autoupdate.in revision 1.1.1.1
1#! @PERL@ -w 2# -*- perl -*- 3# @configure_input@ 4 5# autoupdate - modernize an Autoconf file. 6# Copyright (C) 1994, 1999-2012 Free Software Foundation, Inc. 7 8# This program is free software: you can redistribute it and/or modify 9# it under the terms of the GNU General Public License as published by 10# the Free Software Foundation, either version 3 of the License, or 11# (at your option) any later version. 12 13# This program is distributed in the hope that it will be useful, 14# but WITHOUT ANY WARRANTY; without even the implied warranty of 15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16# GNU General Public License for more details. 17 18# You should have received a copy of the GNU General Public License 19# along with this program. If not, see <http://www.gnu.org/licenses/>. 20 21# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>. 22# Rewritten by Akim Demaille <akim@freefriends.org>. 23 24eval 'case $# in 0) exec @PERL@ -S "$0";; *) exec @PERL@ -S "$0" "$@";; esac' 25 if 0; 26 27BEGIN 28{ 29 my $pkgdatadir = $ENV{'autom4te_perllibdir'} || '@pkgdatadir@'; 30 unshift @INC, $pkgdatadir; 31 32 # Override SHELL. On DJGPP SHELL may not be set to a shell 33 # that can handle redirection and quote arguments correctly, 34 # e.g.: COMMAND.COM. For DJGPP always use the shell that configure 35 # has detected. 36 $ENV{'SHELL'} = '@SHELL@' if ($^O eq 'dos'); 37} 38 39use Autom4te::ChannelDefs; 40use Autom4te::Channels; 41use Autom4te::Configure_ac; 42use Autom4te::FileUtils; 43use Autom4te::General; 44use Autom4te::XFile; 45use File::Basename; 46use strict; 47 48# Lib files. 49my $autom4te = $ENV{'AUTOM4TE'} || '@bindir@/@autom4te-name@'; 50my $autoconf = "$autom4te --language=autoconf"; 51# We need to find m4sugar. 52my @prepend_include; 53my @include = ('@pkgdatadir@'); 54my $force = 0; 55# m4. 56my $m4 = $ENV{"M4"} || '@M4@'; 57 58 59# $HELP 60# ----- 61$help = "Usage: $0 [OPTION]... [TEMPLATE-FILE]... 62 63Update each TEMPLATE-FILE if given, or `configure.ac' if present, 64or else `configure.in', to the syntax of the current version of 65Autoconf. The original files are backed up. 66 67Operation modes: 68 -h, --help print this help, then exit 69 -V, --version print version number, then exit 70 -v, --verbose verbosely report processing 71 -d, --debug don't remove temporary files 72 -f, --force consider all files obsolete 73 74Library directories: 75 -B, --prepend-include=DIR prepend directory DIR to search path 76 -I, --include=DIR append directory DIR to search path 77 78Report bugs to <bug-autoconf\@gnu.org>. 79GNU Autoconf home page: <http://www.gnu.org/software/autoconf/>. 80General help using GNU software: <http://www.gnu.org/gethelp/>. 81"; 82 83# $VERSION 84# -------- 85$version = "autoupdate (@PACKAGE_NAME@) @VERSION@ 86Copyright (C) @RELEASE_YEAR@ Free Software Foundation, Inc. 87License GPLv3+/Autoconf: GNU GPL version 3 or later 88<http://gnu.org/licenses/gpl.html>, <http://gnu.org/licenses/exceptions.html> 89This is free software: you are free to change and redistribute it. 90There is NO WARRANTY, to the extent permitted by law. 91 92Written by David J. MacKenzie and Akim Demaille. 93"; 94 95## ---------- ## 96## Routines. ## 97## ---------- ## 98 99 100# parse_args () 101# ------------- 102# Process any command line arguments. 103sub parse_args () 104{ 105 my $srcdir; 106 107 getopt ('I|include=s' => \@include, 108 'B|prepend-include=s' => \@prepend_include, 109 'f|force' => \$force); 110 111 if (! @ARGV) 112 { 113 my $configure_ac = require_configure_ac; 114 push @ARGV, $configure_ac; 115 } 116} 117 118 119 120# ----------------- # 121# Autoconf macros. # 122# ----------------- # 123 124my (%ac_macros, %au_macros, %m4_builtins); 125 126# HANDLE_AUTOCONF_MACROS () 127# ------------------------- 128# @M4_BUILTINS -- M4 builtins and a useful comment. 129sub handle_autoconf_macros () 130{ 131 # Get the builtins. 132 xsystem ("echo dumpdef | $m4 2>" . shell_quote ("$tmp/m4.defs") . " >/dev/null"); 133 my $m4_defs = new Autom4te::XFile "< " . open_quote ("$tmp/m4.defs"); 134 while ($_ = $m4_defs->getline) 135 { 136 $m4_builtins{$1} = 1 137 if /^(\w+):/; 138 } 139 $m4_defs->close; 140 141 my $macros = new Autom4te::XFile ("$autoconf" 142 . " --trace AU_DEFINE:'AU:\$f:\$1'" 143 . " --trace define:'AC:\$f:\$1'" 144 . " --melt /dev/null |"); 145 while ($_ = $macros->getline) 146 { 147 chomp; 148 my ($domain, $file, $macro) = /^(AC|AU):(.