diff options
Diffstat (limited to 'bin/autoupdate.in')
| -rw-r--r-- | bin/autoupdate.in | 1063 |
1 files changed, 1063 insertions, 0 deletions
diff --git a/bin/autoupdate.in b/bin/autoupdate.in new file mode 100644 index 0000000..9737d49 --- /dev/null +++ b/bin/autoupdate.in @@ -0,0 +1,1063 @@ +#! @PERL@ -w +# -*- perl -*- +# @configure_input@ + +# autoupdate - modernize an Autoconf file. +# Copyright (C) 1994, 1999-2012 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 3 of the License, 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, see <http://www.gnu.org/licenses/>. + +# 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 $pkgdatadir = $ENV{'autom4te_perllibdir'} || '@pkgdatadir@'; + unshift @INC, $pkgdatadir; + + # 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 = ('@pkgdatadir@'); +my $force = 0; +# m4. +my $m4 = $ENV{"M4"} || '@M4@'; + + +# $HELP +# ----- +$help = "Usage: $0 [OPTION]... [TEMPLATE-FILE]... + +Update each TEMPLATE-FILE if given, or `configure.ac' if present, +or else `configure.in', to the syntax of the current version of +Autoconf. 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 obsolete + +Library directories: + -B, --prepend-include=DIR prepend directory DIR to search path + -I, --include=DIR append directory DIR to search path + +Report bugs to <bug-autoconf\@gnu.org>. +GNU Autoconf home page: <http://www.gnu.org/software/autoconf/>. +General help using GNU software: <http://www.gnu.org/gethelp/>. +"; + +# $VERSION +# -------- +$version = "autoupdate (@PACKAGE_NAME@) @VERSION@ +Copyright (C) @RELEASE_YEAR@ Free Software Foundation, Inc. +License GPLv3+/Autoconf: GNU GPL version 3 or later +<http://gnu.org/licenses/gpl.html>, <http://gnu.org/licenses/exceptions.html> +This is free software: you are free to change and redistribute it. +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 | $m4 2>" . shell_quote ("$tmp/m4.defs") . " >/dev/null"); + my $m4_defs = new Autom4te::XFile "< " . open_quote ("$tmp/m4.defs"); + while ($_ = $m4_defs->getline) + { + $m4_builtins{$1} = 1 + if /^(\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 $ac_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/ac.m4"); + print $ac_m4 "# ac.m4 -- autoquoting definitions of the AC macros.\n"; + my $unac_m4 = new Autom4te::XFile "> " . open_quote ("$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 $m4save_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/m4save.m4"); + print $m4save_m4 "# m4save.m4 -- save the m4 builtins.\n"; + my $unm4_m4 = new Autom4te::XFile "> " . open_quote ("$tmp/unm4.m4"); + print $unm4_m4 "# unm4.m4 -- disable the m4 builtins.\n"; + my $m4_m4 = new Autom4te::XFile "> " . open_quote ("$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=', '', map { shell_quote ($_) } @include); +$autoconf .= join (' --prepend-include=', '', map { shell_quote ($_) } @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 " + . ">" . shell_quote ("$tmp/au.m4")); + + + +## ------------------- ## +## Process the files. ## +## ------------------- ## + +foreach my $file (@ARGV) + { + # We need an actual file. + if ($file eq '-') + { + $file = "$tmp/stdin"; + system "cat >" . shell_quote ($file); + } + elsif (! -r "$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__ifdef], defn([ifdef])) + define([_au__include], defn([include])) + define([_au___undefine], defn([undefine])) + define([_au__undefine], [_au__ifdef([$1], [_au___undefine([$1])])]) + define([_au__save], [m4_ifdef([$1], + [m4_define([_au_$1], _m4_defn([$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 namespace + m4_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_dnl +EOF + + $input_m4 =~ s/^ //mg; + $input_m4 =~ s/\$file/$file/g; + + # prepared input -- input, but reenables the quote before each AU macro. + open INPUT_M4, "> " . open_quote ("$tmp/input.m4") + or error "cannot open: $!"; + open FILE, "< " . open_quote ($file) + or error "cannot open: $!"; + print INPUT_M4 "$input_m4"; + while (<FILE>) + { + eval $au_changequote; + print INPUT_M4; + } + close FILE + or error "cannot close $file: $!"; + close INPUT_M4 + or error "cannot close $tmp/input.m4: $!"; + + # Now ask m4 to perform the update. + xsystem ("$m4 --include=" . shell_quote ($tmp) + . join (' --include=', '', map { shell_quote ($_) } reverse (@prepend_include)) + . join (' --include=', '', map { shell_quote ($_) } @include) + . " " . shell_quote ("$tmp/input.m4") . " > " . shell_quote ("$tmp/updated")); + update_file ("$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 an 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 from 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 of extending the +# `sed' scripts with specialized code for complex macros. However, 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 with a sed script. +# +# 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), and its 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 of designing 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 probably uses $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: |