1#! @PERL@ -w 2# -*- perl -*- 3# autoupdate - modernize an Autoconf file. 4# Copyright 1994, 1999, 2000, 2001 Free Software Foundation, Inc. 5 6# This program is free software; you can redistribute it and/or modify 7# it under the terms of the GNU General Public License as published by 8# the Free Software Foundation; either version 2, or (at your option) 9# any later version. 10 11# This program is distributed in the hope that it will be useful, 12# but WITHOUT ANY WARRANTY; without even the implied warranty of 13# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14# GNU General Public License for more details. 15 16# You should have received a copy of the GNU General Public License 17# along with this program; if not, write to the Free Software 18# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 19# 02111-1307, USA. 20 21# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>. 22# Rewritten by Akim Demaille <akim@freefriends.org>. 23 24use 5.005; 25use Getopt::Long; 26use File::Basename; 27use strict; 28 29(my $me = $0) =~ s,.*[\\/],,; 30 31# Lib files. 32my $autoconf_dir = $ENV{"AC_MACRODIR"} || "@datadir@"; 33my $autoconf = ''; 34my $debug = 0; 35my $localdir = '.'; 36# m4. 37my $m4 = $ENV{"M4"} || "@M4@"; 38my $verbose = 0; 39my $SIMPLE_BACKUP_SUFFIX = $ENV{'SIMPLE_BACKUP_SUFFIX'} || '~'; 40my $tmp = ''; 41 42 43## ---------- ## 44## Routines. ## 45## ---------- ## 46 47 48# &mktmpdir () 49# ------------ 50sub mktmpdir () 51{ 52 my $TMPDIR = $ENV{'TMPDIR'} || '/tmp'; 53 54 # If mktemp supports dirs, use it to please Marc E. 55 $tmp = `(umask 077 && mktemp -d -q "$TMPDIR/auXXXXXX") 2>/dev/null`; 56 chomp $tmp; 57 58 if (!$tmp || !-d $tmp) 59 { 60 $tmp = "$TMPDIR/au" . int (rand 10000) . ".$$"; 61 mkdir $tmp, 0700 62 or die "$me: cannot create $tmp: $!\n"; 63 } 64 65 print STDERR "$me:$$: working in $tmp\n" 66 if $debug; 67} 68 69 70# END 71# --- 72# Exit nonzero whenever closing STDOUT fails. 73sub END 74{ 75 use POSIX qw (_exit); 76 77 my ($q) = ($?); 78 79 # FIXME: Heelp! Can't find a means to properly catch system's 80 # exit status (without hair I mean). 81 # my $status = $? >> 8; 82 83 if (!$debug && -d $tmp) 84 { 85 unlink <$tmp/*> 86 or warn ("$me: cannot empty $tmp: $!\n"), _exit (1); 87 rmdir $tmp 88 or warn ("$me: cannot remove $tmp: $!\n"), _exit (1); 89 } 90 91 # This is required if the code might send any output to stdout 92 # E.g., even --version or --help. So it's best to do it unconditionally. 93 close STDOUT 94 or (warn "$me: closing standard output: $!\n"), _exit (1); 95 96 ($!, $?) = (0, $q); 97} 98 99 100# print_usage () 101# -------------- 102# Display usage (--help). 103sub print_usage () 104{ 105 print <<"END"; 106Usage: $0 [OPTION] ... [TEMPLATE-FILE...] 107 108Update the TEMPLATE-FILE... if given, or \`configure.ac' if present, 109or else \`configure.in', to the syntax of the current version of 110Autoconf. The original files are backed up. 111 112Operation modes: 113 -h, --help print this help, then exit 114 -V, --version print version number, then exit 115 -v, --verbose verbosely report processing 116 -d, --debug don't remove temporary files 117 118Library directories: 119 -A, --autoconf-dir=ACDIR Autoconf's macro files location (rarely needed) 120 -l, --localdir=DIR location of \`aclocal.m4' 121 122Environment variables: 123 M4 GNU M4 1.4 or above 124 AUTOCONF autoconf @VERSION@ 125 126Report bugs to <bug-autoconf\@gnu.org>. 127END 128 exit 0; 129} 130 131 132# print_version () 133# ---------------- 134# Display version (--version). 135sub print_version 136{ 137 print <<END; 138autoupdate (@PACKAGE_NAME@) @VERSION@ 139Written by David J. MacKenzie and Akim Demaille. 140 141Copyright 1994, 1999, 2000, 2001 Free Software Foundation, Inc. 142This is free software; see the source for copying conditions. There is NO 143warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 144END 145 exit 0; 146} 147 148 149# $CONFIGURE_AC 150# &find_configure_ac () 151# --------------------- 152sub find_configure_ac () 153{ 154 if (-f 'configure.ac') 155 { 156 if (-f 'configure.in') 157 { 158 warn "warning: `configure.ac' and `configure.in' both present.\n"; 159 warn "warning: proceeding with `configure.ac'.\n"; 160 } 161 return 'configure.ac'; 162 } 163 elsif (-f 'configure.in') 164 { 165 return 'configure.in'; 166 } 167 return; 168} 169 170 171# parse_args () 172# ------------- 173# Process any command line arguments. 