Build Systems &
Build Tools

Main Benefits

Meta Information

• Machine readable meta information
  • Package name and version
  • Maintainer name and email, licenses
  • Dependencies
  • Links to source, doc, issues
  • Arbitrary additional information in the export section
• 
    → Automation, automation, and automation
  • Use dependencies to determine topological order
  • Name, version, maintainers and licenses
    are required for the packaging process
  • Use links to guide users
  • E.g. export plugin information

CMake config file generation (just for convenience)

• In order for find_package(foo) to work
  • You need to have a CMake config file (or module)
  • By convention it should set the following variables:
    • foo_FOUND, foo_VERSION(_...)
    • foo_INCLUDE_DIRECTORIES
    • foo_LIBRARIES (abs. paths or library names)
    • foo_LIBRARY_DIR (if the prev. one contains names)
• Naming Conventions
  • Possible file names (see find_package() docs):
    • <name>Config.cmake
    • <lower-case-name>-config.cmake
  • Existing CMake config files are written inconsistently, you don't know which case the set variable names will have
    • ROS uses the second pattern and ensures that all of the following are lower case: find_package() name, filename, variable prefix.

Environment Setup

• After building and installing packages you might need to
  set / extend environment variables in order to use the software:
  
  • Prepend / append a path to PATH to find executables
    in non-standard locations
  • Set the PYTHONPATH to find Python modules
    in non-standard locations
  • Set application specific information,
    e.g. GAZEBO_MODEL_PATH, ROSDISTRO_NAME
  • Source e.g. a Bash script for completion functionality
• 
  The goal:
  
  • Source a single file which takes care of "everything"

Automation

• Instead of reading the README of each package and execute the steps manually for each package in topological order... ☹
• 
  Build all package in ROS Kinetic with 5 (!) lines:
  • Get the code:
    • rosinstall_generator
    • wstool / vcstool
  • Install dependencies:
    • rosdep install
  • Build a workspace of packages:
    • catkin_make(_isolated) / catkin build / ament build / ?
  • Source single file:
    • . setup.bash
• 
  The ROS buildfarm basically uses the same steps.

Build System vs. Build Tool

• Any build tool should be able to support any build system,
• but that is currently not the case 😞

Build Systems: catkin vs. ament

• For more details see the ROS 2 design article The meta build system ament
• and the doc about the ament resource index.

More Features of both Build Systems

• Convenience functionality
  • Generation of pkg-config files (only in catkin)
  • CMake functions for gtest / nose tests
  • Download test data
  • CMake variables to simplify target arguments
    (e.g. aggregate include dirs and libraries)
• 
  Functionality provided by other packages
  • Code generation for ROS messages / services (e.g. genmsg)
  • Support for launch file based ROS tests (rostest)
  • Linter integration to automate checking code style, static code analysis, etc. (ament_lint)

Build Tools:
catkin_make vs. catkin_tools vs. ament_tools

• We are evaluating options to have one tool merging the best of all,
  maybe even support uses cases like building Gazebo and its dependencies.