#include <time.h>
#include <limits.h>

clock_t clock(void)
{
	struct timespec ts;

	if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts))
		return -1;

	if (ts.tv_sec > LONG_MAX / 1000000 ||
	    ts.tv_nsec / 1000 > LONG_MAX - 1000000 * ts.tv_sec)
		return -1;

	return ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
}