join (' --prepend-include=', '', map { shell_quote ($_) } @prepend_include);
 228
 229 mktmpdir ('au');
 230 handle_autoconf_macros;
 231
 232 # $au_changequote -- enable the quote `[', `]' right before any AU macro.
 233 my $au_changequote =
 234   's/\b(' . join ('|', keys %au_macros) . ')\b/_au_m4_changequote([,])$1/g';
 235
 236 # au.m4 -- definitions the AU macros.
 237 xsystem ("$autoconf --trace AU_DEFINE:'_au_defun(\@<:\@\$1\@:>\@,
 238 \@<:\@\$2\@:>\@)' --melt /dev/null "
 239         . ">" . shell_quote ("$tmp/au.m4"));
 240
 241
 242
 243 ## ------------------- ##
 244 ## Process the files.  ##
 245 ## ------------------- ##
 246
 247 foreach my $file (@ARGV)
 248   {
 249     # We need an actual file.
 250     if ($file eq '-')
 251       {
 252         $file = "$tmp/stdin";
 253         system "cat >" . shell_quote ($file);
 254       }
 255     elsif (! -r "$file")
 256       {
 257         die "$me: $file: No such file or directory";
 258       }
 259
 260     # input.m4 -- m4 program to produce the updated file.
 261     # Load the values, the dispatcher, neutralize m4, and the prepared
 262     # input file.
 263     my $input_m4 = <<\EOF;
 264       divert(-1)                                            -*- Autoconf -*-
 265       changequote([,])
 266
 267       # Define our special macros:
 268       define([_au__defn], defn([defn]))
 269       define([_au__divert], defn([divert]))
 270       define([_au__ifdef], defn([ifdef]))
 271       define([_au__include], defn([include]))
 272       define([_au___undefine], defn([undefine]))
 273       define([_au__undefine], [_au__ifdef([$1], [_au___undefine([$1])])])
 274       define([_au__save], [m4_ifdef([$1],
 275         [m4_define([_au_$1], _m4_defn([$1]))])])
 276       define([_au__restore],
 277         [_au_m4_ifdef([_au_$1],
 278           [_au_m4_define([$1], _au__defn([_au_$1]))])])
 279
 280       # Set up m4sugar.
 281       include(m4sugar/m4sugar.m4)
 282
 283       # Redefine __file__ to make warnings nicer; $file is replaced below.
 284       m4_define([__file__], [$file])
 285
 286       # Redefine m4_location to fix the line number.
 287       m4_define([m4_location], [__file__:m4_eval(__line__ - _au__first_line)])
 288
 289       # Move all the builtins into the `_au_' pseudo namespace
 290       m4_include([m4save.m4])
 291
 292       # _au_defun(NAME, BODY)
 293       # ---------------------
 294       # Define NAME to BODY, plus AU activation/deactivation.
 295       _au_m4_define([_au_defun],
 296       [_au_m4_define([$1],
 297       [_au_enable()dnl
 298       $2[]dnl
 299       _au_disable()])])
 300
 301       # Import the definition of the obsolete macros.
 302       _au__include([au.m4])
 303
 304
 305       ## ------------------------ ##
 306       ## _au_enable/_au_disable.  ##
 307       ## ------------------------ ##
 308
 309       # They work by pair: each time an AU macro is activated, it runs
 310       # _au_enable, and at its end its runs _au_disable (see _au_defun
 311       # above).  AU macros might use AU macros, which should
 312       # enable/disable only for the outer AU macros.
 313       #
 314       # `_au_enabled' is used to this end, determining whether we really
 315       # enable/disable.
 316
 317
 318       # __au_enable
 319       # -----------
 320       # Reenable the builtins, m4sugar, and the autoquoting AC macros.
 321       _au_m4_define([__au_enable],
 322       [_au__divert(-1)
 323       # Enable special characters.
 324       _au_m4_changecom([#])
 325
 326       _au__include([m4.m4])
 327       _au__include([ac.m4])
 328
 329       _au__divert(0)])
 330
 331       # _au_enable
 332       # ----------
 333       # Called at the beginning of all the obsolete macros.  If this is the
 334       # outermost level, call __au_enable.
