The lines

        fprintf(stderr, "rapl_type_id()=%"PRIx64",
rapl_gpu_power()=%"PRIx64"\n",
                rapl_type_id(), rapl_gpu_power());

made the overlay fail to build. I have changed that to (using lx is not
perfect, but PRIx64 made it fail to build):

        fprintf(stderr, "rapl_type_id()=%lx\n",rapl_type_id());
        fprintf(stderr, "rapl_gpu_power()=%lx\n",rapl_gpu_power());

which should result in the intended output. It was:

rapl_type_id()=d
rapl_gpu_power()=4
rapl_gpu_power_scale()=2,000000