CMake export package that relies on external library - c++

Question

I have a project written using C++ and CMake, using Boost, that I'm trying to make a standalone binary/header package for to allow other people to link against my work. I'm using cmake installers for this. However, I'm running into issues with install(EXPORTS ...) when my library links to an external library. In particular, the Boost library and header directory locations are hard-coded into the exported file, and I can't figure out how to make it work better.
Have an example. (Untested; if it's not clear I can elaborate or fix it.)
CMakeLists.txt:
package(MyLibrary)
set(MyLibrary_VERSION 1.0)
find_component(BOOST 1.55.0 REQUIRED COMPONENTS serialization)
set(INSTALL_INCLUDE_DIR "C:/MyLibrary/include")
set(INSTALL_SRC_DIR "C:/MyLibrary/include")
set(INSTALL_BIN_DIR "C:/MyLibrary/bin")
set(INSTALL_LIB_DIR "C:/MyLibrary/lib")
set(INSTALL_CMAKE_DIR "C:/MyLibrary/cmake")
set(HEADERS myfile.hpp)
set(SOURCES myfile.cpp)
install(FILES ${HEADERS} DESTINATION ${INSTALL_INCLUDE_DIR} COMPONENT headers)
install(FILES ${SOURCES} DESTINATION ${INSTALL_SRC_DIR} COMPONENT sources)
add_library(MyLibrary STATIC
${HEADERS} ${SOURCES})
target_link_libraries(MyLibrary
${Boost_SERIALIZATION_LIBRARY})
target_include_directories(MyLibrary
PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR};${Boost_INCLUDE_DIRS}>"
PUBLIC "$<INSTALL_INTERFACE:include;${Boost_INCLUDE_DIRS}>")
install(TARGETS MyLibrary EXPORT MyLibrary-depends
DESTINATION ${INSTALL_LIB_DIR} COMPONENT libraries)
configure_package_config_file(MyLibraryConfig.cmake.in
"${CMAKE_CURRENT_BINARY_DIR}/MyLibraryConfig.cmake"
INSTALL_DESTINATION ${CMAKE_CURRENT_BINARY_DIR})
write_basic_package_version_file("${CMAKE_CURRENT_BINARY_DIR}/MyLibraryConfigVersion.cmake"
VERSION ${MyLibrary_VERSION}
COMPATIBILITY AnyNewerVersion)
install(FILES
"${CMAKE_CURRENT_BINARY_DIR}/MyLibraryConfig.cmake"
"${CMAKE_CURRENT_BINARY_DIR}/MyLibraryConfigVersion.cmake"
DESTINATION "${INSTALL_CMAKE_DIR}")
install(EXPORT MyLibrary-depends
FILE MyLibrary-depends.cmake
DESTINATION "${INSTALL_CMAKE_DIR}")
MyLibraryConfig.cmake.in
#PACKAGE_INIT#
if (NOT MyLibrary_FOUND)
set(MyLibrary_FOUND 1)
find_package(Boost 1.55.0 COMPONENTS SERIALIZATION)
include(MyLibrary-depends.cmake)
# random directory stuff, etc.
endif()
The issue is that MyProject-depends.cmake ends up with the value of ${Boost_INCLUDE_DIRS} and ${Boost_SERIALIZATION_LIBRARY}, which are both absolute paths and screw up the portability of the install.
I've tried a couple of things, none of which seem to fix all my problems.
target_include_directories:
I tried escaping the $, with the hope that MyProject-depends.cmake would pick up the value of the Boost_INCLUDE_DIRS variable on include-time:
target_include_directories(MyProject
PUBLIC "$<INSTALL_INTERFACE:include;\${Boost_INCLUDE_DIRS}>"
...)
But, of course, INSTALL_INTERFACE thinks that ${Boost_INCLUDE_DIRS} is a relative path and prefixes it wit {$_IMPORT_DIR} which breaks everything.
I can ditch the MyProject-depends.cmake route entirely, and add it into MyProjectConfig.cmake.in:
CMakeLists.txt:
target_include_directories(MyProject
PUBLIC "$<INSTALL_INTERFACE:include>"
PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR};${Boost_INCLUDE_DIRS>")
and MyProjectConfig.cmake.in:
include(MyProject-depends.cmake)
set_target_properties(MyProject
INTERFACE_INCLUDE_DIRECTORIES "${Boost_INCLUDE_DIRS}")
That option seems to work but is a pain.
target_link_libraries:
I'm having more trouble with the library linking. I tried the same trick, moving stuff into the MyProjectConfig.cmake.in file for more control, but
target_link_libraries(MyProject ${Boost_SERIALIZATION_LIBRARIES})
doesn't work on imported libraries, and
set_target_properties(MyProject INTERFACE_LINK_LIBRARIES ${Boost_SERIALIZATION_LIBRARY})
fails because ${Boost_SERIALIZATION_LIBRARY} expands to something like optimized;C:/boost/stage/lib/boost_serialization.lib;debug;C:/boost/stage/lib/boost_serialization.libd and set_target_properties doesn't like the keywords.
Now I'm left with some sort of remapping using
"$<$<CONFIG:DEBUG>:${Boost_SERIALIZATION_LIBRARY_DEBUG}>$;<$<CONFIG:RELEASE>:${Boost_SERIALIZATION_LIBRARY_RELEASE}>"
but I'll also have to detect whether or not a debug library is specified... which is doable, but seems like yak shaving to me.
So, sages of the stack... any advice? Is there some obvious module or clever method that I'm overlooking?
(And thanks for making it all the way through!
Also: the cmake install(EXPORTS ...) documentation contains the helpful line "If a library target is included in the export but a target to which it links is not included the behavior is unspecified." Yeah, basically, I'm looking for a workaround.

Answer 1

I ended up with the last target_link_libraries answer, ditching the built-in import structure entirely and writing the CMake module to remap
optimized;C:/boost/stage/lib/boost_serialization.lib;debug;C:/boost/stage/lib/boost_serialization.libd
into
$<$<CONFIG:DEBUG>:${Boost_SERIALIZATION_LIBRARY_DEBUG}>$;<$<CONFIG:RELEASE>:${Boost_SERIALIZATION_LIBRARY_RELEASE}>
Not at all pretty, but it was the best I could come up with. So it goes.