CMake Include-Dependencies for Projects - c++

Question

i'm trying to switch from a large Visual Studio-based project (with static, dynamic libraries, executables) to CMake. It would work well, but as many of the static libraries have export libraries (without the need of linking the library to the project), i need a way to include project's interfaces only without linking the static library.
Situation:
CMakeLists.txt
cmake_minimum_required(VERSION 3.0)
project(Test)
add_subdirectory(Projekt_B)
add_subdirectory(Projekt_A)
Projekt_A/CMakeLists.txt
add_library(Projekt_A
libraryContent.cpp
libHeader.h
libInterfaceOnly.h)
target_include_directories(Projekt_A PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
# could be **INTERFACE** as well
Projekt_B/CMakeLists.txt
add_library(Projekt_B_Public SHARED
libraryContentB.cpp
libHeaderB.h
)
add_library(Projekt_B_Private SHARED
libraryContentB.cpp
libHeaderB.h
)
add_library(Projekt_B_Interface SHARED
libraryContentB.cpp
libHeaderB.h
)
## this Line works but links Projekt_A
target_link_libraries(Projekt_B_Public PUBLIC Projekt_A)
## this Line works too, but links Projekt_A to it without passing them on
target_link_libraries(Projekt_B_Private PRIVATE Projekt_A)
## this Line works **only** if no interface of A is used in B
target_link_libraries(Projekt_B_Interface INTERFACE Projekt_A)
So, all targets compile when no interface of Projekt_A was used in Projekt_B_. When I include a header (which has been exported via traget_include_directories), Projekt_B_Interface won't link anymore.
MsBuild tells for Projekt_B_Interface:
ClCompile:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\amd64\CL.exe
/c /Zi /nologo /W3 /WX- /Od /Ob0 /D WIN32 /D _WINDOWS /D _DEBUG /D
"CMAKE_INTDIR=\"Debug\"" /D Projekt_B_Interface_EXPORTS /D _WINDLL /D
_MBCS /Gm- /RTC1 /MDd /GS /fp:precise /Zc:wchar_t /Zc:forScope
/Fo"Projekt_B_Interface.dir\Debug\\"
/Fd"Projekt_B_Interface.dir\Debug\vc120.pdb" /Gd /TC /errorReport:queue
D:\Develop\CMake\TEST\Projekt_B\libr.c
libr.c
D:\Develop\CMake\TEST\Projekt_B\libr.c(2): fatal error C1083: Cannot open include file:
'libinc.h': No such file or directory
[D:\Develop\CMake\TEST\build\Projekt_B\Projekt_B_Interface.vcxproj]
Within the other Projekt_B_* projects it's successfull:
ClCompile:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\amd64\CL.exe
/c /ID:\Develop\CMake\TEST\Projekt_A /Zi /nologo /W3 /WX- /Od /Ob0 /D
WIN32 /D _WINDOWS /D _DEBUG /D "CMAKE_INTDIR=\"Debug\""
/D Projekt_B_Public_EXPORTS /D _WINDLL /D _MBCS /Gm- /RTC1 /MDd /GS
/fp:precise /Zc:wchar_t /Zc:forScope /Fo"Projekt_B_Public.dir\Debug\\"
/Fd"Projekt_B_Public.dir\Debug\vc120.pdb" /Gd /TC /errorReport:queue
D:\Develop\CMake\TEST\Projekt_B\libr.c
libr.c
Link:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\amd64\link.exe
/ERRORREPORT:QUEUE /OUT:"D:\Develop\CMake\TEST\build\
Projekt_B\Debug\Projekt_B_Public.dll" /INCREMENTAL /NOLOGO
kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib
oleaut32.lib uuid.lib comdlg32.lib advapi32.lib
..\Projekt_A\Debug\Projekt_A.lib /MANIFEST
/MANIFESTUAC:"level='asInvoker' uiAccess='false'" /manifest:embed /DEBUG
/PDB:"D:/Develop/CMake/TEST/build/Projekt_B/Debug/Projekt_B_Public.pdb"
/SUBSYSTEM:CONSOLE /TLBID:1 /DYNAMICBASE /NXCOMPAT
/IMPLIB:"D:/Develop/CMake/TEST/build/Projekt_B/Debug/Projekt_B_Public.lib"
/MACHINE:X64 /machine:x64 /debug /DLL Projekt_B_Public.dir\Debug\libr.obj
Projekt_B_Public.vcxproj -> D:\Develop\CMake\TEST\build\Projekt_B\Debug\
Projekt_B_Public.dll
Any ideas how I could get something like:
target_compile_libraries(Projekt_B HEADERS Projekt_A)
(something that target_include_directoies would sound like...)

Answer 1

I think I've found a solution for this situation (without the need of settings vars in CMake):
Projekt_A/CMakeLists.txt:
...
# create a interface
add_library(IProjekt_A INTERFACE)
# add *export* headers to interface
target_include_directories(IProjekt_A INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
# bind interface to project itself (just in case)
target_link_libraries(Projekt_A INTERFACE IProjekt_A)
Projekt_B/CMakeLists.txt
...
# this will add includes *only* and reexports them within Projekt_B
target_link_libraries(Projekt_B PUBLIC IProjekt_A)
# this will add includes and library for link and reexport
target_link_libraries(Projekt_B PUBLIC Projekt_A)
# this will only add the includes for *this* project
target_link_libraries(Projekt_B PRIVATE IProjekt_A)
This makes it possible to export the headers in the build environment. Very usefull in large projects.
I'll hope it helps someone else either!
Cheers.