#!/bin/sh

# Build portable binary release tarballs for Linux/x64 and Linux/arm64.
#
# Author: Holger Weiss <holger@zedat.fu-berlin.de>.
#
# Copyright (c) 2022 ProcessOne, SARL.
# All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

set -e
set -u

export PATH='/usr/local/bin:/usr/bin:/bin'

myself=${0##*/}

info()
{
	echo "$myself: $*"
}

error()
{
	echo >&2 "$myself: $*"
}

usage()
{
	echo >&2 "Usage: $myself"
	exit 2
}

mix_version()
{
	# Mix insists on SemVer format.
	local vsn="$(printf '%s' "$1" | sed 's/\.0/./')"

	case $vsn in
	*.*.*) printf '%s' "$vsn" ;;
	*.*) printf '%s.0' "$vsn" ;;
	esac
}

if ! [ -e 'mix.exs' ] || ! [ -e "tools/$myself" ]
then
	error "Please call this script from the repository's root directory."
	exit 2
elif [ $# -ne 0 ]
then
	usage
fi

rel_name='ejabberd'
rel_vsn=$(git describe --tags | sed -e 's/-g.*//' -e 's/-/./' | tr -d '[:space:]')
mix_vsn=$(mix_version "$rel_vsn")
crosstool_vsn='1.25.0'
termcap_vsn='1.3.1'
expat_vsn='2.5.0'
zlib_vsn='1.2.13'
yaml_vsn='0.2.5'
ssl_vsn='1.1.1u'
otp_vsn='25.3.2.4'
elixir_vsn='1.15.4'
pam_vsn='1.5.2'
png_vsn='1.6.40'
jpeg_vsn='9e'
webp_vsn='1.3.1'
gd_vsn='2.3.3'
odbc_vsn='2.3.11'
sqlite_vsn='3420000'
root_dir="${BUILD_DIR:-$HOME/build}"
bootstrap_dir="$root_dir/bootstrap"
ct_prefix_dir="$root_dir/x-tools"
build_dir="$root_dir/$rel_name"
crosstool_dir="crosstool-ng-$crosstool_vsn"
termcap_dir="termcap-$termcap_vsn"
expat_dir="expat-$expat_vsn"
zlib_dir="zlib-$zlib_vsn"
yaml_dir="yaml-$yaml_vsn"
ssl_dir="openssl-$ssl_vsn"
otp_dir="otp_src_$otp_vsn"
elixir_dir="elixir-$elixir_vsn"
pam_dir="Linux-PAM-$pam_vsn"
png_dir="libpng-$png_vsn"
jpeg_dir="jpeg-$jpeg_vsn"
webp_dir="libwebp-$webp_vsn"
gd_dir="libgd-$gd_vsn"
odbc_dir="unixODBC-$odbc_vsn"
sqlite_dir="sqlite-autoconf-$sqlite_vsn"
crosstool_tar="$crosstool_dir.tar.xz"
termcap_tar="$termcap_dir.tar.gz"
expat_tar="$expat_dir.tar.gz"
zlib_tar="$zlib_dir.tar.gz"
yaml_tar="$yaml_dir.tar.gz"
ssl_tar="$ssl_dir.tar.gz"
otp_tar="$otp_dir.tar.gz"
elixir_tar="v$elixir_vsn.tar.gz"
pam_tar="$pam_dir.tar.xz"
png_tar="$png_dir.tar.gz"
jpeg_tar="jpegsrc.v$jpeg_vsn.tar.gz"
webp_tar="$webp_dir.tar.gz"
gd_tar="$gd_dir.tar.gz"
sqlite_tar="$sqlite_dir.tar.gz"
odbc_tar="$odbc_dir.tar.gz"
rel_tar="$rel_name-$mix_vsn.tar.gz"
ct_jobs=$(nproc)
src_dir="$root_dir/src"
platform=$(gcc -dumpmachine)
targets='x86_64-linux-gnu aarch64-linux-gnu'
build_start=$(date '+%F %T')
have_current_deps='false'
dep_vsns_file="$build_dir/.dep_vsns"
dep_vsns=''
deps='crosstool
      termcap
      expat
      zlib
      yaml
      ssl
      otp
      elixir
      pam
      png
      jpeg
      webp
      gd
      odbc
      sqlite'

umask 022

#' Try to find a browser for checking dependency versions.
have_browser()
{
	for browser in 'lynx' 'links' 'elinks'
	do
		$browser -dump 'https://ejabberd.im/' >'/dev/null' && return 0
	done
	return 1
}
#.

