Overhauling Amd for the '00s: A Case Study of GNU Autotools

The GNU automatic software configuration tools, Autoconf, Automake, and Libtool, were designed to help the portability of software to multiple platforms. Such autotools also help improve the readability of code and speed up the development cycle of software packages. In this paper we quantify how helpful such autotools are to the open-source software development process. We study several large packages that use these autotools and measure the complexity of their code. We show that total code size is not an accurate measure of code complexity for portability; two better metrics are the distribution of CPP conditionals in that code and the number of new special-purpose Autoconf macros that are written for the package. We studied one package in detail—Am-utils, the Berkeley Automounter. As maintainers and developers of this package, we tracked its evolution over ten years. This package was ported to dozens of different platforms and in 1997 was converted to use GNU autotools. We show how this conversion (autotooling) resulted in a dramatic reduction in code size by over 33%. In addition, the conversion helped speed code development of the Am-utils package by allowing new features and ports to be integrated easily: for the first year after the conversion to GNU autotools, the Am-utils package grew by over 70% in size, adding many new features, and all without increasing the average code complexity.