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    <blockquote> <p>I can see the thread runs, the signal is intercepted</p> </blockquote> <p>Are you sure? I don't think the signal is event sent.</p> <blockquote> <p>but the posted handler is not executed. What am I doing wrong?</p> </blockquote> <p>Your constructor creates a new thread, then waits for it to finish, so the constructor doesn't return until the new thread exits. That means this line in <code>main</code> won't execute until the receiver thread exits:</p> <pre><code> Package1Signals::getInstance()-&gt;signal1(); </code></pre> <p>Maybe you want the <code>boost::thread</code> to be a member of your class, so it has the same lifetime as your class, instead of being a local variable in the constructor.</p> <p>For style considerations, you don't need to use <code>boost::ref(*this)</code> you can just pass <code>this</code>, and you don't need to use <code>boost:bind</code> to create the thread, read the <a href="http://www.boost.org/doc/libs/1_47_0/doc/html/thread/thread_management.html#thread.thread_management.thread.multiple_argument_constructor" rel="nofollow">docs</a> which tell you that constructing a <code>thread</code> with multiple arguments is equivalent to passing those arguments to <code>bind</code> and constructing the thread with the result i.e. you can just say</p> <pre><code>thread(&amp;Class1::classifierBehavior, this); </code></pre> <p>Which is much simpler and easier to read!</p> <p><strong>Update</strong>: Now you've fixed the constructor so it doesn't block you have a race condition between connecting the receiver to the signal, which happens in the new thread, and publishing the signal, which happens in the main thread, as soon as the constructor finishes. If the new thread takes a few milliseconds to start executing then it will be too late and miss the signal, because in the main thread the constructor will have finished and the signal will have been emitted already.</p> <p>Try connecting the receiver <em>before</em> starting the new thread:</p> <pre><code>Class1::Class1(){ Package1Signals::getInstance()-&gt;signal1.connect(boost::bind(&amp;Class1::Reception1, this,_1)); thread = boost::thread(&amp;Class1::classifierBehavior,this); }; void Class1::classifierBehavior(){ service.run(); }; </code></pre> <p>This way the receiver is connected before the signal is emitted.</p> <p>I <em>think</em> the <code>io_service</code> will still get the event even if the event gets posted before the service is running, but you might want to check that, otherwise there's another race condition there.</p>
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    1. USJonathan Wakely
    1. USJonathan Wakely
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    1. COThanks I have changed the code following your suggestions. However I guess the join in the constructor was not the only problem as it seems now neither the signal is received by the object.
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    2. COYou'll have to come up with a [simple self-contained complete example](http://sscce.org) then, showing the definitions of `Class1` and `Package1Signals`. Also, don't forget to call `join()` _somewhere_, maybe in the `Class1::~Class1()` destructor, otherwise the main thread will just return from `main` and the other thread will be killed, maybe before handling the signal.
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      1. USJonathan Wakely
    3. COI can't open your link :(. I have posted the whole code. The signal shall not be handled by the thread but by the instance (the object containing the reference to the thread) which will then post a task to the thread. However I can't either see the cout in the signal reception. Plus I have added the join call in the main function before the cin statement. The strange thing is that I can actually input an integer from the console though I should not as the main should be blocked waiting for the thread to finish its tasks (and the thread should be in the service.run loop)
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