Re: [boost] [FSM] Review library version update

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2007-02-05 16:16:08

Andrey Semashev wrote:
> Hello Andreas,
>
> Monday, February 5, 2007, 11:17:32 PM, you wrote:
>
>> Fabien Niñoles wrote:
>>> Probably you should put it has a static local variable inside a
>>> protected function, like this:
>>>
>>>    //! The method returns a reference to the only dispatcher
>>> instance
>>>
>>>    static state_dispatcher const& get()
>>>    {
>>>      static state_dispatcher instance;
>>>      return instance;
>>>    }
>
>> In a multithreaded app this might work on some platforms, on others
>> it doesn't:
>
>> Quote from http://msdn2.microsoft.com/en-us/library/s1sb61xd.aspx:
>> "Assigning to a static local variable is not thread safe and is not
>> recommended as a programming practice."
>
>> Although this isn't very concise wording (IIRC, the standard says
>> that it should work for literals assigned to PODs) it seems clear
>> that it won't work for non-PODs...
>
> I guess the only way to safely initialize a static local variable is
> through some call_once concept implementation.

I guess so if you want to make it easy for the users. Another option 
would be to require them to call a static initialize function from 
main() before they start any additional threads.

-- 
Andreas Huber
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