Inner of asio use absolute time in timer queue.The absolute time have been calculated when the deadline_timer be constructing,not when the wait() be executing. When you passing a relative time,it then calculate the absolute time when it will timeout. Member function expires_from_now() of deadline_timer also has same behavior. Sorry for my poor english.

While trying to understand the difference between wait() and async_wait, I modified the tutorial example a little to test 2 timers at the same time like this:

int test_timer()

{

boost::asio::io_service io;

size_t delay1 = 5;

size_t delay2 = 3;

boost::asio::deadline_timer t1(io, boost::posix_time::seconds(delay1));

boost::asio::deadline_timer t2(io, boost::posix_time::seconds(delay2));

boost::timer t;

t2.wait();

std::cout << t.elapsed() << " sec elapsed!\n";

t1.wait();

std::cout << t.elapsed() << " sec elapsed!\n";

return 0;

}

I got this output:

3.004 sec elapsed!

5.007 sec elapsed!

However, I was expecting t2 and t1 to execute sequentially and thus getting:

3.004 sec elapsed!

8 sec elapsed!

What was wrong with my understanding about synchronous waiting here? Thanks.

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