 335       _au_m4_define([_au_enable],
 336       [_au_m4_ifdef([_au_enabled],
 337                  [],
 338                  [__au_enable()])_au_dnl
 339       _au_m4_pushdef([_au_enabled])])
 340
 341
 342       # __au_disable
 343       # ------------
 344       # Disable the AC autoquoting macros, m4sugar, and m4.
 345       _au_m4_define([__au_disable],
 346       [_au__divert(-1)
 347       _au__include([unac.m4])
 348       _au__include([unm4.m4])
 349
 350       # Disable special characters.
 351       _au_m4_changequote()
 352       _au_m4_changecom()
 353
 354       _au__divert(0)])
 355
 356       # _au_disable
 357       # -----------
 358       # Called at the end of all the obsolete macros.  If we are at the
 359       # outermost level, call __au_disable.
 360       _au_m4_define([_au_disable],
 361       [_au_m4_popdef([_au_enabled])_au_dnl
 362       _au_m4_ifdef([_au_enabled],
 363                 [],
 364                 [__au_disable()])])
 365
 366
 367       ## ------------------------------- ##
 368       ## Disable, and process the file.  ##
 369       ## ------------------------------- ##
 370       # The AC autoquoting macros are not loaded yet, hence invoking
 371       # `_au_disable' would be wrong.
 372       _au__include([unm4.m4])
 373
 374       # Disable special characters, and set the first line number.
 375       _au_m4_changequote()
 376       _au_m4_changecom()
 377
 378       _au_m4_define(_au__first_line, _au___line__)_au__divert(0)_au_dnl
 379 EOF
 380
 381     $input_m4 =~ s/^      //mg;
 382     $input_m4 =~ s/\$file/$file/g;
 383
 384     # prepared input -- input, but reenables the quote before each AU macro.
 385     open INPUT_M4, "> " . open_quote ("$tmp/input.m4")
 386        or error "cannot open: $!";
 387     open FILE, "< " . open_quote ($file)
 388        or error "cannot open: $!";
 389     print INPUT_M4 "$input_m4";
 390     while (<FILE>)
 391        {
 392          eval $au_changequote;
 393          print INPUT_M4;
 394        }
 395     close FILE
 396        or error "cannot close $file: $!";
 397     close INPUT_M4
 398        or error "cannot close $tmp/input.m4: $!";
 399
 400     # Now ask m4 to perform the update.
 401     xsystem ("$m4 --include=" . shell_quote ($tmp)
 402              . join (' --include=', '', map { shell_quote ($_) } reverse (@prepend_include))
 403              . join (' --include=', '', map { shell_quote ($_) } @include)
 404              . " " . shell_quote ("$tmp/input.m4") . " > " . shell_quote ("$tmp/updated"));
 405     update_file ("$tmp/updated",
 406                  "$file" eq "$tmp/stdin" ? '-' : "$file");
 407   }
 408 exit 0;
 409
 410
 411 #                 ## ---------------------------- ##
 412 #                 ## How `autoupdate' functions.  ##
 413 #                 ## ---------------------------- ##
 414 #
 415 # The task of `autoupdate' is not trivial: the biggest difficulty being
 416 # that you must limit the changes to the parts that really need to be
 417 # updated.  Finding a satisfying implementation proved to be quite hard,
 418 # as this is the fifth implementation of `autoupdate'.
 419 #
 420 # Below, we will use a simple example of an obsolete macro:
 421 #
 422 #     AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])
 423 #     AC_DEFUN([NEW], [echo "sum($1) = $2"])
 424 #
 425 # the input file contains
 426 #
 427 #     dnl The Unbelievable Truth
 428 #     OLD(1, 2)
 429 #     NEW([0, 0], [0])
 430 #
 431 # Of course the expected output is
 432 #
 433 #     dnl The Unbelievable Truth
 434 #     NEW([1, 2], [3])
 435 #     NEW([0, 0], [0])
 436 #
 437 #
 438 # # First implementation: sed
 439 # # =========================
 440 #
 441 # The first implementation was only able to change the name of obsolete
 442 # macros.
 443 #
 444 # The file `acoldnames.m4' defined the old names based on the new names.
