Re: [boost] [future N2561] Implementation comments

Subject: Re: [boost] [future N2561] Implementation comments
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-12-03 09:59:41

----- Original Message ----- 
From: "Anthony Williams" <anthony.ajw_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, December 03, 2008 2:18 PM
Subject: Re: [boost] [future N2561] Implementation comments

> 
> "vicente.botet" <vicente.botet_at_[hidden]> writes:
> 
>> Ok, I see. Do we need to set_value from different threads? Should
>> the promise::set_value() be thread safe or not? What says the C++0x
>> standard?
> 
> The C++0x draft standard is silent on the matter. I think it probably 

So the idea is that a promise should be used only by a thread. Right?
 
>>> Protection of lazy_init would require a different mechanism, such as
>>> the use of boost::call_once.
>>
>> Why not? 

Sorry, I would like to say why not!
 
>> I was not talking of move-assigning but to take the address which
>> preserve the promise contents and is dangerous if concurrent calls
>> to set_value are not supported with this implementation. So, why not
>> delete the operator&()?
> 
> Just because something is not thread safe does not make it appropriate
> to delete the operator&. You can pass things around by pointer without
> making them accessible to more than one thread, and you can pass
> things by reference that ARE accessible by more than one thread, even
> if that isn't safe.

You are right. It is enough to state that this is not thread safe.

Thanks for all,
Vicente