174sub parse_args () 175{ 176 my $srcdir; 177 # F*k. Getopt seems bogus and dies when given `-' with `bundling'. 178 # If fixed some day, use this: '' => sub { push @ARGV, "-" } 179 my $update_stdin = grep /^-$/, @ARGV; 180 @ARGV = grep !/^-$/, @ARGV; 181 Getopt::Long::config ("bundling"); 182 Getopt::Long::GetOptions ('A|autoconf-dir|m|macrodir=s' => \$autoconf_dir, 183 'l|localdir=s' => \$localdir, 184 'd|debug' => \$debug, 185 'h|help' => \&print_usage, 186 'V|version' => \&print_version, 187 'v|verbose' => \$verbose) 188 or exit 1; 189 push @ARGV, '-' 190 if $update_stdin; 191 if (! @ARGV) 192 { 193 my $configure_ac = find_configure_ac; 194 die 'no input file' 195 unless $configure_ac; 196 push @ARGV, $configure_ac; 197 } 198} 199 200 201# find_slaves 202# ----------- 203# Find the lib files and autoconf. 204sub find_slaves () 205{ 206 # Some non-GNU m4's don't reject the --help option, so give them /dev/null. 207# die "Autoconf requires GNU m4 1.4 or later\n" 208# if system "$m4 --help </dev/null 2>&1 | fgrep reload-state >/dev/null"; 209 210 # autoconf. 211 (my $dir = $0) =~ s,[^\\/]*$,,; 212 213 # We test "$dir/autoconf" in case we are in the build tree, in which case 214 # the names are not transformed yet. 215 foreach my $file ($ENV{"AUTOCONF"} || '', 216 "$dir/@autoconf-name@", 217 "$dir/autoconf", 218 "@bindir@/@autoconf-name@") 219 { 220 if (-x $file) 221 { 222 $autoconf = $file; 223 last; 224 } 225 } 226 227 # This is needed because perl's '-x' isn't a smart as bash's; that 228 # is, it won't find autoconf.sh. 229 $autoconf = 'autoconf' 230 if !$autoconf; 231} 232 233 234## -------------- ## 235## Main program. ## 236## -------------- ## 237find_slaves; 238parse_args; 239mktmpdir; 240$autoconf .= " --autoconf-dir $autoconf_dir --localdir $localdir"; 241 242 243# @M4_BUILTINS -- M4 builtins and a useful comment. 244my @m4_builtins = `echo dumpdef | $m4 2>&1 >/dev/null`; 245map { s/:.*//;s/\W// } @m4_builtins; 246 247 248# m4.m4 -- enable the m4 builtins. 249# unm4.m4 -- disable the m4 builtins. 250# savem4.m4 -- save the m4 builtins. 251open M4_M4, ">$tmp/m4.m4" 252 or die "$me: cannot open: $!\n"; 253open UNM4_M4, ">$tmp/unm4.m4" 254 or die "$me: cannot open: $!\n"; 255open M4SAVE_M4, ">$tmp/m4save.m4" 256 or die "$me: cannot open: $!\n"; 257foreach (@m4_builtins) 258 { 259 print M4_M4 "_au_define([$_], _au_defn([_au_$_]))\n"; 260 print UNM4_M4 "_au_undefine([$_])\n"; 261 print M4SAVE_M4 "define([_au_$_], defn([$_]))\n"; 262 } 263close M4SAVE_M4 264 or die "$me: cannot close: $!\n"; 265close UNM4_M4 266 or die "$me: cannot close: $!\n"; 267close M4_M4 268 or die "$me: cannot close: $!\n"; 269 270 271# @AU_MACROS & AC_MACROS -- AU and AC macros and yet another useful comment. 272open MACROS, ("$autoconf " 273 . "--trace AU_DEFUN:'AU:\$f:\$1' --trace define:'AC:\$f:\$1' " 274 . "-i /dev/null |") 275 or die "$me: cannot open: $!\n"; 276my (%ac_macros, %au_macros); 277while (<MACROS>) 278 { 279 chomp; 280 /^(AC|AU):(.*):([^:]*)$/ or next; 281 my $filename = basename ($2); 282 if ($1 eq "AC") 283 { 284 $ac_macros{$3} = $filename; 285 } 286 else 287 { 288 $au_macros{$3} = $filename; 289 } 290 } 291close MACROS 292 or die "$me: cannot close: $!\n"; 293# Don't keep AU macros in @AC_MACROS. 294delete $ac_macros{$_} 295 foreach (keys %au_macros); 296if ($debug) 297 { 298 print STDERR "Current Autoconf macros:\n"; 299 print STDERR join (' ', sort keys %ac_macros) . "\n\n"; 300 print STDERR "Obsolete Autoconf macros:\n"; 301 print STDERR join (' ', sort keys %au_macros) . "\n\n"; 302 } 303 304# $au_changequote -- enable the quote `[', `]' right before any AU macro. 305my $au_changequote = 306 's/\b(' . join ('|', keys %au_macros) . ')\b/_au_changequote([,])$1/g'; 307 308# au.m4 -- definitions the AU macros. 309system ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@, 310\@<:\@\$2\@:>\@)' -i /dev/null " 311 . ">$tmp/au.m4"); 312 313# ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded). 314# disable.m4 -- undefine the macros of AC and m4sugar. 315open AC_M4, ">$tmp/ac.m4" 316 or die "$me: cannot open: $!\n"; 317open DISABLE_M4, ">$tmp/disable.m4" 318 or die "$me: cannot open: $!\n"; 319foreach (sort keys %ac_macros) 320 { 321 print AC_M4 "_au_define([$_], [[\$0(\$\@)]])\n" 322 unless $ac_macros{$_} eq "m4sugar.m4"; 323 print DISABLE_M4 "_au_undefine([$_])\n"; 324 } 325close DISABLE_M4 326 or die "$me: cannot close: $!