[CMake] Idea - integrate superbuild dependency requirements

[David Cole]

Good ideas. Perhaps beyond the scope of our little CMake module named
ExternalProject, but definitely good ideas.

It starts to approach the capabilities of a full blown package manager
with version and dependency management features. And I think that is
quite beyond the scope...

ExternalProject is offered as a convenient way to build stuff. It
leaves the onus on the SuperBuild creator to specify things exactly as
needed for combining multiple projects into something useful. Part of
that is understanding how to build each sub-component and what its
requirements are. ExternalProject helps to codify that in SuperBuild
CMakeLists files, but it does not  have a full understanding, leaving
that to the smart people who are creating SuperBuilds.

If you are tracking something live (origin/master of some git repo)
then you have to notice when requirements for that thing change... and
adapt to the new requirements.

I definitely do NOT see ExternalProject growing into a full blown
package management system: it's a convenience mechanism that helps you
construct a system from pieces, but nothing more.

I'm always open to suggestions and patches, though. I would just hate
to see it become hopelessly complicated. (It's already pretty
complex...)


David


On Wed, Mar 21, 2012 at 2:40 PM, Danielle Pace
<danielle.pace at kitware.com> wrote:
> Clarification - this is because we are tracking CTK's master branch - you
> wouldn't see this problem if you fixed your dependency to be a specific
> release/git commit.
>
> -Danielle
>
>
> On Wed, Mar 21, 2012 at 2:26 PM, Danielle Pace <danielle.pace at kitware.com>
> wrote:
>>
>> 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
>>
>
>
>
> --
> 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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