Core Dumps with No Plugins on ClassLoader constructor

[DLu]

I was refactoring code, and mistakenly didn't change the export tags on a plugin. Hence there were no available plugins for the given type.

terminate called after throwing an instance of 'pluginlib::LibraryLoadException'
  what():  rospack could not find the layered_costmap package containing layered_costmap::CostmapPlugin

Program received signal SIGABRT, Aborted.
0x00007ffff6b05425 in raise () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff6b05425 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007ffff6b08b8b in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2  0x00007ffff715b69d in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007ffff7159846 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007ffff7159873 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007ffff715996e in __cxa_throw () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x00007ffff73e139f in pluginlib::ClassLoader<layered_costmap::CostmapPlugin>::determineAvailableClasses (this=0x7fffffffe010)
    at /opt/ros/fuerte/stacks/pluginlib/include/pluginlib/class_loader_imp.h:418
#7  0x00007ffff73e1947 in pluginlib::ClassLoader<layered_costmap::CostmapPlugin>::ClassLoader (this=0x7fffffffe010, package=..., base_class=..., 
    attrib_name=...) at /opt/ros/fuerte/stacks/pluginlib/include/pluginlib/class_loader_imp.h:51
#8  0x00007ffff73cb25a in layered_costmap::LayeredCostmap::LayeredCostmap (this=0x7fffffffdd40, name=..., tf=...)
    at /wg/stor5/dlu/ros/navigation/layered_costmap/src/layered_costmap.cpp:50

[mirzashah]

I forgot to follow up on this. Could you explain in a little more detail the conditions for recreating the bug:
-What part of the export tags were incorrect, the lookup name, the base class, or the derived class?
-Could you provide a simple sample program recreating the bug?

If the issue turns out to be Fuerte-only, I likely won't backport a fix as it's easy to workaroundl

[DLu]

#include <ros/ros.h>
#include <pluginlib/class_loader.h>
class Jedi { };
int main(int argc, char **argv)
{
  ros::init(argc, argv, "plugin_test");
  pluginlib::ClassLoader<Jedi> x("plugin_test", "Jedi");
  //x.createClassInstance("Obiwan");
  return 0;
}

Here is a simple test case. There are no plugins of type Jedi defined anywhere. However, you would expect it to only error out on the commented out line, not the ClassLoader line.

I have not tested in Groovy.

[mirzashah]

Oh that is odd...that case should be covered by unit test. I'll try to recreate and get back to you.

[mirzashah]

I misread your output, it's actually correct. The SIGABRT is triggered by the exception that is raised, which is the correct behavior. When a ClassLoader is created, it queries rospack for all plugin XML files exported by the package it is bound to. It seems that if there are no XML files exported by a package, it raises a LibraryLoadException.

Though the behavior is correct, the exception type and encapsulating error message is not very helpful I may just prevent the constructor from raising an exception and throwing it at plugin creation time (as you were expecting).. I will refactor this for groovy, but will not bother with fuerte.