update examples to eliminate the deprecated _gencpp build target suffix

[jack-oquin]

Use _generate_message_cpp target suffix in examples, not _gencpp which is deprecated.

[jack-oquin]

The pull request above fixes one instance. I suspect there are more.

[dirk-thomas]

Instead we should recommend to use the catkin_EXPORTED_TARGETS variable so that users do not have to worry about if the target actually exists.

[jack-oquin]

OK.

All the more reason to update the tutorials and examples. They are badly out of date.

[dirk-thomas]

These changes have only been synced into public very recently. So documenting them "before" that is also dangerous. But now is the right time to do it...

[jack-oquin]

@dirk-thomas: would you please review this draft how-to page?

• http://farnsworth.csres.utexas.edu/docs/catkin/html/howto/building_msgs.html

Tell me if it is correct and makes sense to you. Is that boost dependency still required?

[dirk-thomas]

It looks good.

I don't see why the boost dependency should be required. The user should not need to care about that.

I think one paragraph needs more clarification:

However, you can provide scripts and programs in that same package. If you do, message generation targets need to be built before any your other programs:
add_dependencies(your_program ${catkin_EXPORTED_TARGETS})`

Except all the other content of the page this paragraph applys not to the currently described CMakeLists.txt file but to a package which depends on a message package. It contains all exported targets from the packages find_package(catkin COMPONENT ...) was called for.

In the current CMakeLists.txt the user can use ${this_project_name_EXPORTED_TARGETS} after invoking generate_messages() to state the dependency for other targets to depend on the generated stuff.

[jack-oquin]

Thanks for the feedback, Dirk.

I was confused about the meaning of ${catkin_EXPORTED_TARGETS}.

Corrected version here: http://farnsworth.csres.utexas.edu/docs/catkin/html/howto/building_msgs.html

[jack-oquin]

Should I update this patch to use ${beginner_tutorials_EXPORTED_TARGETS}, instead?

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