#include <stdio.h>

extern "C" __device__ void add_u32(
    ulonglong4 *out_c,
    ulonglong4 in_a,
    ulonglong4 in_b
);

__constant__ char ok[] = "ok";
__constant__ char not_ok[] = "not ok";

__global__ void kernel(char *buf) {
    ulonglong4 a = {0, 1, 2, 3};
    ulonglong4 b = {1, 1, 1, 1};
    ulonglong4 c = {1, 2, 3, 4};

    add_u32(&c, a, b);

    memcpy(buf, ok, sizeof(ok));
}

int main() {
	char h_buf[32];
    char *d_buf;   
    cudaMalloc(&d_buf, 32);

	kernel<<<1, 1>>>(d_buf);

    cudaDeviceSynchronize();
    cudaMemcpy(h_buf, d_buf, 32, cudaMemcpyDeviceToHost);
    
	printf("%s\n", h_buf);
    cudaFree(d_buf);
	return 0;
}