#' Check whether the given dependency version is up-to-date.
check_vsn()
{
	local name="$1"
	local our_vsn="$2"
	local src_url="$3"
	local reg_exp="$4"
	local cur_vsn=$($browser -dump "$src_url" |
	                sed -n "s/.*$reg_exp.*/\\1/p" |
	                head -1)

	if [ "$our_vsn" = "$cur_vsn" ]
	then
		return 0
	else
		error "Current $name version is: $cur_vsn"
		error "But our $name version is: $our_vsn"
		error "Update $0 or set CHECK_DEPS=false"
		exit 1
	fi
}
#.

#' Check whether our dependency versions are up-to-date.
check_configured_dep_vsns()
{
	check_vsn 'OpenSSL' "$ssl_vsn" \
	          'https://www.openssl.org/source/' \
	          'openssl-\(1\.[0-9][0-9a-z.]*\)\.tar\.gz'
	check_vsn 'LibYAML' "$yaml_vsn" \
	          'https://pyyaml.org/wiki/LibYAML' \
	          'yaml-\([0-9][0-9.]*\)\.tar\.gz'
	check_vsn 'zlib' "$zlib_vsn" \
	          'https://zlib.net/' \
	          'zlib-\([1-9][0-9.]*\)\.tar\.gz'
	check_vsn 'Expat' "$expat_vsn" \
	          'https://github.com/libexpat/libexpat/releases' \
	          '\([1-9]\.[0-9]*\.[0-9]*\)'
	check_vsn 'Termcap' "$termcap_vsn" \
	          'https://ftp.gnu.org/gnu/termcap/' \
	          'termcap-\([1-9][0-9.]*\)\.tar\.gz'
	check_vsn 'SQLite' "$sqlite_vsn" \
	          'https://www.sqlite.org/download.html' \
	          'sqlite-autoconf-\([1-9][0-9]*\)\.tar\.gz'
	check_vsn 'ODBC' "$odbc_vsn" \
	          'http://www.unixodbc.org/download.html' \
	          'unixODBC-\([1-9][0-9.]*\)\.tar\.gz'
	check_vsn 'Linux-PAM' "$pam_vsn" \
	          'https://github.com/linux-pam/linux-pam/releases' \
	          '[0-9]\]Linux-PAM \([1-9][0-9.]*\)'
	check_vsn 'libpng' "$png_vsn" \
	          'http://www.libpng.org/pub/png/libpng.html' \
		  'libpng-\([1-9][0-9.]*\)\.tar\.gz'
	check_vsn 'JPEG' "$jpeg_vsn" \
	          'https://www.ijg.org' \
	          'jpegsrc.v\([1-9][0-9a-z]*\)\.tar\.gz'
	check_vsn 'WebP' "$webp_vsn" \
	          'https://developers.google.com/speed/webp/download' \
	          'libwebp-\([1-9][0-9.]*\)\.tar\.gz'
	check_vsn 'LibGD' "$gd_vsn" \
	          'https://github.com/libgd/libgd/releases' \
	          'gd-\([1-9][0-9.]*\)'
	check_vsn 'Elixir' "$elixir_vsn" \
	          'https://elixir-lang.org/install.html' \
	          'v\([1-9][0-9.]*\)\.tar\.gz'
}
#.

#' Check whether existing dependencies are up-to-date.
check_built_dep_vsns()
{
	for dep in $deps
	do
		eval dep_vsns=\"\$dep_vsns\$${dep}_vsn\"
	done

	if [ -e "$dep_vsns_file" ]
	then
		if [ "$dep_vsns" = "$(cat "$dep_vsns_file")" ]
		then have_current_deps='true'
		fi
		rm "$dep_vsns_file"
	fi
}
#.

#' Save built dependency versions.
save_built_dep_vsns()
{
	echo "$dep_vsns" >"$dep_vsns_file"
}
#.

