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Future plans for Autotools

From: Zack Weinberg
Subject: Future plans for Autotools
Date: Wed, 20 Jan 2021 17:15:15 -0500

Now we've all had a while to recover from the long-awaited Autoconf
2.70 release, I'd like to start a conversation about where the
Autotools in general might be going in the future.  Clearly any future
development depends on finding people who will do the work, but before
we worry about that I think we might want to figure out what work we
_want_ to do.

As a starting point, I wrote up a "strengths, weaknesses,
opportunities, and threats" analysis for Autotools -- this is a
standard project management technique, if you're not familiar with it,
there's a nice writeup in the draft of the book my friend and
colleague Sumana Harihareswara is writing [ ].
I'm going to paste the full text of this analysis below, please reply
inline.  You can also read it on my blog at .


I’ve been a contributor to GNU projects for many years, notably both
GCC and GNU libc, and recently I led the effort to make the first
release of Autoconf since 2012 (release announcement for Autoconf
2.70). For background and context, see the LWN article my colleague
Sumana Harihareswara of Changeset Consulting wrote.

Autoconf not having made a release in eight years is a symptom of a
deeper problem. Many GNU projects, including all of the other
components of the Autotools (Automake, Libtool, Gnulib, etc.) and the
software they depend upon (GNU M4, GNU Make, etc.) have seen a steady
decline in both contributor enthusiasm and user base over the past
decade. I include myself in the group of declining enthusiasts; I
would not have done the work leading up to the Autoconf 2.70 release
if I had not been paid to do it. (I would like to say thank you to the
project funders: Bloomberg, Keith Bostic, and the GNU Toolchain Fund
of the FSF.)

The Autotools are in particularly bad shape due to the decline in
contributor enthusiasm. Preparation for the Autoconf 2.70 release took
almost twice as long as anticipated; I made five beta releases between
July and December 2020, and merged 157 patches, most of them bugfixes.
On more than one occasion I was asked why I was going to the
trouble—isn’t Autoconf (and the rest of the tools by implication)
thoroughly obsolete? Why doesn’t everyone switch to something newer,
like CMake or Meson? (See the comments on Sumana’s LWN article for

I personally don’t think that the Autotools are obsolete, or even all
that much more difficult to work with than some of the alternatives,
but it is a fair question. Should development of the Autotools
continue? If they are to continue, we need to find people who have the
time and the inclination (and perhaps also the funding) to maintain
them steadily, rather than in six-month release sprints every eight
years. We also need a proper roadmap for where further development
should take these projects. As a starting point for the conversation
about whether the projects should continue, and what the roadmap
should be, I was inspired by Sumana’s book in progress on open source
project management (sample chapters are available from her website) to
write up a strengths, weaknesses, opportunities, and threats analysis
of Autotools.

This inventory can help us figure out how to build on new
opportunities, using the Autotools’ substantial strengths, and where
to invest to guard against threats and shore up current weaknesses.

Followup discussion should go to the Autoconf mailing list.


In summary: as the category leader for decades, the Autotools benefit
from their architectural approach, interoperability, edge case
coverage, standards adherence, user trust, and existing install base.

Autoconf’s feature-based approach to compiled-code portability scales
better than lists of system quirks.
The Autotools carry 30+ years’ worth of embedded knowledge about
portability traps for C programs and shell-based build scripting on
Unix (and to a lesser extent Windows and others), including variants
of Unix that no other comparable configuration tool supports.
Autoconf and Automake support cross-compilation better than competing
build systems.
Autoconf and Automake support software written in multiple languages
better than some competing build systems (but see below).
Autoconf is very extensible, and there are lots of third-party macros available.
Tarball releases produced by Autotools have fewer build dependencies
than tarball releases produced by competing tools.
Tarball releases produced by Autotools have a predictable,
standardized (literally; it’s a key aspect of the GNU Coding
Standards) interface for setting build-time options, building them,
testing them, and installing them.
Automake tries very hard to generate Makefiles that will work with any
Make implementation, not just GNU make, and not even just (GNU or BSD)
The Autotools have excellent reference-level documentation (better
than CMake and Meson’s).
As they are GNU projects, users can have confidence that Autotools are
and will always remain Free Software.
Relatedly, users can trust that architectural decisions are not driven
by the needs of particular large corporations.
There is a large installed base, and switching to a competing build
system is a lot of work.


In summary: Autoconf’s core function is to solve a problem that
software developers, working primarily in C, had in the 1990s/early
2000s (during the Unix wars). System programming interfaces have
become much more standardized since then, and the shell environment,
much less buggy. Developers of new code, today, looking at existing
configure scripts and documentation, cannot easily determine which of
the portability traps Autoconf knows about are still relevant to them.
Similarly, maintainers of older programs have a hard time knowing
which of their existing portability checks are still necessary. And
weak coordination with other Autotools compounds the issue.


Autoconf (and the rest of the Autotools) are written in a combination
of four old and difficult programming languages: Bourne shell, the
portable subset of Make, Perl, and M4. Competing build systems tend to
use newer, more ergonomic languages, which both makes it easier for
them to get things done, and makes it easier for them to attract new
All the supported languages except C and C++ are second-class citizens.
The set of languages that are supported has no particular rationale.
Several new and increasingly popular compiled-code languages (e.g.
Swift and Rust) are not supported, while oddities like Erlang are.
Much of that 30 years’ worth of embedded knowledge about portability
traps is obsolete. There’s no systematic policy for deciding when some
problem is too obsolete to worry about anymore.
Support for newer platforms, C standard editions, etc. is weaker than
support for older things.
Autoconf’s extensibility is unsystematic; many of those third-party
macros reach into its guts, and do things that create awkward
compatibility constraints on core development. Same for existing
The code quality of third-party macros varies widely; bad third-party
macros reflect poorly on Autoconf proper.
Some of the ancillary tools distributed with Autoconf don’t work well;
most importantly, autoupdate (which is supposed to patch a to bring it in line with current Autoconf’s
recommendations) is so limited and unreliable that it might be better
not to have it at all.
Feature gaps in GNU M4 hold back development of Autoconf.

