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I am getting an unbound prefix error when I try to use an xarco macro. I do have the xmlns:xarco defined however. This is my xarco file:

<?xml version="1.0"?>
<robot xmlns:xacro="[link to xarco wiki]" name="flexible">
  <xacro:macro name="test_macro" >
    <test name="x"/>
  </xacro:macro>

  <xarco:test_macro/>
</robot>

And this is the error I am getting:

Expat parsing error.  Check that:
 - Your XML is correctly formed
 - You have the xacro xmlns declaration: xmlns:xacro="[link to xarco wiki]"

Traceback (most recent call last):
  File "/opt/ros/hydro/share/xacro/xacro.py", line 60, in <module>
    xacro.main()
  File "/opt/ros/hydro/lib/python2.7/dist-packages/xacro/__init__.py", line 571, in main
    doc = parse(f)
  File "/usr/lib/python2.7/xml/dom/minidom.py", line 1920, in parse
    return expatbuilder.parse(file)
  File "/usr/lib/python2.7/xml/dom/expatbuilder.py", line 928, in parse
    result = builder.parseFile(file)
  File "/usr/lib/python2.7/xml/dom/expatbuilder.py", line 207, in parseFile
    parser.Parse(buffer, 0)
xml.parsers.expat.ExpatError: unbound prefix: line 7, column 6

Any help would be appreciated.

If the devel space is supposed to mimic the install space, (as described in http://www.ros.org/wiki/catkin/workspaces), should that not be what is added to the ROS_PACKAGE_PATH? It seems confusing to have the package.xml and .launch files remain in the src directory and the binary targets copied to the devel directory...

Do I need to call generate_message() when I am only using a message defined in another package, and not defining one in my package?

It seems like I should not, since the code for the messages are already generated in the package defining it, which I am including. But the tutorial "Writing a Simple Publisher and Subscriber (C++)" has a call to generate_message() even though it only uses the std_msgs/String message, and does not define any of its own.

Can someone clarify the situation?

Ok, thank you. I guess I will just compile from source in github.

The latest version of the ros-hydro-gazebo-plugins package (2.3.2-0precise-20130920-2002-+0000) is broken (this bug) and I want to downgrade it to the previous version. The ROS repository however seems to have only the latest version of the package. Where can I get older versions?

Can specify exactly what error you are getting? And are you using ROS Hydro?

The question was answered in the PCL Users mailing list.

http://www.pcl-users.org/How-do-I-use-PCL-from-ROS-Hydro-td4029613.html

I am trying to understand how PCL is integrated into ROS Hydro. I installed ROS in Ubuntu 12.04 using the ros-hydro-desktop-full package. From "rospack list" I can see that it comes with 4 PCL packages:

1. pcl
2. pcl_conversions
3. pcl_msgs
4. pcl_ros

What is the functionality of these 4 packages, especially pcl_ros and pcl? There is also a pcl-1.7 folder in my /opt/ros/hydro/share folder with some cmake config files. There is no package.xml file though. What does this folder do?

Also, I seem to have 2 copies of the pcl-1.7 libraries. I have it in /usr/lib and also in /opt/ros/hydro/lib. So it seems like I have a standalone pcl library (I am not sure how I got this) and one that is integrated with ROS. Is this going to be a problem?

Finally, and this is the biggest source of my confusion, the wiki page for hydro/migration says:

pcl is no longer packaged by the ROS community as a catkin package, so any packages which directly depend on pcl should instead use the new rosdep rules libpcl-all and libpcl-all-dev and follow the PCL developer's guidelines for using PCL in your CMake.

So, why is there a pcl package in ROS Hydro in the first place with libraries in /opt/ros/hydro/lib?

As you can see I am quite confused, any help will be greatly appreciated!