*):([^:]*)$/ or next; 149 if ($domain eq "AU") 150 { 151 $au_macros{$macro} = 1; 152 } 153 elsif ($file =~ /(^|\/)m4sugar\/(m4sugar|version)\.m4$/) 154 { 155 # Add the m4sugar macros to m4_builtins. 156 $m4_builtins{$macro} = 1; 157 } 158 else 159 { 160 # Autoconf, aclocal, and m4sh macros. 161 $ac_macros{$macro} = 1; 162 } 163 } 164 $macros->close; 165 166 167 # Don't keep AU macros in @AC_MACROS. 168 delete $ac_macros{$_} 169 foreach (keys %au_macros); 170 # Don't keep M4sugar macros which are redefined by Autoconf, 171 # such as `builtin', `changequote' etc. See autoconf/autoconf.m4. 172 delete $ac_macros{$_} 173 foreach (keys %m4_builtins); 174 error "no current Autoconf macros found" 175 unless keys %ac_macros; 176 error "no obsolete Autoconf macros found" 177 unless keys %au_macros; 178 179 if ($debug) 180 { 181 print STDERR "Current Autoconf macros:\n"; 182 print STDERR join (' ', sort keys %ac_macros) . "\n\n"; 183 print STDERR "Obsolete Autoconf macros:\n"; 184 print STDERR join (' ', sort keys %au_macros) . "\n\n"; 185 } 186 187 # ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded). 188 # unac.m4 -- undefine the AC macros. 189 my $ac_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/ac.m4"); 190 print $ac_m4 "# ac.m4 -- autoquoting definitions of the AC macros.\n"; 191 my $unac_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/unac.m4"); 192 print $unac_m4 "# unac.m4 -- undefine the AC macros.\n"; 193 foreach (sort keys %ac_macros) 194 { 195 print $ac_m4 "_au_m4_define([$_], [m4_if(\$#, 0, [[\$0]], [[\$0(\$\@)]])])\n"; 196 print $unac_m4 "_au_m4_undefine([$_])\n"; 197 } 198 199 # m4save.m4 -- save the m4 builtins. 200 # unm4.m4 -- disable the m4 builtins. 201 # m4.m4 -- enable the m4 builtins. 202 my $m4save_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/m4save.m4"); 203 print $m4save_m4 "# m4save.m4 -- save the m4 builtins.\n"; 204 my $unm4_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/unm4.m4"); 205 print $unm4_m4 "# unm4.m4 -- disable the m4 builtins.\n"; 206 my $m4_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/m4.m4"); 207 print $m4_m4 "# m4.m4 -- enable the m4 builtins.\n"; 208 foreach (sort keys %m4_builtins) 209 { 210 print $m4save_m4 "_au__save([$_])\n"; 211 print $unm4_m4 "_au__undefine([$_])\n"; 212 print $m4_m4 "_au__restore([$_])\n"; 213 } 214} 215 216 217## -------------- ## 218## Main program. ## 219## -------------- ## 220 221parse_args; 222$autoconf .= " --debug" if $debug; 223$autoconf .= " --force" if $force; 224$autoconf .= " --verbose" if $verbose; 225$autoconf .= join (' --include=', '', map { shell_quote ($_) } @include); 226$autoconf .= join (' --prepend-include=', '', map { shell_quote ($_) } @prepend_include); 227 228mktmpdir ('au'); 229handle_autoconf_macros; 230 231# $au_changequote -- enable the quote `[', `]' right before any AU macro. 232my $au_changequote = 233 's/\b(' . join ('|', keys %au_macros) . ')\b/_au_m4_changequote([,])$1/g'; 234 235# au.m4 -- definitions the AU macros. 236xsystem ("$autoconf --trace AU_DEFINE:'_au_defun(\@<:\@\$1\@:>\@, 237\@<:\@\$2\@:>\@)' --melt /dev/null " 238 . ">" . shell_quote ("$tmp/au.m4")); 239 240 241 242## ------------------- ## 243## Process the files. ## 244## ------------------- ## 245 246foreach my $file (@ARGV) 247 { 248 # We need an actual file. 249 if ($file eq '-') 250 { 251 $file = "$tmp/stdin"; 252 system "cat >" . shell_quote ($file); 253 } 254 elsif (! -r "$file") 255 { 256 die "$me: $file: No such file or directory"; 257 } 258 259 # input.m4 -- m4 program to produce the updated file. 260 # Load the values, the dispatcher, neutralize m4, and the prepared 261 # input file. 262 my $input_m4 = <<\EOF; 263 divert(-1) -*- Autoconf -*- 264 changequote([,]) 265 266 # Define our special macros: 267 define([_au__defn], defn([defn])) 268 define([_au__divert], defn([divert])) 269 define([_au__ifdef], defn([ifdef])) 270 define([_au__include], defn([include])) 271 define([_au___undefine], defn([undefine])) 272 define([_au__undefine], [_au__ifdef([$1], [_au___undefine([$1])])]) 273 define([_au__save], [m4_ifdef([$1], 274 [m4_define([_au_$1], _m4_defn([$1]))])]) 275 define([_au__restore], 276 [_au_m4_ifdef([_au_$1], 277 [_au_m4_define([$1], _au__defn([_au_$1]))])]) 278 279 # Set up m4sugar. 