boost asio post不工作​​，io_service :: run后post [英] boost asio post not working , io_service::run exits right after post

问题描述

我尝试使用asio混合boost信号来执行基于分派的处理程序调用。当post方法从线程调用时，io_service :: run立即退出，处理到post的回调从不被调用，回调是一个C ++ 11 lambda例程。我粘贴代码进行更多的分析。

 ＃include< iostream> 
＃include< thread> 
＃include< boost / signals2 / signal.hpp> 
＃include< boost / asio.hpp> 
 
 static boost :: asio :: io_service svc; 
 static boost :: signals2 :: signal< void（std :: string）> textEntered; 
 
 static void 
 handleInputText（std :: string text）
 {
 std :: cout<<handleInputText（）<< ：<< text; 
 return; 
} 
 
 static void 
 worker（）
 {
 sleep（2）; 
 svc.post（[]（）{
 std :: cout<<\\\
Raising signal。; 
 std :: string hello（hello world）; 
 textEntered（hello）; 
}）; 
 return; 
} 
 
 int main（int ac，char ** av）
 {
 try 
 {
 textEntered.connect（& handleInputText ）; 
 std :: thread w（std :: bind（& worker））; 
 svc.run（）; 
 w.join（）; 
} 
 catch（std :: exception& ex）
 {
 std :: cerr<<main（）退出with exception：<什么（）; 
} 
 return 0; 
} 
  

解决方案

您开始一个可以可最终发布工作的主题，但主线程已经退出。 / p>

要么在线程上运行ioservice，要么确保它具有 io_service :: work

这里有一个专用的服务线程和工作项目的修复：

Live On Coliru

 ＃include< boost / asio.hpp> 
＃include< iostream> 
＃include< boost / asio.hpp> 
＃include< boost / signals2.hpp> 
＃include< boost / thread.hpp> 
＃include< boost / make_shared.hpp> 
 
 static boost :: asio :: io_service svc; 
 static boost :: shared_ptr& boost :: asio :: io_service :: work> work_lock; 
 
 static boost :: signals2 :: signal< void（std :: string）> textEntered; 
 
 static void 
 handleInputText（std :: string text）
 {
 std :: cout<<handleInputText（）<< ：<< text; 
 return; 
} 
 
 static void 
 worker（）
 {
 sleep（2）; 
 svc.post（[]（）{
 std :: cout<<\\\
Raising signal。; 
 std :: string hello（hello world）; 
 textEntered（hello）; 
}）; 
 return; 
} 
 
 int main（）
 {
 try 
 {
 work_lock = boost :: make_shared& boost :: asio :: io_service :: work>（svc）; 
 textEntered.connect（& handleInputText）; 
 
 boost :: thread_group tg; 
 tg.create_thread（boost :: bind（& boost :: asio :: io_service :: run，& svc））; 
 tg.create_thread（& worker）; 
 
 boost :: this_thread :: sleep_for（boost :: chrono :: seconds（3））; 
 work_lock.reset（）; 
 
 tg.join_all（）; 
} 
 catch（std :: exception& ex）
 {
 std :: cerr<<main（）退出with exception：<什么（）; 
} 
 return 0; 
} 
  

列印：

 提高signal.handleInputText（）文本提供：hello world 
  

I am trying to mix boost signals with asio to do a dispatch based handler invocation. when the post method is invoked from a thread the io_service::run exits immediately, the callback handled to post is never invoked, callback is a C++11 lambda routine. I am pasting the code for more analysis.

#include<iostream>
#include<thread>
#include<boost/signals2/signal.hpp>
#include<boost/asio.hpp>

static boost::asio::io_service svc;
static boost::signals2::signal<void(std::string)> textEntered;

static void
handleInputText(std::string text)
{
    std::cout<<"handleInputText()"<<" text provided: "<<text;
    return;
}

static void 
worker()
{
    sleep(2);
    svc.post([](){
            std::cout<<"\nRaising signal.";
            std::string hello("hello world");
            textEntered(hello);
            });
    return;
}

int main(int ac, char **av)
{
    try
    {
        textEntered.connect(&handleInputText);
        std::thread w(std::bind(&worker));
        svc.run();
        w.join();
    }
    catch(std::exception &ex)
    {
        std::cerr<<"main() exited with exception:"<<ex.what();
    }
    return 0;
}

解决方案

You don't actually post any work to the service.

You start a thread that may eventually post work, but the main thread has already exited by that time.

Either, run the ioservice on the thread or make sure it has io_service::work

Here's a fix with a dedicated service thread and a work item:

Live On Coliru

#include<boost/asio.hpp>
#include<iostream>
#include<boost/asio.hpp>
#include<boost/signals2.hpp>
#include<boost/thread.hpp>
#include<boost/make_shared.hpp>

static boost::asio::io_service svc;
static boost::shared_ptr<boost::asio::io_service::work> work_lock;

static boost::signals2::signal<void(std::string)> textEntered;

static void
handleInputText(std::string text)
{
    std::cout<<"handleInputText()"<<" text provided: "<<text;
    return;
}

static void 
worker()
{
    sleep(2);
    svc.post([](){
            std::cout<<"\nRaising signal.";
            std::string hello("hello world");
            textEntered(hello);
       });
    return;
}

int main()
{
    try
    {
        work_lock = boost::make_shared<boost::asio::io_service::work>(svc);
        textEntered.connect(&handleInputText);

        boost::thread_group tg;
        tg.create_thread(boost::bind(&boost::asio::io_service::run, &svc));
        tg.create_thread(&worker);

        boost::this_thread::sleep_for(boost::chrono::seconds(3));
        work_lock.reset();

        tg.join_all();
    }
    catch(std::exception &ex)
    {
        std::cerr<<"main() exited with exception:"<<ex.what();
    }
    return 0;
}

Prints:

Raising signal.handleInputText() text provided: hello world

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