#! @PERL@ -w# -*- perl -*-# @configure_input@# autoupdate - modernize an Autoconf file.# Copyright (C) 1994, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006# Free Software Foundation, Inc.# This program is free software; you can redistribute it and/or modify# it under the terms of the GNU General Public License as published by# the Free Software Foundation; either version 2, or (at your option)# any later version.# This program is distributed in the hope that it will be useful,# but WITHOUT ANY WARRANTY; without even the implied warranty of# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the# GNU General Public License for more details.# You should have received a copy of the GNU General Public License# along with this program; if not, write to the Free Software# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA# 02110-1301, USA.# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>.# Rewritten by Akim Demaille <akim@freefriends.org>.eval 'case $# in 0) exec @PERL@ -S "$0";; *) exec @PERL@ -S "$0" "$@";; esac'if 0;BEGIN{my $datadir = $ENV{'autom4te_perllibdir'} || '@datadir@';unshift @INC, $datadir;# Override SHELL. On DJGPP SHELL may not be set to a shell# that can handle redirection and quote arguments correctly,# e.g.: COMMAND.COM. For DJGPP always use the shell that configure# has detected.$ENV{'SHELL'} = '@SHELL@' if ($^O eq 'dos');}use Autom4te::ChannelDefs;use Autom4te::Channels;use Autom4te::Configure_ac;use Autom4te::FileUtils;use Autom4te::General;use Autom4te::XFile;use File::Basename;use strict;# Lib files.my $autom4te = $ENV{'AUTOM4TE'} || '@bindir@/@autom4te-name@';my $autoconf = "$autom4te --language=autoconf";# We need to find m4sugar.my @prepend_include;my @include = ('@datadir@');my $force = 0;# m4.my $m4 = $ENV{"M4"} || '@M4@';# $HELP# -----$help = "Usage: $0 [OPTION] ... [TEMPLATE-FILE...]Update the TEMPLATE-FILE... if given, or `configure.ac' if present,or else `configure.in', to the syntax of the current version ofAutoconf. The original files are backed up.Operation modes:-h, --help print this help, then exit-V, --version print version number, then exit-v, --verbose verbosely report processing-d, --debug don't remove temporary files-f, --force consider all files obsoleteLibrary directories:-B, --prepend-include=DIR prepend directory DIR to search path-I, --include=DIR append directory DIR to search pathReport bugs to <bug-autoconf\@gnu.org>.";# $VERSION# --------$version = "autoupdate (@PACKAGE_NAME@) @VERSION@Copyright (C) 2006 Free Software Foundation, Inc.This is free software. You may redistribute copies of it under the terms ofthe GNU General Public License <http://www.gnu.org/licenses/gpl.html>.There is NO WARRANTY, to the extent permitted by law.Written by David J. MacKenzie and Akim Demaille.";## ---------- #### Routines. #### ---------- ### parse_args ()# -------------# Process any command line arguments.sub parse_args (){my $srcdir;getopt ('I|include=s' => \@include,'B|prepend-include=s' => \@prepend_include,'f|force' => \$force);if (! @ARGV){my $configure_ac = require_configure_ac;push @ARGV, $configure_ac;}}# ----------------- ## Autoconf macros. ## ----------------- #my (%ac_macros, %au_macros, %m4_builtins);# HANDLE_AUTOCONF_MACROS ()# -------------------------# @M4_BUILTINS -- M4 builtins and a useful comment.sub handle_autoconf_macros (){# Get the builtins.xsystem ("echo dumpdef | $m4 2>$tmp/m4.defs >/dev/null");my $m4_defs = new Autom4te::XFile "$tmp/m4.defs";while ($_ = $m4_defs->getline){$m4_builtins{$1} = 1if /^(\w+):/;}$m4_defs->close;my $macros = new Autom4te::XFile ("$autoconf". " --trace AU_DEFINE:'AU:\$f:\$1'". " --trace define:'AC:\$f:\$1'". " --melt /dev/null |");while ($_ = $macros->getline){chomp;my ($domain, $file, $macro) = /^(AC|AU):(.*):([^:]*)$/ or next;if ($domain eq "AU"){$au_macros{$macro} = 1;}elsif ($file =~ /(^|\/)m4sugar\/(m4sugar|version)\.m4$/){# Add the m4sugar macros to m4_builtins.$m4_builtins{$macro} = 1;}else{# Autoconf, aclocal, and m4sh macros.