How to use thrust with classes?

I have done some programs with thrust, specially remove_if function with no problem.
However instead of simple types I would like to use arrays of pre-defined classes. (For example opencv’s cv::KeyPoint ) However my code is not building.

This is not my final code or how I want to do it in the end (in the end I want to process in the device not the host) but is very basic yet still failing.

#include <thrust/host_vector.h>
#include <thrust/device_vector.h>

//#include <thrust/copy.h>
#include <thrust/remove.h>
#include <cuda.h>
#include <cuda_runtime.h>

#include <opencv2/opencv.hpp>
#include <opencv2/core.hpp>
#include <opencv2/cudaarithm.hpp>

#include <iostream>

struct is_zero
  __host__  __device__ 
  bool operator()(const cv::KeyPoint x)
    return x.response  == 0.0;

int main(void){

cv::KeyPoint h_data[5]; 

h_data[0]=  cv::KeyPoint(cv::Point2f(3,4),0.3);
h_data[1]=  cv::KeyPoint(cv::Point2f(2,6),0.3);
h_data[2]=  cv::KeyPoint(cv::Point2f(1,1),0.3);
h_data[3]=  cv::KeyPoint(cv::Point2f(2,8),0.3);
h_data[4]=  cv::KeyPoint(cv::Point2f(2,6),0.3);


cv::KeyPoint *new_data_end = thrust::remove_if(h_data, h_data + 5, is_zero());  //this does not work


When I try to build this I get

/usr/local/cuda/include/thrust/system/cuda/detail/par.h(141): warning: calling a __host__ function("cv::Point_<float> ::Point_") from a __host__ __device__ function("cv::KeyPoint::KeyPoint") is not allowed

/usr/local/cuda/include/thrust/system/cuda/detail/par.h(141): warning: calling a __host__ function("cv::Point_<float> ::Point_") from a __host__ __device__ function("cv::KeyPoint::KeyPoint [subobject]") is not allowed

/usr/local/cuda/include/thrust/system/cuda/detail/par.h(141): warning: calling a __host__ function("cv::Point_<float> ::operator =") from a __host__ __device__ function("cv::KeyPoint::operator =") is not allowed

What am I doing wrong and what is the correct way to do this.

(take into account that in the end I would like to do this not for an array in host memory but for one in device memory)

cross posting with relevant comments is here