\n"; 327close AC_M4 328 or die "$me: cannot close: $!\n"; 329 330 331 332## ------------------- ## 333## Process the files. ## 334## ------------------- ## 335 336foreach my $file (@ARGV) 337 { 338 my $filename = $file; 339 # We need an actual file. 340 if ($file eq '-') 341 { 342 $file = "$tmp/stdin"; 343 system "cat >$file"; 344 } 345 elsif (! -r "$file") 346 { 347 die "$me: $file: No such file or directory"; 348 } 349 350 # input.m4 -- m4 program to produce the updated file. 351 # Load the values, the dispatcher, neutralize m4, and the prepared 352 # input file. 353 my $input_m4 = <<EOF; 354 divert(-1) -*- Autoconf -*- 355 changequote([, ]) 356 357 # Move all the builtins into the \`_au_' pseudo namespace 358 include([$tmp/m4save.m4]) 359 360 # _au_defun(NAME, BODY) 361 # --------------------- 362 # Define NAME to BODY, plus AU activation/deactivation. 363 _au_define([_au_defun], 364 [_au_define([\$1], 365 [_au_enable()dnl 366 \$2[]dnl 367 _au_disable()])]) 368 369 # Import the definition of the obsolete macros. 370 _au_include([$tmp/au.m4]) 371 372 373 ## ------------------------ ## 374 ## _au_enable/_au_disable. ## 375 ## ------------------------ ## 376 377 # They work by pair: each time an AU macro is activated, it runs 378 # _au_enable, and at its end its runs _au_disable (see _au_defun 379 # above). But since AU macros might use AU macros, which should 380 # enable/disable only for the outter AU macros. 381 # 382 # \`_au_enabled' is used to this end, condionning whether we really 383 # enable/disable. 384 385 386 # __au_enable 387 # ----------- 388 # Reenable the builtins, and m4sugar. 389 _au_define([__au_enable], 390 [_au_divert(-1) 391 # Enable special characters. 392 _au_changecom([#]) 393 394 # Enable the m4 builtins, m4sugar and the autoquoting AC macros. 395 _au_include([$tmp/m4.m4]) 396 _au_include([$autoconf_dir/m4sugar.m4]) 397 _au_include([$tmp/ac.m4]) 398 399 _au_divert(0)]) 400 401 # _au_enable 402 # ---------- 403 # Called at the beginning of all the obsolete macros. Reenable the 404 # builtins, and m4sugar if needed. 405 _au_define([_au_enable], 406 [_au_ifdef([_au_enabled], 407 [], 408 [__au_enable()])_au_dnl 409 _au_pushdef([_au_enabled])]) 410 411 412 # __au_disable 413 # ------------ 414 # Disable the builtins, and m4sugar. 415 _au_define([__au_disable], 416 [_au_divert(-1) 417 # Disable m4sugar, the AC autoquoting macros, and m4. 418 _au_include([$tmp/disable.m4]) 419 _au_include([$tmp/unm4.m4]) 420 421 # Disable special characters. 422 _au_changequote() 423 _au_changecom() 424 425 _au_divert(0)]) 426 427 # _au_disable 428 # ----------- 429 # Called at the end of all the obsolete macros. Disable the 430 # builtins, and m4sugar if needed.. 431 _au_define([_au_disable], 432 [_au_popdef([_au_enabled])_au_dnl 433 _au_ifdef([_au_enabled], 434 [], 435 [__au_disable()])]) 436 437 438 ## ------------------------------- ## 439 ## Disable, and process the file. ## 440 ## ------------------------------- ## 441 _au_disable()_au_dnl 442EOF 443 444 $input_m4 =~ s/^ //mg; 445 446 # prepared input -- input, but reenables the quote before each AU macro. 447 open INPUT_M4, ">$tmp/input.m4" 448 or die "$me: cannot open: $!\n"; 449 open FILE, "<$file" 450 or die "$me: cannot open: $!\n"; 451 print INPUT_M4 "$input_m4"; 452 while (<FILE>) 453 { 454 eval $au_changequote; 455 print INPUT_M4; 456 } 457 close FILE 458 or die "$me: cannot close: $!\n"; 459 close INPUT_M4 460 or die "$me: cannot close: $!\n"; 461 462 # Now ask m4 to perform the update. 463 print STDERR "$me: running $m4 $tmp/input.m4\n" 464 if $verbose; 465 if (system ("$m4 $tmp/input.m4 >$tmp/updated")) 466 { 467 # Exit status of system() is in the upper byte. 468 $! >>= 8; 469 die "$me: cannot update \`$filename'\n"; 470 }; 471 472 if ("$file" eq "$tmp/stdin") 473 { 474 system ("cat $tmp/updated"); 475 } 476 elsif (! system ("cmp -s $tmp/updated $file")) 477 { 478 # File didn't change, so don't update its mod time. 479 print STDERR "$me: \`$file' is unchanged\n" 480 } 481 else 482 { 483 # Back up and install the new one. 484 if (system ("mv $file $file${SIMPLE_BACKUP_SUFFIX} && " 485 . "mv $tmp/updated $file") == 0) 486 { 487 print STDERR "$me: \`$file' is updated\n"; 488 } 489 else 490 { 491 die "$me: cannot update \`$file'\n"; 492 } 493 } 494 } 495 496exit 0; 497 498 499# ## ---------------------------- ## 500# ## How `autoupdate' functions. ## 501# ## ---------------------------- ## 502# 503# The task of `autoupdate' is not trivial: the biggest difficulty being 504# that you must limit the changes to the parts that really need to be 505# updated. Finding a satisfying implementation proved to be quite hard, 506# as this is the fourth implementation of `autoupdate'. 