Learn Makefiles

Summary

I built this guide because I could never quite wrap my head around Makefiles. They seemed awash with hidden rules and esoteric symbols, and asking simple questions didn’t yield simple answers. To solve this, I sat down for several weekends and read everything I could about Makefiles. I've condensed the most critical knowledge into this guide. Each topic has a brief description and a self contained example that you can run yourself. If you mostly understand Make, consider checking out the Makefile Cookbook, which has a template for medium sized projects with ample comments about what each part of the Makefile is doing. Good luck, and I hope you are able to slay the confusing world of Makefiles! Getting Started Why do Makefiles exist? Makefiles are used to help decide which parts of a large program need to be recompiled. In the vast majority of cases, C or C++ files are compiled. Other languages typically have their own tools that serve a similar purpose as Make. Make can also be used beyond compilation too, when you need a series of instructions to run depending on what files have changed. This tutorial will focus on the C/C++ compilation use case. Here's an example dependency graph that you might build with Make. If any file's dependencies changes, then the file will get recompiled: What alternatives are there to Make? Popular C/C++ alternative build systems are SCons, CMake, Bazel, and Ninja. Some code editors like Microsoft Visual Studio have their own built in build tools. For Java, there's Ant, Maven, and Gradle. Other languages like Go, Rust, and TypeScript have their own build tools. Interpreted languages like Python, Ruby, and raw Javascript don't require an analogue to Makefiles. The goal of Makefiles is to compile whatever files need to be compiled, based on what files have changed. But when files in interpreted languages change, nothing needs to get recompiled. When the program runs, the most recent version of the file is used. The versions and types of Ma...