Re: [boost] Re: shared_ptr and BOOST_DISABLE_THREADS

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2004-04-25 09:38:35

On Apr 25, 2004, at 6:52 AM, Peter Dimov wrote:

>> In the std::locale implementation I am careful to wrap each use of the
>> locale implementation with a mutex lock.  I believe I would have to do
>> this whether or not shared_ptr protected its count.  And yet
>> std::locale is just a library, not an application.
>
> I am not sure whether you can skip the count synchronization here. Even
> though you do not expose a shared_ptr directly, the user can still 
> copy a
> std::locale at will. When two threads copy the same std::locale at the 
> same
> time, a non-synchronized count leads to undefined behavior.

I don't think I was clear.  The access is synchronized.  The 
synchronization happens at the locale level, making the synchronization 
at the shared_ptr level redundant.  I need to synchronize more than 
just the counts in the shared_ptr, namely access to the stuff that the 
shared_ptr is pointing to.

-Howard