#' Create common part of Crosstool-NG configuration file.
create_common_config()
{
	local file="$1"

	cat >"$file" <<-'EOF'
		CT_CONFIG_VERSION="4"
		CT_DOWNLOAD_AGENT_CURL=y
		CT_OMIT_TARGET_VENDOR=y
		CT_CC_LANG_CXX=y
		CT_ARCH_64=y
		CT_KERNEL_LINUX=y
		CT_LINUX_V_3_16=y
		CT_LOG_PROGRESS_BAR=n
	EOF
}
#.

#' Create Crosstool-NG configuration file for glibc.
create_gnu_config()
{
	local file="$1"

	create_common_config "$file"

	cat >>"$file" <<-'EOF'
		CT_GLIBC_V_2_19=y
	EOF
}
#.

#' Create Crosstool-NG configuration file for musl.
create_musl_config()
{
	local file="$1"

	create_common_config "$file"

	cat >>"$file" <<-'EOF'
		CT_EXPERIMENTAL=y
		CT_LIBC_MUSL=y
	EOF
}
#.

#' Create Crosstool-NG configuration file for x64.
create_x64_config()
{
	local file="$1"
	local libc="$2"

	create_${libc}_config "$file"

	cat >>"$file" <<-'EOF'
		CT_ARCH_X86=y
	EOF
}
#.

#' Create Crosstool-NG configuration file for arm64.
create_arm64_config()
{
	local file="$1"
	local libc="$2"

	create_${libc}_config "$file"

	cat >>"$file" <<-'EOF'
		CT_ARCH_ARM=y
	EOF
}
#.

#' Return our name for the given platform.
arch_name()
{
	local target="$1"

	case $target in
	x86_64*)
		printf 'x64'
		;;
	aarch64*)
		printf 'arm64'
		;;
	*)
		error "Unsupported target platform: $target"
		exit 1
		;;
	esac
}
#.

#' Add native Erlang/OTP "bin" directory to PATH (for bootstrapping and Mix).
add_otp_path()
{
	local mode="$1"
	local prefix="$2"

	if [ "$mode" = 'native' ]
	then native_otp_bin="$prefix/bin"
	elif [ -n "${INSTALL_DIR_FOR_OTP+x}" ] && [ -n "${INSTALL_DIR_FOR_ELIXIR+x}" ]
	then
		# For github runners to build for non-native systems:
		# https://github.com/erlef/setup-beam#environment-variables
		native_otp_bin="$INSTALL_DIR_FOR_OTP/bin"
		native_elixir_bin="$INSTALL_DIR_FOR_ELIXIR/bin"
		export PATH="$native_elixir_bin:$PATH"
	fi
	export PATH="$native_otp_bin:$PATH"
}
#.

#' Create and populate /opt/ejabberd directory.
create_data_dir()
{
	local code_dir="$1"
	local data_dir="$2"

	mkdir "$data_dir" "$data_dir/database" "$data_dir/logs"
	mv "$code_dir/conf" "$data_dir"
	chmod 'o-rwx' "$data_dir/"*
	curl --no-progress-meter -o "$data_dir/conf/cacert.pem" 'https://curl.se/ca/cacert.pem'
	sed -i '/^loglevel:/a\
\
ca_file: /opt/ejabberd/conf/cacert.pem\
\
certfiles:\
  - /opt/ejabberd/conf/server.pem' "$data_dir/conf/$rel_name.yml"
}
#.

#' Add systemd unit and init script.
add_systemd_unit()
{
	local code_dir="$1"

	sed -e "s|@ctlscriptpath@|/opt/$rel_name-$rel_vsn/bin|g" \
	    -e "s|@installuser@|$rel_name|g" 'ejabberd.service.template' \
	    >"$code_dir/bin/ejabberd.service"
	sed -e "s|@ctlscriptpath@|/opt/$rel_name-$rel_vsn/bin|g" \
	    -e "s|@installuser@|$rel_name|g" 'ejabberd.init.template' \
	    >"$code_dir/bin/ejabberd.init"
	chmod '+x' "$code_dir/bin/ejabberd.init"
}
#.

#' Add CAPTCHA script(s).
add_captcha_script()
{
	local code_dir="$1"

	cp -p 'tools/captcha'*'.sh' "$code_dir/lib"
}
#.

