doc: Added warning to not instantiate Clock directly with RCL_ROS_TIME (#2768)

Signed-off-by: Janosch Machowinski <[email protected]>
Signed-off-by: Janosch Machowinski <[email protected]>
Co-authored-by: Janosch Machowinski <[email protected]>
Co-authored-by: Tomoya Fujita <[email protected]>

Author: 3 people

rclcpp/include/rclcpp/clock.hpp

@@ -60,6 +60,13 @@ class Clock
   /**
    * Initializes the clock instance with the given clock_type.
    *
+   * WARNING Don't instantiate a clock using RCL_ROS_TIME directly,
+   * unless you really know what you are doing. By default no TimeSource
+   * is attached to a new clock. This will lead to the unexpected behavior,
+   * that your RCL_ROS_TIME will run always on system time. If you want
+   * a RCL_ROS_TIME use Node::get_clock(), or make sure to attach a
+   * TimeSource yourself.
+   *
    * \param clock_type type of the clock.
    * \throws anything rclcpp::exceptions::throw_from_rcl_error can throw.
    */