280 include(m4sugar/m4sugar.m4) 281 282 # Redefine __file__ to make warnings nicer; $file is replaced below. 283 m4_define([__file__], [$file]) 284 285 # Redefine m4_location to fix the line number. 286 m4_define([m4_location], [__file__:m4_eval(__line__ - _au__first_line)]) 287 288 # Move all the builtins into the `_au_' pseudo namespace 289 m4_include([m4save.m4]) 290 291 # _au_defun(NAME, BODY) 292 # --------------------- 293 # Define NAME to BODY, plus AU activation/deactivation. 294 _au_m4_define([_au_defun], 295 [_au_m4_define([$1], 296 [_au_enable()dnl 297 $2[]dnl 298 _au_disable()])]) 299 300 # Import the definition of the obsolete macros. 301 _au__include([au.m4]) 302 303 304 ## ------------------------ ## 305 ## _au_enable/_au_disable. ## 306 ## ------------------------ ## 307 308 # They work by pair: each time an AU macro is activated, it runs 309 # _au_enable, and at its end its runs _au_disable (see _au_defun 310 # above). AU macros might use AU macros, which should 311 # enable/disable only for the outer AU macros. 312 # 313 # `_au_enabled' is used to this end, determining whether we really 314 # enable/disable. 315 316 317 # __au_enable 318 # ----------- 319 # Reenable the builtins, m4sugar, and the autoquoting AC macros. 320 _au_m4_define([__au_enable], 321 [_au__divert(-1) 322 # Enable special characters. 323 _au_m4_changecom([#]) 324 325 _au__include([m4.m4]) 326 _au__include([ac.m4]) 327 328 _au__divert(0)]) 329 330 # _au_enable 331 # ---------- 332 # Called at the beginning of all the obsolete macros. If this is the 333 # outermost level, call __au_enable. 334 _au_m4_define([_au_enable], 335 [_au_m4_ifdef([_au_enabled], 336 [], 337 [__au_enable()])_au_dnl 338 _au_m4_pushdef([_au_enabled])]) 339 340 341 # __au_disable 342 # ------------ 343 # Disable the AC autoquoting macros, m4sugar, and m4. 344 _au_m4_define([__au_disable], 345 [_au__divert(-1) 346 _au__include([unac.m4]) 347 _au__include([unm4.m4]) 348 349 # Disable special characters. 350 _au_m4_changequote() 351 _au_m4_changecom() 352 353 _au__divert(0)]) 354 355 # _au_disable 356 # ----------- 357 # Called at the end of all the obsolete macros. If we are at the 358 # outermost level, call __au_disable. 359 _au_m4_define([_au_disable], 360 [_au_m4_popdef([_au_enabled])_au_dnl 361 _au_m4_ifdef([_au_enabled], 362 [], 363 [__au_disable()])]) 364 365 366 ## ------------------------------- ## 367 ## Disable, and process the file. ## 368 ## ------------------------------- ## 369 # The AC autoquoting macros are not loaded yet, hence invoking 370 # `_au_disable' would be wrong. 371 _au__include([unm4.m4]) 372 373 # Disable special characters, and set the first line number. 374 _au_m4_changequote() 375 _au_m4_changecom() 376 377 _au_m4_define(_au__first_line, _au___line__)_au__divert(0)_au_dnl 378EOF 379 380 $input_m4 =~ s/^ //mg; 381 $input_m4 =~ s/\$file/$file/g; 382 383 # prepared input -- input, but reenables the quote before each AU macro. 384 open INPUT_M4, "> " . open_quote ("$tmp/input.m4") 385 or error "cannot open: $!"; 386 open FILE, "< " . open_quote ($file) 387 or error "cannot open: $!"; 388 print INPUT_M4 "$input_m4"; 389 while (<FILE>) 390 { 391 eval $au_changequote; 392 print INPUT_M4; 393 } 394 close FILE 395 or error "cannot close $file: $!"; 396 close INPUT_M4 397 or error "cannot close $tmp/input.m4: $!"; 398 399 # Now ask m4 to perform the update. 400 xsystem ("$m4 --include=" . shell_quote ($tmp) 401 . join (' --include=', '', map { shell_quote ($_) } reverse (@prepend_include)) 402 . join (' --include=', '', map { shell_quote ($_) } @include) 403 . " " . shell_quote ("$tmp/input.m4") . " > " . shell_quote ("$tmp/updated")); 404 update_file ("$tmp/updated", 405 "$file" eq "$tmp/stdin" ? '-' : "$file"); 406 } 407exit 0; 408 409 410# ## ---------------------------- ## 411# ## How `autoupdate' functions. ## 412# ## ---------------------------- ## 413# 414# The task of `autoupdate' is not trivial: the biggest difficulty being 415# that you must limit the changes to the parts that really need to be 416# updated. Finding a satisfying implementation proved to be quite hard, 417# as this is the fifth implementation of `autoupdate'. 