[PATCH 3/3] Add a bootstrap script like Automake has.

[Zack Weinberg]

The bootstrap script generates the same files ‘autoreconf -vi’ would,
in a normal package, but it uses autoconf *from the git sources* to do
it.  This means people building from git do not need autoconf to be
installed already.  More importantly, it eliminates the extra steps
when building from git, of re-generating autoconf’s own configure
script with the just-built autoconf, then rebuilding the entire tree.

(This process still requires Automake to be installed already, and
Automake’s bootstrap script requires Autoconf to be installed already,
so there is still a dependency loop between Autoconf and Automake when
building from git—you need at least one of them installed from a
tarball to get started.)

The bootstrap script works by creating a partial installation tree in
a temporary directory, containing bin/autoconf, bin/autom4te, and just
enough of the usual contents of $(pkgdatadir) for autoconf and
autom4te to work.  It then runs a hardcoded list of commands,
corresponding to what ‘autoreconf -i -Wall,error’ would run, but
setting environment variables AUTOCONF and AUTOM4TE to ensure the
bootstrap versions of these tools are used.  (We have to create both,
because automake runs autoconf, not autom4te, to trace configure.ac.)

The ‘Autom4te’, ‘autoconf’, and ‘m4sugar’ subdirectories of the
partial installation tree are symlinked back to the source tree; this
is why version.m4 needed to be moved out of the m4sugar subdirectory,
so the bootstrap script can create it without scribbling on the source
tree.  autom4te is run in --melt mode, so we don’t need to create
freeze files in any subdirectories either.  All of the substitution
variables that are needed for autoconf and autom4te to both run, and
create the same output that they would have if fully configured, are
honored (unfortunately this does involve some messy digging around in
configure.ac with sed expressions).
---
 README-hacking |  22 +++--
 bootstrap      | 235 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 248 insertions(+), 9 deletions(-)
 create mode 100755 bootstrap

diff --git a/README-hacking b/README-hacking
index 1743dd37..6f766e70 100644
--- a/README-hacking
+++ b/README-hacking
@@ -14,7 +14,6 @@ requirements on anyone wishing to build from the 
just-checked-out sources.
 For example, you have to use recent stable versions of the maintainer
 tools we depend upon, including:
 
-- Autoconf 2.62+ <https://www.gnu.org/software/autoconf/>
 - Automake 1.11+ <https://www.gnu.org/software/automake/>
 - Help2man 1.29+ <https://www.gnu.org/software/help2man/>
 - M4 1.4.6+ <https://www.gnu.org/software/m4/>
@@ -71,18 +70,17 @@ project, you should use this instead:
 The next step is to generate files like configure and Makefile.in:
 
   $ cd autoconf
-  $ autoreconf -vi
+  $ ./bootstrap
 
-Since we're building autoconf itself, and its tests are picky, the
-following procedure includes an extra step to ensure that some
-generated files are regenerated using the tools just built by "make"
-(if you use GNU make, the file GNUmakefile sets PATH for you):
+The bootstrap script generates the same files ‘autoreconf -vi’ would,
+in a normal package, but it uses autoconf *from the git sources* to do
+it.  This means you do not need autoconf installed already, and you do
+not need to re-generate ‘configure’ after building Autoconf.
+
+You can now build and test the package:
 
   $ ./configure
   $ make
-  $ ( PATH=`pwd`/tests:$PATH; autoreconf -vi )
-  $ make distclean
-  $ ./configure
   $ make check
 
 At this point, there should be no difference between your local copy,
@@ -103,6 +101,12 @@ setting the configure_options variable:
 
   $ make check TESTSUITEFLAGS='configure_options="CC=gcc-2.95"'
 
+The test suite is not automatically parallelized by ‘make -j’.  If you
+want to parallelize the testsuite, you need to use TESTSUITEFLAGS for
+that, too:
+
+  $ make check TESTSUITEFLAGS=-j8
+
 * Submitting patches
 
