[CMake] Creating dependencies after adding an external project?

[Lori Pritchett-Sheats]

I have a project that depends on HDF5. A user can either specify an 
existing installation and thus use a find_package or choose to have HDF5 
built with the project.  I've been using Paraview as a template to 
implement this but I can't seem to get the dependencies for my project 
defined correctly when it builds HDF5.

So what I'm doing is an ExternalProject_Add command like this:

ExternalProject_Add(hdf5
                        URL     ${HDF5_url}/${HDF5_gz}
                        URL_MD5 ${HDF5_md5}
                        UPDATE_COMMAND ""
                        PREFIX  ${HDF5_prefix}
                        CMAKE_ARGS
                           -DBUILD_SHARED_LIBS:Bool=OFF
                           -DBUILD_TESTING:Bool=OFF
                           -DHDF5_ENABLE_Z_LIB_SUPPORT:Bool=ON
                           -DZLIB_INCLUDE_DIR:STRING=${ZLIB_INCLUDE_DIR}
                           -DZLIB_LIBRARY:STRING=${ZLIB_LIBRARY}
                           -DHDF5_BUILD_HL_LIB:Bool=ON
                           -DHDF5_BUILD_TOOLS:Bool=ON
                           -DCMAKE_INSTALL_PREFIX:PATH=${HDF5_prefix}
                        )

and then to be consistent with the find_package logic, I define 
HDF5_INCLUDE_DIR, HDF5_LIBRARIES based on the installation paths I know 
eventually will exist like this

set(HDF5_LIBRARY_DIR "${HDF5_prefix}/lib")
set(HDF5_LIBRARY 
"${HDF5_LIBRARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}hdf5${CMAKE_STATIC_LIBRARY_PREFIX}")
set(HDF5_HL_LIBRARY 
"${HDF5_LIBRARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}hdf5_hl${CMAKE_STATIC_LIBRARY_PREFIX}")

set(HDF5_LIBRARIES "${HDF5_HL_LIBRARY};${HDF5_LIBRARY}")

and then when I need to build a binary that links against HDF5, I have 
in a CMakeLists.txt file

add_executable(test.x ${test_src_files})
target_link_libraries(test.x ${HDF5_LIBRARIES})

But at build time I see errors complaining about "No rule to make target 
<path to HDF5_prefix>/libhdf5.a needed for test.x". I am confused. Do I 
need to do more than just define HDF5_LIBRARIES? Do I need to define 
libhdf5.a as a target? How do I do that? Defining libhd5 through 
add_library( .. UNKNOWN IMPORTED) call does seem right because they are 
not imported.





-- 
Lori A. Pritchett-Sheats, PhD.
CCS-2, Computational Physics and Methods
Office: 505-665-6675
Fax: 505-665-4972

Los Alamos National Laboratory
P.O. Box 1663
MS D413
Los Alamos, NM 87544