418# 419# Below, we will use a simple example of an obsolete macro: 420# 421# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))]) 422# AC_DEFUN([NEW], [echo "sum($1) = $2"]) 423# 424# the input file contains 425# 426# dnl The Unbelievable Truth 427# OLD(1, 2) 428# NEW([0, 0], [0]) 429# 430# Of course the expected output is 431# 432# dnl The Unbelievable Truth 433# NEW([1, 2], [3]) 434# NEW([0, 0], [0]) 435# 436# 437# # First implementation: sed 438# # ========================= 439# 440# The first implementation was only able to change the name of obsolete 441# macros. 442# 443# The file `acoldnames.m4' defined the old names based on the new names. 444# It was simple then to produce a sed script such as: 445# 446# s/OLD/NEW/g 447# 448# Updating merely consisted in running this script on the file to 449# update. 450# 451# This scheme suffers from an obvious limitation: that `autoupdate' was 452# unable to cope with new macros that just swap some of its arguments 453# compared to the old macro. Fortunately, that was enough to upgrade 454# from Autoconf 1 to Autoconf 2. (But I have no idea whether the 455# changes in Autoconf 2 were precisely limited by this constraint.) 456# 457# 458# # Second implementation: hooks 459# # ============================ 460# 461# The version 2.15 of Autoconf brought a vast number of changes compared 462# to 2.13, so a solution was needed. One could think of extending the 463# `sed' scripts with specialized code for complex macros. However, this 464# approach is of course full of flaws: 465# 466# a. the Autoconf maintainers have to write these snippets, which we 467# just don't want to, 468# 469# b. I really don't think you'll ever manage to handle the quoting of 470# m4 with a sed script. 471# 472# To satisfy a., let's remark that the code which implements the old 473# features in term of the new feature is exactly the code which should 474# replace the old code. 475# 476# To answer point b, as usual in the history of Autoconf, the answer, at 477# least on the paper, is simple: m4 is the best tool to parse m4, so 478# let's use m4. 479# 480# Therefore the specification is: 481# 482# I want to be able to tell Autoconf, well, m4, that the macro I 483# am currently defining is an obsolete macro (so that the user is 484# warned), and its code is the code to use when running autoconf, 485# but that the very same code has to be used when running 486# autoupdate. To summarize, the interface I want is 487# `AU_DEFUN(OLD-NAME, NEW-CODE)'. 488# 489# 490# Now for the technical details. 491# 492# When running autoconf, except for the warning, AU_DEFUN is basically 493# AC_DEFUN. 494# 495# When running autoupdate, we want *only* OLD-NAMEs to be expanded. 496# This obviously means that acgeneral.m4 and acspecific.m4 must not be 497# loaded. Nonetheless, because we want to use a rich set of m4 498# features, m4sugar.m4 is needed. Please note that the fact that 499# Autoconf's macros are not loaded is positive on two points: 500# 501# - we do get an updated `configure.ac', not a `configure'! 502# 503# - the old macros are replaced by *calls* to the new-macros, not the 504# body of the new macros, since their body is not defined!!! 505# (Whoa, that's really beautiful!). 506# 507# Additionally we need to disable the quotes when reading the input for 508# two reasons: first because otherwise `m4' will swallow the quotes of 509# other macros: 510# 511# NEW([1, 2], 3) 512# => NEW(1, 2, 3) 513# 514# and second, because we want to update the macro calls which are 515# quoted, i.e., we want 516# 517# FOO([OLD(1, 2)]) 518# => FOO([NEW([1, 2], [3])]) 519# 520# If we don't disable the quotes, only the macros called at the top 521# level would be updated. 522# 523# So, let's disable the quotes. 524# 525# Well, not quite: m4sugar.m4 still needs to use quotes for some macros. 526# Well, in this case, when running in autoupdate code, each macro first 527# reestablishes the quotes, expands itself, and disables the quotes. 528# 529# Thinking a bit more, you realize that in fact, people may use `define', 530# `ifelse' etc. in their files, and you certainly don't want to process 531# them. Another example is `dnl': you don't want to remove the 532# comments. You then realize you don't want exactly to import m4sugar: 533# you want to specify when it is enabled (macros active), and disabled. 534# m4sugar provides m4_disable/m4_enable to this end. 535# 536# You're getting close to it. Now remains one task: how to handle 537# twofold definitions? 