Jobs flags not propagated to ExternalProject_Add

[sarlinpe]

System Info

• Operating System: Ubuntu 14.04
• Python Version: 2.7.6
• Version of catkin_tools: 0.4.4
• ROS Distro: Indigo

Actual Problem

The doc of catkin build says that the jobs flags -jN are passed directly to make when issuing catkin build <package> -jN. Turns out that they are not passed to the build and install commands of ExternalProject_Add.

Steps to Reproduce the Issue

Excerpt of CMakeLists.txt:

include(ExternalProject)

ExternalProject_Add(example
  GIT_REPOSITORY <repo>
  GIT_TAG b874783ccdf4cc36cb3546e6b6a998cb8f3470bb
  UPDATE_COMMAND ""
  SOURCE_DIR src
  BINARY_DIR build
)

Here the BUILD_COMMAND and INSTALL_COMMAND are implicitly make and make install respectively. Shouldn't the jobs flags -jN be passed to these commands as well ?

[peci1]

In my tests, it seems it's really just make without arguments what's called by the ExternalProject, but for some reason, it only runs the number of build jobs I've specified for catkin build. I tried cleaning the workspace with the same results.

[peci1]

Hmm, I think what happens at my computer is that catkin build runs multiple jobs, each of which is a single-threaded make. So it must somehow take over the jobs generated by the external project (even though it's a plain CMake project).

In the end, the build process utilizes as much cores as I wish, but I see that you were probably expecting a single multithreaded make call.

[sarlinpe]

When building a single package there should anyway be only a single catkin build job running. I thought that catkin build would run the make jobs in a multithreaded fashion with -jN.