boost::asio::steady_timer的一个错误用法

boost::asio::steady_timer的一个错误用法。

//使用boost.chrono代替std.chrono,
#define BOOST_ASIO_DISABLE_STD_CHRONO
#include <boost/asio.hpp>
#include <boost/asio/steady_timer.hpp>
#include <boost/asio/placeholders.hpp>
#include <boost/thread.hpp>
#include <boost/format.hpp>

bool g_isExit = false;

void DoSth(int idx, const boost::system::error_code& errCode)
{
    if (errCode)
    {
        std::string str = (boost::format("idx=%|d|, value=%|d|, message=%|s|") % idx%errCode.value() % errCode.message()).str();
        std::cout << str << std::endl;
        return;
    }
    else
    {
        std::string str = (boost::format("idx=%|d|, doing") % idx).str();
        std::cout << str << std::endl;
    }

    boost::this_thread::sleep_for(boost::chrono::seconds(3));//做什么事情,花费了3秒钟,
    g_isExit = true;
    return;
}
int main(int argc, char** argv)
{
    boost::thread_group thgp;
    boost::asio::io_service io;
    boost::asio::io_service::work wk(io);
    thgp.create_thread(boost::bind(&boost::asio::io_service::run, boost::ref(io)));
    thgp.create_thread(boost::bind(&boost::asio::io_service::run, boost::ref(io)));
    boost::asio::steady_timer timer(io);

    //boost::asio::steady_timer注册了一个回调函数,这个回调函数将在1000ms后被回调,
    timer.expires_from_now(boost::chrono::milliseconds(1000));
    timer.async_wait(boost::bind(&DoSth, 1, boost::asio::placeholders::error));

    //回调函数没有被处理之前,又注册了一个回调函数,那么上一个回调函数就会执行失败,
    //错误信息: value=995, message=由于线程退出或应用程序请求，已中止 I/O 操作。
    timer.expires_from_now(boost::chrono::milliseconds(1000));
    timer.async_wait(boost::bind(&DoSth, 2, boost::asio::placeholders::error));

    while (false == g_isExit)
    {
        boost::this_thread::sleep_for(boost::chrono::milliseconds(10));
    }

    std::cout << "press ENTER to exit..." << std::endl;
    std::cin.sync();
    while (getchar() != '\n') {}
}

完。