538# 539# Remember that the same AU_DEFUN must be understood in two different 540# ways, the AC way, and the AU way. 541# 542# One first solution is to check whether acgeneral.m4 was loaded. But 543# that's definitely not cute. Another is simply to install `hooks', 544# that is to say, to keep in some place m4 knows, late `define' to be 545# triggered *only* in AU mode. 546# 547# You first think of designing AU_DEFUN like this: 548# 549# 1. AC_DEFUN(OLD-NAME, 550# [Warn the user OLD-NAME is obsolete. 551# NEW-CODE]) 552# 553# 2. Store for late AU binding([define(OLD_NAME, 554# [Reestablish the quotes. 555# NEW-CODE 556# Disable the quotes.])]) 557# 558# but this will not work: NEW-CODE probably uses $1, $2 etc. and these 559# guys will be replaced with the argument of `Store for late AU binding' 560# when you call it. 561# 562# I don't think there is a means to avoid this using this technology 563# (remember that $1 etc. are *always* expanded in m4). You may also try 564# to replace them with $[1] to preserve them for a later evaluation, but 565# if `Store for late AU binding' is properly written, it will remain 566# quoted till the end... 567# 568# You have to change technology. Since the problem is that `$1' 569# etc. should be `consumed' right away, one solution is to define now a 570# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME 571# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By 572# the way, the same method was used in autoheader. 573# 574# 575# # Third implementation: m4 namespaces by m4sugar 576# # ============================================== 577# 578# Actually, this implementation was just a clean up of the previous 579# implementation: instead of defining hooks by hand, m4sugar was equipped 580# with `namespaces'. What are they? 581# 582# Sometimes we want to disable some *set* of macros, and restore them 583# later. We provide support for this via namespaces. 584# 585# There are basically three characters playing this scene: defining a 586# macro in a namespace, disabling a namespace, and restoring a namespace 587# (i.e., all the definitions it holds). 588# 589# Technically, to define a MACRO in NAMESPACE means to define the macro 590# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append 591# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and 592# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in 593# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of 594# NAMESPACE and to unbind them at will. 595# 596# Of course this implementation is really inefficient: m4 has to grow 597# strings which can become quickly huge, which slows it significantly. 598# 599# In particular one should avoid as much as possible to use `define' for 600# temporaries. Now that `define' has quite a complex meaning, it is an 601# expensive operations that should be limited to macros. Use 602# `m4_define' for temporaries. 603# 604# Private copies of the macros we used in entering / exiting the m4sugar 605# namespace. It is much more convenient than fighting with the renamed 606# version of define etc. 607# 608# 609# 610# Those two implementations suffered from serious problems: 611# 612# - namespaces were really expensive, and incurred a major performance 613# loss on `autoconf' itself, not only `autoupdate'. One solution 614# would have been the limit the use of namespaces to `autoupdate', but 615# that's again some complications on m4sugar, which really doesn't need 616# this. So we wanted to get rid of the namespaces. 617# 618# - since the quotes were disabled, autoupdate was sometimes making 619# wrong guesses, for instance on: 620# 621# foo([1, 2]) 622# 623# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat 624# fragile, is to reestablish the quotes right before all the obsolete 625# macros, i.e., to use sed so that the previous text becomes 626# 627# changequote([, ])foo([1, 2]) 628# 629# To this end, one wants to trace the definition of obsolete macros. 630# 631# It was there that the limitations of the namespace approach became 632# painful: because it was a complex machinery playing a lot with the 633# builtins of m4 (hence, quite fragile), tracing was almost impossible. 634# 635# 636# So this approach was dropped. 637# 638# 639# # The fourth implementation: two steps 640# # ==================================== 641# 642# If you drop the uses of namespaces, you no longer can compute the 643# updated value, and replace the old call with it simultaneously. 