 All patches should be submitted to <autoconf-patches@gnu.org> for
diff --git a/bootstrap b/bootstrap
new file mode 100755
index 00000000..8ea1b286
--- /dev/null
+++ b/bootstrap
@@ -0,0 +1,235 @@
+#! /bin/sh
+
+# This script helps bootstrap autoconf, when checked out from git.
+#
+# Copyright (C) 2021 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, see <https://www.gnu.org/licenses/>.
+
+# Autoconf's own configure script is generated using Autoconf.  This
+# script does what running `autoreconf -i` in an Autoconf git checkout
+# would do, except that it uses autoconf from the source tree we are
+# preparing, not any version of autoconf that might or might not be
+# installed already.  Note that automake, Perl, and GNU M4 _are_
+# required to be installed already.
+
+# Don't ignore failures.
+set -e
+(set -o pipefail 2> /dev/null) && set -o pipefail
+
+# Avoid problems due to various shell wrinkles.
+# We assume we have a shell new enough to implement unset correctly.
+(set -o posix 2> /dev/null) && set -o posix
+
+PS1='$ '
+PS2='> '
+PS4='+ '
+unset BASH_ENV CDPATH ENV IFS MAIL MAILPATH POSIXLY_CORRECT
+unset LANG LANGUAGE LC_ADDRESS LC_COLLATE LC_CTYPE LC_IDENTIFICATION
+unset LC_MEASUREMENT LC_MESSAGES LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER
+unset LC_TELEPHONE LC_TIME
+
+LC_ALL=C
+export LC_ALL
+
+# Set program basename.
+me=${0##*/}
+usage="usage: $me [options]
+
+Prepare to build a git checkout of autoconf.
+Functionally equivalent to \`autoreconf -i\`, but uses autoconf code
+from the git checkout itself to create \`configure\`.
+
+Options:
+  -f, --force      consider all files to be obsolete
+  -v, --verbose    verbosely report processing (repeat for more detail)
+"
+
+# Options.
+verbose=
+subverbose=
+force=
+while [ $# -gt 0 ]; do
+    case "$1" in
+        (-v | --verbose)
+            if [ -n "$verbose" ]; then
+                subverbose=--verbose
+            else
+                verbose=--verbose
+            fi
+        ;;
+        (-f | --force)
+            force=--force
+        ;;
+        (-h | --help)
+            printf '%s' "$usage"
+            exit 0
+        ;;
+        (*)
+            printf '%s' "$usage" >&2
+            exit 1
+        ;;
+    esac
+    shift
+done
+
+
+# Let the user choose which version of aclocal, automake, m4, and perl to use.
+: ${ACLOCAL=aclocal}
+: ${AUTOMAKE=automake}
+: ${M4=m4}
+: ${PERL=perl}
+export ACLOCAL AUTOMAKE M4 PERL
+
+# $PERL needs to be an absolute path because we're going to substitute it
+# into #! lines.
+set fnord $PERL
+shift
+PERL=$(command -v $1)
+shift
+if [ $# -gt 0 ]; then
+    PERL="$PERL $*"
+fi
+
+# Override SHELL.  This is required on DJGPP so that Perl's system()
+# uses bash, not COMMAND.COM which doesn't quote arguments properly.
+# It's not used otherwise.
+if test -n "$DJDIR"; then
+  BOOTSTRAP_SHELL=/dev/env/DJDIR/bin/bash.exe
+else
+  BOOTSTRAP_SHELL=/bin/sh
+fi
+
+# Determine whether we have a usable version of M4.
+# This rule is pickier than the rule in autoconf's actual configure script.
+m4_version="$($M4 --version | head -1)"
+case "$m4_version" in
+  ( *\ 0.*                \
+  | *\ 1.[0123]           \
+  | *\ 1.[0123].*         \
+  | *\ 1.4.[0123456789]   \
+  | *\ 1.4.1[012345]      \
+  )
+    printf '%s\n' "$me: $M4 ($m4_version) is too old" >&2
+    exit 1
+    ;;
+esac
+
+# Substitutions related to the version of M4 available.
+M4_DEBUGFILE=
+M4_GNU=
+m4_help=$($M4 --help)
+case "$m4_help" in
+  (*--debugfile*)