$ac_macros{$macro} = 1;}}$macros->close;# Don't keep AU macros in @AC_MACROS.delete $ac_macros{$_}foreach (keys %au_macros);# Don't keep M4sugar macros which are redefined by Autoconf,# such as `builtin', `changequote' etc. See autoconf/autoconf.m4.delete $ac_macros{$_}foreach (keys %m4_builtins);error "no current Autoconf macros found"unless keys %ac_macros;error "no obsolete Autoconf macros found"unless keys %au_macros;if ($debug){print STDERR "Current Autoconf macros:\n";print STDERR join (' ', sort keys %ac_macros) . "\n\n";print STDERR "Obsolete Autoconf macros:\n";print STDERR join (' ', sort keys %au_macros) . "\n\n";}# ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded).# unac.m4 -- undefine the AC macros.my $ac_m4 = new Autom4te::XFile ">$tmp/ac.m4";print $ac_m4 "# ac.m4 -- autoquoting definitions of the AC macros.\n";my $unac_m4 = new Autom4te::XFile ">$tmp/unac.m4";print $unac_m4 "# unac.m4 -- undefine the AC macros.\n";foreach (sort keys %ac_macros){print $ac_m4 "_au_m4_define([$_], [m4_if(\$#, 0, [[\$0]], [[\$0(\$\@)]])])\n";print $unac_m4 "_au_m4_undefine([$_])\n";}# m4save.m4 -- save the m4 builtins.# unm4.m4 -- disable the m4 builtins.# m4.m4 -- enable the m4 builtins.my $m4save_m4 = new Autom4te::XFile ">$tmp/m4save.m4";print $m4save_m4 "# m4save.m4 -- save the m4 builtins.\n";my $unm4_m4 = new Autom4te::XFile ">$tmp/unm4.m4";print $unm4_m4 "# unm4.m4 -- disable the m4 builtins.\n";my $m4_m4 = new Autom4te::XFile ">$tmp/m4.m4";print $m4_m4 "# m4.m4 -- enable the m4 builtins.\n";foreach (sort keys %m4_builtins){print $m4save_m4 "_au__save([$_])\n";print $unm4_m4 "_au__undefine([$_])\n";print $m4_m4 "_au__restore([$_])\n";}}## -------------- #### Main program. #### -------------- ##parse_args;$autoconf .= " --debug" if $debug;$autoconf .= " --force" if $force;$autoconf .= " --verbose" if $verbose;$autoconf .= join (' --include=', '', @include);$autoconf .= join (' --prepend-include=', '', @prepend_include);mktmpdir ('au');handle_autoconf_macros;# $au_changequote -- enable the quote `[', `]' right before any AU macro.my $au_changequote ='s/\b(' . join ('|', keys %au_macros) . ')\b/_au_m4_changequote([,])$1/g';# au.m4 -- definitions the AU macros.xsystem ("$autoconf --trace AU_DEFINE:'_au_defun(\@<:\@\$1\@:>\@,\@<:\@\$2\@:>\@)' --melt /dev/null ". ">$tmp/au.m4");## ------------------- #### Process the files. #### ------------------- ##foreach my $file (@ARGV){# We need an actual file.if ($file eq '-'){$file = "$tmp/stdin";system "cat >$file";}elsif (! -r "$file"){die "$me: $file: No such file or directory";}# input.m4 -- m4 program to produce the updated file.# Load the values, the dispatcher, neutralize m4, and the prepared# input file.my $input_m4 = <<\EOF;divert(-1) -*- Autoconf -*-changequote([,])# Define our special macros:define([_au__defn], defn([defn]))define([_au__divert], defn([divert]))define([_au__include], defn([include]))define([_au__undefine], defn([undefine]))define([_au__save], [m4_ifdef([$1], [m4_copy([$1], [_au_$1])])])define([_au__restore],[_au_m4_ifdef([_au_$1],[_au_m4_define([$1], _au__defn([_au_$1]))])])# Set up m4sugar.include(m4sugar/m4sugar.m4)# Redefine __file__ to make warnings nicer; $file is replaced below.m4_define([__file__], [$file])# Redefine m4_location to fix the line number.m4_define([m4_location], [__file__:m4_eval(__line__ - _au__first_line)])# Move all the builtins into the `_au_' pseudo namespacem4_include([m4save.m4])# _au_defun(NAME, BODY)# ---------------------# Define NAME to BODY, plus AU activation/deactivation._au_m4_define([_au_defun],[_au_m4_define([$1],[_au_enable()dnl$2[]dnl_au_disable()])])# Import the definition of the obsolete macros._au__include([au.m4])## ------------------------ #### _au_enable/_au_disable. #### ------------------------ ### They work by pair: each time an AU macro is activated, it runs# _au_enable, and at its end its runs _au_disable (see _au_defun# above). AU macros might use AU macros, which should# enable/disable only for the outer AU macros.## `_au_enabled' is used to this end, determining whether we really# enable/disable.