644# 645# Obviously you will use m4 to compute the updated values, but you may 646# use some other tool to achieve the replacement. Personally, I trust 647# nobody but m4 to parse m4, so below, m4 will perform the two tasks. 648# 649# How can m4 be used to replace *some* macros calls with newer values. 650# Well, that's dead simple: m4 should learn the definitions of obsolete 651# macros, forget its builtins, disable the quotes, and then run on the 652# input file, which amounts to doing this: 653# 654# divert(-1)dnl 655# changequote([, ]) 656# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()]) 657# undefine([dnl]) 658# undefine([m4_eval]) 659# # Some more undefines... 660# changequote() 661# divert(0)dnl 662# dnl The Unbelievable Truth 663# changequote([, ])OLD(1, 2) 664# NEW([0, 0], 665# 0) 666# 667# which will result in 668# 669# dnl The Unbelievable Truth 670# NEW(1, 2, m4_eval(1 + 2)) 671# NEW([0, 0], 672# 0) 673# 674# Grpmh. Two problems. A minor problem: it would have been much better 675# to have the `m4_eval' computed, and a major problem: you lost the 676# quotation in the result. 677# 678# Let's address the big problem first. One solution is to define any 679# modern macro to rewrite its calls with the proper quotation, thanks to 680# `$@'. Again, tracing the `define's makes it possible to know which 681# are these macros, so you input is: 682# 683# divert(-1)dnl 684# changequote([, ]) 685# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()]) 686# define([NEW], [[NEW($@)]changequote()]) 687# undefine([dnl]) 688# undefine([m4_eval]) 689# # Some more undefines... 690# changequote() 691# divert(0)dnl 692# dnl The Unbelievable Truth 693# changequote([, ])OLD(1, 2) 694# changequote([, ])NEW([0, 0], 695# 0) 696# 697# which results in 698# 699# dnl The Unbelievable Truth 700# NEW([1, 2],[m4_eval(1 + 2)]) 701# NEW([0, 0],[0]) 702# 703# Our problem is solved, i.e., the first call to `NEW' is properly 704# quoted, but introduced another problem: we changed the layout of the 705# second calls, which can be a drama in the case of huge macro calls 706# (think of `AC_TRY_RUN' for instance). This example didn't show it, 707# but we also introduced parens to macros which did not have some: 708# 709# AC_INIT 710# => AC_INIT() 711# 712# No big deal for the semantics (unless the macro depends upon $#, which 713# is bad), but the users would not be happy. 714# 715# Additionally, we introduced quotes that were not there before, which is 716# OK in most cases, but could change the semantics of the file. 717# 718# Cruel dilemma: we do want the auto-quoting definition of `NEW' when 719# evaluating `OLD', but we don't when we evaluate the second `NEW'. 720# Back to namespaces? 721# 722# No. 723# 724# 725# # Second step: replacement 726# # ------------------------ 727# 728# No, as announced above, we will work in two steps: in a first step we 729# compute the updated values, and in a second step we replace them. Our 730# goal is something like this: 731# 732# divert(-1)dnl 733# changequote([, ]) 734# define([OLD], [NEW([1, 2], [3])changequote()]) 735# undefine([dnl]) 736# undefine([m4_eval]) 737# # Some more undefines... 738# changequote() 739# divert(0)dnl 740# dnl The Unbelievable Truth 741# changequote([, ])OLD(1, 2) 742# NEW([0, 0], 743# 0) 744# 745# i.e., the new value of `OLD' is precomputed using the auto-quoting 746# definition of `NEW' and the m4 builtins. We'll see how afterwards, 747# let's finish with the replacement. 748# 749# Of course the solution above is wrong: if there were other calls to 750# `OLD' with different values, we would smash them to the same value. 751# But it is quite easy to generalize the scheme above: 752# 753# divert(-1)dnl 754# changequote([, ]) 755# define([OLD([1],[2])], [NEW([1, 2], [3])]) 756# define([OLD], [defn([OLD($@)])changequote()]) 757# undefine([dnl]) 758# undefine([m4_eval]) 759# # Some more undefines... 760# changequote() 761# divert(0)dnl 762# dnl The Unbelievable Truth 763# changequote([, ])OLD(1, 2) 764# NEW([0, 0], 765# 0) 766# 767# i.e., for each call to obsolete macros, we build an array `call => 768# value', and use a macro to dispatch these values. This results in: 769# 770# dnl The Unbelievable Truth 771# NEW([1, 2], [3]) 772# NEW([0, 0], 773# 0) 774# 775# In French, we say `Youpi !', which you might roughly translate as 776# `Yippee!'