#' Use our VT100 to avoid depending on Terminfo, adjust options/paths.
edit_ejabberdctl()
{
	local code_dir="$1"

	sed -i \
	    -e "2iexport TERM='internal'" \
	    -e '/ERL_OPTIONS=/d' \
	    -e 's|^ERLANG_NODE=ejabberd$|ERLANG_NODE=ejabberd@localhost|' \
	    -e 's|_DIR:=".*}/|_DIR:="/opt/ejabberd/|' \
	    -e 's|/database|/database/$ERLANG_NODE|' \
	    "$code_dir/bin/${rel_name}ctl"
}
#.

#' Delete unused files and directories, just to save some space.
remove_unused_files()
{
	local code_dir="$1"

	# Remove shared object file used only in test suite:
	find "$code_dir/lib" -name 'otp_test_engine.so' -delete

	# Remove shared object files of statically linked NIFs:
	find "$code_dir/lib/crypto-"* "$code_dir/lib/asn1-"* \
	    '(' -name 'asn1rt_nif.so' -o \
	        -name 'crypto.so' -o \
	        -name 'lib' -o \
	        -name 'priv' ')' \
	    -delete

	# Remove unused ERTS binaries (see systools_make:erts_binary_filter/0):
	find "$code_dir/erts-"*'/bin' \
	    '(' -name 'ct_run' -o \
	        -name 'dialyzer' -o \
	        -name 'erlc' -o \
	        -name 'typer' -o \
	        -name 'yielding_c_fun' ')' \
	    -delete

	# Remove unused Mix stuff:
	find "$code_dir/bin" -name 'ejabberd' -delete
	find "$code_dir/releases" -name 'COOKIE' -delete
}
#.

#' Strip ERTS binaries, shared objects, and BEAM files.
strip_files()
{
	local code_dir="$1"
	local strip_cmd="$2"

	find "$code_dir/lib" \
	    -type f \
	    -name '*.so' \
	    -exec "$strip_cmd" -s '{}' '+'
	find "$code_dir/erts-"*'/bin' "$code_dir/lib/"*'/priv/bin' \
	    -type f \
	    -perm '-u+x' \
	    -exec "$strip_cmd" -s '{}' '+' 2>'/dev/null' || :
	erl -noinput -eval \
	    "{ok, _} = beam_lib:strip_release('$code_dir'), halt()"
}
#.

#' Build toochain for a given target.
build_toolchain()
{
	local target="$1"
	local prefix="$2"
	local arch=$(arch_name "$target")
	local libc="${target##*-}"

	if [ -d "$prefix" ]
	then
		info "Using existing toolchain in $prefix ..."
	else
		if ! [ -x "$bootstrap_dir/bin/ct-ng" ]
		then
			info "Extracting Crosstool-NG $crosstool_vsn ..."
			cd "$src_dir"
			tar -xJf "$crosstool_tar"
			cd "$OLDPWD"

			info "Building Crosstool-NG $crosstool_vsn ..."
			cd "$src_dir/$crosstool_dir"
			./configure --prefix="$bootstrap_dir"
			make V=0
			make install
			cd "$OLDPWD"
		fi

		info "Building toolchain for $arch-$libc ..."
		cd "$root_dir"
		create_${arch}_config 'defconfig' "$libc"
		ct-ng defconfig
		sed -i -e "s|^CT_ZLIB_VERSION=.*|CT_ZLIB_VERSION=\"$zlib_vsn\"|" .config
		sed -i -e 's|^CT_ZLIB_MIRRORS=.*|CT_ZLIB_MIRRORS="https://github.com/madler/zlib/releases/download/v${CT_ZLIB_VERSION} https://www.zlib.net/ https://www.zlib.net/fossils/"|' .config
		ct-ng build CT_PREFIX="$ct_prefix_dir" CT_JOBS="$ct_jobs"
		rm -rf '.config' '.build' 'build.log'
		cd "$OLDPWD"
	fi
}
#.

