[CMake] Idea - integrate superbuild dependency requirements

[Danielle Pace]

Hi all,

An idea for future cmake improvements -

We ran into an issue on one of the open-source toolkits I'm working on
(Tubetk, http://public.kitware.com/Wiki/TubeTK).  TubeTK uses superbuild
(ExternalProject_Add) to handle a dependency on CTK, which in turn requires
CMake 2.8.4.  However, the TubeTK requirements were not kept in sync (was
set to require CMake 2.8).

On a dashboard machine with CMake < 2.8.4, this gives a somewhat cryptic
error message related to CTK, but not referencing the root problem with
CMake:
https://www.kitware.com/CDash/viewConfigure.php?buildid=197007
Such an error message would be very confusing for end-users.

Of course, the fix is to manually change a project's requirements whenever
a dependency's requirements change, but this is somewhat annoying.

Has anyone given any thought to automatic integration of requirements
across dependencies?  Ex. if dependency A requires CMake 2.8.4, dependency
B requires CMake 2.8.2, and the main project requires CMake 2.8, the actual
requirement is CMake 2.8.4.  Besides this particular example with
cmake_minimum_required, it would be super cool if this kind of thing could
work with other dependencies, ex. versions of Qt.

Best,

Danielle

-- 
Danielle Pace, M.ESc.
Research and Development Engineer
Kitware Inc.,
North Carolina Office

www.kitware.com
919-969-6990 X 319
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