One of the subtle advantages of Unix make over the dependency databases built into many IDEs is that makefiles are simple text files — files that can be generated by programs.

In the mid-1980s it was fairly common for large Unix program distributions to include elaborate custom shellscripts that would probe their environment and use the information they gathered to construct custom makefiles. These custom configurators reached absurd sizes. I wrote one once that was 3000 lines of shell, about twice as large as any single module in the program it was configuring — and this was not unusual.

The community eventually said “Enough!” and various people set out to write tools that would automate away part or all of the process of maintaining makefiles. These tools generally tried to address two issues:

One issue is portability . Makefile generators are commonly built to run on many different hardware platforms and Unix variants. They generally try to deduce things about the local system (including everything from machine word size up to which tools, languages, service libraries, and even document formatters it has available). They then try to use those deductions to write makefiles that exploit the local system's facilities and compensate for its quirks.

The other issue is dependency derivation . It's possible to deduce a great deal about the dependencies of a collection of C sources by analyzing the sources themselves (especially by looking at what include files they use and share). Many makefile generators do this in order to mechanically generate make dependencies.

Each different makefile generator tackles these objectives in a slightly different way. Probably a dozen or more generators have been attempted, but most proved inadequate or too difficult to drive or both, and only a few are still in live use. We'll survey the major ones here. All are available as open-source software on the Internet.