+    M4_DEBUGFILE=--debugfile ;;
+  (*--error-output*)
+    M4_DEBUGFILE=--error-output ;;
+esac
+case "$m4_help" in
+  (*--gnu*)
+    M4_GNU=--gnu ;;
+esac
+
+# Autoconf's version number and identifiers.
+RELEASE_YEAR=$(sed -ne 's/^RELEASE_YEAR=\([0-9][0-9]*\)$/\1/p' configure.ac)
+VERSION=$(build-aux/git-version-gen .tarball-version)
+
+# PACKAGE_NAME and PACKAGE_BUGREPORT from the bootstrap autoconf can
+# get copied into the generated configure script, so we need to get them
+# right.  Caution: there is a hard tab in one of the regexes below.
+PACKAGE_NAME=$(sed -ne 's/^AC_INIT(\[\([^]]*\)\].*$/\1/p' configure.ac)
+PACKAGE_BUGREPORT=$(sed -ne '
+    /^AC_INIT/,/^A[CHMU]_/s/^[         ]*\[\(bug-[^]]*\)\].*$/\1/p' 
configure.ac)
+
+# PACKAGE_TARNAME and PACKAGE_URL from the bootstrap autoconf should not
+# get copied into the configure script.
+PACKAGE_URL='<<not available>>'
+PACKAGE_TARNAME='<<not available>>'
+
+# Root for temporary partial installation tree.
+ACBOOTDIR=$(mktemp -d acboot.XXXXXXXXXX)
+
+# dosubst options infile outfile -- performs the substitutions that
+# config.status would perform on INFILE, creating OUTFILE.  INFILE is
+# relative to the source directory, OUTFILE is relative to $ACBOOTDIR.
+# If OPTIONS is the letter 'x', OUTFILE is made executable after creation.
+dosubst ()
+{
+    in=${2##*/}
+    out="$ACBOOTDIR/$3"
+    if [ -n "$verbose" ]; then
+        printf '%s: creating %s\n' "$me" "$out"
+    fi
+    rm -f "$out"
+    sed -e "s%@configure_input@%Generated from $in; do not edit by hand.%g" \
+        -e "s%@M4@%$M4%g" \
+        -e "s%@M4_DEBUGFILE@%$M4_DEBUGFILE%g" \
+        -e "s%@M4_GNU@%$M4_GNU%g" \
+        -e "s%@PACKAGE_BUGREPORT@%$PACKAGE_BUGREPORT%g" \
+        -e "s%@PACKAGE_NAME@%$PACKAGE_NAME%g" \
+        -e "s%@PACKAGE_STRING@%$PACKAGE_NAME $VERSION%g" \
+        -e "s%@PACKAGE_TARNAME@%$PACKAGE_TARNAME%g" \
+        -e "s%@PACKAGE_URL@%$PACKAGE_URL%g" \
+        -e "s%@PACKAGE_VERSION@%$VERSION%g" \
+        -e "s%@PERL@%$PERL%g" \
+        -e "s%@PERL_FLOCK@%0%g" \
+        -e "s%@RELEASE_YEAR@%$RELEASE_YEAR%g" \
+        -e "s%@SHELL@%$BOOTSTRAP_SHELL%g" \
+        -e "s%@VERSION@%$VERSION%g" \
+        -e "s%@pkgdatadir@%$ACBOOTDIR/lib%g" \
+        "$2" > "$out"
+    if [ "$1" = "x" ]; then
+        chmod +x "$out"
+    fi
+}
+
+# Create the bootstrap installation.
+mkdir "$ACBOOTDIR"/bin "$ACBOOTDIR"/lib "$ACBOOTDIR"/tmp
+(
+    cd "$ACBOOTDIR"/lib
+    for sub in Autom4te autoconf m4sugar ; do
+        if [ -n "$verbose" ]; then
+            printf '%s: creating %s\n' "$me" "$ACBOOTDIR/lib/$sub"
+        fi
+        ln -s ../../lib/$sub .
+    done
+)
+
+# automake invokes autoconf, and autoconf and aclocal both invoke autom4te,
+# so we need to create both of them.
+dosubst x bin/autoconf.in bin/autoconf
+dosubst x bin/autom4te.in bin/autom4te
+dosubst . lib/autom4te.in lib/autom4te.cfg
+dosubst . lib/version.in  lib/version.m4
+
+AUTOCONF="$ACBOOTDIR"/bin/autoconf
+AUTOM4TE="$ACBOOTDIR/bin/autom4te -M -C $ACBOOTDIR/tmp/autom4te.cache"
+export AUTOCONF AUTOM4TE
+
+# We can now do what autoreconf would have done.
+# Order is critical -- first aclocal, then autoconf, then automake.
+run ()
+{
+    if [ -n "$verbose" ]; then
+        printf '%s: running %s\n' "$me" "$*"
+    fi
+    "$@"
+}
+
+run $ACLOCAL -I m4 -Wall -Werror $subverbose $force
+run $AUTOCONF -Wall -Werror $subverbose $force
+run $AUTOMAKE --add-missing --copy -Wall -Werror $subverbose $force
+
+# Clean up.
+rm -rf "$ACBOOTDIR"
-- 
2.30.0