[cmake-developers] Exported targets with imported dependencies in CMake 3.0

[Philipp Möller]

Stephen Kelly <steveire at gmail.com> writes:

> Philipp Möller wrote:
>> It would be great, if I could export imported targets and if CMake could
>> walk the dependency tree automatically and import those targets on an
>> as-needed basis.
>
> Part of the problem is that the place where you import your dependent 
> targets from (and the locations calculated) are not necessarily the same for 
> your downstreams.

I understand the issue and have been fighting it in versions prior 3.0
as well. It also arises if you simply export targets that have been
target_link_librarie'd against full library paths returned by a
find_package.

That's why I thought some build-in functionality could be helpful for
this, e.g. exporting and imported target would lead to a definition in
the exports file that automatically triggers a corresponding
find_package call.

> You export your targets to and -exports file, and presumably you import that 
> in a -config file. In the same config file, you should add code to find your 
> dependencies too.
>
>  http://www.cmake.org/cmake/help/v3.0/manual/cmake-packages.7.html#creating-packages
>
> The find_dependency macro can help with forwarding some find_package 
> arguments.
>
>  http://www.cmake.org/cmake/help/v3.0/module/CMakeFindDependencyMacro.html

The documentation is a little sparse, but I think I understand the
purpose. I still need to traverse IMPORTED_LINK_INTERFACE_LIBRARIES and
figure out which of the list members constitutes a target that needs to
trigger a find_dependency and what a full library path is, correct?

I can also not rely on a find_package call to actually produce imported
targets and need to ship the code that turns the results of find_package
in targets.

Thanks for your help,
Philipp