leak due to std::shared_ptr circular reference between Context and GuardCondition #2497
Description
Bug report
Required Info:
- Operating System:
- Ubuntu 22.04
- Installation type:
- binaries
- Version or commit hash:
- iron
- DDS implementation:
- Cyclone DDS
- Client library (if applicable):
- rclcpp
Steps to reproduce issue
Compile the following standalone executable and run with RMW_IMPLEMENTATION=rmw_cyclonedds_cpp valgrind --leak-check=full:
#include <memory>
#include <rclcpp/context.hpp>
#include <rclcpp/guard_condition.hpp>
int main(int argc, char** argv) {
auto context = std::make_shared<rclcpp::Context>();
context->init(argc, argv);
context->get_sub_context<rclcpp::GuardCondition>(context);
context->shutdown("shutdown");
return 0;
}
(Abusing GuardCondition as a 'sub-context' here is a simplified stand-in for GraphListener which is created as a sub-context by NodeGraph on behalf of Node, and itself owns a GuardCondition constructed with a std::shared_ptr to the context.)
Expected behavior
Optimally, no complaints, however there will be a couple leaks from liblttng-ust.so outside the scope of this issue.
Actual behavior
In addition to the above, this complaint:
==580480== 2,136 bytes in 1 blocks are possibly lost in loss record 42 of 44
==580480== at 0x4848899: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==580480== by 0x691434C: ddsrt_malloc (heap.c:26)
==580480== by 0x68CC4A9: UnknownInlinedFun (q_thread.c:79)
==580480== by 0x68CC4A9: thread_states_init (q_thread.c:103)
==580480== by 0x68EAB92: dds_init (dds_init.c:116)
==580480== by 0x6901351: dds_create_guardcondition (dds_guardcond.c:45)
==580480== by 0x67E6311: create_guard_condition() [clone .lto_priv.0] (rmw_node.cpp:4146)
==580480== by 0x4AB1945: ??? (in /opt/ros/iron/lib/librcl.so)
==580480== by 0x497F6BF: rclcpp::GuardCondition::GuardCondition(std::shared_ptr<rclcpp::Context>, rcl_guard_condition_options_s) (in /opt/ros/iron/lib/librclcpp.so)
==580480== by 0x10AF2F: std::shared_ptr<rclcpp::GuardCondition> rclcpp::Context::get_sub_context<rclcpp::GuardCondition, std::shared_ptr<rclcpp::Context>&>(std::shared_ptr<rclcpp::Context>&) (in /home/bmartin/tmp)
==580480== by 0x10A6B4: main (in /home/bmartin/tmp)
Additional information
If using fastDDS the above valgrind complaint will not appear. However I do believe the failure to shut down correctly is the fault of rclcpp and not any rmw implementation: that is, the context and the guard condition both own each other via std::shared_ptrs, so neither can ever be deleted. Possibly GuardCondition should be holding a weak pointer to the context instead?