#' Build target dependencies.
build_deps()
{
	local mode="$1"
	local target="$2"
	local prefix="$3"
	local arch="$(arch_name "$target")"
	local libc="${target##*-}"
	local target_src_dir="$prefix/src"
	local saved_path="$PATH"

	if [ "$mode" = 'cross' ]
	then configure="./configure --host=$target --build=$platform"
	else configure='./configure'
	fi

	mkdir "$prefix"

	info 'Extracting dependencies ...'
	mkdir "$target_src_dir"
	cd "$target_src_dir"
	tar -xzf "$src_dir/$termcap_tar"
	tar -xzf "$src_dir/$sqlite_tar"
	tar -xzf "$src_dir/$odbc_tar"
	tar -xzf "$src_dir/$expat_tar"
	tar -xzf "$src_dir/$zlib_tar"
	tar -xzf "$src_dir/$yaml_tar"
	tar -xzf "$src_dir/$ssl_tar"
	tar -xzf "$src_dir/$otp_tar"
	tar -xzf "$src_dir/$elixir_tar"
	tar -xzf "$src_dir/$png_tar"
	tar -xzf "$src_dir/$jpeg_tar"
	tar -xzf "$src_dir/$webp_tar"
	tar -xzf "$src_dir/$gd_tar"
	tar -xJf "$src_dir/$pam_tar"
	cd "$OLDPWD"

	info "Building Termcap $termcap_vsn for $arch-$libc ..."
	cd "$target_src_dir/$termcap_dir"
	$configure --prefix="$prefix"
	cat >'config.h' <<-'EOF'
		#ifndef CONFIG_H
		#define CONFIG_H
		#define INTERNAL_TERMINAL "internal:\\\n" \
			"\t:am:bs:ms:xn:xo:\\\n" \
			"\t:co#80:it#8:li#24:vt#3:\\\n" \
			"\t:@8=\\EOM:DO=\\E[%dB:K1=\\EOq:K2=\\EOr:K3=\\EOs:K4=\\EOp:K5=\\EOn:\\\n" \
			"\t:LE=\\E[%dD:RA=\\E[?7l:RI=\\E[%dC:SA=\\E[?7h:UP=\\E[%dA:\\\n" \
			"\t:ac=``aaffggjjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~:\\\n" \
			"\t:ae=^O:as=^N:bl=^G:cb=\\E[1K:cd=\\E[J:ce=\\E[K:cl=\\E[H\\E[J:\\\n" \
			"\t:cm=\\E[%i%d;%dH:cr=^M:cs=\\E[%i%d;%dr:ct=\\E[3g:do=^J:\\\n" \
			"\t:eA=\\E(B\\E)0:ho=\\E[H:k0=\\EOy:k1=\\EOP:k2=\\EOQ:k3=\\EOR:\\\n" \
			"\t:k4=\\EOS:k5=\\EOt:k6=\\EOu:k7=\\EOv:k8=\\EOl:k9=\\EOw:k;=\\EOx:\\\n" \
			"\t:kb=^H:kd=\\EOB:ke=\\E[?1l\\E>:kl=\\EOD:kr=\\EOC:ks=\\E[?1h\\E=:\\\n" \
			"\t:ku=\\EOA:le=^H:mb=\\E[5m:md=\\E[1m:me=\\E[m\\017:mr=\\E[7m:\\\n" \
			"\t:nd=\\E[C:rc=\\E8:rs=\\E>\\E[?3l\\E[?4l\\E[?5l\\E[?7h\\E[?8h:\\\n" \
			"\t:..sa=\\E[0%?%p1%p6%|%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;m%?%p9%t\\016%e\\017%;:\\\n" \
			"\t:sc=\\E7:se=\\E[m:sf=^J:so=\\E[7m:sr=\\EM:st=\\EH:ta=^I:ue=\\E[m:\\\n" \
			"\t:up=\\E[A:us=\\E[4m:"
		#endif
	EOF
	make CPPFLAGS="$CPPFLAGS -DHAVE_CONFIG_H=1"
	make install
	cd "$OLDPWD"

	info "Building zlib $zlib_vsn for $arch-$libc ..."
	cd "$target_src_dir/$zlib_dir"
	CFLAGS="$CFLAGS -O3 -fPIC" ./configure --prefix="$prefix" --static
	make
	make install
	cd "$OLDPWD"

