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 25eval 'case $# in 0) exec /usr/bin/perl -S "$0";; *) exec /usr/bin/perl -S "$0" "$@";; esac' 26 if 0; 27 28BEGIN 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 40use Autom4te::ChannelDefs; 41use Autom4te::Channels; 42use Autom4te::Configure_ac; 43use Autom4te::FileUtils; 44use Autom4te::General; 45use Autom4te::XFile; 46use File::Basename; 47use strict; 48 49# Lib files. 50my $autom4te = $ENV{'AUTOM4TE'} || '/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/bin/autom4te'; 51my $autoconf = "$autom4te --language=autoconf"; 52# We need to find m4sugar. 53my @prepend_include; 54my @include = ('/projects/hnd/tools/linux/hndtools-arm-linux-2.6.36-uclibc-4.5.3/share/autoconf'); 55my $force = 0; 56# m4. 57my $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 64Update each TEMPLATE-FILE if given, or `configure.ac' if present, 65or else `configure.in', to the syntax of the current version of 66Autoconf. The original files are backed up. 67 68Operation 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 75Library directories: 76 -B, --prepend-include=DIR prepend directory DIR to search path 77 -I, --include=DIR append directory DIR to search path 78 79Report bugs to <bug-autoconf\@gnu.org>. 80GNU Autoconf home page: <http://www.gnu.org/software/autoconf/>. 81General help using GNU software: <http://www.gnu.org/gethelp/>. 82"; 83 84# $VERSION 85# -------- 86$version = "autoupdate (GNU Autoconf) 2.65 87Copyright (C) 2009 Free Software Foundation, Inc. 88License GPLv3+/Autoconf: GNU GPL version 3 or later 89<http://gnu.org/licenses/gpl.html>, <http://gnu.org/licenses/exceptions.html> 90This is free software: you are free to change and redistribute it. 91There is NO WARRANTY, to the extent permitted by law. 92 93Written 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. 104sub 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 125my (%ac_macros, %au_macros, %m4_builtins); 126 127# HANDLE_AUTOCONF_MACROS () 128# ------------------------- 129# @M4_BUILTINS -- M4 builtins and a useful comment. 130sub 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 222parse_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 229mktmpdir ('au'); 230handle_autoconf_macros; 231 232# $au_changequote -- enable the quote `[', `]' right before any AU macro. 233my $au_changequote = 234 's/\b(' . join ('|', keys %au_macros) . ')\b/_au_m4_changequote([,])$1/g'; 235 236# au.m4 -- definitions the AU macros. 237xsystem ("$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 247foreach 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 379EOF 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 } 408exit 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: 1065