 445 # It was simple then to produce a sed script such as:
 446 #
 447 #     s/OLD/NEW/g
 448 #
 449 # Updating merely consisted in running this script on the file to
 450 # update.
 451 #
 452 # This scheme suffers from an obvious limitation: that `autoupdate' was
 453 # unable to cope with new macros that just swap some of its arguments
 454 # compared to the old macro.  Fortunately, that was enough to upgrade
 455 # from Autoconf 1 to Autoconf 2.  (But I have no idea whether the
 456 # changes in Autoconf 2 were precisely limited by this constraint.)
 457 #
 458 #
 459 # # Second implementation: hooks
 460 # # ============================
 461 #
 462 # The version 2.15 of Autoconf brought a vast number of changes compared
 463 # to 2.13, so a solution was needed.  One could think of extending the
 464 # `sed' scripts with specialized code for complex macros.  However, this
 465 # approach is of course full of flaws:
 466 #
 467 # a. the Autoconf maintainers have to write these snippets, which we
 468 #    just don't want to,
 469 #
 470 # b. I really don't think you'll ever manage to handle the quoting of
 471 #    m4 with a sed script.
 472 #
 473 # To satisfy a., let's remark that the code which implements the old
 474 # features in term of the new feature is exactly the code which should
 475 # replace the old code.
 476 #
 477 # To answer point b, as usual in the history of Autoconf, the answer, at
 478 # least on the paper, is simple: m4 is the best tool to parse m4, so
 479 # let's use m4.
 480 #
 481 # Therefore the specification is:
 482 #
 483 #     I want to be able to tell Autoconf, well, m4, that the macro I
 484 #     am currently defining is an obsolete macro (so that the user is
 485 #     warned), and its code is the code to use when running autoconf,
 486 #     but that the very same code has to be used when running
 487 #     autoupdate.  To summarize, the interface I want is
 488 #     `AU_DEFUN(OLD-NAME, NEW-CODE)'.
 489 #
 490 #
 491 # Now for the technical details.
 492 #
 493 # When running autoconf, except for the warning, AU_DEFUN is basically
 494 # AC_DEFUN.
 495 #
 496 # When running autoupdate, we want *only* OLD-NAMEs to be expanded.
 497 # This obviously means that acgeneral.m4 and acspecific.m4 must not be
 498 # loaded.  Nonetheless, because we want to use a rich set of m4
 499 # features, m4sugar.m4 is needed.  Please note that the fact that
 500 # Autoconf's macros are not loaded is positive on two points:
 501 #
 502 # - we do get an updated `configure.ac', not a `configure'!
 503 #
 504 # - the old macros are replaced by *calls* to the new-macros, not the
 505 #   body of the new macros, since their body is not defined!!!
 506 #   (Whoa, that's really beautiful!).
 507 #
 508 # Additionally we need to disable the quotes when reading the input for
 509 # two reasons: first because otherwise `m4' will swallow the quotes of
 510 # other macros:
 511 #
 512 #     NEW([1, 2], 3)
 513 #     => NEW(1, 2, 3)
 514 #
 515 # and second, because we want to update the macro calls which are
 516 # quoted, i.e., we want
 517 #
 518 #     FOO([OLD(1, 2)])
 519 #     => FOO([NEW([1, 2], [3])])
 520 #
 521 # If we don't disable the quotes, only the macros called at the top
 522 # level would be updated.
 523 #
 524 # So, let's disable the quotes.
 525 #
 526 # Well, not quite: m4sugar.m4 still needs to use quotes for some macros.
 527 # Well, in this case, when running in autoupdate code, each macro first
 528 # reestablishes the quotes, expands itself, and disables the quotes.
 529 #
 530 # Thinking a bit more, you realize that in fact, people may use `define',
 531 # `ifelse' etc. in their files, and you certainly don't want to process
 532 # them.  Another example is `dnl': you don't want to remove the
 533 # comments.  You then realize you don't want exactly to import m4sugar:
 534 # you want to specify when it is enabled (macros active), and disabled.
 535 # m4sugar provides m4_disable/m4_enable to this end.
 536 #
 537 # You're getting close to it.  Now remains one task: how to handle
 538 # twofold definitions?