	info "Building OpenSSL $ssl_vsn for $arch-$libc ..."
	cd "$target_src_dir/$ssl_dir"
	CFLAGS="$CFLAGS -O3 -fPIC" ./Configure no-shared no-ui-console \
	    --prefix="$prefix" \
	    --openssldir="$prefix" \
	    "linux-${target%-linux-*}"
	make build_libs
	make install_dev
	cd "$OLDPWD"

	info "Building Expat $expat_vsn for $arch-$libc ..."
	cd "$target_src_dir/$expat_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    --without-docbook \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building LibYAML $yaml_vsn for $arch-$libc ..."
	cd "$target_src_dir/$yaml_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building SQLite $sqlite_vsn for $arch-$libc ..."
	cd "$target_src_dir/$sqlite_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building ODBC $odbc_vsn for $arch-$libc ..."
	cd "$target_src_dir/$odbc_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building Linux-PAM $pam_vsn for $arch ..."
	cd "$target_src_dir/$pam_dir"
	$configure --prefix="$prefix" --includedir="$prefix/include/security" \
	    --enable-static --disable-shared --disable-doc --disable-examples \
	    --enable-db=no \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building libpng $png_vsn for $arch-$libc ..."
	cd "$target_src_dir/$png_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building JPEG $jpeg_vsn for $arch-$libc ..."
	cd "$target_src_dir/$jpeg_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building WebP $webp_vsn for $arch-$libc ..."
	cd "$target_src_dir/$webp_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building LibGD $gd_vsn for $arch-$libc ..."
	cd "$target_src_dir/$gd_dir"
	$configure --prefix="$prefix" --enable-static --disable-shared \
	    --with-zlib="$prefix" \
	    --with-webp="$prefix" \
	    --with-jpeg="$prefix" \
	    --with-png="$prefix" \
	    --without-avif \
	    --without-fontconfig \
	    --without-freetype \
	    --without-heif \
	    --without-libiconv-prefix \
	    --without-liq \
	    --without-raqm \
	    --without-tiff \
	    --without-x \
	    --without-xpm \
	    CFLAGS="$CFLAGS -O3 -fPIC"
	make
	make install
	cd "$OLDPWD"

	info "Building Erlang/OTP $otp_vsn for $arch-$libc ..."
	if [ "$mode" = 'cross' ]
	then
		add_otp_path "$mode" "$prefix"
		export erl_xcomp_sysroot="$prefix"
	fi
	cd "$target_src_dir/$otp_dir"
	# The additional CFLAGS/LIBS below are required by --enable-static-nifs.
	# The "-ldl" flag specifically is only needed for ODBC, though.
	$configure \
	    --prefix="$prefix" \
	    --with-ssl="$prefix" \
	    --with-odbc="$prefix" \
	    --without-javac \
	    --disable-dynamic-ssl-lib \
	    --enable-static-nifs \
	    CFLAGS="$CFLAGS -Wl,-L$prefix/lib" \
	    LIBS='-lcrypto -ldl'
	make
	make install
	if [ "$mode" = 'native' ]
	then add_otp_path "$mode" "$prefix"
	else unset erl_xcomp_sysroot
	fi
	cd "$OLDPWD"

	info "Building Elixir $elixir_vsn for $arch-$libc ..."
	cd "$target_src_dir/$elixir_dir"
	make install PREFIX="$prefix"
	cd "$OLDPWD"

	export PATH="$saved_path"
}
#.

#' Build the actual release.
build_rel()
{
	local mode="$1"
	local target="$2"
	local prefix="$3"
	local arch="$(arch_name "$target")"
	local libc="${target##*-}"
	local rel_dir="$PWD/_build/prod"
	local target_data_dir="$prefix/$rel_name"
	local target_dst_dir="$prefix/$rel_name-$rel_vsn"
	local target_dst_tar="$rel_name-$rel_vsn-linux-$libc-$arch.tar.gz"
	local saved_path="$PATH"

