My $0.02......I just completed a CMake system for a code project that required several TPLs (third party libraries) two of which were the NetCDF and HDF5. I struggled with the same problems you mention here. When I wrote my FindXXX modules, the standard I adopted was, XXX_INCLUDE_DIR only contained the path to the XXX include directory while XXX_INCLUDE_DIRS contained XXX include directory any other TPL include directory required to compile. Parts of the code was calling NetCDF directly but not HDF5. I wanted the project CMakeLists.txt files to be as clean as possible and placed the logic to determine if NetCDF had HDF5 and adjusted the NetCDF_INCLUDE_DIRS if needed in our FindNetCDF module. This allowed the developers to simply put

find_package(NetCDF)
include_directories(NetCDF_INCLUDE_DIRS)

in their CMakeLists.txt files not worry about testing for HDF5, etc. This complicated the FindNetCDF module, but I think it improved the stability of our CMake system.

If you decide not to cascade, then you will need to provide a flag like you mention in (1) to help out whoever calls your module, so they can call find_package(HDF5) when needed.

When NetCDF split the language APIs, I used the FindMPI module as a template and created NetCDF_C_* NetCDF_CXX_* NetCDF_Fortran_* variables in the FindNetCDF module. You may what to look at how that module handles different language libraries and include directories for inspiration.


Good luck!




On 12/12/12 17:35, esatel wrote:
Hi all,
I am trying to adapt an existing FindNetCDF.cmake file to work with NetCDF
4.2. I have read the Modules/Readme.txt but I am still a little unclear to
the best approach in my case.

In 4.2 the Fortran bindings and C bindings are not necessarily installed in
the same place. One motive for NetCDF_INCLUDE_DIRS to be plural is that
there might be a NetCDF_C_INCLUDE_DIR and a NetCDF_Fortran_INCLUDE_DIR that
together form NetCDF_INCLUDE_DIRS.

There is a second motive that I am less clear on. The FindNetCDF.cmake files
I have seen handle the HDF5 dependency differently:
1. One sets a variable NETCDF_HAS_HDF5 by querying a config executable but
does nothing else.
2. The other sets a similar variable but then does find_package on HDF5 and
loads the dependencies into NetCDF_INCLUDE_DIRS and NetCDF_LIBRARIES.

This design (2) cascades. FindHDF5.cmake represents a similar decision about
whether to find_package its dependencies like the zlib compression library.
I believe the one in the cmake distro doesn't do that.

What is the best practice here? To handle dual locations for the library at
hand or to accumulate or both? The first seems unavoidable ... the second
seems to be an unevenly applied standard.

Thanks
Eli



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Lori A. Pritchett-Sheats, PhD.
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