Hi everyone,

In a test node I just have one publisher that publishes the node state once on the constructor and once on the destructor of my node class. I figured out that this works on Python3 (rclpy) and not on C++ (rclcpp).

import rclpy
from rclpy.node import Node
import time

from std_msgs.msg import String


class Test(Node):

    def __init__(self):
        super().__init__('test')

        self.publisher = self.create_publisher(String, 'state_test', 10)
        msg = String()
        msg.data = "Node started"
        self.publisher.publish(msg)

    def __del__(self):
        msg = String()
        msg.data = "Node crashed"
        self.publisher.publish(msg)

def main(args=None):
    rclpy.init(args=args)

    node_test = Test()
    rclpy.spin(node_test)

    node_test.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

C++ code:

#include <chrono>
#include <functional>
#include <memory>
#include <string>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std::chrono_literals;

class Test : public rclcpp::Node
{
  public:
    Test()
    : Node("test"), count_(0)
    {
      pub_state = this->create_publisher<std_msgs::msg::String>("state_test", 10);
      auto message = std_msgs::msg::String();
      message.data = "Node started";
      pub_state->publish(message);
    }

    ~Test()
    {
      auto message = std_msgs::msg::String();
      message.data = "Node crashed";
      pub_state->publish(message);
    }

  private:
    rclcpp::Publisher<std_msgs::msg::String>::SharedPtr pub_state;
    size_t count_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<Test>());
  rclcpp::shutdown();
  return 0;
}

Why is the result different on those two examples ?

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  {
    auto node = std::make_shared<Test>();
    rclcpp::spin(node);
  }
  rclcpp::spin_some(); // need to let ros spin a bit more to process the publish queued by the destructor
  rclcpp::shutdown();
  return 0;
}