Autotools

Description

autoconf is a tool that belongs to the autotools suite, also known as the GNU build system. The tool automates the process of generating the custom Makefiles necessary to build a program on different systems, with (perhaps) different compilers. When a program is built with the help of autoconf, the first step is to call the configure script:

./configure

This verifies that compilers and other relevant software are installed on the computer and that appropriate versions are available, and generates a Makefile customised for your system.

After that, you call make as usual:

make

Finally, make install installs the files at the right places. If you do not want to install the software for all users of the server, but only for yourself, you normally need to specify where to install your software. You can (usually) do this in the following manner:

mkdir $HOME/SOFTWARE
make install --prefix=$HOME/SOFTWARE

In other cases you must supply the --prefix option to ./configure instead of to make; see the documentation for the particular software you are trying to install. You may also wish to create a module to show the system the paths to your newly installed software.

A basic compilation of a program using autoconf can thus be as simple as

./configure && make && make install --prefix=$HOME/SOFTWARE

Frequently used options for configure scripts

configure scripts generally accept a large number of options. They vary from project to project. Nevertheless, certain options are very common and deserve mentioning. In all cases you can run

./configure --help

to get a detailed list of all supported options.

Installation directory

An option that is always available is --prefix. This option allows you to define the directory where the command make install installs the application or the library. For example, to install an application into the subdirectory programs within your home directory, you could use

./configure --prefix=$HOME/programs/

Feature options

Most configuration scripts allow you to enable or to disable certain features of the program or library that you compile. Those options are generally of the type --enable-feature or --disable-feature. Within advanced computing, those options often include, for example, parallelisation using threads or using MPI. You could thus have

./configure --enable-mpi

or also

./configure --enable-threads

Often there are also options like --with-... to configure some features specifically.

Recommendation

It is generally recommended not to use such options and to let autoconf find the parameters automatically. Nevertheless, it is sometimes necessary to specify some parameters using --with-... options.

For example, you could specify

./configure --enable-mpi --with-mpi-dir=$MPIDIR

Options defined by variables

You can generally specify the compiler that is used and the options that should be passed to it by declaring variables after the ./configure command. For example, to define the C compiler and the options to give it, you could run

./configure CC=icc CFLAGS="-O3 -xHost"

The most commonly used variables include

Option	Description
CFLAGS	Options to pass to the C compiler
CPPFLAGS	Options to pass to the preprocessor and to C, C++, Objective C, and Objective C++ compilers
CXXFLAGS	Options to pass to the C++ compiler
DEFS	Allows the definition of a preprocessor macro
FCFLAGS	Options to pass to the Fortran compiler
FFLAGS	Options to pass to the Fortran 77 compiler
LDFLAGS	Options to pass to the linker
LIBS	Libraries to link

A more exhaustive list of variables and typical options is available in the autoconf documentation.