	#
	# The "$ct_prefix_dir/$target/$target/bin" directory contains cross
	# compilation tools without "$target-" prefix. We add it to the PATH,
	# just in case tools are called without prefix somewhere. However, we
	# try to use the prefixed tools everywhere, so it should be possible to
	# omit this directory from the path if desired. See also:
	#
	# https://stackoverflow.com/a/24243789
	#
	export PATH="$ct_prefix_dir/$target/bin:$ct_prefix_dir/$target/$target/bin:$PATH"
	export CC="$target-gcc"
	export CXX="$target-g++"
	export CPP="$target-cpp"
	export LD="$target-ld"
	export AS="$target-as"
	export AR="$target-ar"
	export NM="$target-nm"
	export RANLIB="$target-ranlib"
	export OBJCOPY="$target-objcopy"
	export STRIP="$target-strip"
	export CPPFLAGS="-I$prefix/include"
	export CFLAGS="-g0 -O2 -pipe -fomit-frame-pointer -static-libgcc $CPPFLAGS"
	export CXXFLAGS="$CFLAGS -static-libstdc++"
	export LDFLAGS="-L$prefix/lib -static-libgcc -static-libstdc++"
	export ERL_COMPILER_OPTIONS='[no_debug_info]' # Building 25.x fails with 'deterministic'.

	if [ "$mode" = 'cross' ]
	then configure="./configure --host=$target --build=$platform"
	else configure='./configure'
	fi

	if [ $have_current_deps = false ]
	then build_deps "$mode" "$target" "$prefix"
	fi

	add_otp_path "$mode" "$prefix"

	if [ "$mode" = 'native' ] # In order to only do this once.
	then
		info "Fetching Mix dependencies"
		mix local.hex --force
		mix local.rebar --force
	fi

	info "Removing old $rel_name builds"
	rm -rf '_build' 'deps'

	info "Building $rel_name $rel_vsn for $arch-$libc ..."
	./autogen.sh
	eimp_cflags='-fcommon'
	eimp_libs='-lwebp -ljpeg -lpng -lz -lm'
	export CC="$CC -Wl,-ldl" # Required by (statically linking) epam.
	export LIBS="$eimp_libs -lcrypto -lpthread -ldl"
	export CFLAGS="$CFLAGS $eimp_cflags"
	export LDFLAGS="$LDFLAGS $eimp_libs"
	if [ "$mode" = 'cross' ]
	then
		# Hand over --host/--build to configure scripts of dependencies.
		export host_alias="$target"
		export build_alias="$platform"
	fi
	# The cache variable makes cross compilation work.
	ac_cv_erlang_root_dir="$prefix/lib/erlang" $configure \
	    --with-rebar='mix' \
	    --with-sqlite3="$prefix" \
	    --enable-user="$rel_name" \
	    --enable-all \
	    --disable-erlang-version-check
	make deps
	sed -i 's/ *-lstdc++//g' 'deps/'*'/rebar.config'* # Link statically.
	if [ "$mode" = 'cross' ]
	then
		ln -s "$prefix/lib/erlang" 'lib/erlang'
		erts_dir=$(ls -1d 'lib/erlang/erts-'*)
		ei_inc="$prefix/lib/erlang/lib/erl_interface-"*'/include'
		ei_lib="$prefix/lib/erlang/lib/erl_interface-"*'/lib'
		export LDLIBS='-lpthread'
		export ERL_EI_INCLUDE_DIR=$(ls -1d $ei_inc)
		export ERL_EI_LIBDIR=$(ls -1d $ei_lib)
		sed -i "/include_executables/a\\
		    include_erts: \"$erts_dir\"," 'mix.exs'
	fi
	make rel
	if [ "$mode" = 'cross' ]
	then
		sed -i '/include_erts/d' 'mix.exs'
		rm 'lib/erlang'
		unset LDLIBS ERL_EI_INCLUDE_DIR ERL_EI_LIBDIR
		unset host_alias build_alias
	fi

	info "Putting together $rel_name $rel_vsn archive for $arch-$libc ..."
	mkdir "$target_dst_dir"
	tar -C "$target_dst_dir" -xzf "$rel_dir/$rel_tar"
	create_data_dir "$target_dst_dir" "$target_data_dir"
	add_systemd_unit "$target_dst_dir"
	add_captcha_script "$target_dst_dir"
	edit_ejabberdctl "$target_dst_dir"
	remove_unused_files "$target_dst_dir"
	strip_files "$target_dst_dir" "$STRIP"
	tar -C "$prefix" --owner="$rel_name" --group="$rel_name" -cf - \
	    "$rel_name" "$rel_name-$rel_vsn" | gzip -9 >"$target_dst_tar"
	rm -rf "$target_dst_dir" "$target_data_dir"

	info "Created $target_dst_tar successfully."