507# 508# Below, we will use a simple example of obsolete macro: 509# 510# AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))]) 511# AC_DEFUN([NEW], [echo "sum($1) = $2"]) 512# 513# the input file contains 514# 515# dnl The Unbelievable Truth 516# OLD(1, 2) 517# NEW([0, 0], [0]) 518# 519# Of course the expected output is 520# 521# dnl The Unbelievable Truth 522# NEW([1, 2], [3]) 523# NEW([0, 0], [0]) 524# 525# 526# # First implementation: sed 527# # ========================= 528# 529# The first implementation was only able to change the name of obsolete 530# macros. 531# 532# The file `acoldnames.m4' defined the old names based on the new names. 533# It was simple then to produce a sed script such as: 534# 535# s/OLD/NEW/g 536# 537# Updating merely consisted in running this script on the file to 538# update. 539# 540# This scheme suffers an obvious limitation: that `autoupdate' was 541# unable to cope with new macros that just swap some of its arguments 542# compared to the old macro. Fortunately, that was enough to upgrade 543# from Autoconf 1 to Autoconf 2. (But I have no idea whether the 544# changes in Autoconf 2 were precisely limited by this constraint.) 545# 546# 547# # Second implementation: hooks 548# # ============================ 549# 550# The version 2.15 of Autoconf brought a vast number of changes compared 551# to 2.13, so a solution was needed. One could think to extend the 552# `sed' scripts with specialized code for complex macros. But this 553# approach is of course full of flaws: 554# 555# a. the Autoconf maintainers have to write these snippets, which we 556# just don't want to, 557# 558# b. I really don't think you'll ever manage to handle the quoting of 559# m4 from sed. 560# 561# To satisfy a., let's remark that the code which implements the old 562# features in term of the new feature is exactly the code which should 563# replace the old code. 564# 565# To answer point b, as usual in the history of Autoconf, the answer, at 566# least on the paper, is simple: m4 is the best tool to parse m4, so 567# let's use m4. 568# 569# Therefore the specification is: 570# 571# I want to be able to tell Autoconf, well, m4, that the macro I 572# am currently defining is an obsolete macro (so that the user is 573# warned), which code is the code to use when running autoconf, 574# but that the very same code has to be used when running 575# autoupdate. To summarize, the interface I want is 576# `AU_DEFUN(OLD-NAME, NEW-CODE)'. 577# 578# 579# Now for the technical details. 580# 581# When running autoconf, except for the warning, AU_DEFUN is basically 582# AC_DEFUN. 583# 584# When running autoupdate, we want *only* OLD-NAMEs to be expanded. 585# This obviously means that acgeneral.m4 and acspecific.m4 must not be 586# loaded. Nonetheless, because we want to use a rich set of m4 587# features, m4sugar.m4 is needed. Please note that the fact that 588# Autoconf's macros are not loaded is positive on two points: 589# 590# - we do get an updated `configure.ac', not a `configure'! 591# 592# - the old macros are replaced by *calls* to the new-macros, not the 593# body of the new macros, since their body is not defined!!! 594# (Whoa, that's really beautiful!). 595# 596# Additionally we need to disable the quotes when reading the input for 597# two reasons: first because otherwise `m4' will swallow the quotes of 598# other macros: 599# 600# NEW([1, 2], 3) 601# => NEW(1, 2, 3) 602# 603# and second, because we want to update the macro calls which are 604# quoted, i.e., we want 605# 606# FOO([OLD(1, 2)]) 607# => FOO([NEW([1, 2], [3])]) 608# 609# If we don't disable the quotes, only the macros called at the top 610# level would be updated. 611# 612# So, let's disable the quotes. 613# 614# Well, not quite: m4sugar.m4 still needs to use quotes for some macros. 615# Well, in this case, when running in autoupdate code, each macro first 616# reestablishes the quotes, expands itself, and disables the quotes. 