CMake: C++ include relative to base directory

Question

Say I have the following file structure:

project/
  - src/
    - main.cpp
    moduleA/
      - moduleA.cpp
      - moduleA.hpp
    moduleB/
      - moduleB.cpp
      - moduleB.hpp

Within moduleB I would like to use moduleA. As such, I would like to include moduleA.hpp but as a relative path to src. Aka, I would like to be able to write #include moduleA/moduleA.hpp to use moduleA. I have control over all files, and can put CMakeLists.txt or FindModule<>.cmake in any directories.

Note: I want to do this because there are files in each module that have the same name (in this case, parameters.hpp). Therefore, I would like to be able to include parameters.hpp relative to src directory for readability purposes, and to ensure that the correct parameters file is being included.

If this is confusing, or any other information is required, please ask. Thanks for all the help everyone!

Answer 1

You can use a structure similar to the following:

project/
  - CMakeLists.txt
  - src/
    - CMakeLists.txt
    - main.cpp
  - moduleA/
      - CMakeLists.txt
      - moduleA/
          - moduleA.cpp
          - moduleA.hpp
  - moduleB/
      - CMakeLists.txt
      - moduleB/
          - moduleB.cpp
          - moduleB.hpp

with the following files:

---

project/CMakeLists.txt:

cmake_minimum_required(VERSION 3.0.2)

project(myProject)

add_subdirectory(moduleA)
add_subdirectory(moduleB)
add_subdirectory(src)

---

project/moduleX/CMakeLists.txt (X = A or B):

add_library(X STATIC ${moduleX_sources})
# The following line is very practical:
# it will allow you to automatically add the correct include directories with "target_link_libraries"
target_include_directories(X PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

# only in CMakeLists.txt of module B, possibly with PRIVATE instead of PUBLIC
target_link_libraries(X PUBLIC A)

---

project/src/CMakeLists.txt:

add_executable(myExe ${exe_sources})
target_link_libraries(myExe A B) # <-- Automatically sets the correct include directories!!

---

With all this, you can use

#include "moduleX/moduleX.hpp"

See here for a similar question and more detailed answer.