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diff --git a/autoupdate.in b/autoupdate.in new file mode 100644 index 0000000..7ab3f28 --- /dev/null +++ b/autoupdate.in @@ -0,0 +1,1136 @@ +#! @PERL@ -w +# -*- perl -*- +# autoupdate - modernize an Autoconf file. +# Copyright 2010-2022,2023 Thomas E. Dickey +# Copyright 1994, 1999, 2000, 2001 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., 59 Temple Place - Suite 330, Boston, MA +# 02111-1307, USA. + +# Originally written by David MacKenzie <djm@gnu.ai.mit.edu>. +# Rewritten by Akim Demaille <akim@freefriends.org>. + +use 5.005; +use Getopt::Long; +use File::Basename; +use strict; + +(my $me = $0) =~ s,.*[\\/],,; + +# Lib files. +my $autoconf_dir = $ENV{"AC_MACRODIR"} || "@datadir@"; +my $autoconf = ''; +my $debug = 0; +my $localdir = '.'; +# m4. +my $m4 = $ENV{"M4"} || "@M4@"; +my $verbose = 0; +my $SIMPLE_BACKUP_SUFFIX = $ENV{'SIMPLE_BACKUP_SUFFIX'} || '~'; +my $tmp = ''; + + +## ---------- ## +## Routines. ## +## ---------- ## + + +# &mktmpdir () +# ------------ +sub mktmpdir () +{ + my $TMPDIR = $ENV{'TMPDIR'} || '/tmp'; + + # If mktemp supports dirs, use it to please Marc E. + $tmp = `(umask 077 && mktemp -d -q "$TMPDIR/auXXXXXX") 2>/dev/null`; + chomp $tmp; + + if (!$tmp || !-d $tmp) + { + $tmp = "$TMPDIR/au" . int (rand 10000) . ".$$"; + mkdir $tmp, 0700 + or die "$me: cannot create $tmp: $!\n"; + } + + print STDERR "$me:$$: working in $tmp\n" + if $debug; +} + + +# END +# --- +# Exit nonzero whenever closing STDOUT fails. +sub END +{ + use POSIX qw (_exit); + + my ($q) = ($?); + + # FIXME: Heelp! Can't find a means to properly catch system's + # exit status (without hair I mean). + # my $status = $? >> 8; + + if (!$debug && -d $tmp) + { + unlink <$tmp/*> + or warn ("$me: cannot empty $tmp: $!\n"), _exit (1); + rmdir $tmp + or warn ("$me: cannot remove $tmp: $!\n"), _exit (1); + } + + # This is required if the code might send any output to stdout + # E.g., even --version or --help. So it's best to do it unconditionally. + close STDOUT + or (warn "$me: closing standard output: $!\n"), _exit (1); + + ($!, $?) = (0, $q); +} + + +# print_usage () +# -------------- +# Display usage (--help). +sub print_usage () +{ + print <<"END"; +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 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 + +Library directories: + -A, --autoconf-dir=ACDIR Autoconf's macro files location (rarely needed) + -l, --localdir=DIR location of \`aclocal.m4' + +Environment variables: + M4 GNU M4 1.4 or above + AUTOCONF autoconf @VERSION@ + +Report bugs to <@PACKAGE_BUGREPORT@>. +END + exit 0; +} + + +# print_version () +# ---------------- +# Display version (--version). +sub print_version +{ + print <<END; +autoupdate (@PACKAGE_NAME@) @VERSION@ +Written by David J. MacKenzie and Akim Demaille. + +Copyright 1994, 1999, 2000, 2001 Free Software Foundation, Inc. +This is free software; see the source for copying conditions. There is NO +warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. +END + exit 0; +} + + +# $CONFIGURE_AC +# &find_configure_ac () +# --------------------- +sub find_configure_ac () +{ + if (-f 'configure.ac') + { + if (-f 'configure.in') + { + warn "warning: `configure.ac' and `configure.in' both present.\n"; + warn "warning: proceeding with `configure.ac'.\n"; + } + return 'configure.ac'; + } + elsif (-f 'configure.in') + { + return 'configure.in'; + } + return; +} + + +# parse_args () +# ------------- +# Process any command line arguments. +sub parse_args () +{ + my $srcdir; + # F*k. Getopt seems bogus and dies when given `-' with `bundling'. + # If fixed some day, use this: '' => sub { push @ARGV, "-" } + my $update_stdin = grep /^-$/, @ARGV; + @ARGV = grep !