Code versions matter, not only for reproducibility but also to document API capabilities or simplify support requests and bug reporting. The source code is typically under some version control, and additional semantic version numbers (see e.g. https://semver.org) can be attached using Git tags, for example. However, not only does the source code need to be versioned, but the executable needs to record the project version so that it can be printed to the code output or user interface.

In this example, we will define the version number inside of the CMake sources. Our goal is to record the program version to a header file at the moment when we configure the project. The generated header file can then be included in the code at the right place and time, to print the code version to the output file(s) or screen.