RE: [boost] Race condition in boost::spirit?

From: Hartmut Kaiser (hartmutkaiser_at_[hidden])
Date: 2005-01-17 13:12:48

Roland Schwarz wrote:

> > I am afraid the usage of thread_specific_ptr as a local 
> static object 
> > is "implementation dependant".
> > The constructors might be called when "first time control passes 
> > through its declaration".
> > This would be bad. As far as I know thread_specific_ptr is 
> expected to 
> > be constructed before main.
> > Also what does "first time" mean when MT is involved? The standard 
> > does not know about MT.
> > Will it be called twice?
> >
> > I think the poiner should be moved to file scope.
> 
> Some additional information:
> Altough the thread_specific_ptr ctor tries to guard itself 
> against concurrent access of its underlying tss_data struct, 
> it is not prepared to be multiply called.
> 
> Declaring a local static object on the other hand protects 
> multiple calls to the ctor by setting a local flag and 
> scheduling a call for its dtor to atexit. It is exactly this 
> setting of the flag that poses a race condition, since it is 
> not protected by a critical section. Altough it might work to 
> internally protect the ctor against multiple invocation, this 
> would not solve the race condition. The side effect would be 
> to schedule two calls to atexit for the destructor, which is 
> equally bad.

Could you provide a patch?

Regards Hartmut