/^-$/, @ARGV; + Getopt::Long::config ("bundling"); + Getopt::Long::GetOptions ('A|autoconf-dir|m|macrodir=s' => \$autoconf_dir, + 'l|localdir=s' => \$localdir, + 'd|debug' => \$debug, + 'h|help' => \&print_usage, + 'V|version' => \&print_version, + 'v|verbose' => \$verbose) + or exit 1; + push @ARGV, '-' + if $update_stdin; + if (! @ARGV) + { + my $configure_ac = find_configure_ac; + die 'no input file' + unless $configure_ac; + push @ARGV, $configure_ac; + } +} + + +# find_slaves +# ----------- +# Find the lib files and autoconf. +sub find_slaves () +{ + # Some non-GNU m4's don't reject the --help option, so give them /dev/null. + die "Autoconf requires GNU m4 1.4 or later\n" + if system "$m4 --help </dev/null 2>&1 | @FGREP@ reload-state >/dev/null"; + + # autoconf. + (my $dir = $0) =~ s,[^\\/]*$,,; + + # We test "$dir/autoconf" in case we are in the build tree, in which case + # the names are not transformed yet. + foreach my $file ($ENV{"AUTOCONF"} || '', + "$dir/@autoconf-name@", + "$dir/autoconf", + "@bindir@/@autoconf-name@") + { + if (-x $file) + { + $autoconf = $file; + last; + } + } + + # This is needed because perl's '-x' isn't a smart as bash's; that + # is, it won't find autoconf.sh. + $autoconf = 'autoconf' + if !$autoconf; +} + + +## -------------- ## +## Main program. ## +## -------------- ## +find_slaves; +parse_args; +mktmpdir; +$autoconf .= " --autoconf-dir $autoconf_dir --localdir $localdir"; + + +# @M4_BUILTINS -- M4 builtins and a useful comment. +my @m4_builtins = `echo dumpdef | $m4 2>&1 >/dev/null`; +map { s/:.*//;s/\W// } @m4_builtins; + + +# m4.m4 -- enable the m4 builtins. +# unm4.m4 -- disable the m4 builtins. +# savem4.m4 -- save the m4 builtins. +open M4_M4, ">$tmp/m4.m4" + or die "$me: cannot open: $!\n"; +open UNM4_M4, ">$tmp/unm4.m4" + or die "$me: cannot open: $!\n"; +open M4SAVE_M4, ">$tmp/m4save.m4" + or die "$me: cannot open: $!\n"; +foreach (@m4_builtins) + { + print M4_M4 "_au_define([$_], _au_defn([_au_$_]))\n"; + print UNM4_M4 "_au_undefine([$_])\n"; + print M4SAVE_M4 "define([_au_$_], defn([$_]))\n"; + } +close M4SAVE_M4 + or die "$me: cannot close: $!\n"; +close UNM4_M4 + or die "$me: cannot close: $!\n"; +close M4_M4 + or die "$me: cannot close: $!\n"; + + +# @AU_MACROS & AC_MACROS -- AU and AC macros and yet another useful comment. +open MACROS, ("$autoconf " + . "--trace AU_DEFUN:'AU:\$f:\$1' --trace define:'AC:\$f:\$1' " + . "-i /dev/null |") + or die "$me: cannot open: $!\n"; +my (%ac_macros, %au_macros); +while (<MACROS>) + { + chomp; + /^(AC|AU):(.*):([^:]*)$/ or next; + my $filename = basename ($2); + if ($1 eq "AC") + { + $ac_macros{$3} = $filename; + } + else + { + $au_macros{$3} = $filename; + } + } +close MACROS + or die "$me: cannot close: $!\n"; +# Don't keep AU macros in @AC_MACROS. +delete $ac_macros{$_} + foreach (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"; + } + +# $au_changequote -- enable the quote `[', `]' right before any AU macro. +my $au_changequote = + 's/\b(' . join ('|', keys %au_macros) . ')\b/_au_changequote([,])$1/g'; + +# au.m4 -- definitions the AU macros. +system ("$autoconf --trace AU_DEFUN:'_au_defun(\@<:\@\$1\@:>\@, +\@<:\@\$2\@:>\@)' -i /dev/null " + . ">$tmp/au.m4"); + +# ac.m4 -- autoquoting definitions of the AC macros (M4sugar excluded). +# disable.m4 -- undefine the macros of AC and m4sugar. +open AC_M4, ">$tmp/ac.m4" + or die "$me: cannot open: $!\n"; +open DISABLE_M4, ">$tmp/disable.m4" + or die "$me: cannot open: $!\n"; +foreach (sort keys %ac_macros) + { + print AC_M4 "_au_define([$_], [[\$0(\$\@)]])\n" + unless $ac_macros{$_} eq "m4sugar.m4"; + print DISABLE_M4 "_au_undefine([$_])\n"; + } +close DISABLE_M4 + or die "$me: cannot close: $!\n"; +close AC_M4 + or die "$me: cannot close: $!\n"; + + + +## ------------------- ## +## Process the files. ## +## ------------------- ## + +foreach my $file (@ARGV) + { + my $filename = $file; + # We need an actual file. + if ($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 $input_m4 = <<EOF; + divert(-1) -*- Autoconf -*- + changequote([, ]) + + # Move all the builtins into the \`_au_' pseudo namespace + include([$tmp/m4save.m4]) + + # _au_defun(NAME, BODY) + # --------------------- + # Define NAME to BODY, plus AU activation/deactivation. + _au_define([_au_defun], + [_au_define([\$1], + [_au_enable()dnl + \$2[]dnl + _au_disable()])]) + + # Import the definition of the obsolete macros. + _au_include([$tmp/au.m4]) + + + ## ------------------------ ## + ## _au_enable/_au_disable. ## + ## ------------------------ ## + + # They work by pair: each time an AU macro is activated, it runs + # _au_enable, and at its end its runs _au_disable (see _au_defun + # above). But since AU macros might use AU macros, which should + # enable/disable only for the outer AU macros. + # + # \`_au_enabled' is used to this end, condionning whether we really + # enable/disable. + + + # __au_enable + # ----------- + # Reenable the builtins, and m4sugar. + _au_define([__au_enable], + [_au_divert(-1) + # Enable special characters. + _au_changecom([#]) + + # Enable the m4 builtins, m4sugar and the autoquoting AC macros. + _au_include([$tmp/m4.m4]) + _au_include([$autoconf_dir/m4sugar.m4]) + _au_include([$tmp/ac.m4]) + + _au_divert(0)]) + + # _au_enable + # ---------- + # Called at the beginning of all the obsolete macros. Reenable the + # builtins, and m4sugar if needed. + _au_define([_au_enable], + [_au_ifdef([_au_enabled], + [], + [__au_enable()])_au_dnl + _au_pushdef([_au_enabled])]) + + + # __au_disable + # ------------ + # Disable the builtins, and m4sugar. + _au_define([__au_disable], + [_au_divert(-1) + # Disable m4sugar, the AC autoquoting macros, and m4. + _au_include([$tmp/disable.m4]) + _au_include([$tmp/unm4.m4]) + + # Disable special characters. + _au_changequote() + _au_changecom() + + _au_divert(0)]) + + # _au_disable + # ----------- + # Called at the end of all the obsolete macros. Disable the + # builtins, and m4sugar if needed.. + _au_define([_au_disable], + [_au_popdef([_au_enabled])_au_dnl + _au_ifdef([_au_enabled], + [], + [__au_disable()])]) + + + ## ------------------------------- ## + ## Disable, and process the file. ## + ## ------------------------------- ## + _au_disable()_au_dnl +EOF + + $input_m4 =~ s/^ //mg; + + # prepared input -- input, but reenables the quote before each AU macro. + open INPUT_M4, ">$tmp/input.m4" + or die "$me: cannot open: $!\n"; + open FILE, "<$file" + or die "$me: cannot open: $!\n"; + print INPUT_M4 "$input_m4"; + while (<FILE>) + { + eval $au_changequote; + print INPUT_M4; + } + close FILE + or die "$me: cannot close: $!\n"; + close INPUT_M4 + or die "$me: cannot close: $!\n"; + + # Now ask m4 to perform the update. + print STDERR "$me: running $m4 $tmp/input.m4\n" + if $verbose; + if (system ("$m4 $tmp/input.m4 >$tmp/updated")) + { + # Exit status of system() is in the upper byte. + $! >>= 8; + die "$me: cannot update \`$filename'\n"; + }; + + if ("$file" eq "$tmp/stdin") + { + system ("cat $tmp/updated"); + } + elsif (! system ("cmp -s $tmp/updated $file")) + { + # File didn't change, so don't update its mod time. + print STDERR "$me: \`$file' is unchanged\n" + } + else + { + # Back up and install the new one. + if (system ("mv $file $file${SIMPLE_BACKUP_SUFFIX} && " + . "mv $tmp/updated $file") == 0) + { + print STDERR "$me: \`$file' is updated\n"; + } + else + { + die "$me: cannot update \`$file'\n"; + } + } + } + +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 fourth 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' as 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 $#, which +# is bad), but the users would not be happy. +# +# Additionally, we introduced quotes that we not there before, which is +# OK in most cases, but could change the semantics of the file. +# +# Cruel dilemma: we do want the auto-quoting definition of `NEW' when +# evaluating `OLD', but we don't when we evaluate the second `NEW'. +# Back to namespaces? +# +# No. +# +# +# # Second step: replacement +# # ------------------------ +# +# No, as announced above, we will work in two steps: in a first step we +# compute the updated values, and in a second step we replace them. Our +# goal is something like this: +# +# divert(-1)dnl +# changequote([, ]) +# define([OLD], [NEW([1, 2], [3])changequote()]) +# undefine([dnl]) +# undefine([m4_eval]) +# # Some more undefines... +# changequote() +# divert(0)dnl +# dnl The Unbelievable Truth +# changequote([, ])OLD(1, 2) +# NEW([0, 0], +# 0) +# +# i.e., the new value of `OLD' is precomputed using the auto-quoting +# definition of `NEW' and the m4 builtins. We'll see how afterwards, +# let's finish with the replacement. +# +# Of course the solution above is wrong: if there were other calls to +# `OLD' with different values, we would smash them to the same value. +# But it is quite easy to generalize the scheme above: +# +# divert(-1)dnl +# changequote([, ]) +# define([OLD([1],[2])], [NEW([1, 2], [3])]) +# define([OLD], [defn([OLD($@)])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 +# `yipeee!'. +# +# +# # 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... nothinhg, 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.) |