# __au_enable# -----------# Reenable the builtins, m4sugar, and the autoquoting AC macros._au_m4_define([__au_enable],[_au__divert(-1)# Enable special characters._au_m4_changecom([#])_au__include([m4.m4])_au__include([ac.m4])_au__divert(0)])# _au_enable# ----------# Called at the beginning of all the obsolete macros. If this is the# outermost level, call __au_enable._au_m4_define([_au_enable],[_au_m4_ifdef([_au_enabled],[],[__au_enable()])_au_dnl_au_m4_pushdef([_au_enabled])])# __au_disable# ------------# Disable the AC autoquoting macros, m4sugar, and m4._au_m4_define([__au_disable],[_au__divert(-1)_au__include([unac.m4])_au__include([unm4.m4])# Disable special characters._au_m4_changequote()_au_m4_changecom()_au__divert(0)])# _au_disable# -----------# Called at the end of all the obsolete macros. If we are at the# outermost level, call __au_disable._au_m4_define([_au_disable],[_au_m4_popdef([_au_enabled])_au_dnl_au_m4_ifdef([_au_enabled],[],[__au_disable()])])## ------------------------------- #### Disable, and process the file. #### ------------------------------- ### The AC autoquoting macros are not loaded yet, hence invoking# `_au_disable' would be wrong._au__include([unm4.m4])# Disable special characters, and set the first line number._au_m4_changequote()_au_m4_changecom()_au_m4_define(_au__first_line, _au___line__)_au__divert(0)_au_dnlEOF$input_m4 =~ s/^ //mg;$input_m4 =~ s/\$file/$file/g;# prepared input -- input, but reenables the quote before each AU macro.open INPUT_M4, ">$tmp/input.m4"or error "cannot open: $!";open FILE, "<$file"or error "cannot open: $!";print INPUT_M4 "$input_m4";while (<FILE>){eval $au_changequote;print INPUT_M4;}close FILEor error "cannot close $file: $!";close INPUT_M4or error "cannot close $tmp/input.m4: $!";# Now ask m4 to perform the update.xsystem ("$m4 --include=$tmp". join (' --include=', '', reverse (@prepend_include)). join (' --include=', '', @include). " $tmp/input.m4 >$tmp/updated");update_file ("$tmp/updated","$file" eq "$tmp/stdin" ? '-' : "$file");}exit 0;# ## ---------------------------- ### ## How `autoupdate' functions. ### ## ---------------------------- #### The task of `autoupdate' is not trivial: the biggest difficulty being# that you must limit the changes to the parts that really need to be# updated. Finding a satisfying implementation proved to be quite hard,# as this is the fifth implementation of `autoupdate'.## Below, we will use a simple example of obsolete macro:## AU_DEFUN([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))])# AC_DEFUN([NEW], [echo "sum($1) = $2"])## the input file contains## dnl The Unbelievable Truth# OLD(1, 2)# NEW([0, 0], [0])## Of course the expected output is## dnl The Unbelievable Truth# NEW([1, 2], [3])# NEW([0, 0], [0])### # First implementation: sed# # =========================## The first implementation was only able to change the name of obsolete# macros.## The file `acoldnames.m4' defined the old names based on the new names.# It was simple then to produce a sed script such as:## s/OLD/NEW/g## Updating merely consisted in running this script on the file to# update.## This scheme suffers an obvious limitation: that `autoupdate' was# unable to cope with new macros that just swap some of its arguments# compared to the old macro. Fortunately, that was enough to upgrade# from Autoconf 1 to Autoconf 2. (But I have no idea whether the# changes in Autoconf 2 were precisely limited by this constraint.)### # Second implementation: hooks# # ============================## The version 2.15 of Autoconf brought a vast number of changes compared# to 2.13, so a solution was needed. One could think to extend the# `sed' scripts with specialized code for complex macros. But this# approach is of course full of flaws:## a. the Autoconf maintainers have to write these snippets, which we# just don't want to,## b. I really don't think you'll ever manage to handle the quoting of# m4 from sed.## To satisfy a., let's remark that the code which implements the old# features in term of the new feature is exactly the code which should# replace the old code.## To answer point b, as usual in the history of Autoconf, the answer, at# least on the paper, is simple: m4 is the best tool to parse m4, so# let's use m4.## Therefore the specification is:## I want to be able to tell Autoconf, well, m4, that the macro I# am currently defining is an obsolete macro (so that the user is# warned), which code is the code to use when running autoconf,# but that the very same code has to be used when running# autoupdate. To summarize, the interface I want is# `AU_DEFUN(OLD-NAME, NEW-CODE)'.### Now for the technical details.## When running autoconf, except for the warning, AU_DEFUN is basically# AC_DEFUN.## When running autoupdate, we want *only* OLD-NAMEs to be expanded.