The Autotools as a whole

There are few active developers and no continuing funders.
GNU project status discourages new contributors because of the
paperwork requirements and the perceived lack of executive-level
There is no continuous integration and no culture of code review. Test
suites exist but are not comprehensive enough (and at the same time
they’re very slow).
Bugs, feature requests, and submitted patches are not tracked
systematically. (This is partially dependent on FSF/GNU infrastructure
improvements which are indefinitely delayed.)
There’s a history of releases breaking compatibility, and thus people
are hesitant to upgrade. At the same time, Linux distributions
actively want to force-upgrade everything they ship to ensure
architecture support, leading to upstream/downstream friction.
Guide-level documentation is superficial and outdated.
Building an Autotools-based project directly from its VCS checkout is
often significantly harder than building it from a tarball release,
and may involve tracking down and installing any number of unusual
The Autotools depend on other GNU software that is not actively
maintained, most importantly GNU M4, and to a lesser extent GNU Make.
Coordination among the Autotools is weak, even though the tools are
tightly coupled to each other. There are portions of codebases that
exist solely for interoperability with other tools in the toolchain,
which leads to overlapping maintainer and reviewer responsibility,
slow code review and inconvenient copyright assignment processes
multiplying, and causing confusion and dropped balls. For instance,
there is code shared among Autoconf, Automake, and/or Gnulib by
copying files between source repositories; changes to these files are
extra inconvenient. The lack of coordination also makes it harder for
tool maintainers to deprecate old functionality, or to decouple
interfaces to make things more extensible; maintainers do not
negotiate policies with each other to help. For instance, Autoconf has
trouble knowing when it is safe to remove internal kludges that old
versions of Automake depend on, and certain shell commands (e.g.
aclocal) are distributed with one package but abstractly belong to
Division of labor among the Autotools, and the sources of third-party
macros, is ad-hoc and unclear. (Which macros should be part of
Autoconf proper? Which should be part of Gnulib? Which should be part
of the Autoconf Macro Archive? Which should be shipped with Automake?
Which tools should autoreconf know how to run? Etc.)
Automake and Libtool are not nearly as extensible as Autoconf is.
Unlike several competitors, Automake only works with Make, not with
newer build drivers (e.g. Ninja).
Because Automake tries to generate Makefiles that will work with any
Make implementation, the Makefiles it generates are much more
complicated and slow than they would be if they took advantage of GNU
and/or BSD extensions.
Libtool is notoriously slow, brittle, and difficult to modify (even
worse than Autoconf proper). This is partially due to technical debt
and partially due to maintaining support for completely obsolete
platforms (e.g. old versions of AIX).
Libtool has opinions about the proper way to manage shared libraries
that Linux distributions actively disagree with, forcing them to
kludge around its code during package builds.
Alternatives to Libtool have all failed to gain traction, largely
because Automake only supports building shared libraries using Libtool
or an exact drop-in replacement.


Because of its extensible architecture, install base, and wellspring
of user trust, Autotools can react to these industry changes and thus
spur increases in usage, investment, and developer contribution.

Renewed interest in Autotools due to the Autoconf 2.70 release.
Renewed interest in systems programming due to the new generation of
systems programming languages (Go, Rust, D, Swift(?), Dart(?), etc.
may create an opportunity for a build system that handles them well
particularly if it handles polyglot projects well (see below).
Cross-compilation is experiencing new appeal because of the increasing
popularity of ARM and RISC-V CPUs, and of small devices (too small to
compile their own code) based on these chips.
The Free software ecosystem as a whole would benefit from a
reconciliation between the traditional model of software distribution
(compiled code with stable interfaces, released as tarballs at regular
intervals, installed once on any given computer and depended on as
shared libraries and/or binaries) and the newer depend directly on VCS
checkouts and bundle everything model described below. Autotools
contributors have the experience and knowledge to lead this effort.
Funding may be available for projects targeting the weaknesses listed above.


These threats may lead to a further decrease in Autotools developer
contribution, funding, and momentum.

Increasing mindshare of competing projects (CMake, Meson, Generate-Ninja, …).
Increasing mindshare of programming languages that come with a build
system that works out of the box, as long as you only use that one
language in your project. (These systems typically cannot handle a
polyglot project at all, hence the above opportunity for a third-party
system that handles polyglot projects well.)
Increasing preference for building software from VCS checkouts
(perhaps at a specific tag, perhaps not) rather than via tarballs.
Increasing mindshare of the software distribution model originated by
Node.js, Ruby, etc. where each application bundles all of its
dependencies. While this is considered a profoundly bad idea by Linux
distribution maintainers in particular (because it makes it much
harder to find and patch a buggy dependency) and makes it harder for
end-users to modify the software (because out-of-date dependencies may
be very different from what their own documentation—describing the
latest version—says), it is significantly more convenient for upstream
developers. Competing build systems handle this model much better than
Autoconf does.

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