CMake Modulation

Most CMake projects will start to break the project up:

.
+-- CMakeLists.txt
+-- src
|   +-- main.cpp
|   +-- drivers
|   |   +-- CMakeLists.txt
|   |   +-- bldc.cpp
|   |   +-- bldc.hpp
|   |   +-- currentSense.cpp
|   |   +-- currentSense.hpp
+-- test
|   +-- mock
|   +-- ..etc

We would like to include the bldc library in our app, but define the compilation of that library in the drivers folder.

In the root CMakeLists.txt:

# ...
add_executable(MyApp src/main.cpp)
add_subdirectory(src/drivers)
target_link_libraries(MyApp bldc)

We can now define the bldc library in the src/drivers/CMakeLists.txt:

add_library(bldc STATIC bldc.cpp currentSense.cpp)
target_include_directories(bldc PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

target_include_directories(...) provides include directories for anything linking to the library.

The keyword PUBLIC states that the include directories are part of the library’s interface. If the library requires an implementation only include directory, then we can specify this with PRIVATE. The same is true for linking libraries with target_link_libraries.