 539 #
 540 # Remember that the same AU_DEFUN must be understood in two different
 541 # ways, the AC way, and the AU way.
 542 #
 543 # One first solution is to check whether acgeneral.m4 was loaded.  But
 544 # that's definitely not cute.  Another is simply to install `hooks',
 545 # that is to say, to keep in some place m4 knows, late `define' to be
 546 # triggered *only* in AU mode.
 547 #
 548 # You first think of designing AU_DEFUN like this:
 549 #
 550 # 1. AC_DEFUN(OLD-NAME,
 551 #             [Warn the user OLD-NAME is obsolete.
 552 #              NEW-CODE])
 553 #
 554 # 2. Store for late AU binding([define(OLD_NAME,
 555 #                               [Reestablish the quotes.
 556 #                                NEW-CODE
 557 #                                Disable the quotes.])])
 558 #
 559 # but this will not work: NEW-CODE probably uses $1, $2 etc. and these
 560 # guys will be replaced with the argument of `Store for late AU binding'
 561 # when you call it.
 562 #
 563 # I don't think there is a means to avoid this using this technology
 564 # (remember that $1 etc. are *always* expanded in m4).  You may also try
 565 # to replace them with $[1] to preserve them for a later evaluation, but
 566 # if `Store for late AU binding' is properly written, it will remain
 567 # quoted till the end...
 568 #
 569 # You have to change technology.  Since the problem is that `$1'
 570 # etc. should be `consumed' right away, one solution is to define now a
 571 # second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME
 572 # to AU_OLD-NAME.  Then, autoupdate.m4 just need to run the hooks.  By
 573 # the way, the same method was used in autoheader.
 574 #
 575 #
 576 # # Third implementation: m4 namespaces by m4sugar
 577 # # ==============================================
 578 #
 579 # Actually, this implementation was just a clean up of the previous
 580 # implementation: instead of defining hooks by hand, m4sugar was equipped
 581 # with `namespaces'.  What are they?
 582 #
 583 # Sometimes we want to disable some *set* of macros, and restore them
 584 # later.  We provide support for this via namespaces.
 585 #
 586 # There are basically three characters playing this scene: defining a
 587 # macro in a namespace, disabling a namespace, and restoring a namespace
 588 # (i.e., all the definitions it holds).
 589 #
 590 # Technically, to define a MACRO in NAMESPACE means to define the macro
 591 # named `NAMESPACE::MACRO' to the VALUE.  At the same time, we append
 592 # `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and
 593 # similarly a binding of NAME to the value of `NAMESPACE::MACRO' in
 594 # `m4_enable(NAMESPACE)'.  These mechanisms allow to bind the macro of
 595 # NAMESPACE and to unbind them at will.
 596 #
 597 # Of course this implementation is really inefficient: m4 has to grow
 598 # strings which can become quickly huge, which slows it significantly.
 599 #
 600 # In particular one should avoid as much as possible to use `define' for
 601 # temporaries.  Now that `define' has quite a complex meaning, it is an
 602 # expensive operations that should be limited to macros.  Use
 603 # `m4_define' for temporaries.
 604 #
 605 # Private copies of the macros we used in entering / exiting the m4sugar
 606 # namespace.  It is much more convenient than fighting with the renamed
 607 # version of define etc.
 608 #
 609 #
 610 #
 611 # Those two implementations suffered from serious problems:
 612 #
 613 # - namespaces were really expensive, and incurred a major performance
 614 #   loss on `autoconf' itself, not only `autoupdate'.  One solution
 615 #   would have been the limit the use of namespaces to `autoupdate', but
 616 #   that's again some complications on m4sugar, which really doesn't need
 617 #   this.  So we wanted to get rid of the namespaces.
 618 #
 619 # - since the quotes were disabled, autoupdate was sometimes making
 620 #   wrong guesses, for instance on:
 621 #
 622 #     foo([1, 2])
 623 #
 624 #   m4 saw 2 arguments: `[1'and `2]'.  A simple solution, somewhat
 625 #   fragile, is to reestablish the quotes right before all the obsolete
 626 #   macros, i.e., to use sed so that the previous text becomes
 627 #
 628 #     changequote([, ])foo([1, 2])
 629 #
 630 #   To this end, one wants to trace the definition of obsolete macros.