. 777# 778# 779# # First step: computation 780# # ----------------------- 781# 782# Let's study the anatomy of the file, and name its sections: 783# 784# prologue 785# divert(-1)dnl 786# changequote([, ]) 787# values 788# define([OLD([1],[2])], [NEW([1, 2], [3])]) 789# dispatcher 790# define([OLD], [defn([OLD($@)])changequote()]) 791# disabler 792# undefine([dnl]) 793# undefine([m4_eval]) 794# # Some more undefines... 795# changequote() 796# divert(0)dnl 797# input 798# dnl The Unbelievable Truth 799# changequote([, ])OLD(1, 2) 800# NEW([0, 0], 801# 0) 802# 803# 804# # Computing the `values' section 805# # .............................. 806# 807# First we need to get the list of all the AU macro uses. To this end, 808# first get the list of all the AU macros names by tracing `AU_DEFUN' in 809# the initialization of autoconf. This list is computed in the file 810# `au.txt' below. 811# 812# Then use this list to trace all the AU macro uses in the input. The 813# goal is obtain in the case of our example: 814# 815# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)] 816# 817# This is the file `values.in' below. 818# 819# We want to evaluate this with only the builtins (in fact m4sugar), the 820# auto-quoting definitions of the new macros (`new.m4'), and the 821# definition of the old macros (`old.m4'). Computing these last two 822# files is easy: it's just a matter of using the right `--trace' option. 823# 824# So the content of `values.in' is: 825# 826# include($autoconf_dir/m4sugar.m4) 827# m4_include(new.m4) 828# m4_include(old.m4) 829# divert(0)dnl 830# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)] 831# 832# We run m4 on it, which yields: 833# 834# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@) 835# 836# Transform `@<<@' and `@>>@' into quotes and we get 837# 838# define([OLD([1],[2])],[NEW([1, 2], [3])]) 839# 840# This is `values.m4'. 841# 842# 843# # Computing the `dispatcher' section 844# # .................................. 845# 846# The `prologue', and the `disabler' are simple and need no commenting. 847# 848# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple 849# matter of using the right `--trace'. 850# 851# Finally, the input is not exactly the input file, rather it is the 852# input file with the added `changequote'. To this end, we build 853# `quote.sed'. 854# 855# 856# # Putting it all together 857# # ....................... 858# 859# We build the file `input.m4' which contains: 860# 861# divert(-1)dnl 862# changequote([, ]) 863# include(values.m4) 864# include(dispatch.m4) 865# undefine([dnl]) 866# undefine([eval]) 867# # Some more undefines... 868# changequote() 869# divert(0)dnl 870# dnl The Unbelievable Truth 871# changequote([, ])OLD(1, 2) 872# NEW([0, 0], 873# 0) 874# 875# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui. 876# 877# Well, there are a few additional technicalities. For instance, we 878# rely on `changequote', `ifelse' and `defn', but we don't want to 879# interpret the changequotes of the user, so we simply use another name: 880# `_au_changequote' etc. 881# 882# 883# # Failure of the fourth approach 884# # ------------------------------ 885# 886# This approach is heavily based on traces, but then there is an obvious 887# problem: non expanded code will never be seen. In particular, the body 888# of a `define' definition is not seen, so on the input 889# 890# define([idem], [OLD(0, [$1])]) 891# 892# autoupdate would never see the `OLD', and wouldn't have updated it. 893# Worse yet, if `idem(0)' was used later, then autoupdate sees that 894# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a 895# dispatcher for `OLD'. Since there was no computed value for `OLD(0, 896# [$1])', the dispatcher would have replaced with... nothing, leading 897# to 898# 899# define([idem], []) 900# 901# With some more thinking, you see that the two step approach is wrong, 902# the namespace approach was much saner. 903# 904# But you learned a lot, in particular you realized that using traces 905# can make it possible to simulate namespaces! 906# 907# 908# 909# # The fifth implementation: m4 namespaces by files 910# # ================================================ 911# 912# The fourth implementation demonstrated something unsurprising: you 913# cannot precompute, i.e., the namespace approach was the right one. 914# Still, we no longer want them, they're too expensive. Let's have a 915# look at the way it worked. 