Force rclcpp_lifecycle to be a shared lib#589
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Any chance this can be solved with a patch? |
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@mvukov Its not going to be a trivial change. We have to revert back-ported fix ros2/rclcpp#2183 and then apply the original fix ros2/rclcpp#1756 assuming it will apply cleanly and work as intended. |
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rclcpp_lifecycle contains an global variable that is accessed by some plugins and libraries. We want the plugin and libraries that uses the rclcpp_lifecycle to have the same global variable rather than the plugin which loads the .so and library that will staticly link.
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This PR forces rclcpp_lifecycle to link as a shared library.
rclcpp_lifecycle contains an global variable that is indirectly used by plugins and libraries. We want the plugin and libraries that uses the rclcpp_lifecycle to have the same global variable. Current statically linking behavior will result in plugin having its own global variable (its a .so) and library/node that loads the plugin having its own global variable. This fixes this issue by forcing rclcpp_lifecycle to link as a shared library. The Dynamic Linker ensures that only one instance of the library’s global data is mapped into the process memory. Now the both plugin and library/node will load rclcpp_lifecycle.so and will result in a single global variable. End result is that rclcpp_lifecycle node in the main binary can control the lifecycle of plugin and node itself.
This PR is needed as ROS2_Control package controls its loaded ros2_plugins lifecycle from the main node. Without this PR, ros2_control_node will crash on runtime as it expects loaded ros2 plugins lifecycle be present in the global variable. In addition, dynamic loading of rclcpp_lifecycle is the default cmake ros2 behavior.