library is linked but reference is undefined-Collection of common programming errors

I’m trying to compile an openCL program on Ubuntu with an NVIDIA card that worked once before,

#include 
#include 
#include 

using namespace std;

int main() {
  cl_platform_id platform;
  cl_device_id device;
  cl_context context;
  cl_command_queue command_queue;
  cl_int error;

  if(clGetPlatformIDs(1, &platform, NULL) != CL_SUCCESS) {
    cout