choice of build system

[eqvinox]

autoconf was a key element in hiding the xz backdoor (build-to-host.m4, cf. https://www.sentinelone.com/blog/xz-utils-backdoor-threat-actor-planned-to-inject-further-vulnerabilities/ ) This has prompted other FOSS projects to reevaluate their choice of build system, and I think we should do that too.

First, to be fair, the hiding was done in the dist tarball, which included the extra build-to-host.m4 file, this is the one thing of the backdoor that was never in xz git. We stopped providing dist tarballs, so this doesn't quite apply for us. (Unless other people create and distribute a dist tarball, which is in fact the case for some distros.)

That said, m4/*.m4 in our git would be the place to hide a backdoor in just the same. I'm not confident that we would catch in review a PR importing a slightly modified version of some common autoconf m4 macro.

As we've seen on the community call, discussing this without pointing at some other system to contrast against. @qlyoung and I have spent time on this several (4?) years ago and ended up with meson as the most appropriate choice.

Meson has a list of projects using it, it notably includes systemd, libvirt, lxc and a whole bunch of GNOME packages. [cf. https://mesonbuild.com/Users.html]

A minor non-security related improvement of meson over autoconf would be that the double-build-directory (hosttools) hack to build clippy (cf.

frr/configure.ac

Lines 109 to 177 in 84d1fb1

	hosttools_clippy="false"
	build_clippy="true"
	dnl case 1: external clippy
	if test -n "$with_clippy" -a "$with_clippy" != "no" -a "$with_clippy" != "yes"; then
	if test "$enable_clippy_only" = "yes"; then
	AC_MSG_ERROR([--enable-clippy-only does not make sense with --with-clippy])
	fi
	CLIPPY="$with_clippy"
	build_clippy="false"
	if test ! -x "$with_clippy"; then
	AC_MSG_ERROR([clippy tool ($with_clippy) is not executable])
	fi
	dnl case 2: cross-compiling internal clippy
	elif test "$host" != "$build"; then
	if test "$srcdir" = "."; then
	AC_MSG_ERROR([cross-compilation is only possible with builddir separate from srcdir or by building clippy separately and using the --with-clippy option. create a separate directory and run as .../path-to-frr/configure.])
	fi
	test -d hosttools || mkdir hosttools
	abssrc="`cd \"${srcdir}\"; pwd`"
	AC_MSG_NOTICE([...])
	AC_MSG_NOTICE([... cross-compilation: creating hosttools directory and self-configuring for build platform tools])
	AC_MSG_NOTICE([... use HOST_CPPFLAGS / HOST_CFLAGS / HOST_LDFLAGS if necessary])
	AC_MSG_NOTICE([...])
	(
	for var in $ac_precious_vars; do
	dnl special cases
	case "$var" in
	YACC|YFLAGS) continue;;
	PYTHON*) retain=true;;
	*) retain=false;
	esac
	eval "hostvar=\"\${HOST_$var}\""
	eval "targetvar=\"\${$var}\""
	if test -n "$hostvar"; then
	eval "$var='$hostvar'"
	_AS_ECHO_LOG([host $var='$hostvar'])
	elif $retain; then
	_AS_ECHO_LOG([host retain $var='$targetvar'])
	else
	eval "unset $var"
	_AS_ECHO_LOG([host unset $var])
	fi
	done
	cd hosttools
	"${abssrc}/configure" "--host=$build" "--build=$build" "--enable-clippy-only" "--disable-nhrpd" "--disable-vtysh"
	) || exit 1
	AC_MSG_NOTICE([...])
	AC_MSG_NOTICE([... cross-compilation: finished self-configuring for build platform tools])
	AC_MSG_NOTICE([...])
	build_clippy="false"
	hosttools_clippy="true"
	CLIPPY="hosttools/lib/clippy"
	dnl case 3: normal build internal clippy
	else
	CLIPPY="lib/clippy\$(EXEEXT)"
	fi
	AC_SUBST([CLIPPY])
	AM_CONDITIONAL([BUILD_CLIPPY], [$build_clippy])
	AM_CONDITIONAL([HOSTTOOLS_CLIPPY], [$hosttools_clippy])
	AM_CONDITIONAL([ONLY_CLIPPY], [test "$enable_clippy_only" = "yes"])

) would be gone because meson can do this natively. (And autoconf will never be able to do it because it conceptually collides with how autoconf works.)

(I haven't looked what else meson does better, this specific thing I just happen to remember from evaluating it those few years back.)

[vjardin]

Same, for DPDK, it was decided to migrate to meson for the new build framework: https://www.dpdk.org/wp-content/uploads/sites/35/2020/11/dpdk-India-2019-TechBoardSession-v2-1.pdf

It was done during a transition period during which both compilation framework were maintained and the the initial one was phased out.