gcc bug in condition variable::wait_for

Question

Seems there is a bug in gcc's std::condition_variable::cv.wait_for() .

If the system time change during the wait, it will return after the wrong period.

Most often - it just doesn't return if the time is moved to the past, or awakes immediately if time moves to the future.

I think the cause is that it uses system clock instead if steady_clock ( https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/std/condition_variable#L67 ).

Did anybody come across this issue ? what could be a workaround ?

Answer 1

It looks like the standard agrees with you that the clock used should be std::chrono::steady_clock .

§ 30.5.1

39. Effects: as if
    return wait_until(lock, chrono::steady_clock::now() + rel_time, std::move(pred));

This bug also appears to be tracked by the GCC folks already.

As for fixes/workarounds you could:

• Submit a fix to libstdc++
• Use libc++ , which appears to get it right .