topic_tools: demux crashes when using __none

[lfdebrux]

The demux node in topic_tools crashes when it receives a message and the selected topic is the magic "__none" topic

Steps to reproduce

rosrun topic_tools demux in out_1 out_2
rosservice call /demux/select "__none"
rostopic pub -1 /in std_msgs/Empty

demux then crashes with a segmentation fault

This was tested in kinetic on Ubuntu 16.04.

I believe this is due to a null pointer dereference in

ros_comm/tools/topic_tools/src/demux.cpp

Line 156 in 2838185

g_selected->pub->publish(msg);

[peci1]

Argh... bumped into this now on melodic... When will there finally be a new release of ros_comm???

[peci1]

For others who suffer by this bug: as a workaround, you can always add a "blackhole" topic which nobody subscribes, and redirect the output to it instead of __none.

[dirk-thomas]

Argh... bumped into this now on melodic... When will there finally be a new release of ros_comm???

This issue was closed when the referenced commit was merged: 2b3f43d on Apr 24, 2018. And that commit has been released for a very long time into Melodic (around May 2018). So if you still experience issues you might want to double check if there is an open ticket describing it or create a new issue.

[peci1]

You're right, in the end it looks like a different issue, but with very similar symptoms. See #1889 .