[CMake] Why is XXX_INCLUDE_DIRS plural and should it be deep?

[Lori A. Pritchett-Sheats]

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
>
>
>
> --
> View this message in context: http://cmake.3232098.n2.nabble.com/Why-is-XXX-INCLUDE-DIRS-plural-and-should-it-be-deep-tp7582623.html
> Sent from the CMake mailing list archive at Nabble.com.
> --
>
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.cmake.org/mailman/listinfo/cmake


-- 
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