Subproject

Separating the project into subproject makes it possible to import/build any component of the project as standalone, or against a different version of the main project, e.g. against a pre-installed version.

Examples of where you could make a project’s feature into a subproject is for bindings to other languages and for the project’s test-suite.

When to define a subproject?

• The subproject is in a self-contained folder

• The feature is controlled by a project option

• The main project can be imported within the subproject

Making it two-way compatible

Use <PROJECT>_VERSION and/or if(TARGET) to check if the project is run from within the main project, and otherwise import the main project.

How do I keep it in sync with the main

When calling the subproject through add_subdirectory, the version compatibility is guaranteed. The issue is with importing the main project to match commits in FetchContent_Declare. Using built-in CMake functionality, you do not have such a feature, but this can be done with an external module: DynamicVersion.