	unset CC CXX CPP LD AS AR NM RANLIB OBJCOPY STRIP
	unset CFLAGS CXXFLAGS LDFLAGS LIBS ERL_COMPILER_OPTIONS
	export PATH="$saved_path"
}
#.

if [ "${CHECK_DEPS:-true}" = 'true' ]
then
	if have_browser
	then
		check_configured_dep_vsns
	else
		error 'Cannot check dependency versions.'
		error 'Install a browser or set CHECK_DEPS=false'
		exit 1
	fi
else
	info "Won't check dependency versions."
fi

if ! mkdir -p "$root_dir"
then
	error 'Set BUILD_DIR to a usable build directory path.'
	exit 1
fi

check_built_dep_vsns

info 'Removing old bootstrap tools ...'
rm -rf "$bootstrap_dir"
mkdir "$bootstrap_dir"

if [ $have_current_deps = true ]
then
	info 'Dependencies are up-to-date ...'
else
	# Keep existing toolchains but rebuild everything else.
	info 'Removing old builds ...'
	rm -rf "$build_dir"
	mkdir "$build_dir"

	info 'Removing old source ...'
	rm -rf "$src_dir"
	mkdir "$src_dir"

	info 'Downloading dependencies ...'
	cd "$src_dir"
	curl --no-progress-meter -LO "https://github.com/crosstool-ng/crosstool-ng/releases/download/$crosstool_dir/$crosstool_tar"
	curl --no-progress-meter -LO "https://ftp.gnu.org/gnu/termcap/$termcap_tar"
	curl --no-progress-meter -LO "https://github.com/libexpat/libexpat/releases/download/R_$(printf '%s' "$expat_vsn" | sed 's/\./_/g')/$expat_tar"
	curl --no-progress-meter -LO "https://zlib.net/fossils/$zlib_tar"
	curl --no-progress-meter -LO "https://pyyaml.org/download/libyaml/$yaml_tar"
	curl --no-progress-meter -LO "https://www.openssl.org/source/$ssl_tar"
	curl --no-progress-meter -LO "https://github.com/erlang/otp/releases/download/OTP-$otp_vsn/$otp_tar"
	curl --no-progress-meter -LO "https://github.com/elixir-lang/elixir/archive/v$elixir_vsn.tar.gz"
	curl --no-progress-meter -LO "https://github.com/linux-pam/linux-pam/releases/download/v$pam_vsn/$pam_tar"
	curl --no-progress-meter -LO "https://download.sourceforge.net/libpng/$png_tar"
	curl --no-progress-meter -LO "https://www.ijg.org/files/$jpeg_tar"
	curl --no-progress-meter -LO "https://storage.googleapis.com/downloads.webmproject.org/releases/webp/$webp_tar"
	curl --no-progress-meter -LO "https://github.com/libgd/libgd/releases/download/gd-$gd_vsn/$gd_tar"
	curl --no-progress-meter -LO "http://www.unixodbc.org/$odbc_tar"
	curl --no-progress-meter -LO "https://www.sqlite.org/$(date '+%Y')/$sqlite_tar" \
	    || curl --no-progress-meter -LO "https://www.sqlite.org/$(date -d '1 year ago' '+%Y')/$sqlite_tar" \
	    || curl --no-progress-meter -LO "https://www.sqlite.org/$(date -d '2 years ago' '+%Y')/$sqlite_tar"
	cd "$OLDPWD"
fi

mkdir "$bootstrap_dir/bin"
export PATH="$bootstrap_dir/bin:$PATH" # For ct-ng.
export LC_ALL='C.UTF-8' # Elixir insists on a UTF-8 environment.

for target in $targets
do
	prefix="$build_dir/$target"
	toolchain_dir="$ct_prefix_dir/$target"

	if [ "$platform" = "$target" ]
	then mode='native'
	else mode='cross'
	fi
	build_toolchain "$target" "$toolchain_dir"
	build_rel "$mode" "$target" "$prefix"
done

save_built_dep_vsns

info "Build started: $build_start"
info "Build ended: $(date '+%F %T')"

# vim:set foldmarker=#',#. foldmethod=marker: