Setting C++ Defines with CMake - Video

To build parts of the code optionally, or to inject CMake variables into C++, you need pre-processor definitions like -DENABLE_FEATURE on the command-line or #define ENABLE_FEATURE 1 in code.

This video shows 3 different ways of setting such pre-processor definitions with CMake. add_compile_definitions() and target_compile_definitions() trigger too much recompilation when changing a define, while configure_file() is the best solution to this problem, and saves compilation time in your projects. In addition, the video explains how and why you should use #if rather than #ifdef for on/off defines.

Corresponding blog post: https://www.kdab.com/setting-defines-with-cmake/