 631 #
 632 # It was there that the limitations of the namespace approach became
 633 # painful: because it was a complex machinery playing a lot with the
 634 # builtins of m4 (hence, quite fragile), tracing was almost impossible.
 635 #
 636 #
 637 # So this approach was dropped.
 638 #
 639 #
 640 # # The fourth implementation: two steps
 641 # # ====================================
 642 #
 643 # If you drop the uses of namespaces, you no longer can compute the
 644 # updated value, and replace the old call with it simultaneously.
 645 #
 646 # Obviously you will use m4 to compute the updated values, but you may
 647 # use some other tool to achieve the replacement.  Personally, I trust
 648 # nobody but m4 to parse m4, so below, m4 will perform the two tasks.
 649 #
 650 # How can m4 be used to replace *some* macros calls with newer values.
 651 # Well, that's dead simple: m4 should learn the definitions of obsolete
 652 # macros, forget its builtins, disable the quotes, and then run on the
 653 # input file, which amounts to doing this:
 654 #
 655 #     divert(-1)dnl
 656 #     changequote([, ])
 657 #     define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
 658 #     undefine([dnl])
 659 #     undefine([m4_eval])
 660 #     # Some more undefines...
 661 #     changequote()
 662 #     divert(0)dnl
 663 #     dnl The Unbelievable Truth
 664 #     changequote([, ])OLD(1, 2)
 665 #     NEW([0, 0],
 666 #         0)
 667 #
 668 # which will result in
 669 #
 670 #     dnl The Unbelievable Truth
 671 #     NEW(1, 2, m4_eval(1 + 2))
 672 #     NEW([0, 0],
 673 #         0)
 674 #
 675 # Grpmh.  Two problems.  A minor problem: it would have been much better
 676 # to have the `m4_eval' computed, and a major problem: you lost the
 677 # quotation in the result.
 678 #
 679 # Let's address the big problem first.  One solution is to define any
 680 # modern macro to rewrite its calls with the proper quotation, thanks to
 681 # `$@'.  Again, tracing the `define's makes it possible to know which
 682 # are these macros, so you input is:
 683 #
 684 #     divert(-1)dnl
 685 #     changequote([, ])
 686 #     define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])
 687 #     define([NEW], [[NEW($@)]changequote()])
 688 #     undefine([dnl])
 689 #     undefine([m4_eval])
 690 #     # Some more undefines...
 691 #     changequote()
 692 #     divert(0)dnl
 693 #     dnl The Unbelievable Truth
 694 #     changequote([, ])OLD(1, 2)
 695 #     changequote([, ])NEW([0, 0],
 696 #         0)
 697 #
 698 # which results in
 699 #
 700 #     dnl The Unbelievable Truth
 701 #     NEW([1, 2],[m4_eval(1 + 2)])
 702 #     NEW([0, 0],[0])
 703 #
 704 # Our problem is solved, i.e., the first call to `NEW' is properly
 705 # quoted, but introduced another problem: we changed the layout of the
 706 # second calls, which can be a drama in the case of huge macro calls
 707 # (think of `AC_TRY_RUN' for instance).  This example didn't show it,
 708 # but we also introduced parens to macros which did not have some:
 709 #
 710 #     AC_INIT
 711 #     => AC_INIT()
 712 #
 713 # No big deal for the semantics (unless the macro depends upon $#, which
 714 # is bad), but the users would not be happy.
 715 #
 716 # Additionally, we introduced quotes that were not there before, which is
 717 # OK in most cases, but could change the semantics of the file.
 718 #
 719 # Cruel dilemma: we do want the auto-quoting definition of `NEW' when
 720 # evaluating `OLD', but we don't when we evaluate the second `NEW'.
 721 # Back to namespaces?
 722 #
 723 # No.
 724 #
 725 #
 726 # # Second step: replacement
 727 # # ------------------------
 728 #
 729 # No, as announced above, we will work in two steps: in a first step we
 730 # compute the updated values, and in a second step we replace them.  Our
 731 # goal is something like this:
 732 #
 733 #     divert(-1)dnl
 734 #     changequote([, ])
 735 #     define([OLD], [NEW([1, 2], [3])changequote()])
 736 #     undefine([dnl])
 737 #     undefine([m4_eval])
 738 #     # Some more undefines...
