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NodeHandle and ROS_DEBUG [closed]

asked 2014-07-20 23:05:14 -0600

ST-Lab gravatar image

Dear ROS members.

I had a trouble to use ROS_DEBUG macro after destructing a private node handle in a local scope.

As the following codes, when the "priv_nh1" node handle in the 1st local scope was destructed, ROS_DEBUG macro will never say anything at all. it's occurred in ROS::Groovy and ROS::Indigo.

In other words, the 1st and 2nd local scopes are meaning multi-threads or functions.

Is there bettwer way to use private node handles in each scopes?

Thank you.

#include <ros/ros.h>
#include <ros/console.h>
int main( int  argc, char**  argv )
  ros::init( argc, argv, "test" );
  { // <1st local scope>
    ROS_INFO("local scope : enter");
    ros::NodeHandle  priv_nh1("~");
    /* ... do something ... */
    ROS_INFO("local scope : exit");
  } // </1st local scope>
  // I can not get following ROS_DEBUG messages ...
  { // <2nd local scope>
    ROS_INFO("local scope : enter");
    ros::NodeHandle  priv_nh2("~");
    int              value = 0;
    priv_nh2.param( "value", value, 0 );
    ROS_INFO("value %d", value);
    ROS_INFO("local scope : exit");
  } // </2nd local scope>
  return 0;
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Closed for the following reason the question is answered, right answer was accepted by ST-Lab
close date 2014-07-21 02:03:48.382702


Does ROS_DEBUG work if you use it elsewhere in your program?

ahendrix gravatar image ahendrix  ( 2014-07-21 00:02:37 -0600 )edit

Thank you, ahendrix. ROS_DEBUG can work anywhere, if I do not use such a private(disposable) node handle. When I remove such a private node handle and get parameters by ros::param::get directly, there is no problem occurred.

ST-Lab gravatar image ST-Lab  ( 2014-07-21 00:46:36 -0600 )edit

I'm seeing this with all of the rosconsle output macros, including ROS_INFO, not just ROS_DEBUG.

ahendrix gravatar image ahendrix  ( 2014-07-21 01:16:58 -0600 )edit

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answered 2014-07-21 01:21:37 -0600

ahendrix gravatar image

The trouble here is that you don't have a persistent NodeHandle throughout the scope of your program.

As explained on the NodeHandle wiki page, once all NodeHandles go out of scope, the internal node is shut down.

Private NodeHandles with limited scope are generally a good idea, but you should also maintain a NodeHandle (public or private) that lasts for the entire duration of your program.

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Dear, ahendrix. Thank you for your advice. I've read the class reference of the node handle, and I also got the same conclution as well as you. The problem is based on the complexity of the global reference counter in the node handle. But I hope that the above made codes clean and safe.

ST-Lab gravatar image ST-Lab  ( 2014-07-21 02:02:52 -0600 )edit

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Asked: 2014-07-20 23:05:14 -0600

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Last updated: Jul 21 '14