Why does std::timed_mutex::try_lock_for not work?

Question

I used gcc-4.8.1(configure: ./configure --prefix=/usr/local) to compile following code in Ubuntu 12.04, but when I ran it, it didn't work. it didn't stop to wait the mutex. It returned false, and outputed "Hello world!"

command: g++ -std=c++11 main.cpp -omain -pthread

When I used gcc-4.6(apt-get install g++) to compile it, it worked well. The program waited about ten seconds, and outputed "Hello world!"

#include <thread>
#include <iostream>
#include <chrono>
#include <mutex>

std::timed_mutex test_mutex;

void f()
{
    test_mutex.try_lock_for(std::chrono::seconds(10));
    std::cout << "hello world\n";
}

int main()
{
    std::lock_guard<std::timed_mutex> l(test_mutex);
    std::thread t(f);
    t.join();
      return 0;
}

Answer 1

If I am not mistaken, that is Bug 54562 -mutex and condition variable timers.

The reason for the bug is also mentioned:

This is because it uses the CLOCK_MONOTONIC clock (if available on the platform) to calculate the absolute time when it needs to return, which is incorrect as the POSIX pthread_mutex_timedlock() call uses the CLOCK_REALTIME clock, and on my platform the monotonic clock is way behind the real time clock.

However, this doesn't explain why you see the correct behavior on gcc-4.6 though. Perhaps _GLIBCXX_USE_CLOCK_MONOTONIC is not enabled?