# This obviously means that acgeneral.m4 and acspecific.m4 must not be# loaded. Nonetheless, because we want to use a rich set of m4# features, m4sugar.m4 is needed. Please note that the fact that# Autoconf's macros are not loaded is positive on two points:## - we do get an updated `configure.ac', not a `configure'!## - the old macros are replaced by *calls* to the new-macros, not the# body of the new macros, since their body is not defined!!!# (Whoa, that's really beautiful!).## Additionally we need to disable the quotes when reading the input for# two reasons: first because otherwise `m4' will swallow the quotes of# other macros:## NEW([1, 2], 3)# => NEW(1, 2, 3)## and second, because we want to update the macro calls which are# quoted, i.e., we want## FOO([OLD(1, 2)])# => FOO([NEW([1, 2], [3])])## If we don't disable the quotes, only the macros called at the top# level would be updated.## So, let's disable the quotes.## Well, not quite: m4sugar.m4 still needs to use quotes for some macros.# Well, in this case, when running in autoupdate code, each macro first# reestablishes the quotes, expands itself, and disables the quotes.## Thinking a bit more, you realize that in fact, people may use `define'# `ifelse' etc. in their files, and you certainly don't want to process# them. Another example is `dnl': you don't want to remove the# comments. You then realize you don't want exactly to import m4sugar:# you want to specify when it is enabled (macros active), and disabled.# m4sugar provides m4_disable/m4_enable to this end.## You're getting close to it. Now remains one task: how to handle# twofold definitions?## Remember that the same AU_DEFUN must be understood in two different# ways, the AC way, and the AU way.## One first solution is to check whether acgeneral.m4 was loaded. But# that's definitely not cute. Another is simply to install `hooks',# that is to say, to keep in some place m4 knows, late `define' to be# triggered *only* in AU mode.## You first think to design AU_DEFUN like this:## 1. AC_DEFUN(OLD-NAME,# [Warn the user OLD-NAME is obsolete.# NEW-CODE])## 2. Store for late AU binding([define(OLD_NAME,# [Reestablish the quotes.# NEW-CODE# Disable the quotes.])])## but this will not work: NEW-CODE has probably $1, $2 etc. and these# guys will be replaced with the argument of `Store for late AU binding'# when you call it.## I don't think there is a means to avoid this using this technology# (remember that $1 etc. are *always* expanded in m4). You may also try# to replace them with $[1] to preserve them for a later evaluation, but# if `Store for late AU binding' is properly written, it will remain# quoted till the end...## You have to change technology. Since the problem is that `$1'# etc. should be `consumed' right away, one solution is to define now a# second macro, `AU_OLD-NAME', and to install a hook than binds OLD-NAME# to AU_OLD-NAME. Then, autoupdate.m4 just need to run the hooks. By# the way, the same method was used in autoheader.### # Third implementation: m4 namespaces by m4sugar# # ==============================================## Actually, this implementation was just a clean up of the previous# implementation: instead of defining hooks by hand, m4sugar was equipped# with `namespaces'. What are they?## Sometimes we want to disable some *set* of macros, and restore them# later. We provide support for this via namespaces.## There are basically three characters playing this scene: defining a# macro in a namespace, disabling a namespace, and restoring a namespace# (i.e., all the definitions it holds).## Technically, to define a MACRO in NAMESPACE means to define the macro# named `NAMESPACE::MACRO' to the VALUE. At the same time, we append# `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)', and# similarly a binding of NAME to the value of `NAMESPACE::MACRO' in# `m4_enable(NAMESPACE)'. These mechanisms allow to bind the macro of# NAMESPACE and to unbind them at will.## Of course this implementation is really inefficient: m4 has to grow# strings which can become quickly huge, which slows it significantly.## In particular one should avoid as much as possible to use `define' for# temporaries. Now that `define' has quite a complex meaning, it is an# expensive operations that should be limited to macros. Use# `m4_define' for temporaries.