[cmake-developers] Volunteering to maintain a new module: FindGSL.cmake

[Thompson, KT]

Stephen Kelly wrote:

>> #  GSL_INCLUDE_DIRS   - Location of GSL header files.
>> #  GSL_LIBRARIES      - The GSL libraries.

> I'm curious: Given that you provide IMPORTED targets, what would a user need
> these variables for? Do you have a particular use-case that needs them?

These are defined mostly as a courtesy for folks who don't use imported targets yet.  Additionally, the CMake documentation for developers::Modules (http://www.cmake.org/cmake/help/v3.0/manual/cmake-developer.7.html#modules) mentions these as typical outputs from FindXXX.cmake modules.  In my own projects, I use these to provide informational output during the configuration.  I suppose I could query the imported targets for the same information.

After thinking about this for a couple of minutes, I don't have a strong opinion on it.  However, I will leave them in place (to make this module have similar behavior to other incorporated modules) unless I hear a strong consensus from this list to remove them.

>>     # Windows with dlls, but only Release libraries.
>>     # If we have both Debug and Release libraries

> You should populate the IMPORTED_CONFIGURATIONS target property to record
> configurations which have a corresponding location. See the files shipped
> with Qt5 or the files generated by CMake itself when exporting targets for
> example.

I've added this target property for the "Windows with dlls" case.  I will be responding to comments that Brad King made yesterday in my next email to the list.  Can you review my updated implementation as presented in that email?

> Is it possible/reasonable to determine if a particular GSL package has a
> dependency? On ATLAS, for example.

You can certainly build GSL against any BLAS implementation, but I've never seen that done in production.  If a custom BLAS is used, the pkgconfig script will correctly report the alternate BLAS library (Unix/Linux platforms).  For other types of installations, I'm not sure how to query for the BLAS using when compiling GSL (e.g. Windows).  If the GSL is a shred library, I might be able to use system tools to inspect the rpath - but I'm not sure that level of complexity is required for this simple module.  In this case, the user of FindGSL might need to manually specify GSL_CBLAS_LIBRARY before calling find_package.

-kt
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