[CMake] Is there a way to delay "find_package" until link-time when the package is actually needed?

[Eric Noulard]

Le jeu. 14 févr. 2019 à 18:22, Timothy Wrona <tjwrona1992 at gmail.com> a
écrit :

> I have a collection of interdependent CMake projects (lots of legacy code)
> that I want to convert to using CMake targets for linking. The code is
> built in such a way that all projects run cmake generation, then all
> projects build, then all projects link.
>
> I would like to export a CMake target from one of the projects and link to
> it in another, but the issue is the project I am exporting from runs its
> cmake generation AFTER the project I am linking the target in. This causes
> "find_package" to fail because the target has not been exported yet, but
> realistically the exported target is not needed until link-time.
>

This heavily depends on the target. Modern CMake target convey compile time
information as well like compile flags, include directory etc...

Can't you re-order the cmake generation order of your projects?
If you [ever] have the graph dependency of your projects you may
topologically sort them in order to avoid this issue and superbuild them in
appropriate order.


> Is there a way to delay "find_package" to not look for the package until
> link-time?
>

I don't think so.


> At link-time the package will have been exported already and if
> "find_package" was not called until then, it would be found successfully
> and the target could be pulled in and linked to.
>

But the build compile line options used to generate build system files are
computed during CMake configuration/generation step.
So I don't think what you ask is possible.

-- 
Eric
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