 739 #     changequote()
 740 #     divert(0)dnl
 741 #     dnl The Unbelievable Truth
 742 #     changequote([, ])OLD(1, 2)
 743 #     NEW([0, 0],
 744 #         0)
 745 #
 746 # i.e., the new value of `OLD' is precomputed using the auto-quoting
 747 # definition of `NEW' and the m4 builtins.  We'll see how afterwards,
 748 # let's finish with the replacement.
 749 #
 750 # Of course the solution above is wrong: if there were other calls to
 751 # `OLD' with different values, we would smash them to the same value.
 752 # But it is quite easy to generalize the scheme above:
 753 #
 754 #     divert(-1)dnl
 755 #     changequote([, ])
 756 #     define([OLD([1],[2])], [NEW([1, 2], [3])])
 757 #     define([OLD], [defn([OLD($@)])changequote()])
 758 #     undefine([dnl])
 759 #     undefine([m4_eval])
 760 #     # Some more undefines...
 761 #     changequote()
 762 #     divert(0)dnl
 763 #     dnl The Unbelievable Truth
 764 #     changequote([, ])OLD(1, 2)
 765 #     NEW([0, 0],
 766 #         0)
 767 #
 768 # i.e., for each call to obsolete macros, we build an array `call =>
 769 # value', and use a macro to dispatch these values.  This results in:
 770 #
 771 #     dnl The Unbelievable Truth
 772 #     NEW([1, 2], [3])
 773 #     NEW([0, 0],
 774 #         0)
 775 #
 776 # In French, we say `Youpi !', which you might roughly translate as
 777 # `Yippee!'.
 778 #
 779 #
 780 # # First step: computation
 781 # # -----------------------
 782 #
 783 # Let's study the anatomy of the file, and name its sections:
 784 #
 785 # prologue
 786 #     divert(-1)dnl
 787 #     changequote([, ])
 788 # values
 789 #     define([OLD([1],[2])], [NEW([1, 2], [3])])
 790 # dispatcher
 791 #     define([OLD], [defn([OLD($@)])changequote()])
 792 # disabler
 793 #     undefine([dnl])
 794 #     undefine([m4_eval])
 795 #     # Some more undefines...
 796 #     changequote()
 797 #     divert(0)dnl
 798 # input
 799 #     dnl The Unbelievable Truth
 800 #     changequote([, ])OLD(1, 2)
 801 #     NEW([0, 0],
 802 #         0)
 803 #
 804 #
 805 # # Computing the `values' section
 806 # # ..............................
 807 #
 808 # First we need to get the list of all the AU macro uses.  To this end,
 809 # first get the list of all the AU macros names by tracing `AU_DEFUN' in
 810 # the initialization of autoconf.  This list is computed in the file
 811 # `au.txt' below.
 812 #
 813 # Then use this list to trace all the AU macro uses in the input.  The
 814 # goal is obtain in the case of our example:
 815 #
 816 #     [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
 817 #
 818 # This is the file `values.in' below.
 819 #
 820 # We want to evaluate this with only the builtins (in fact m4sugar), the
 821 # auto-quoting definitions of the new macros (`new.m4'), and the
 822 # definition of the old macros (`old.m4').  Computing these last two
 823 # files is easy: it's just a matter of using the right `--trace' option.
 824 #
 825 # So the content of `values.in' is:
 826 #
 827 #     include($autoconf_dir/m4sugar.m4)
 828 #     m4_include(new.m4)
 829 #     m4_include(old.m4)
 830 #     divert(0)dnl
 831 #     [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]
 832 #
 833 # We run m4 on it, which yields:
 834 #
 835 #     define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)
 836 #
 837 # Transform `@<<@' and `@>>@' into quotes and we get
 838 #
 839 #     define([OLD([1],[2])],[NEW([1, 2], [3])])
 840 #
 841 # This is `values.m4'.
 842 #
 843 #
 844 # # Computing the `dispatcher' section
 845 # # ..................................
 846 #
 847 # The `prologue', and the `disabler' are simple and need no commenting.
