CLion is an IDE that offers a lot of features to help developers. It shows documentation popups, detects mistakes on the fly, suggests fixes, and more. An internal code analyzer always works in the background, analyzing C and C++ code as you type. C and C++ are challenging languages for automatic analyzers because compiler-specific data is required to parse the code correctly. The engine needs to know the header search paths, predefined macro definitions, and some other details.
For a predefined set of known compilers, CLion runs the project's compiler with special options and gathers the req