CODEWITHSUNDEEP
c++pointerssegmentation-faultsimulinkros
Michael
Michael

Reputation: 11

segmentation fault (core dumped) ROS c++ arrow

I'm trying to read a geometry_msgs::PoseArray and convert it to a geometry_msgs::Pose in c++ for ROS. It should only convert the data when there is data on topic /tag_detections_pose. When I run this node( see code), I get a segmentation fault (core dumped) at the marked location when there is an empty array on /tag_detections_pose. I expect this to be an issue with pointers, but cannot find where exactly. I think I have to initialize my pointer, but I don't see where exactly. (b.t.w. The code is to convert apriltag_ros messages to be readable by simulink)

#include "ros/ros.h"
#include <geometry_msgs/Pose.h>
#include <geometry_msgs/PoseArray.h>
#include <std_msgs/Bool.h>
#include <array>


class SubscribeAndPublish
{
public:
  SubscribeAndPublish()
  {
    //Topic you want to publish
    pub_ = n_.advertise<geometry_msgs::Pose>("/tag_pose", 1);

    //Topic you want to subscribe
    sub_ = n_.subscribe<geometry_msgs::PoseArray>("/tag_detections_pose", 1, &SubscribeAndPublish::callback, this);
  }

  void callback(const geometry_msgs::PoseArray::ConstPtr& input)
  {
    if (input) {
      geometry_msgs::Pose output;

      output.position.x = input->poses[0].position.x; //Here I get the segmentation fault
      output.position.y = input->poses[0].position.y;
      output.position.z = input->poses[0].position.z;
      output.orientation.x = input->poses[0].orientation.x;
      output.orientation.y = input->poses[0].orientation.y;
      output.orientation.z = input->poses[0].orientation.z;
      output.orientation.w = input->poses[0].orientation.w;
      pub_.publish(output);
    }

  }

private:
  ros::NodeHandle n_;
  ros::Publisher pub_;
  ros::Subscriber sub_;

};//End of class SubscribeAndPublish

int main(int argc, char **argv)
{
  //Initiate ROS
  ros::init(argc, argv, "apriltag_to_simu_V2");

  SubscribeAndPublish SAPObject;

  ros::spin();

  return 0;
}

EDIT: some extra information. Whenever I read the next data from /tag_detections_pose, the segmentation fault occurs.

header: 
  seq: 14192
  stamp: 
    secs: 1519941974
    nsecs: 650975624
  frame_id: usb_cam
poses: []
---
header: 
  seq: 14193
  stamp: 
    secs: 1519941974
    nsecs: 995796728
  frame_id: usb_cam
poses: []
---

Whenever I see an apriltag, there is no segmentation fault. Then the following code comes from /tag_detections_pose:

---
header: 
  seq: 80
  stamp: 
    secs: 1519981664
    nsecs: 100302767
  frame_id: usb_cam
poses: 
  - 
    position: 
      x: 0.110443956833
      y: -0.080843233518
      z: 0.753152633488
    orientation: 
      x: 0.706039345202
      y: 0.705726892216
      z: -0.0580458686961
      w: 0.00941667438916
---
header: 
  seq: 81
  stamp: 
    secs: 1519981664
    nsecs: 368606478
  frame_id: usb_cam
poses: 
  - 
    position: 
      x: 0.110435802307
      y: -0.0808251086937
      z: 0.753089835655
    orientation: 
      x: 0.706068882885
      y: 0.705719138117
      z: -0.0577643573596
      w: 0.0095136604333
---

Upvotes: 1

Views: 4602

Answers (3)

man Out
man Out

Reputation: 1

Here's how I solved this problem. Add if(msg->detections.size()>0) before data = msg->detections[0].pose.pose;

Upvotes: 0

Mohammad Ali
Mohammad Ali

Reputation: 574

maybe seg fault happening cause You are declaring a Non-Pointer type in subscriber Constructor(i haven't tested This).

U Don't Have to Initilize a geometry_msgs::PoseArray::ConstPtr& u can just do geometry_msgs::PoseArray and be rid of pointer

Upvotes: 0

mikkola
mikkola

Reputation: 3476

Instead of checking if (input), you should check for what you actually care about: whether the poses field is non-empty.

In ROS messages, the arrays are stored as C++ vectors. To check if the poses vector has any elements, you can replace your condition by if (!input->poses.empty())

Upvotes: 1

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