 848 #
 849 # To compute the `dispatcher' (`dispatch.m4'), again, it is a simple
 850 # matter of using the right `--trace'.
 851 #
 852 # Finally, the input is not exactly the input file, rather it is the
 853 # input file with the added `changequote'.  To this end, we build
 854 # `quote.sed'.
 855 #
 856 #
 857 # # Putting it all together
 858 # # .......................
 859 #
 860 # We build the file `input.m4' which contains:
 861 #
 862 #     divert(-1)dnl
 863 #     changequote([, ])
 864 #     include(values.m4)
 865 #     include(dispatch.m4)
 866 #     undefine([dnl])
 867 #     undefine([eval])
 868 #     # Some more undefines...
 869 #     changequote()
 870 #     divert(0)dnl
 871 #     dnl The Unbelievable Truth
 872 #     changequote([, ])OLD(1, 2)
 873 #     NEW([0, 0],
 874 #         0)
 875 #
 876 # And we just run m4 on it.  Et voila`, Monsieur !  Mais oui, mais oui.
 877 #
 878 # Well, there are a few additional technicalities.  For instance, we
 879 # rely on `changequote', `ifelse' and `defn', but we don't want to
 880 # interpret the changequotes of the user, so we simply use another name:
 881 # `_au_changequote' etc.
 882 #
 883 #
 884 # # Failure of the fourth approach
 885 # # ------------------------------
 886 #
 887 # This approach is heavily based on traces, but then there is an obvious
 888 # problem: non expanded code will never be seen.  In particular, the body
 889 # of a `define' definition is not seen, so on the input
 890 #
 891 #         define([idem], [OLD(0, [$1])])
 892 #
 893 # autoupdate would never see the `OLD', and wouldn't have updated it.
 894 # Worse yet, if `idem(0)' was used later, then autoupdate sees that
 895 # `OLD' is used, computes the result for `OLD(0, 0)' and sets up a
 896 # dispatcher for `OLD'.  Since there was no computed value for `OLD(0,
 897 # [$1])', the dispatcher would have replaced with... nothing, leading
 898 # to
 899 #
 900 #         define([idem], [])
 901 #
 902 # With some more thinking, you see that the two step approach is wrong,
 903 # the namespace approach was much saner.
 904 #
 905 # But you learned a lot, in particular you realized that using traces
 906 # can make it possible to simulate namespaces!
 907 #
 908 #
 909 #
 910 # # The fifth implementation: m4 namespaces by files
 911 # # ================================================
 912 #
 913 # The fourth implementation demonstrated something unsurprising: you
 914 # cannot precompute, i.e., the namespace approach was the right one.
 915 # Still, we no longer want them, they're too expensive.  Let's have a
 916 # look at the way it worked.
 917 #
 918 # When updating
 919 #
 920 #     dnl The Unbelievable Truth
 921 #     OLD(1, 2)
 922 #     NEW([0, 0], [0])
 923 #
 924 # you evaluate `input.m4':
 925 #
 926 #     divert(-1)
 927 #     changequote([, ])
 928 #     define([OLD],
 929 #     [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
 930 #     ...
 931 #     m4_disable()
 932 #     dnl The Unbelievable Truth
 933 #     OLD(1, 2)
 934 #     NEW([0, 0], [0])
 935 #
 936 # where `m4_disable' undefines the m4 and m4sugar, and disables the quotes
 937 # and comments:
 938 #
 939 #     define([m4_disable],
 940 #     [undefine([__file__])
 941 #     ...
 942 #     changecom(#)
 943 #     changequote()])
 944 #
 945 # `m4_enable' does the converse: reestablish quotes and comments
 946 # --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and
 947 # reenable the builtins.  This later task requires that you first save
 948 # the builtins.  And BTW, the definition above of `m4_disable' cannot
 949 # work: you undefined `changequote' before using it!  So you need to use
 950 # your privates copies of the builtins.  Let's introduce three files for
 951 # this:
 952 #
 953 #  `m4save.m4'
 954 #    moves the m4 builtins into the `_au_' pseudo namespace,
 955 #  `unm4.m4'
 956 #    undefines the builtins,
 957 #  `m4.m4'
 958 #    restores them.
