CMake – a short history

In the Beginning, if you wanted to create an executable application in C, you’d run a program that translated C code to assembly language, run an assembler on the translated code, then run a linker to bundle it all up into an executable file. And it was Good.

But it was also annoying after a while, so someone (probably Dennis Ritchie or one of his friends) wrote a wrapper compiler – the “cc” program. Now with a single command, you could compile, assemble and link. Incidentally, linking for most other systems (which may or may not have compiled to assembler) was generally a separate program. And it was Good.

But as projects got larger, with a dozen or more source modules, something more was needed. Generally, when you’re working on a large project, you’re only changing a small number of files at a time, and back when a Raspberry Pi would have been welcomed as a virtual super-computer, you didn’t want to continually re-compile stuff that hadn’t changed. So Stuart Feldman created the “make” utility. Make could not only intelligently choose what to compile, it provided a central control point with user-designable goals like “make clean”, “make install” and “make all”. And it was Good.

But Unixes came in many flavors. And eventually, that Included Linux. With multiple distros of its own. And building for each of these disparate platforms often required slightly different rules. And more and more often, there were external dependencies. As a result, David Mackenzie of the Free Software Project developed automake, which extended to become the Gnu Build Systems, or as it’s often known, Autotools. With this framework, you could build Unix/Linux apps portable using 3 magic commands: “./configure; make; (sudo) make install”. And it was Good.

But that still didn’t cover everything. Although the Microsoft Windows™ Operating system (among others) is very different platform, many open-source app authors wanted to be able to use a common source system to be able to build both Windows™ and Unix/Linux versions of their apps. So a team of people developed CMake, which takes over the capabilities of Autotools and adds OS portability to the mix. With CMake, you can not only compile on many platforms, you can cross-compile between platforms. Plus, you can build to external target directories, which allows both support for multiple targets at once and an easy and safe way to blank out a build completely and start over. With CMake, you can do a build as simply as ‘cmake -S source_dir -B build-dir; cd build_dir; make; (sudo) make install)”. And if you script it right, even the “make install” can be automated. And it is Very Good.

It doesn’t stop there. A shop that does nightly builds might use something like Jenkins to further manage and track builds, but CMake is the place where you go if you want to build manually. If, for example, you’re the developer doing the code editing.

Author:

Evil Genius specializing in OS's, special hardware and other digital esoterica with a bent for Java.