Segmentation fault core dump. publisher/subscriber

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The below code works for sometime before giving a segmentation fault. I have been looking at some of the answers on the page but haven't been able to solve this issue. I am using the following code as a plugin and then running the code using rosrun. Changing the rate does not seem to improve the situation as well.
There are two other class definitions that are used, both of them do not crash, but the below code crashes after a few minutes of running.
Any suggestions on what to change in the code or logical errors would be helpful!

#ifndef FUNCTIONBLOCKS_FUNCTION_ASSETS_H_
#define FUNCTIONBLOCKS_FUNCTION_ASSETS_H_

#include <ros/ros.h>
#include "functionblocks/functionBlock.h"
#include "functionblocks/sensor.h"
#include "functionblocks/actuator.h"
#include <unistd.h>

namespace function_assets {

class SubscribeAndPublish_fb {
public:
  SubscribeAndPublish_fb() {
    // Topic you want to publish
    pub_ = n_.advertise<functionblocks::functionBlock>("functionBlocks", 1000);

    // Topic you want to subscribe
    publish();
    sub_ =
        n_.subscribe("sensors", 1000, &SubscribeAndPublish_fb::callback, this);
    ros::spin();
  }

  void callback(const functionblocks::sensor::ConstPtr &input) {
    ROS_INFO("sensor state : %d", input->state);
    ROS_INFO("sensor name : %s", input->name.c_str());
    if (!input->name.empty()) {
      msg1.sensor.push_back(input->name.c_str());
    }
    ROS_INFO("sensor id : %d", input->id);
    ROS_INFO("sensor memory : %ld", (long int)input->memory);
    msg1.spare = msg1.spare - input->memory;
    // ros::Rate loop_rate(10);
    while (ros::ok()) {
      pub_.publish(msg1);
      msg1.spare = mem;
      ros::spinOnce(); // done to handle callbacks
      // loop_rate.sleep(); //sleep till the time is done --10
    }
  }

  void publish() {
    std::cout << "Enter block name:";
    std::cin >> block_n;
    std::cout << "Enter block memory:";
    std::cin >> mem;
    std::cout << "Enter block handling:";
    std::cin >> handling;
    msg1.block_n = block_n;
    msg1.spare = mem;
    msg1.memory = mem;
    msg1.handling = handling;
  }

private:
  ros::NodeHandle n_;
  ros::Publisher pub_;
  ros::Subscriber sub_;
  functionblocks::functionBlock msg1;
  long int mem;
  std::string block_n;
  int handling;

}; // End of class SubscribeAndPublish

};

#endif here