Segmentation fault when ros2_control tag has no gazebo description

[delipl]

Hello,
I have found an interesting bug during switching between the simulation and the real robot.

This is the error:

[gzserver-1] [INFO] [1651705814.192470228] [gazebo_ros2_control]: Loading joint: id_3
[gzserver-1] [INFO] [1651705814.192480124] [gazebo_ros2_control]:       Command:
[gzserver-1] [INFO] [1651705814.192489733] [gazebo_ros2_control]:                position
[gzserver-1] [INFO] [1651705814.192499904] [gazebo_ros2_control]:       State:
[gzserver-1] [INFO] [1651705814.192510058] [gazebo_ros2_control]:                position
[gzserver-1] [INFO] [1651705814.192520313] [gazebo_ros2_control]:                velocity
[gzserver-1] [INFO] [1651705814.192530941] [gazebo_ros2_control]:                effort
[gzserver-1] Segmentation fault (core dumped)
[ERROR] [gzserver-1]: process has died [pid 32467, exit code 139, ...]

This is my ros2_control.xacro description what throws segmentation fault

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">

    <xacro:macro name="ariadna_system_position_only" params="name use_sim use_hw_stubs">

        <ros2_control name="${name}" type="system">

            <xacro:if value="${use_sim}">
                <hardware>
                    <plugin>gazebo_ros2_control/GazeboSystem</plugin>
                </hardware>
                <joint name="right_wheel_0_joint">
                    <command_interface name="velocity">
                        <param name="min">-1</param>
                        <param name="max">1</param>
                    </command_interface>
                    <state_interface name="position" />
                    <state_interface name="velocity" />
                </joint>
                <joint name="left_wheel_0_joint">
                    <command_interface name="velocity">
                        <param name="min">-1</param>
                        <param name="max">1</param>
                    </command_interface>
                    <state_interface name="position" />
                    <state_interface name="velocity" />
                </joint>
            </xacro:if>

            <xacro:unless value="${use_sim}">
                <hardware>
                    <plugin>ariadna_manipulator_hardware/AriadnaManipulatorHardware</plugin>
                    <param name="usb_port">/dev/ttyUSB0</param>
                    <param name="baud_rate">57600</param>
                    <param name="joint_ids">1,2,3</param>
                    <xacro:if value="${use_hw_stubs}">
                        <param name="use_stub">true</param>
                    </xacro:if>
                </hardware>
            </xacro:unless>

            <joint name="id_1">
                <param name="id">1</param>
                <param name="Return_Delay_Time">0</param>
                <param name="CW_Angle_Limit">0</param>
                <param name="CCW_Angle_Limit">1023</param>
                <param name="Moving_Speed">1023</param>
                <command_interface name="position" />
                <state_interface name="position" />
                <state_interface name="velocity" />
                <state_interface name="effort" />
            </joint>
            <joint name="id_2">
                <param name="id">2</param>
                <param name="Return_Delay_Time">0</param>
                <param name="CW_Angle_Limit">0</param>
                <param name="CCW_Angle_Limit">1023</param>
                <param name="Moving_Speed">1023</param>
                <command_interface name="position" />
                <state_interface name="position" />
                <state_interface name="velocity" />
                <state_interface name="effort" />
            </joint>
            <joint name="id_3">
                <param name="id">3</param>
                <param name="Return_Delay_Time">0</param>
                <param name="CW_Angle_Limit">0</param>
                <param name="CCW_Angle_Limit">1023</param>
                <param name="Moving_Speed">1023</param>
                <command_interface name="position" />
                <state_interface name="position" />
                <state_interface name="velocity" />
                <state_interface name="effort" />
            </joint>
        </ros2_control>

        <ros2_control name="${name}_odrive" type="system">
            <xacro:unless value="$(arg use_sim)">
                <hardware>
                    <plugin>ariadna_odrive_hardware/AriadnaOdriveHardware</plugin>
                    <param name="velocity_limit">5</param>
                     <xacro:if value="${use_hw_stubs}">
                        <param name="use_stub">true</param>
                    </xacro:if>
                </hardware>
            </xacro:unless>

            <joint name="back_left_gear_joint">
                <param name="id">-1</param>
                <command_interface name="velocity" />
                <state_interface name="position" />
                <state_interface name="velocity" />
            </joint>
            
            <joint name="back_right_gear_joint">
                <param name="id">1</param>
                <command_interface name="velocity" />
                <state_interface name="position" />
                <state_interface name="velocity" />
            </joint>
        </ros2_control>

        <ros2_control name="AriadnaGripper" type="actuator">
            <xacro:if value="${use_sim}">
                <hardware>
                    <plugin>gazebo_ros2_control/GazeboSystem</plugin>
                </hardware>
            </xacro:if>
            <xacro:unless value="${use_sim}">
                <hardware>
                    <plugin>ariadna_electromagnet_hardware/AriadnaElectromagnetHardware</plugin>
                    <xacro:if value="${use_hw_stubs}">
                        <param name="use_stub">true</param>
                    </xacro:if>
                </hardware>
            </xacro:unless>
            <joint name="gripper_tool_joint">
                <command_interface name="effort"/>
                <state_interface name="effort" />
                <state_interface name="position" />
            </joint>
        </ros2_control>
    </xacro:macro>

</robot>

In tag <ros2_control name="${name}_odrive" type="system"> there is no <plugin>gazebo_ros2_control/GazeboSystem</plugin>.

When I split the motors and manipulator like below and now the <plugin>gazebo_ros2_control/GazeboSystem</plugin> tag existis in the ros2_control tag and error don't pops up.

 <ros2_control name="${name}_motors" type="system">
            <xacro:if value="${use_sim}">
                <hardware>
                    <plugin>gazebo_ros2_control/GazeboSystem</plugin>
                </hardware>
                <joint name="right_wheel_0_joint">
                    <command_interface name="velocity">
                        <param name="min">-1</param>
                        <param name="max">1</param>
                    </command_interface>
                    <state_interface name="position" />
                    <state_interface name="velocity" />
                </joint>
                <joint name="left_wheel_0_joint">
                    <command_interface name="velocity">
                        <param name="min">-1</param>
                        <param name="max">1</param>
                    </command_interface>
                    <state_interface name="position" />
                    <state_interface name="velocity" />
                </joint>
            </xacro:if>

I know this is my mistake in the description but the error could be described.
It would be great if this segmentation was fixed.

Regards,
Deli

[delipl]

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