 959 #
 960 # So `input.m4' is:
 961 #
 962 #     divert(-1)
 963 #     changequote([, ])
 964 #
 965 #     include([m4save.m4])
 966 #
 967 #     # Import AU.
 968 #     define([OLD],
 969 #     [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])
 970 #
 971 #     define([_au_enable],
 972 #     [_au_changecom([#])
 973 #     _au_include([m4.m4])
 974 #     _au_include(m4sugar.m4)])
 975 #
 976 #     define([_au_disable],
 977 #     [# Disable m4sugar.
 978 #     # Disable the m4 builtins.
 979 #     _au_include([unm4.m4])
 980 #     # 1. Disable special characters.
 981 #     _au_changequote()
 982 #     _au_changecom()])
 983 #
 984 #     m4_disable()
 985 #     dnl The Unbelievable Truth
 986 #     OLD(1, 2)
 987 #     NEW([0, 0], [0])
 988 #
 989 # Based on what we learned in the fourth implementation we know that we
 990 # have to enable the quotes *before* any AU macro, and we know we need
 991 # to build autoquoting versions of the AC macros.  But the autoquoting
 992 # AC definitions must be disabled in the rest of the file, and enabled
 993 # inside AU macros.
 994 #
 995 # Using `autoconf --trace' it is easy to build the files
 996 #
 997 #   `ac.m4'
 998 #     define the autoquoting AC fake macros
 999 #   `disable.m4'
1000 #     undefine the m4sugar and AC autoquoting macros.
1001 #   `au.m4'
1002 #     definitions of the AU macros (such as `OLD' above).
1003 #
1004 # Now, `input.m4' is:
1005 #
1006 #     divert(-1)
1007 #     changequote([, ])
1008 #
1009 #     include([m4save.m4])
1010 #     # Import AU.
1011 #     include([au.m4])
1012 #
1013 #     define([_au_enable],
1014 #     [_au_changecom([#])
1015 #     _au_include([m4.m4])
1016 #     _au_include(m4sugar.m4)
1017 #     _au_include(ac.m4)])
1018 #
1019 #     define([_au_disable],
1020 #     [_au_include([disable.m4])
1021 #     _au_include([unm4.m4])
1022 #     # 1. Disable special characters.
1023 #     _au_changequote()
1024 #     _au_changecom()])
1025 #
1026 #     m4_disable()
1027 #     dnl The Unbelievable Truth
1028 #     _au_changequote([, ])OLD(1, 2)
1029 #     NEW([0, 0], [0])
1030 #
1031 # Finally, version V is ready.
1032 #
1033 # Well... almost.
1034 #
1035 # There is a slight problem that remains: if an AU macro OUTER includes
1036 # an AU macro INNER, then _au_enable will be run when entering OUTER
1037 # and when entering INNER (not good, but not too bad yet).  But when
1038 # getting out of INNER, _au_disable will disable everything while we
1039 # were still in OUTER.  Badaboom.
1040 #
1041 # Therefore _au_enable and _au_disable have to be written to work by
1042 # pairs: each _au_enable pushdef's _au_enabled, and each _au_disable
1043 # popdef's _au_enabled.  And of course _au_enable and _au_disable are
1044 # effective when _au_enabled is *not* defined.
1045 #
1046 # Finally, version V' is ready.  And there is much rejoicing.  (And I
1047 # have free time again.  I think.  Yeah, right.)
1048
1049 ### Setup "GNU" style for perl-mode and cperl-mode.
1050 ## Local Variables:
1051 ## perl-indent-level: 2
1052 ## perl-continued-statement-offset: 2
1053 ## perl-continued-brace-offset: 0
1054 ## perl-brace-offset: 0
1055 ## perl-brace-imaginary-offset: 0
1056 ## perl-label-offset: -2
1057 ## cperl-indent-level: 2
1058 ## cperl-brace-offset: 0
1059 ## cperl-continued-brace-offset: 0
1060 ## cperl-label-offset: -2
1061 ## cperl-extra-newline-before-brace: t
1062 ## cperl-merge-trailing-else: nil
1063 ## cperl-continued-statement-offset: 2
1064 ## End: