[CMake] external projects and transitive dependencies

[Brian Lewis]

On 2014.03.19, at 07:21, Micha Hergarden wrote:

Hi, thanks for answering. Could you please elaborate a little?

> ExternalProject_Add has a DEPENDS option. What you can do is let X
> depend on Y

DEPENDS seems to mean that the external project depends on something
else. If I wanted to make X depend on Y, wouldn't I use
ADD_DEPENDENCIES?

> and use the CMAKE_CACHE_ARGS option to provide the include path

I don't think I understand how to use CMAKE_CACHE_ARGS. It seems to be a
way to pass information from the calling project to the external project
via a cache. But I need to send information the other way, from the
external project back to the caller.

> or use the buildsystem in project X to find the headers itself.

I'm not sure how to do this. X would need to spelunk around in Y's
external dependencies, I think?