std::clock(), threading, and Linux

I had a strange experience with the boost::timer class the other day, since it never elapsed within a certain thread. As it turns out, this was because std::clock() itself doesn’t tick but returns the same value over and over again - a value that probably indicates the time the tread was started. The solution is rather simple: I implemented the boost::timer interface based upon boost::xtime from the boost threading library like this:

class XTimer {
  XTimer() {
    xtime_get(&_start_time, boost::TIME_UTC);

  XTimer(const XTimer& other)
  : _start_time(other._start_time)

  ~XTimer() {

  double elapsed() const {
    boost::xtime now;
    xtime_get(&now, boost::TIME_UTC);
    return boost::lexical_cast<double>(now.sec - _start_time.sec);

  boost::xtime _start_time;

Published: September 09 2006