Issue

My project is organized in subdirectories (a dozen), there are some includes between subdirectories. Some of these subdirectories contains only header files (dir1 for example).

Here is a look at the organization of the project:

project
 |
 |----- src -- dir1  <-- header-only library
 |       |      |--- dir1.h
 |       |      |--- CMakeLists.txt
 |       |
 |       |
 |       | --- dir2
 |       |      |--- dir2.cpp
 |       |      |--- dir2.h
 |       |      |--- CMakeLists.txt
 |       |
 |       | --- file.h
 |       | --- CMakeLists.txt 
 |
 |
 |----- test -- dir1 -- test.cpp
 |       | ---- dir2 -- test.cpp
 |       | ---- includeFile.h
 |
 |
 |----- CMakeLists.txt

I want to have a library containing all the code from src directory and an executable to run unit tests. After some research on stackOverFlow and Cmake examples, I arrived to these CMake files. There is one makefile per src subdirectories, one for grouping all the library and one global.

dir1 CMakeLists

add_library(dir1 INTERFACE)
target_sources(dir1 INTERFACE dir1.h)
target_include_directories(dir1 INTERFACE
  "${PROJECT_SOURCE_DIR}/src/dir1"
)

dir2 CMakeLists

set(dir2_src
  dir2.cpp dir2.h
)

add_library(dir2 ${dir2_src})

src CMakeLists

add_subdirectory(dir1)
add_subdirectory(dir2)


add_library(TheProject INTERFACE)
target_sources(TheProject INTERFACE file.h)
target_include_directories(TheProject INTERFACE
  "${PROJECT_SOURCE_DIR}/src/"
)
target_link_libraries(TheProject INTERFACE dir1
                                dir2
                                ${Boost_LIBRARIES})

main CMakeLists.txt

project(TheProject)

# gtest
# boost
# compilation flags ...

####### include paths
include_directories("./src/")
include_directories(${Boost_INCLUDE_DIRS})

####### library to compile
add_subdirectory(src)


####### executable
file(GLOB SRCS utest/*/*.cpp)
add_executable(utest ${SRCS} test/includeFile.h)

target_link_libraries(utest gtest_main TheProject)

I almost used the same organization on a smaller project without header only libraries and INTERFACE and it worked. Here, I have an error with the different interface libraries:

CMake Error at CMakeLists.txt:88 (add_executable):
  Cannot find source file:

    file.h

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx

I think I have not well understood the use of INTERFACE. I have done some research but nothing solve my problem.

And I have also a few questions:

There is some dependancies between directories, (e.g. code in dir1 has an include of some dir2 files), should I specify these dependance in their cmake file (with target_link_libraries(dir2 dir1)) ?
In the code, include are specified with relative paths in src and utest, is it not better to use paths like "dir1/dir1.h"?

Solution

Before CMake 3.13 relative paths, passed to target_sources, are interpreted relative to further invocations of add_executable (or add_library).

Because you call add_executable() from the top directory, CMake searches test.h relative to the top directory, not relative to the src/ one.

Use absolute paths for target_sources calls:

target_sources(TheProject INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/file.h)

Since CMake 3.13 relative paths passed to target_sources are resolved immediately, relative to the current source directory. See @markhc's answer.

Answered By - Tsyvarev

Saturday, October 30, 2021

[SOLVED] How to use 'target_sources' command with INTERFACE library?

Issue

Solution