Why use build tools like Autotools when we can just write our own makefiles?

Question

Recently, I switched my development environment from Windows to Linux. So far, I have only used Visual Studio for C++ development, so many concepts, like make and Autotools, are new to me. I have read the GNU makefile documentation and got almost an idea about it. But I am kind of confused about Autotools.

As far as I know, makefiles are used to make the build process easier.

1. Why do we need tools like Autotools just for creating the makefiles? Since all knows how to create a makefile, I am not getting the real use of Autotools.
2. What is the standard? Do we need to use tools like this or would just handwritten makefiles do?

Answer 1

You are talking about two separate but intertwined things here:

• Autotools
• GNU coding standards

Within Autotools, you have several projects:

• Autoconf
• Automake
• Libtool

Let's look at each one individually.

Autoconf

Autoconf easily scans an existing tree to find its dependencies and create a configure script that will run under almost any kind of shell. The configure script allows the user to control the build behavior (i.e. --with-foo, --without-foo, --prefix, --sysconfdir, etc..) as well as doing checks to ensure that the system can compile the program.

Configure generates a config.h file (from a template) which programs can include to work around portability issues. For example, if HAVE_LIBPTHREAD is not defined, use forks instead.

I personally use Autoconf on many projects. It usually takes people some time to get used to m4. However, it does save time.

You can have makefiles inherit some of the values that configure finds without using automake.

Automake

By providing a short template that describes what programs will be built and what objects need to be linked to build them, Makefiles that adhere to GNU coding standards can automatically be created. This includes dependency handling and all of the required GNU targets.

Some people find this easier. I prefer to write my own makefiles.

Libtool

Libtool is a very cool tool for simplifying the building and installation of shared libraries on any Unix-like system. Sometimes I use it; other times (especially when just building static link objects) I do it by hand.

There are other options too, see StackOverflow question Alternatives to Autoconf and Autotools?.

Build automation & GNU coding standards

In short, you really should use some kind of portable build configuration system if you release your code to the masses. What you use is up to you. GNU software is known to build and run on almost anything. However, you might not need to adhere to such (and sometimes extremely pedantic) standards.

If anything, I'd recommend giving Autoconf a try if you're writing software for POSIX systems. Just because Autotools produce part of a build environment that's compatible with GNU standards doesn't mean you have to follow those standards (many don't!) :) There are plenty of other options, too.

Edit

Don't fear m4 :) There is always the Autoconf macro archive. Plenty of examples, or drop in checks. Write your own or use what's tested. Autoconf is far too often confused with Automake. They are two separate things.

Answer 2

First of all, the Autotools are not an opaque build system but a loosely coupled tool-chain, as tinkertim already pointed out. Let me just add some thoughts on Autoconf and Automake:

Autoconf is the configuration system that creates the configure script based on feature checks that are supposed to work on all kinds of platforms. A lot of system knowledge has gone into its m4 macro database during the 15 years of its existence. On the one hand, I think the latter is the main reason Autotools have not been replaced by something else yet. On the other hand, Autoconf used to be far more important when the target platforms were more heterogeneous and Linux, AIX, HP-UX, SunOS, ..., and a large variety of different processor architecture had to be supported. I don't really see its point if you only want to support recent Linux distributions and Intel-compatible processors.

Automake is an abstraction layer for GNU Make and acts as a Makefile generator from simpler templates. A number of projects eventually got rid of the Automake abstraction and reverted to writing Makefiles manually because you lose control over your Makefiles and you might not need all the canned build targets that obfuscate your Makefile.

Now to the alternatives (and I strongly suggest an alternative to Autotools based on your requirements):

CMake's most notable achievement is replacing AutoTools in KDE. It's probably the closest you can get if you want to have Autoconf-like functionality without m4 idiosyncrasies. It brings Windows support to the table and has proven to be applicable in large projects. My beef with CMake is that it is still a Makefile-generator (at least on Linux) with all its immanent problems (e.g. Makefile debugging, timestamp signatures, implicit dependency order).

SCons is a Make replacement written in Python. It uses Python scripts as build control files allowing very sophisticated techniques. Unfortunately, its configuration system is not on par with Autoconf. SCons is often used for in-house development when adaptation to specific requirements is more important than following conventions.

If you really want to stick with Autotools, I strongly suggest to read Recursive Make Considered Harmful and write your own GNU Makefile configured through Autoconf.