GCC 4.9.2 / GCC 4.8.1 - std::condition_variable::wait_until(…) bug?

Question

I have a problem with the method wait_until on c++11 conditional variables. It looks like the method return std::cv_status::no_timeout even if there are no notifications. The code below shows the problem.

There are comments in the code below illustrating the problem.

Compiler used: gcc 4.9.2 (on arch linux) gcc 4.8.1 (on ubuntu 14.04)

I am greatful for any help i can get to solve this.

Best regars, Mats

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


std::mutex m;
std::condition_variable v;

void test_wait_until(int ms)
{
    std::unique_lock<std::mutex> lock(m);

    std::cout << ms << "ms start\n";
    auto expires = std::chrono::system_clock::now() + std::chrono::milliseconds(ms);
    bool run = true;

    do
    {
        // This loop will run at 100% cpu time until
        // the timeout expires.

        auto status = v.wait_until(lock, expires);

        if(status == std::cv_status::timeout){
            std::cout << ms << "ms expired\n";
            run=false;
        }

        if(status == std::cv_status::no_timeout){
            // If the commend below is removed the
            // termial will be filled by the printout.
            // until the timeout expires.

            //std::cout << ms << "ms did not expire\n";
        }
    }while(run);
}


int main()
{
    test_wait_until(20000);
    test_wait_until( 5000);
    test_wait_until(  100);
    test_wait_until(  100);
    test_wait_until(   10);
    test_wait_until(    0);
    test_wait_until(   -10);
    test_wait_until(  -100);
    test_wait_until(  -100);
    test_wait_until( -5000);
    test_wait_until(-20000);
}

Answer 1

You probably need to build your executable with threading support. On Linux with gcc 4.9.2 this would go something like this:

g++ -std=c++11 test.cpp -o test -pthread

Answer 2

Ok the problem was: I / we were using the -lpthread option instead of the -pthread option for gcc.

The strange this is other things works rather well, but this seams to the solution.

Thank you all!