# Introduction

The Autotools plug-in for Eclipse is an optional feature of the CDT (C/C++ Development Tools) that adds support for maintaining and building C/C++ projects that use GNU Autotools. The Autotools plug-ins were migrated from the Linux Tools project into the CDT as part of the Eclipse Juno release.

The GNU Autotools are a set of tools used to make a project portable to multiple systems or build environments. The tools aid the developer to create a configure script which is meant to be invoked prior to performing the build. The configure script may perform tests such as testing the current platform, the OS, what is locally installed, or any number of things. Parameters can be passed as well to provide information that is not calculable (e.g. what will be the target platform the project will be run on). Results of tests and parameters are used to create the Makefiles for the build or in some cases, additional files such as header files or code sequences.

What gets tested is fully controllable by the developer by way of special input files which are fed to the Autotools. Typically, the most commonly used Autotools are 'autoconf', 'automake', and 'aclocal'. The 'autoconf' tool takes a 'configure.in' or 'configure.ac' input file and creates the 'configure' script previously discussed. It is possible to have multiple configure scripts in various subdirectories, but a project should be designed so there is one top-level configure script that calls any lower-level ones automatically.

The 'automake' tool takes a 'Makefile.am' input file and creates a 'Makefile.in' file which is used at configuration time by the configure script as a template for creating a Makefile. Each Makefile will have its own corresponding Makefile.in file. There may be if/else logic used to determine what ends up in the Makefile or there may be requests to directly substitute variables calculated in the configure step.

The 'aclocal' tool creates a repository of macros that are specified directly or indirectly in the 'autoconf' input files. Such macros are provided to perform commonly used tests or actions (e.g. test that a certain header file exists or find the C compiler). The macros are written in a language called m4 and the developer is free to create their own macros to add to the repository.

The Autotools plug-in adds support for running the configure script prior to the build. As well, support is added for invoking the Autotools themselves as well as maintaining the files they use. An Autotools project extends a CDT Makefile project. Therefore, functionality in the CDT for supporting such a project applies to an Autotools project as well (e.g. C/C++ Property pages).

For more details on the GNU Autotools, see https://www.gnu.org/software/autoconf/ and https://www.gnu.org/software/automake/