RCUTILS logging macro vs ROS_INFO

asked 2021-04-11 05:29:13 -0500

91 ●8 ●11 ●18

Hi Community, I am starting to studying ROS2 in order to start to work with Realtime and Lifecycle nodes. I would like to ask which are the differences between the rcutils and the classical debugging/printout methods provided by ROS2 like ROS_INFO. The usage of these tools like rcutils have better performances for realtime and are suitable for these applications?

answered 2021-04-20 12:02:17 -0500

sgvandijk

flag of United Kingdom of Great Britain and Northern Ireland

649 ●2 ●24 ●19

It should not matter too much, because the RCLCPP logging macros (which replace the ROS_INFO calls from ROS 1) are implemented by using rcutils. See for instance RCLCPP_DEBUG:

  do { \
    static_assert( \
      ::std::is_same<typename std::remove_cv<typename std::remove_reference<decltype(logger)>::type>::type, \
      typename ::rclcpp::Logger>::value, \
      "First argument to logging macros must be an rclcpp::Logger"); \
 \
    RCUTILS_LOG_DEBUG_NAMED( \
      logger.get_name(), \
      rclcpp::get_c_string(RCLCPP_FIRST_ARG(__VA_ARGS__, "")), \
        RCLCPP_ALL_BUT_FIRST_ARGS(__VA_ARGS__,"")); \
  } while (0)

So decoding this, it basically just calls RCUTILS_LOG_DEBUG_NAMED, with a little bit of extra overhead to get the name of the logger you are using, which is negligible, and some magic to ensure the first argument is a C string that also should be very cheap, and some static type checks at the beginning that only affect compilation time.

So I'd just continue using the RCLCPP macros if you're working in C++, unless your profiling shows you have a bottleneck here :)

NB the snippet above is from Foxy, but for Dashing it is not different in a way that affects your question.