Segmentation fault if sensor is unpowered on start-up

[tombrodie]

Describe the bug
When the Ouster is not powered and the code is started, a segmentation fault occurs.

To Reproduce

1. Checkout the master branch on c6f66d2c439aa27a6018a09a5e5b02fa222b52db
2. Ensure the sensor is not on
3. Run the Ouster driver: <include file="$(find ouster_ros)/launch/sensor.launch">

Debugging information
Journal logs:

kernel: nodelet[1922]: segfault at 0 ip 00007f42c4649ae8 sp 00007ffe1f8638e0 error 4 in libouster_ros_nodelets.so[7f42c463a000+7a000]

Stack trace:

Core was generated by `/opt/ros/noetic/lib/nodelet/nodelet manager __name:=os_nodelet_mgr __log:=/var/'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007fac5ef63ae8 in ouster_ros::OusterSensor::stop_sensor_connection_thread() () from /opt/ros/noetic/lib//libouster_ros_nodelets.so
[Current thread is 1 (Thread 0x7fac7286d780 (LWP 68))]
(gdb) bt
#0  0x00007fac5ef63ae8 in ouster_ros::OusterSensor::stop_sensor_connection_thread() () from /opt/ros/noetic/lib//libouster_ros_nodelets.so
#1  0x00007fac5ef6482d in ouster_ros::OusterSensor::~OusterSensor() () from /opt/ros/noetic/lib//libouster_ros_nodelets.so
#2  0x00007fac5ef64e8d in ouster_ros::OusterSensor::~OusterSensor() () from /opt/ros/noetic/lib//libouster_ros_nodelets.so
#3  0x00007fac75dd4567 in void class_loader::ClassLoader::onPluginDeletion<nodelet::Nodelet>(nodelet::Nodelet*) () from /opt/ros/noetic/lib/libnodeletlib.so
#4  0x00007fac75dcb999 in boost::detail::sp_counted_impl_pd<nodelet::Nodelet*, boost::_bi::bind_t<void, boost::_mfi::mf1<void, class_loader::ClassLoader, nodelet::Nodelet*>, boost::_bi::list2<boost::_bi::value<class_loader::ClassLoader*>, boost::arg<1> > > >::dispose() ()
   from /opt/ros/noetic/lib/libnodeletlib.so
#5  0x000055831b95e07a in boost::detail::sp_counted_base::release() ()
#6  0x00007fac75dca3bf in nodelet::Loader::unload(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) () from /opt/ros/noetic/lib/libnodeletlib.so
#7  0x00007fac75dda13d in nodelet::LoaderROS::unload(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) () from /opt/ros/noetic/lib/libnodeletlib.so
#8  0x00007fac75d3de41 in bond::Bond::flushPendingCallbacks() () from /opt/ros/noetic/lib/libbondcpp.so
#9  0x00007fac75d3df9d in bond::Bond::onConnectTimeout() () from /opt/ros/noetic/lib/libbondcpp.so
#10 0x00007fac75ca8dc1 in ros::TimerManager<ros::SteadyTime, ros::WallDuration, ros::SteadyTimerEvent>::TimerQueueCallback::call() () from /opt/ros/noetic/lib/libroscpp.so
#11 0x00007fac75c76162 in ros::CallbackQueue::callOneCB(ros::CallbackQueue::TLS*) () from /opt/ros/noetic/lib/libroscpp.so
#12 0x00007fac75c77873 in ros::CallbackQueue::callAvailable(ros::WallDuration) () from /opt/ros/noetic/lib/libroscpp.so
#13 0x00007fac75ccb02f in ros::SingleThreadedSpinner::spin(ros::CallbackQueue*) () from /opt/ros/noetic/lib/libroscpp.so
#14 0x00007fac75cb324f in ros::spin() () from /opt/ros/noetic/lib/libroscpp.so
#15 0x000055831b95c234 in main ()

My thought:
The start() function returns before start_sensor_connection_thread() is called. Thus, when stop_sensor_connection_thread() is called in the destructor, the std::unique_ptr that is sensor_connection_thread is not initialised, and remains null. A check for a nullptr should be performed in stop_sensor_connection_thread() before checking sensor_connection_thread->joinable().

Platform:

• Ouster Sensor? OS1-32
• Ouster Firmware Version? 3.1
• ROS version/distro? Noetic
• Operating System? Linux Ubuntu 20.4
• Machine Architecture? x86
• git commit hash c6f66d2c439aa27a6018a09a5e5b02fa222b52db

[Samahu]

Resolved by #411