"Warning : Non-POD class type passed through ellipsis" for simple thrust program - c++11

Question

In spite of reading many answers on the same kind of questions on SO I am not able to figure out solution in my case. I have written the following code to implement a thrust program. Program performs simple copy and display operation.
#include <stdio.h>
#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
int main(void)
{
// H has storage for 4 integers
thrust::host_vector<int> H(4);
H[0] = 14;
H[1] = 20;
H[2] = 38;
H[3] = 46;
// H.size() returns the size of vector H
printf("\nSize of vector : %d",H.size());
printf("\nVector Contents : ");
for (int i = 0; i < H.size(); ++i) {
printf("\t%d",H[i]);
}
thrust::device_vector<int> D = H;
printf("\nDevice Vector Contents : ");
for (int i = 0; i < D.size(); i++) {
printf("%d",D[i]); //This is where I get the warning.
}
return 0;
}

Answer 1

Thrust implements certain operations to facilitate using elements of a device_vector in host code, but this apparently isn't one of them.
There are many approaches to addressing this issue. The following code demonstrates 3 possible approaches:
explicitly copy D[i] to a host variable, and thrust has an appropriate method defined for that.
copy the thrust device_vector back to a host_vector before print-out.
use thrust::copy to directly copy the elements of the device_vector to a stream.
Code:
#include <stdio.h>
#include <iostream>
#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include <thrust/copy.h>
int main(void)
{
// H has storage for 4 integers
thrust::host_vector<int> H(4);
H[0] = 14;
H[1] = 20;
H[2] = 38;
H[3] = 46;
// H.size() returns the size of vector H
printf("\nSize of vector : %d",H.size());
printf("\nVector Contents : ");
for (int i = 0; i < H.size(); ++i) {
printf("\t%d",H[i]);
}
thrust::device_vector<int> D = H;
printf("\nDevice Vector Contents : ");
//method 1
for (int i = 0; i < D.size(); i++) {
int q = D[i];
printf("\t%d",q);
}
printf("\n");
//method 2
thrust::host_vector<int> Hnew = D;
for (int i = 0; i < Hnew.size(); i++) {
printf("\t%d",Hnew[i]);
}
printf("\n");
//method 3
thrust::copy(D.begin(), D.end(), std::ostream_iterator<int>(std::cout, ","));
std::cout << std::endl;
return 0;
}
Note that for methods like these, thrust is generating various kinds of device-> host copy operations to facilitate the use of device_vector in host code. This has performance implications, so you might want to use the defined copy operations for large vectors.