617# 618# Thinking a bit more, you realize that in fact, people may use `define' 619# `ifelse' etc. in their files, and you certainly don't want to process 620# them. Another example is `dnl': you don't want to remove the 621# comments. You then realize you don't want exactly to import m4sugar: 622# you want to specify when it is enabled (macros active), and disabled. 623# m4sugar provides m4_disable/m4_enable to this end. 624# 625# You're getting close to it. Now remains one task: how to handle 626# twofold definitions? 627# 628# Remember that the same AU_DEFUN must be understood in two different 629# ways, the AC way, and the AU way. 630# 631# One first solution is to check whether acgeneral.m4 was loaded. But 632# that's definitely not cute. Another is simply to install `hooks', 633# that is to say, to keep in some place m4 knows, late `define' to be 634# triggered *only* in AU mode. 635# 636# You first think to design AU_DEFUN like this: 637# 638# 1. AC_DEFUN(OLD-NAME, 639# [Warn the user OLD-NAME is obsolete. 640# NEW-CODE]) 641# 642# 2. Store for late AU binding([define(OLD_NAME, 643# [Reestablish the quotes. 644# NEW-CODE 645# Disable the quotes.])]) 646# 647# but this will not work: NEW-CODE has probably $1, $2 etc. and these 648# guys will be replaced with the argument of `Store for late AU binding' 649# when you call it. 650# 651# I don't think there is a means to avoid this using this technology 652# (remember that $1 etc. are *always* expanded in m4). You may also try 653# to replace them with $[1] to preserve them for a later evaluation, but 654# if `Store for late AU binding' is properly written, it will remain 655# quoted till the end... 656# 657# You have to change technology. Since the problem is that `$1' 658# etc. should be `consumed' right away, one solution is to define now a 659# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME 660# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By 661# the way, the same method was used in autoheader. 662# 663# 664# # Third implementation: m4 namespaces by m4sugar 665# # ============================================== 666# 667# Actually, this implementation was just a clean up of the previous 668# implementation: instead of defining hooks by hand, m4sugar was equipped 669# with `namespaces'. What are they? 670# 671# Sometimes we want to disable some *set* of macros, and restore them 672# later. We provide support for this via namespaces. 673# 674# There are basically three characters playing this scene: defining a 675# macro in a namespace, disabling a namespace, and restoring a namespace 676# (i.e., all the definitions it holds). 677# 678# Technically, to define a MACRO in NAMESPACE means to define the macro 679# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append 680# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and 681# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in 682# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of 683# NAMESPACE and to unbind them at will. 684# 685# Of course this implementation is really inefficient: m4 has to grow 686# strings which can become quickly huge, which slows it significantly. 687# 688# In particular one should avoid as much as possible to use `define' for 689# temporaries. Now that `define' as quite a complex meaning, it is an 690# expensive operations that should be limited to macros. Use 691# `m4_define' for temporaries. 692# 693# Private copies of the macros we used in entering / exiting the m4sugar 694# namespace. It is much more convenient than fighting with the renamed 695# version of define etc. 696# 697# 698# 699# Those two implementations suffered from serious problems: 700# 701# - namespaces were really expensive, and incurred a major performance 702# loss on `autoconf' itself, not only `autoupdate'. One solution 703# would have been the limit the use of namespaces to `autoupdate', but 704# that's again some complications on m4sugar, which really doesn't need 705# this. So we wanted to get rid of the namespaces. 706# 707# - since the quotes were disabled, autoupdate was sometimes making 708# wrong guesses, for instance on: 709# 710# foo([1, 2]) 711# 712# m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat 713# fragile, is to reestablish the quotes right before all the obsolete 714# macros, i.e., to use sed so that the previous text becomes 715# 716# changequote([, ])foo([1, 2]) 717# 718# To this end, one wants to trace the definition of obsolete macros. 719# 720# It was there that the limitations of the namespace approach became 721# painful: because it was a complex machinery playing a lot with the 722# builtins of m4 (hence, quite fragile), tracing was almost impossible. 723# 724# 725# So this approach was dropped. 726# 727# 728# # The fourth implementation: two steps 729# # ==================================== 730# 731# If you drop the uses of namespaces, you no longer can compute the 732# updated value, and replace the old call with it simultaneously. 733# 734# Obviously you will use m4 to compute the updated values, but you may 735# use some other tool to achieve the replacement. Personally, I trust 736# nobody but m4 to parse m4, so below, m4 will perform the two tasks. 737# 738# How can m4 be used to replace *some* macros calls with newer values. 739# Well, that's dead simple: m4 should learn the definitions of obsolete 740# macros, forget its builtins, disable the quotes, and then run on the 741# input file, which amounts to doing this: 742# 743# divert(-1)dnl 744# changequote([, ]) 745# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()]) 746# undefine([dnl]) 747# undefine([m4_eval]) 748# # Some more undefines... 749# changequote() 750# divert(0)dnl 751# dnl The Unbelievable Truth 752# changequote([, ])OLD(1, 2) 753# NEW([0, 0], 754# 0) 755# 756# which will result in 757# 758# dnl The Unbelievable Truth 759# NEW(1, 2, m4_eval(1 + 2)) 760# NEW([0, 0], 761# 0) 762# 763# Grpmh. Two problems. A minor problem: it would have been much better 764# to have the `m4_eval' computed, and a major problem: you lost the 765# quotation in the result. 766# 767# Let's address the big problem first. One solution is to define any 768# modern macro to rewrite its calls with the proper quotation, thanks to 769# `$@'. Again, tracing the `define's makes it possible to know which 770# are these macros, so you input is: 771# 772# divert(-1)dnl 773# changequote([, ]) 774# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()]) 775# define([NEW], [[NEW($@)]changequote()]) 776# undefine([dnl]) 777# undefine([m4_eval]) 778# # Some more undefines... 779# changequote() 780# divert(0)dnl 781# dnl The Unbelievable Truth 782# changequote([, ])OLD(1, 2) 783# changequote([, ])NEW([0, 0], 784# 0) 785# 786# which results in 787# 788# dnl The Unbelievable Truth 789# NEW([1, 2],[m4_eval(1 + 2)]) 790# NEW([0, 0],[0]) 791# 792# Our problem is solved, i.e., the first call to `NEW' is properly 793# quoted, but introduced another problem: we changed the layout of the 794# second calls, which can be a drama in the case of huge macro calls 795# (think of `AC_TRY_RUN' for instance). This example didn't show it, 796# but we also introduced parens to macros which did not have some: 797# 798# AC_INIT 799# => AC_INIT() 800# 801# No big deal for the semantics (unless the macro depends upon $#, which 802# is bad), but the users would not be happy. 803# 804# Additionally, we introduced quotes that we not there before, which is 805# OK in most cases, but could change the semantics of the file. 806# 807# Cruel dilemma: we do want the auto-quoting definition of `NEW' when 808# evaluating `OLD', but we don't when we evaluate the second `NEW'. 809# Back to namespaces? 810# 811# No. 812# 813# 814# # Second step: replacement 815# # ------------------------ 816# 817# No, as announced above, we will work in two steps: in a first step we 818# compute the updated values, and in a second step we replace them. Our 819# goal is something like this: 820# 821# divert(-1)dnl 822# changequote([, ]) 823# define([OLD], [NEW([1, 2], [3])changequote()]) 824# undefine([dnl]) 825# undefine([m4_eval]) 826# # Some more undefines... 827# changequote() 828# divert(0)dnl 829# dnl The Unbelievable Truth 830# changequote([, ])OLD(1, 2) 831# NEW([0, 0], 832# 0) 833# 834# i.e., the new value of `OLD' is precomputed using the auto-quoting 835# definition of `NEW' and the m4 builtins. We'll see how afterwards, 836# let's finish with the replacement. 837# 838# Of course the solution above is wrong: if there were other calls to 839# `OLD' with different values, we would smash them to the same value. 840# But it is quite easy to generalize the scheme above: 841# 842# divert(-1)dnl 843# changequote([, ]) 844# define([OLD([1],[2])], [NEW([1, 2], [3])]) 845# define([OLD], [defn([OLD($@)])changequote()]) 846# undefine([dnl]) 847# undefine([m4_eval]) 848# # Some more undefines... 849# changequote() 850# divert(0)dnl 851# dnl The Unbelievable Truth 852# changequote([, ])OLD(1, 2) 853# NEW([0, 0], 854# 0) 855# 856# i.e., for each call to obsolete macros, we build an array `call => 857# value', and use a macro to dispatch these values. This results in: 858# 859# dnl The Unbelievable Truth 860# NEW([1, 2], [3]) 861# NEW([0, 0], 862# 0) 863# 864# In French, we say `Youpi !', which you might roughly translate as 865# `yipeee!'. 866# 867# 868# # First step: computation 869# # ----------------------- 870# 871# Let's study the anatomy of the file, and name its sections: 872# 873# prologue 874# divert(-1)dnl 875# changequote([, ]) 876# values 877# define([OLD([1],[2])], [NEW([1, 2], [3])]) 878# dispatcher 879# define([OLD], [defn([OLD($@)])changequote()]) 880# disabler 881# undefine([dnl]) 882# undefine([m4_eval]) 883# # Some more undefines... 884# changequote() 885# divert(0)dnl 886# input 887# dnl The Unbelievable Truth 888# changequote([, ])OLD(1, 2) 889# NEW([0, 0], 890# 0) 891# 892# 893# # Computing the `values' section 894# # .............................. 895# 896# First we need to get the list of all the AU macro uses. To this end, 897# first get the list of all the AU macros names by tracing `AU_DEFUN' in 898# the initialization of autoconf. This list is computed in the file 899# `au.txt' below. 900# 901# Then use this list to trace all the AU macro uses in the input. The 902# goal is obtain in the case of our example: 903# 904# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)] 905# 906# This is the file `values.in' below. 907# 908# We want to evaluate this with only the builtins (in fact m4sugar), the 909# auto-quoting definitions of the new macros (`new.m4'), and the 910# definition of the old macros (`old.m4'). Computing these last two 911# files is easy: it's just a matter of using the right `--trace' option. 912# 913# So the content of `values.in' is: 914# 915# include($autoconf_dir/m4sugar.m4) 916# m4_include(new.m4) 917# m4_include(old.m4) 918# divert(0)dnl 919# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)] 920# 921# We run m4 on it, which yields: 922# 923# define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@) 924# 925# Transform `@<<@' and `@>>@' into quotes and we get 926# 927# define([OLD([1],[2])],[NEW([1, 2], [3])]) 928# 929# This is `values.m4'. 930# 931# 932# # Computing the `dispatcher' section 933# # .................................. 934# 935# The `prologue', and the `disabler' are simple and need no commenting. 936# 937# To compute the `dispatcher' (`dispatch.m4'), again, it is a simple 938# matter of using the right `--trace'. 939# 940# Finally, the input is not exactly the input file, rather it is the 941# input file with the added `changequote'. To this end, we build 942# `quote.sed'. 943# 944# 945# # Putting it all together 946# # ....................... 947# 948# We build the file `input.m4' which contains: 949# 950# divert(-1)dnl 951# changequote([, ]) 952# include(values.m4) 953# include(dispatch.m4) 954# undefine([dnl]) 955# undefine([eval]) 956# # Some more undefines... 957# changequote() 958# divert(0)dnl 959# dnl The Unbelievable Truth 960# changequote([, ])OLD(1, 2) 961# NEW([0, 0], 962# 0) 963# 964# And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui. 965# 966# Well, there are a few additional technicalities. For instance, we 967# rely on `changequote', `ifelse' and `defn', but we don't want to 968# interpret the changequotes of the user, so we simply use another name: 969# `_au_changequote' etc. 970# 971# 972# # Failure of the fourth approach 973# # ------------------------------ 974# 975# This approach is heavily based on traces, but then there is an obvious 976# problem: non expanded code will never be seen/ In particular, the body 977# of a `define' definition is not seen, so on the input 978# 979# define([idem], [OLD(0, [$1])]) 980# 981# autoupdate would never see the `OLD', and wouldn't have updated it. 982# Worse yet, if `idem(0)' was used later, then autoupdate sees that 983# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a 984# dispatcher for `OLD'. Since there was no computed value for `OLD(0, 985# [$1])', the dispatcher would have replaced with... nothinhg, leading 986# to 987# 988# define([idem], []) 989# 990# With some more thinking, you see that the two step approach is wrong, 991# the namespace approach was much saner. 