## Private copies of the macros we used in entering / exiting the m4sugar# namespace. It is much more convenient than fighting with the renamed# version of define etc.#### Those two implementations suffered from serious problems:## - namespaces were really expensive, and incurred a major performance# loss on `autoconf' itself, not only `autoupdate'. One solution# would have been the limit the use of namespaces to `autoupdate', but# that's again some complications on m4sugar, which really doesn't need# this. So we wanted to get rid of the namespaces.## - since the quotes were disabled, autoupdate was sometimes making# wrong guesses, for instance on:## foo([1, 2])## m4 saw 2 arguments: `[1'and `2]'. A simple solution, somewhat# fragile, is to reestablish the quotes right before all the obsolete# macros, i.e., to use sed so that the previous text becomes## changequote([, ])foo([1, 2])## To this end, one wants to trace the definition of obsolete macros.## It was there that the limitations of the namespace approach became# painful: because it was a complex machinery playing a lot with the# builtins of m4 (hence, quite fragile), tracing was almost impossible.### So this approach was dropped.### # The fourth implementation: two steps# # ====================================## If you drop the uses of namespaces, you no longer can compute the# updated value, and replace the old call with it simultaneously.## Obviously you will use m4 to compute the updated values, but you may# use some other tool to achieve the replacement. Personally, I trust# nobody but m4 to parse m4, so below, m4 will perform the two tasks.## How can m4 be used to replace *some* macros calls with newer values.# Well, that's dead simple: m4 should learn the definitions of obsolete# macros, forget its builtins, disable the quotes, and then run on the# input file, which amounts to doing this:## divert(-1)dnl# changequote([, ])# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])# undefine([dnl])# undefine([m4_eval])# # Some more undefines...# changequote()# divert(0)dnl# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# NEW([0, 0],# 0)## which will result in## dnl The Unbelievable Truth# NEW(1, 2, m4_eval(1 + 2))# NEW([0, 0],# 0)## Grpmh. Two problems. A minor problem: it would have been much better# to have the `m4_eval' computed, and a major problem: you lost the# quotation in the result.## Let's address the big problem first. One solution is to define any# modern macro to rewrite its calls with the proper quotation, thanks to# `$@'. Again, tracing the `define's makes it possible to know which# are these macros, so you input is:## divert(-1)dnl# changequote([, ])# define([OLD], [NEW([$1, $2], m4_eval([$1 + $2]))changequote()])# define([NEW], [[NEW($@)]changequote()])# undefine([dnl])# undefine([m4_eval])# # Some more undefines...# changequote()# divert(0)dnl# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# changequote([, ])NEW([0, 0],# 0)## which results in## dnl The Unbelievable Truth# NEW([1, 2],[m4_eval(1 + 2)])# NEW([0, 0],[0])## Our problem is solved, i.e., the first call to `NEW' is properly# quoted, but introduced another problem: we changed the layout of the# second calls, which can be a drama in the case of huge macro calls# (think of `AC_TRY_RUN' for instance). This example didn't show it,# but we also introduced parens to macros which did not have some:## AC_INIT# => AC_INIT()## No big deal for the semantics (unless the macro depends upon $#, which# is bad), but the users would not be happy.## Additionally, we introduced quotes that were not there before, which is# OK in most cases, but could change the semantics of the file.## Cruel dilemma: we do want the auto-quoting definition of `NEW' when# evaluating `OLD', but we don't when we evaluate the second `NEW'.# Back to namespaces?## No.### # Second step: replacement# # ------------------------## No, as announced above, we will work in two steps: in a first step we# compute the updated values, and in a second step we replace them. Our# goal is something like this:## divert(-1)dnl# changequote([, ])# define([OLD], [NEW([1, 2], [3])changequote()])# undefine([dnl])# undefine([m4_eval])# # Some more undefines...