Yarp: Move Companion out of YARP_OS

[drdanz]

I suggest we make a separate library for that.

[drdanz]

Also the yarprun related classes should be moved in that library

[Nicogene]

Closed by #1711

[PeterBowman]

It looks like Eigen is a hard dependency for the (mandatory) YARP_companion library:

https://github.com/robotology/yarp/blob/c18e29b4253c76883fac15986449630487588cc4/src/libYARP_companion/CMakeLists.txt#L31

...which conflicts with the following recent statement (https://github.com/robotology/yarp/issues/1559#issuecomment-391650201):

As discussed, YARP_math will still be optional, but, if eigen is found, the default value will be ON

In fact, I'm unable to compile latest devel (https://github.com/robotology/yarp/commit/c18e29b4253c76883fac15986449630487588cc4) on a system with no Eigen3 installed, see this Travis build. Anyway, those include_directories() calls are probably superfluous (and misused given the modern target_include_directories() alternative) since grepping ace and eigen doesn't produce any relevant result in this library's source tree.

[drdanz]

I think the include_directories was fixed in #1715

[PeterBowman]

Now (https://github.com/robotology/yarp/commit/e2b85eb2ef7537ef07db127432c47b8077c1cb1e), YARP_eigen fails due to not finding Eigen headers: Travis build.

[drdanz]

@PeterBowman The problem was that you can still install YARP_eigen if eigen is not available, but you will still need eigen3 in order to use it. Now it should be fixed, but if you want to install YARP and install eigen3 later you will need eigen3 3.3.1 or later, i.e. this won't work on ubuntu trusty. I don't think this is going to be a real problem...

[PeterBowman]

That's https://github.com/robotology/yarp/commit/1f0fcb36104d16ca6d7d364d3e9734c00b86a34e. Thanks! (and sorry for the OT)

[drdanz]

No problem :wink: