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!

include_directories(${CMAKE_SOURCE_DIR}), or maybe include_directories(${CMAKE_SOURCE_DIR}/src), depends what your root folder is. — Antonio
– Antonio, Commented May 9, 2017 at 8:15
Possible duplicate of How to properly add include directories with CMake? — Antonio
– Antonio, Commented May 9, 2017 at 8:18
If I'm not mistaken, the problem (in this case) with include_directories(bar/foo.h) is that within a file, I can then just write #include "foo.h". I would like that to error out - and instead require the relative path. As such, you would need to write #include "bar/foo.h". — Sam
– Sam, Commented May 9, 2017 at 8:34

oLen · Accepted Answer · 2019-11-13 12:17:39Z

9

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.

edited Nov 13, 2019 at 12:17

answered May 9, 2017 at 12:39

oLen

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2 Comments

Sam Over a year ago

Hey, that's a nice little setup! I love it. I guess this was more of a question about directory setup than anything else. I'll tweak this idea to work with my directory setup a little more, but this should totally work. Thanks so much for the idea oLen!

Spidey Over a year ago

You missed the inter-module dependency. Something like target_include_directories(B PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/../moduleA) on the project/moduleB/CMakeLists.txt file.

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