# changequote()# divert(0)dnl# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# NEW([0, 0],# 0)## i.e., the new value of `OLD' is precomputed using the auto-quoting# definition of `NEW' and the m4 builtins. We'll see how afterwards,# let's finish with the replacement.## Of course the solution above is wrong: if there were other calls to# `OLD' with different values, we would smash them to the same value.# But it is quite easy to generalize the scheme above:## divert(-1)dnl# changequote([, ])# define([OLD([1],[2])], [NEW([1, 2], [3])])# define([OLD], [defn([OLD($@)])changequote()])# undefine([dnl])# undefine([m4_eval])# # Some more undefines...# changequote()# divert(0)dnl# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# NEW([0, 0],# 0)## i.e., for each call to obsolete macros, we build an array `call =># value', and use a macro to dispatch these values. This results in:## dnl The Unbelievable Truth# NEW([1, 2], [3])# NEW([0, 0],# 0)## In French, we say `Youpi !', which you might roughly translate as# `Yippee!'.### # First step: computation# # -----------------------## Let's study the anatomy of the file, and name its sections:## prologue# divert(-1)dnl# changequote([, ])# values# define([OLD([1],[2])], [NEW([1, 2], [3])])# dispatcher# define([OLD], [defn([OLD($@)])changequote()])# disabler# undefine([dnl])# undefine([m4_eval])# # Some more undefines...# changequote()# divert(0)dnl# input# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# NEW([0, 0],# 0)### # Computing the `values' section# # ..............................## First we need to get the list of all the AU macro uses. To this end,# first get the list of all the AU macros names by tracing `AU_DEFUN' in# the initialization of autoconf. This list is computed in the file# `au.txt' below.## Then use this list to trace all the AU macro uses in the input. The# goal is obtain in the case of our example:## [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]## This is the file `values.in' below.## We want to evaluate this with only the builtins (in fact m4sugar), the# auto-quoting definitions of the new macros (`new.m4'), and the# definition of the old macros (`old.m4'). Computing these last two# files is easy: it's just a matter of using the right `--trace' option.## So the content of `values.in' is:## include($autoconf_dir/m4sugar.m4)# m4_include(new.m4)# m4_include(old.m4)# divert(0)dnl# [define([OLD([1],[2])],]@<<@OLD([1],[2])@>>@[)]## We run m4 on it, which yields:## define([OLD([1],[2])],@<<@NEW([1, 2], [3])@>>@)## Transform `@<<@' and `@>>@' into quotes and we get## define([OLD([1],[2])],[NEW([1, 2], [3])])## This is `values.m4'.### # Computing the `dispatcher' section# # ..................................## The `prologue', and the `disabler' are simple and need no commenting.## To compute the `dispatcher' (`dispatch.m4'), again, it is a simple# matter of using the right `--trace'.## Finally, the input is not exactly the input file, rather it is the# input file with the added `changequote'. To this end, we build# `quote.sed'.### # Putting it all together# # .......................## We build the file `input.m4' which contains:## divert(-1)dnl# changequote([, ])# include(values.m4)# include(dispatch.m4)# undefine([dnl])# undefine([eval])# # Some more undefines...# changequote()# divert(0)dnl# dnl The Unbelievable Truth# changequote([, ])OLD(1, 2)# NEW([0, 0],# 0)## And we just run m4 on it. Et voila`, Monsieur ! Mais oui, mais oui.## Well, there are a few additional technicalities. For instance, we# rely on `changequote', `ifelse' and `defn', but we don't want to# interpret the changequotes of the user, so we simply use another name:# `_au_changequote' etc.### # Failure of the fourth approach# # ------------------------------## This approach is heavily based on traces, but then there is an obvious# problem: non expanded code will never be seen. In particular, the body# of a `define' definition is not seen, so on the input## define([idem], [OLD(0, [$1])])## autoupdate would never see the `OLD', and wouldn't have updated it.# Worse yet, if `idem(0)' was used later, then autoupdate sees that# `OLD' is used, computes the result for `OLD(0, 0)' and sets up a# dispatcher for `OLD'. Since there was no computed value for `OLD(0,# [$1])', the dispatcher would have replaced with... nothing, leading# to## define([idem], [])## With some more thinking, you see that the two step approach is wrong,# the namespace approach was much saner.