Re: [Boost-users] How to call destructor on thread object?

Subject: Re: [Boost-users] How to call destructor on thread object?
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2015-05-19 16:53:20

On Tue, May 19, 2015 at 4:40 PM, Lane
<software.research.development_at_[hidden]> wrote:
> Thanks for the explanation, that helps. But what I'm looking to do is find a
> way to call the destructor on the thread object. The ClassA and classB
> objects are connected to a USB device and I need to find a way to properly
> shut them down before destroying the threads in on_exit(). Any thoughts?

It sounds like an obvious response, but, "when it goes out of scope"?
So there must be some instance, reference, pointer (if dynamically
allocated, shared pointer, etc), holding onto it?

> On Tue, May 19, 2015 at 12:49 AM, Gavin Lambert <gavinl_at_[hidden]>
> wrote:
>>
>> Mere moments ago, quoth I:
>>>
>>> On 19/05/2015 15:26, Lane wrote:
>>>>
>>>>
>>>> I'm using the boost meta state machine and upon entry of this state, I
>>>> create two threads, and stop these threads in the on_exit().
>>>>
>>>> In on_entry(), I call the functors of each class and create threads and
>>>> add those to a boost thread_group. What I need to do now is call the
>>>> destructor of the objects on the threads ( of ClassA and ClassB) within
>>>> on_exit(). I'm unclear as to how the destructors of the objects
>>>> would/should be called when interrupting the threads. The destructors
>>>> are currently not being called.
>>>
>>>
>>> Since you are passing a copy of the object as the thread's state, the
>>> destructor for the local instances will be called in on_entry(), and the
>>> destructor for the instances owned by the thread will be called when the
>>> thread_group is destroyed, which is when MyEvent is destroyed.
>>>
>>> I'm not really familiar enough with Boost.MSM to know whether the event
>>> instance is destroyed when the event is handled (which if this were the
>>> case, you shouldn't be keeping threads in it), or when the containing
>>> state machine is destroyed, or only when the program exits.
>>
>>
>> Sorry, pressed Send too quickly.
>>
>> If you want to destroy the threads in on_exit instead, then since
>> thread_group lacks a means to remove a thread (unless you still have a
>> reference to it), you will have to destroy the thread_group instead.
>>
>> The simplest way to do that is to wrap it in a std::unique_ptr and reset()
>> it in on_exit.
>>
>>
>>
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>
>
>
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