#!/usr/bin/env bash
# systemd: two build options Arch can hold and s390x cannot.
#
# Neither is a missing host package -- both are hard errors raised by meson
# because the PKGBUILD ASKS for something that does not exist on this
# architecture, so no amount of apt-get makes them go away. The libraries
# systemd wants (libbpf, clang, libfdisk, libkmod, ...) ARE host packages and
# belong in install_host_deps, not here.
set -euo pipefail

# 1. -Dbootloader=enabled: systemd-boot is EFI, and s390x has no EFI.
#
# The message you get is NOT about EFI:
#
#   systemd/meson.build:1638:19: ERROR: python3 is missing modules: elftools
#
# because meson.build:1638 asks for pyelftools with
# `required : get_option('bootloader')`, and the PKGBUILD set that to enabled.
#
# THE TRAP is that this reads like a missing host package, and
# `apt install python3-pyelftools` looks like the fix. It is not. It buys four
# lines, and then meson.build:1642 says what is really wrong:
#
#   ERROR: Feature bootloader cannot be enabled: unsupported EFI arch or
#          EFI support is disabled
#
# (verified by planting a stub elftools module on PYTHONPATH; without it the
#  EFI message is unreachable, which is why nobody ever sees it first.)
#
# meson.build:1627 maps a cpu family to an EFI machine type name -- aa64, arm,
# loongarch32/64, riscv32/64, x64, ia32 -- and s390x is not in that table, so
# efi_arch is ''. -Defi is still true; the architecture simply has no EFI.
# IBM Z boots from an IPL record, there is no ESP for systemd-boot to write
# into, and no configuration invents one.
#
# The cost is the systemd-boot artefacts. bootctl itself is still built and
# installed -- checked in the install plan -- package_systemd() names neither,
# and the arch.conf/loader.conf/splash-arch.bmp it ships are `install`ed from
# $srcdir rather than built. Packaging is untouched. Disabling also drops the
# pyelftools requirement in the same line.
sed -i 's/-Dbootloader=enabled/-Dbootloader=disabled/' PKGBUILD
grep -q -- '-Dbootloader=disabled' PKGBUILD || {
    echo "systemd: bootloader option not rewritten" >&2; exit 1; }
echo "systemd: bootloader disabled (s390x has no EFI machine type)"

# 2. -Dvmlinux-h=provided: the file Arch points at is an Arch file.
#
#   src/bpf/meson.build:  error('Path to provided vmlinux.h does not exist.')
#
# Arch's linux-headers ships /usr/src/linux/vmlinux.h, the path hard-coded in
# the PKGBUILD. Ubuntu's linux-headers-* ship no vmlinux.h anywhere. This
# failure only appears AFTER libbpf and clang are installed, because the whole
# block is skipped while BPF_FRAMEWORK is off -- fixing libbpf uncovers it.
#
# systemd's own fallback dumps the header out of the running kernel's BTF,
# which is what 'generated' selects:
#
#   bpftool btf dump file /sys/kernel/btf/vmlinux format c
#
# Checked on this host: exit 0, 122471 lines, and enum lsm_integrity_type is
# there at line 15931, so restrict-fsaccess.bpf.c builds rather than being
# quietly dropped.
#
# THE TRAP is that 'auto' would NOT have done this for us. The auto branch
# generates only when `host_machine.cpu_family() in ['x86_64', 'aarch64']`; on
# s390x it falls through to "neither provided nor generated" and silently
# drops the BPF programs that need the header. s390x has to say it out loud.
#
# Note the asymmetry this buys: on the 'provided' branch systemd probes the
# header with cc.compiles() before deciding what to build. On 'generated' it
# sets have_lsm_integrity_type = true outright. So the build now depends on
# the BTF of the kernel RUNNING when it starts -- fine on 6.17.0-41, and on an
# older kernel it turns into a compile error with no fallback.
#
# -Dvmlinux-h-path goes with it: 'generated' ignores the value, and leaving a
# path that resolves to nothing invites the next reader to "repair" it.
sed -i 's/-Dvmlinux-h=provided/-Dvmlinux-h=generated/' PKGBUILD
sed -i '/-Dvmlinux-h-path=/d' PKGBUILD
grep -q -- '-Dvmlinux-h=generated' PKGBUILD || {
    echo "systemd: vmlinux.h still read from a provided path" >&2; exit 1; }
grep -q -- '-Dvmlinux-h-path' PKGBUILD && {
    echo "systemd: stale vmlinux-h-path left in place" >&2; exit 1; }
echo "systemd: vmlinux.h generated from /sys/kernel/btf/vmlinux"

# 3. -Dsplit-bin=auto: the question is answered by the HOST, not the target.
#
#   systemd/meson.build:123
#     sbindir = prefixdir / (split_bin ? 'sbin' : 'bin')
#
# split-bin is a combo defaulting to 'auto', and 'auto' probes whether
# /usr/sbin on the BUILD MACHINE is a symlink to bin. On Arch it is, so
# split_bin is false and everything lands in /usr/bin. Here /usr/sbin is a
# real directory, and meson-log.txt says so:
#
#   split bin-sbin                           : true
#
# THE TRAP is that arch-meson ALREADY passes --sbindir bin, and
# `meson configure` dutifully reports sbindir = bin. It is ignored: systemd
# computes its own sbindir from split_bin and never reads meson's builtin. The
# option that looks like the fix is not the fix, and the one that is mentions
# neither sbin nor a directory in its name.
#
# Nothing fails in build(). It fails much later, in package_systemd(), on the
# first line that names a path:
#
#   rm: cannot remove '<pkgdir>/usr/bin/halt': No such file or directory
#
# because halt, init, poweroff, reboot, shutdown and resolvconf all went to
# /usr/sbin -- along with mount.ddi, mount.mstack and mount.storage, which the
# PKGBUILD never mentions at all. The rm is only the first victim. Suppress it
# and the package ships /usr/sbin as a DIRECTORY, which collides on the target
# with the ["usr/sbin"]="bin" SYMLINK our own filesystem package declares.
#
# Measured on a configured copy: with split-bin=false there is no /usr/sbin in
# the install tree at all, and all six paths are where package() looks.
#
# Same species as arch-meson's --libdir -- an Ubuntu default standing in for
# an Arch one -- but it cannot live in arch-meson: split-bin is systemd's own
# option, not a meson builtin. --auto-features does not reach it either; it is
# a combo, not a feature.
test "$(grep -c -- '-Dcompat-sysv-interfaces=false' PKGBUILD)" -eq 1 || {
    echo "systemd: expected exactly one _meson_options array" >&2; exit 1; }
test "$(grep -c -- '-Dsplit-bin' PKGBUILD)" -eq 0 || {
    echo "systemd: PKGBUILD already sets split-bin, re-read it" >&2; exit 1; }
sed -i 's/^\( *\)-Dcompat-sysv-interfaces=false/\1-Dsplit-bin=false\n\1-Dcompat-sysv-interfaces=false/' PKGBUILD
grep -q -- '-Dsplit-bin=false' PKGBUILD || {
    echo "systemd: split-bin still auto (would install into /usr/sbin)" >&2; exit 1; }
echo "systemd: split-bin=false (Ubuntu's /usr/sbin is not Arch's)"