992# 993# But you learned a lot, in particular you realized that using traces 994# can make it possible to simulate namespaces! 995# 996# 997# 998# # The fifth implementation: m4 namespaces by files 999# # ================================================ 1000# 1001# The fourth implementation demonstrated something unsurprising: you 1002# cannot precompute, i.e., the namespace approach was the right one. 1003# Still, we no longer want them, they're too expensive. Let's have a 1004# look at the way it worked. 1005# 1006# When updating 1007# 1008# dnl The Unbelievable Truth 1009# OLD(1, 2) 1010# NEW([0, 0], [0]) 1011# 1012# you evaluate `input.m4': 1013# 1014# divert(-1) 1015# changequote([, ]) 1016# define([OLD], 1017# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()]) 1018# ... 1019# m4_disable() 1020# dnl The Unbelievable Truth 1021# OLD(1, 2) 1022# NEW([0, 0], [0]) 1023# 1024# where `m4_disable' undefines the m4 and m4sugar, and disables the quotes 1025# and comments: 1026# 1027# define([m4_disable], 1028# [undefine([__file__]) 1029# ... 1030# changecom(#) 1031# changequote()]) 1032# 1033# `m4_enable' does the converse: reestablish quotes and comments 1034# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and 1035# reenable the builtins. This later task requires that you first save 1036# the builtins. And BTW, the definition above of `m4_disable' cannot 1037# work: you undefined `changequote' before using it! So you need to use 1038# your privates copies of the builtins. Let's introduce three files for 1039# this: 1040# 1041# `m4save.m4' 1042# moves the m4 builtins into the `_au_' pseudo namespace 1043# `unm4.m4' 1044# undefines the builtins 1045# `m4.m4' 1046# restores them 1047# 1048# So `input.m4' is: 1049# 1050# divert(-1) 1051# changequote([, ]) 1052# 1053# include([m4save.m4]) 1054# 1055# # Import AU. 1056# define([OLD], 1057# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()]) 1058# 1059# define([_au_enable], 1060# [_au_changecom([#]) 1061# _au_include([m4.m4]) 1062# _au_include(m4sugar.m4)]) 1063# 1064# define([_au_disable], 1065# [# Disable m4sugar. 1066# # Disable the m4 builtins. 1067# _au_include([unm4.m4]) 1068# # 1. Disable special characters. 1069# _au_changequote() 1070# _au_changecom()]) 1071# 1072# m4_disable() 1073# dnl The Unbelievable Truth 1074# OLD(1, 2) 1075# NEW([0, 0], [0]) 1076# 1077# Based on what we learned in the fourth implementation we know that we 1078# have to enable the quotes *before* any AU macro, and we know we need 1079# to build autoquoting versions of the AC macros. But the autoquoting 1080# AC definitions must be disabled in the rest of the file, and enabled 1081# inside AU macros. 1082# 1083# Using `autoconf --trace' it is easy to build the files 1084# 1085# `ac.m4' 1086# define the autoquoting AC fake macros 1087# `disable.m4' 1088# undefine the m4sugar and AC autoquoting macros. 1089# `au.m4' 1090# definitions of the AU macros (such as `OLD' above). 1091# 1092# Now, `input.m4' is: 1093# 1094# divert(-1) 1095# changequote([, ]) 1096# 1097# include([m4save.m4]) 1098# # Import AU. 1099# include([au.m4]) 1100# 1101# define([_au_enable], 1102# [_au_changecom([#]) 1103# _au_include([m4.m4]) 1104# _au_include(m4sugar.m4) 1105# _au_include(ac.m4)]) 1106# 1107# define([_au_disable], 1108# [_au_include([disable.m4]) 1109# _au_include([unm4.m4]) 1110# # 1. Disable special characters. 1111# _au_changequote() 1112# _au_changecom()]) 1113# 1114# m4_disable() 1115# dnl The Unbelievable Truth 1116# _au_changequote([, ])OLD(1, 2) 1117# NEW([0, 0], [0]) 1118# 1119# Finally, version V is ready. 1120# 1121# Well... almost. 1122# 1123# There is a slight problem that remains: if an AU macro OUTTER includes 1124# an AU macro INNER, then _au_enable will be run when entering OUTTER 1125# and when entering INNER (not good, but not too bad yet). But when 1126# getting out of INNER, _au_disable will disable everything while we 1127# were still in OUTTER. Badaboom. 1128# 1129# Therefore _au_enable and _au_disable have to be written to work by 1130# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable 1131# popdef's _au_enabled. And of course _au_enable and _au_disable are 1132# effective when _au_enabled is *not* defined. 1133# 1134# Finally, version V' is ready. And there is much rejoicing. (And I 1135# have free time again. I think. Yeah, right.) 1136