tl;dr: How am I supposed to export the include search-path containing a target’s public headers when using the export command?
I thought about trying to use the export command for a library target mylib in order to not have to install the library before using it.
export( TARGETS mylib myotherObjectLib FILE mylib-config.cmake )
In general, this works, however…
As libraries very often have some public header files, containing the public API of the library, I thought it would be useful to set the include search-directory (and thereby export it as well):
target_include_directories( mylib INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/include" )
However, this results in CMake complaining:
CMake Error in CMakeLists.txt:
Target "mylib" INTERFACE_INCLUDE_DIRECTORIES property contains path:
"/home/user/workspace/source/include"
which is prefixed in the source directory.
OK… then I maybe try the build-directory instead:
target_include_directories( mylib INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/include" )
However, this again results in a CMake error:
CMake Error in CMakeLists.txt:
Target "mylib" INTERFACE_INCLUDE_DIRECTORIES property contains path:
"/home/user/workspace/build/include"
which is prefixed in the build directory.
Uhhm… skipping the variable prefix maybe?
target_include_directories( mylib INTERFACE "include" )
CMake:
CMake Error in CMakeLists.txt:
Target "mylib" INTERFACE_INCLUDE_DIRECTORIES property contains path:
"/home/user/workspace/source/include"
which is prefixed in the source directory.
… How about I use some other absolute path neither prefixed with the source or build directory?
target_include_directories( mylib INTERFACE "/tmp/installed/include" )
CMake: “Yes, I like that.”
Whaaat? I thought the idea behind export was that there is no need for the library to be “installed” outside the build-directory?
On a side-note: As expected, the private build-dependency from mylib to the OBJECT target myotherObjectLib is also exported (which is expected because CMake told me I have to do so), but interestingly its include search path, which is prefixed with the source directory, is exported just fine in the resulting mylib-config.cmake.