## But you learned a lot, in particular you realized that using traces# can make it possible to simulate namespaces!#### # The fifth implementation: m4 namespaces by files# # ================================================## The fourth implementation demonstrated something unsurprising: you# cannot precompute, i.e., the namespace approach was the right one.# Still, we no longer want them, they're too expensive. Let's have a# look at the way it worked.## When updating## dnl The Unbelievable Truth# OLD(1, 2)# NEW([0, 0], [0])## you evaluate `input.m4':## divert(-1)# changequote([, ])# define([OLD],# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])# ...# m4_disable()# dnl The Unbelievable Truth# OLD(1, 2)# NEW([0, 0], [0])## where `m4_disable' undefines the m4 and m4sugar, and disables the quotes# and comments:## define([m4_disable],# [undefine([__file__])# ...# changecom(#)# changequote()])## `m4_enable' does the converse: reestablish quotes and comments# --easy--, reestablish m4sugar --easy: just load `m4sugar.m4' again-- and# reenable the builtins. This later task requires that you first save# the builtins. And BTW, the definition above of `m4_disable' cannot# work: you undefined `changequote' before using it! So you need to use# your privates copies of the builtins. Let's introduce three files for# this:## `m4save.m4'# moves the m4 builtins into the `_au_' pseudo namespace,# `unm4.m4'# undefines the builtins,# `m4.m4'# restores them.## So `input.m4' is:## divert(-1)# changequote([, ])## include([m4save.m4])## # Import AU.# define([OLD],# [m4_enable()NEW([$1, $2], m4_eval([$1 + $2]))m4_disable()])## define([_au_enable],# [_au_changecom([#])# _au_include([m4.m4])# _au_include(m4sugar.m4)])## define([_au_disable],# [# Disable m4sugar.# # Disable the m4 builtins.# _au_include([unm4.m4])# # 1. Disable special characters.# _au_changequote()# _au_changecom()])## m4_disable()# dnl The Unbelievable Truth# OLD(1, 2)# NEW([0, 0], [0])## Based on what we learned in the fourth implementation we know that we# have to enable the quotes *before* any AU macro, and we know we need# to build autoquoting versions of the AC macros. But the autoquoting# AC definitions must be disabled in the rest of the file, and enabled# inside AU macros.## Using `autoconf --trace' it is easy to build the files## `ac.m4'# define the autoquoting AC fake macros# `disable.m4'# undefine the m4sugar and AC autoquoting macros.# `au.m4'# definitions of the AU macros (such as `OLD' above).## Now, `input.m4' is:## divert(-1)# changequote([, ])## include([m4save.m4])# # Import AU.# include([au.m4])## define([_au_enable],# [_au_changecom([#])# _au_include([m4.m4])# _au_include(m4sugar.m4)# _au_include(ac.m4)])## define([_au_disable],# [_au_include([disable.m4])# _au_include([unm4.m4])# # 1. Disable special characters.# _au_changequote()# _au_changecom()])## m4_disable()# dnl The Unbelievable Truth# _au_changequote([, ])OLD(1, 2)# NEW([0, 0], [0])## Finally, version V is ready.## Well... almost.## There is a slight problem that remains: if an AU macro OUTER includes# an AU macro INNER, then _au_enable will be run when entering OUTER# and when entering INNER (not good, but not too bad yet). But when# getting out of INNER, _au_disable will disable everything while we# were still in OUTER. Badaboom.## Therefore _au_enable and _au_disable have to be written to work by# pairs: each _au_enable pushdef's _au_enabled, and each _au_disable# popdef's _au_enabled. And of course _au_enable and _au_disable are# effective when _au_enabled is *not* defined.## Finally, version V' is ready. And there is much rejoicing. (And I# have free time again. I think. Yeah, right.)### Setup "GNU" style for perl-mode and cperl-mode.## Local Variables:## perl-indent-level: 2## perl-continued-statement-offset: 2## perl-continued-brace-offset: 0## perl-brace-offset: 0## perl-brace-imaginary-offset: 0## perl-label-offset: -2## cperl-indent-level: 2## cperl-brace-offset: 0## cperl-continued-brace-offset: 0## cperl-label-offset: -2## cperl-extra-newline-before-brace: t## cperl-merge-trailing-else: nil## cperl-continued-statement-offset: 2## End: