catkin_make errors while subscribing to diagnostic topic

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I am trying to subscribe to diagnostic topic and based on the level published by the topic, I am trying to start and stop my operation. I have created 2 functions requestStart and requestNotStart for these purposes. I am getting the CMake errors which I am unable to fix (posted at the end of the post).

Following is my code -

using namespace std;
namespace errorLib
{
  class errorH
  {
    public:
      errorH(EC value, string text, int sec):
        value_(value),
        text_(text),
        is_started_(false),
        sec_(sec)
        {
        }
      EC value_;
      string text_;
      bool is_started_;
      int retry_seconds_;
  };
}
 void diagnosticCallback(const diagnostic_msgs::DiagnosticArrayPtr &diags_msg)
  {
    if (diags_msg[0].level == diagnostic_msgs::DiagnosticStatus::ERROR)
      errorcode = NodeToErrorCode[diags_msg[0].name];
      requestStart();

    else (diags_msg[0].level == diagnostic_msgs::DiagnosticStatus::OK)
      errorcode = NodeToErrorCode[diags_msg[0].name];
      requestNotStart();
  }

int requestStart(errorLib::errorH& c)
{
  if(!c.is_started_)
    retry_seconds_ = 2;
    // Start timer
    // Timer expired
  c.is_started_ = true;
  return 0;
}
int requestNotStart(errorLib::errorH& c)
{
   return 0;
}
int main(int argc, char **argv)
{
  errorLib::errorH c("For starting/ending", 2);
  requestStart(c);
  requestNotStart(c);
  ros::init(argc, argv, "<node_name>");
  ros::NodeHandle nh;
  std::map<std::string, int> NodeToErrorCode =
    {{"rosout", 1},
     {"<Node1>", 2},
     {"<Node2>", 3}};

  ros::Subscriber sub = nh.subscribe("diagnostics", 1000, diagnosticCallback);
  ros::spin();
  return 0;
}

Following are the errors for reference -

In function ‘void diagnosticCallback(const DiagnosticArrayPtr&)’:
/home/default_ws/src/err_pack/src/errors_node.cpp:52:21: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
     if (diags_msg[0].level == diagnostic_msgs::DiagnosticStatus::ERROR)
                     ^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:7: error: ‘errorcode’ was not declared in this scope
       errorcode = NodeToErrorCode[diags_msg[0].name];
       ^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:19: error: ‘NodeToErrorCode’ was not declared in this scope
       errorcode = NodeToErrorCode[diags_msg[0].name];
                   ^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:47: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
       errorcode = NodeToErrorCode[diags_msg[0].name];
                                               ^
/home/default_ws/src/err_pack/src/errors_node.cpp:55:18: error: ‘requestStart’ was not declared in this scope
       requestStart();
                  ^
/home/default_ws/src/err_pack/src/errors_node.cpp:58:26: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
     else if (diags_msg[0].level == diagnostic_msgs::DiagnosticStatus::OK)
                          ^
/home/default_ws/src/err_pack/src/errors_node.cpp:59:47: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
       errorcode = NodeToErrorCode[diags_msg[0].name];
                                               ^
/home/default_ws/src/err_pack/src/errors_node.cpp:60:21: error: ‘requestNotStart’ was not declared in this scope
       requestNotStart();
                     ^
/home/default_ws/src/err_pack/src/errors_node.cpp: In function ‘int requestStart(errorLib::errorH&)’:
/home/default_ws/src/err_pack/src/errors_node.cpp: In function ‘int main(int, char**)’:
/home/default_ws/src/err_pack/src/errors_node.cpp:93:53: error: no matching function for call to ‘errorLib::errorH::errorH(const char [21], int)’
   errorLib::errorH c("For starting/ending", 2);
                                                     ^
/home/default_ws/src/err_pack/src/errors_node.cpp:93:53: note: candidates are:
/home/default_ws/src/err_pack/src/errors_node.cpp:21:7: note: errorLib::errorH::errorH(EC, std::string, int)
       errorH(EC value, string ...