CMake can't find include file from subfolder

Question

I want to add to my CMake project some subfolder which contains some additional functionality. MyProject is a shared library. Ideally it will be fine to just include files from subfolder and to compile all them together. But so far I've found a way only to include that as a static library that suits me too. So my files structure should look like the following:

MyProject src main.cpp include main.h CMakeLists.txt 3dparty SomeFolder src file.cpp include file.h CMakeLists.txt

MyProject/CMakeLists.txt:

cmake_minimum_required(VERSION 2.8) project(MyProject) file(GLOB SRC . src/*.cpp) file(GLOB INC . include/*.h) set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/lib) set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/bin) add_library(${PROJECT_NAME} SHARED ${SRC} ${INC}) target_include_directories(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include ) add_subdirectory(3dparty/SomeFolder)

and 3dparty/SomeFolder/CMakeLists.txt:

project (SomeFolder) file(GLOB SRC . src/*.cpp) file(GLOB INC . include/*.h) add_library(${PROJECT_NAME} STATIC ${SRC} ${INC}) target_include_directories(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include )

I can compile the project and I see that compiler produses SomeFolder.a so it looks good. But for some reason I can't include files from 3dparty/SomeFolder/include in main.*. So far I've tried:

#include "file.h" #include "3dparty/SomeFolder/file.h"

but nothing works. I get error: 'file.h' file not found.

What I did wrong? How can I include files from subproject?

Arne J · Accepted Answer · 2019-08-11 13:03:11Z

1

Because you forgot to link the sublibrary to your main library. Usr target_link_libraries()

answered Aug 11, 2019 at 13:03

Arne J

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2 Comments

folibis Over a year ago

Ok, I've added target_link_libraries(${PROJECT_NAME} SomeFolder) to the main CMakeLists.txt and looks that that works. Is that possible to add somehow this line inside 3dparty/SomeFolder/CMakeLists.txt ? It would be nice to add subfolder with only one instruction only (add_subdirectory).

Arne J Over a year ago

No, and I believe you're making a few wrong assumptions here. add_subirectory() will do nothing for linking (as you experienced), and the arguments of target_link_libraries() are targets (executable or library), not directory paths. The normal way to link is just to specify the dependencies for each target with target_link_libraries(). If CMake can at some point uniquely identify one of the dependencies as another target, it will know what to do.

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