916# 917# When updating 918# 919# dnl The Unbelievable Truth 920# OLD(1, 2) 921# NEW([0, 0], [0]) 922# 923# you evaluate `input.m4': 924# 925# divert(-1) 926# changequote([, ]) 927# define([OLD], 928# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()]) 929# ... 930# m4_disable() 931# dnl The Unbelievable Truth 932# OLD(1, 2) 933# NEW([0, 0], [0]) 934# 935# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes 936# and comments: 937# 938# define([m4_disable], 939# [undefine([__file__]) 940# ... 941# changecom(#) 942# changequote()]) 943# 944# `m4_enable' does the converse: reestablish quotes and comments 945# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and 946# reenable the builtins. This later task requires that you first save 947# the builtins. And BTW, the definition above of `m4_disable' cannot 948# work: you undefined `changequote' before using it! So you need to use 949# your privates copies of the builtins. Let's introduce three files for 950# this: 951# 952# `m4save.m4' 953# moves the m4 builtins into the `_au_' pseudo namespace, 954# `unm4.m4' 955# undefines the builtins, 956# `m4.m4' 957# restores them. 958# 959# So `input.m4' is: 960# 961# divert(-1) 962# changequote([, ]) 963# 964# include([m4save.m4]) 965# 966# # Import AU. 967# define([OLD], 968# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()]) 969# 970# define([_au_enable], 971# [_au_changecom([#]) 972# _au_include([m4.m4]) 973# _au_include(m4sugar.m4)]) 974# 975# define([_au_disable], 976# [# Disable m4sugar. 977# # Disable the m4 builtins. 978# _au_include([unm4.m4]) 979# # 1. Disable special characters. 980# _au_changequote() 981# _au_changecom()]) 982# 983# m4_disable() 984# dnl The Unbelievable Truth 985# OLD(1, 2) 986# NEW([0, 0], [0]) 987# 988# Based on what we learned in the fourth implementation we know that we 989# have to enable the quotes *before* any AU macro, and we know we need 990# to build autoquoting versions of the AC macros. But the autoquoting 991# AC definitions must be disabled in the rest of the file, and enabled 992# inside AU macros. 993# 994# Using `autoconf --trace' it is easy to build the files 995# 996# `ac.m4' 997# define the autoquoting AC fake macros 998# `disable.m4' 999# undefine the m4sugar and AC autoquoting macros. 1000# `au.m4' 1001# definitions of the AU macros (such as `OLD' above). 1002# 1003# Now, `input.m4' is: 1004# 1005# divert(-1) 1006# changequote([, ]) 1007# 1008# include([m4save.m4]) 1009# # Import AU. 1010# include([au.m4]) 1011# 1012# define([_au_enable], 1013# [_au_changecom([#]) 1014# _au_include([m4.m4]) 1015# _au_include(m4sugar.m4) 1016# _au_include(ac.m4)]) 1017# 1018# define([_au_disable], 1019# [_au_include([disable.m4]) 1020# _au_include([unm4.m4]) 1021# # 1. Disable special characters. 1022# _au_changequote() 1023# _au_changecom()]) 1024# 1025# m4_disable() 1026# dnl The Unbelievable Truth 1027# _au_changequote([, ])OLD(1, 2) 1028# NEW([0, 0], [0]) 1029# 1030# Finally, version V is ready. 1031# 1032# Well... almost. 1033# 1034# There is a slight problem that remains: if an AU macro OUTER includes 1035# an AU macro INNER, then _au_enable will be run when entering OUTER 1036# and when entering INNER (not good, but not too bad yet). But when 1037# getting out of INNER, _au_disable will disable everything while we 1038# were still in OUTER. Badaboom. 1039# 1040# Therefore _au_enable and _au_disable have to be written to work by 1041# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable 1042# popdef's _au_enabled. And of course _au_enable and _au_disable are 1043# effective when _au_enabled is *not* defined. 1044# 1045# Finally, version V' is ready. And there is much rejoicing. (And I 1046# have free time again. I think. Yeah, right.) 1047 1048### Setup "GNU" style for perl-mode and cperl-mode. 1049## Local Variables: 1050## perl-indent-level: 2 1051## perl-continued-statement-offset: 2 1052## perl-continued-brace-offset: 0 1053## perl-brace-offset: 0 1054## perl-brace-imaginary-offset: 0 1055## perl-label-offset: -2 1056## cperl-indent-level: 2 1057## cperl-brace-offset: 0 1058## cperl-continued-brace-offset: 0 1059## cperl-label-offset: -2 1060## cperl-extra-newline-before-brace: t 1061## cperl-merge-trailing-else: nil 1062## cperl-continued-statement-offset: 2 1063## End: 1064